Latest / Boring Science / CERN Is Forcing Scientists to Rethink Reality_s Rules _ Science For Sleep

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CERN Is Forcing Scientists to Rethink Reality_s Rules _ Science For Sleep · Boring Science

0:00
Speaker 1: At 5.52 in the morning on June 27th, 2026, the
0:05
Speaker 1: last protons in the Large Hadron Collider completed their final
0:10
Speaker 1: loop through 27 kilometers of underground tunnel beneath the Swiss-French border,
0:16
Speaker 1: and the most powerful particle accelerator ever built went quiet.
0:21
Speaker 1: No alarm sounded. No ceremony marked the moment. A number
0:26
Speaker 1: on a monitoring dashboard ticked to zero. and the beams
0:30
Speaker 1: that had been circling at nearly the speed of light
0:33
Speaker 1: simply stopped. The control room staff noted the time in
0:38
Speaker 1: a log. For most of the world, it was an
0:41
Speaker 1: ordinary Friday morning. For the people who had spent careers building, running,
0:46
Speaker 1: and analyzing data from that machine, it was something harder
0:50
Speaker 1: to name. The Large Hadron Collider had been running in
0:54
Speaker 1: some form since 2008. three separate data-taking runs. More than
1:01
Speaker 1: a decade of proton collisions at energies no previous machine
1:06
Speaker 1: had reached. The numbers from Run 3 alone are almost
1:10
Speaker 1: meaningless in ordinary terms. 125.4 inverse femtobarns of integrated luminosity,
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Speaker 1: the largest data set a particle collider had ever produced
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Speaker 1: in a single operational period. To translate that into something human,
1:28
Speaker 1: hundreds of billions of individual collision events, each one a
1:33
Speaker 1: tiny controlled explosion at the scale of atomic nuclei, each
1:38
Speaker 1: one producing sprays of particles that detect as the size
1:42
Speaker 1: of apartment buildings recorded in fractions of a second. What
1:46
Speaker 1: physicists were looking for in all of that data was
1:50
Speaker 1: something that didn't fit. That is not a metaphor for
1:54
Speaker 1: open-minded science. It is the literal goal. The standard model
1:59
Speaker 1: of particle physics, the theoretical framework assembled over roughly 50 years,
2:06
Speaker 1: finalized in something close to its current form by the mid-1970s,
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Speaker 1: tells physicists exactly what should come out of those collisions.
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Speaker 1: Every known particle, every known force, The model is precise
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Speaker 1: enough that its predictions and the measurements from experiments agree
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Speaker 1: to ten decimal places in some cases. That level of
2:28
Speaker 1: agreement is almost unreasonable. It is one of the most
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Speaker 1: tested and confirmed theories in the history of science. If
2:36
Speaker 1: you find comfort in these gentle explorations of space and science,
2:41
Speaker 1: I'd be grateful if you'd consider subscribing and giving this
2:44
Speaker 1: video a like. I'd love to know where you're watching
2:48
Speaker 1: from and what time it is for you. Feel free
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Speaker 1: to drop your location and time in the comments below.
3:00
Speaker 1: And it is not enough. Not because it is wrong, exactly.
3:05
Speaker 1: Because it is incomplete in ways that are too large
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Speaker 1: to ignore. The Standard Model says nothing about dark matter.
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Speaker 1: which appears to make up roughly 27% of the universe.
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Speaker 1: It says nothing about dark energy, which appears to drive
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Speaker 1: the accelerating expansion of space and accounts for another 68%.
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Speaker 1: It cannot incorporate gravity into its framework at all. Add
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Speaker 1: those gaps together and the most successful theory in particle
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Speaker 1: physics describes, at best, about 5% of what actually exists.
3:45
Speaker 1: For 50 years, physicists have known this. The question was
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Speaker 1: always where the cracks would appear first. The LHC was
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Speaker 1: built in part to find them. What made the shutdown
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Speaker 1: of June 27th different from a routine pause was not
4:02
Speaker 1: just the scale of the data collected. It was what
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Speaker 1: the data contained. Over three runs, The machine had been
4:11
Speaker 1: producing results that sat in an uncomfortable position. Not clean confirmations,
4:18
Speaker 1: not clean refutations, but signals. Measurements that drifted away from
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Speaker 1: standard model predictions by amounts too large to dismiss easily
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Speaker 1: and too small, so far, to declare a discovery. Particles
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Speaker 1: that shouldn't exist in the configurations they were found in.
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Speaker 1: decay patterns that didn't match the model's arithmetic, asymmetries between
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Speaker 1: matter and antimatter that pointed somewhere the theory couldn't follow.
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Speaker 1: None of this made headlines the way the Higgs boson
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Speaker 1: did in 2012. A hint of new physics buried in
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Speaker 1: a statistical distribution is harder to explain than a particle
5:03
Speaker 1: with a name. But the physicists tracking these results were
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Speaker 1: not treating them as noise, They were treating them as clues.
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Speaker 1: Something was nudging the data in a consistent direction, and
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Speaker 1: the standard model offered no explanation for what that something was.
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Speaker 1: This is where physics stands right now. Not at a
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Speaker 1: moment of collapse. The standard model still works, still predicts,
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Speaker 1: still matches experiment across an enormous range of measurements with
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Speaker 1: extraordinary precision. But at the edges of what it can describe,
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Speaker 1: The seams are showing. Measurements that should agree with the
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Speaker 1: theory don't. Quite. Particles are appearing that require explanations. The
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Speaker 1: theory isn't built to give. The machine that spent 15
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Speaker 1: years probing these edges has now gone offline. It's tunnel sealed.
6:00
Speaker 1: It's magnets warming up for the first time in years.
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Speaker 1: And the data it left behind is still being analysed
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Speaker 1: by thousands of researchers at institutions across dozens of countries.
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Speaker 1: The questions that data is meant to answer are not small.
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Speaker 1: Why does matter exist? What is the 95% of the
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Speaker 1: universe the Standard Model cannot see? Why do certain particles
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Speaker 1: decay the way they do when the equations say they shouldn't?
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Speaker 1: Is there a deeper framework underneath the one physicists have built?
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Speaker 1: Something that would explain the Standard Model the way the
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Speaker 1: Standard Model explains the behaviour of atoms? These are not
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Speaker 1: rhetorical questions. They have specific, measurable answers, and the LHC
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Speaker 1: was designed to find them. Whether it succeeded and how,
6:57
Speaker 1: and what exactly was sitting in the data that nobody expected,
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Speaker 1: That is a longer story. What the machine had found
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Speaker 1: over three runs and more than a decade of collisions
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Speaker 1: was not nothing. And understanding what it actually means requires
7:15
Speaker 1: starting from the beginning. The standard model of particle physics
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Speaker 1: is one of the most successful scientific theories ever written,
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Speaker 1: which makes its blind spots all the more disturbing. To
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Speaker 1: understand what the standard model actually is, Start with a
7:31
Speaker 1: simple idea. Everything around you, the chair, the air, your
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Speaker 1: own hands, is made of particles. Not just atoms, but
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Speaker 1: things smaller than atoms. And those particles do not simply
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Speaker 1: float in space doing nothing. They push and pull on
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Speaker 1: each other through forces. The standard model is the theory
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Speaker 1: that names all of these particles describes all of those
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Speaker 1: forces in a single coherent framework. It took physicists roughly
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Speaker 1: four decades to build it, from the late 1920s through
8:09
Speaker 1: the early 1970s, assembling piece by piece through experiments, arguments,
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Speaker 1: and mathematical predictions that turned out to be right in
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Speaker 1: ways that still seem almost unreasonable. The particle list runs deep. Quarks,
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Speaker 1: which combine to form protons and neutrons. Electrons, which orbit
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Speaker 1: atomic nuclei and make chemistry possible. Neutrinos, which pass through
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Speaker 1: ordinary matter almost without interaction. Trillions of them are moving
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Speaker 1: through your body right now. Photons, which carry light. Gluons,
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Speaker 1: which hold quarks together with something called the strong force.
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Speaker 1: the W and Z bosons which govern radioactive decay, and
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Speaker 1: finally in 2012 the Higgs boson which had been predicted
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Speaker 1: since 1964. Each of these was found. Each confirmed a prediction.
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Speaker 1: The theory's track record is essentially unbroken across five decades
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Speaker 1: of increasingly precise experimental tests. To get a sense of
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Speaker 1: just how precise, Consider this. The standard model predicts the
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Speaker 1: magnetic strength of the electron to 11 decimal places. When
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Speaker 1: physicists actually measure it, the answer matches to 11 decimal places.
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Speaker 1: That is not luck. That is a theory that is
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Speaker 1: capturing something genuinely true about the structure of reality. No
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Speaker 1: other scientific framework in history has made predictions accurate to
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Speaker 1: that level and been right. By any reasonable measure, the
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Speaker 1: standard model is a triumph. And yet, something is wrong.
10:04
Speaker 1: Not wrong in a small way, wrong in a way
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Speaker 1: that sits quietly behind every conference paper and every seminar slide,
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Speaker 1: like a door in the back of the room that
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Speaker 1: nobody can open. The standard model describes particles and forces
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Speaker 1: with extraordinary precision, but the universe contains things that the
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Speaker 1: model simply does not see. Start with gravity. Gravity is
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Speaker 1: not in the standard model. This sounds impossible given that
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Speaker 1: gravity is the most obvious force in daily experience. Pull
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Speaker 1: a book off a shelf and gravity is why it falls.
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Speaker 1: Hold planets in orbit. shape galaxies, determine the large-scale structure
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Speaker 1: of the universe. Gravity does all of this, and the
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Speaker 1: Standard Model has nothing to say about it. Physicists have
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Speaker 1: a separate framework for gravity, called General Relativity, and it
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Speaker 1: works beautifully at the scale of planets and galaxies. But
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Speaker 1: General Relativity and the Standard Model cannot be combined into
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Speaker 1: a single consistent theory. At the smallest scales, where quantum
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Speaker 1: mechanics dominates, gravity stops making sense. The two best theories
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Speaker 1: in all of physics are fundamentally incompatible, and no one
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Speaker 1: has resolved this. That is problem one. Problem two is darker,
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Speaker 1: quite literally. Everywhere astronomers look, galaxies are spinning in ways
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Speaker 1: they should not be able to. Stars on the outer
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Speaker 1: edges of galaxies are moving far too fast. If the
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Speaker 1: only matter in a galaxy were the matter you can see, stars, gas, dust,
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Speaker 1: the gravity it generates would not be enough to hold
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Speaker 1: those outer stars in orbit at that speed. They should
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Speaker 1: fly off. They do not. Something is holding them in place.
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Speaker 1: That something has gravitational pull. which means it has mass,
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Speaker 1: which means it is matter. But it does not emit light.
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Speaker 1: It does not absorb light. It does not interact with
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Speaker 1: the particles in the standard model at all. Physicists call
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Speaker 1: it dark matter, and it makes up roughly 27% of
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Speaker 1: everything the universe contains. The standard model has no candidate
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Speaker 1: for it. Not a single particle in the entire framework
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Speaker 1: matches what dark matter appears to be. Then comes dark energy.
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Speaker 1: In 1998, two independent teams measuring distant supernovae discovered something
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Speaker 1: that genuinely shocked the physics community. The universe is not
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Speaker 1: just expanding, it is expanding faster and faster. Something is
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Speaker 1: pushing space itself outward with increasing force, working against gravity
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Speaker 1: on the largest possible scale. That something is called dark energy,
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Speaker 1: and it accounts for approximately 68% of the total energy
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Speaker 1: content of the universe. The standard model does not describe it.
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Speaker 1: The standard model does not predict it. The standard model
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Speaker 1: cannot explain it. When physicists try to calculate what the
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Speaker 1: energy of empty space should be based on quantum mechanics,
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Speaker 1: they get a number that is off from the observed
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Speaker 1: value by something in the range of 120 orders of magnitude,
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Speaker 1: the largest discrepancy between theory and observation in the history
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Speaker 1: of science. Add these numbers together and the picture sharpens
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Speaker 1: into something unsettling. Dark energy is 68% of the universe.
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Speaker 1: Dark matter is 27%. Everything else, every star, every planet,
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Speaker 1: every atom ever measured, every particle the Standard Model accounts for,
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Speaker 1: makes up the remaining 5%. The most precisely tested physical
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Speaker 1: theory in history describes a small fraction of what actually exists.
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Speaker 1: The Standard Model is not a map of the universe.
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Speaker 1: It is a map of a small corner of it,
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Speaker 1: drawn with extraordinary detail, surrounded on all sides by territory
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Speaker 1: that remains completely blank. There is one more silence worth
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Speaker 1: sitting with. The Big Bang, according to the best understanding
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Speaker 1: of physics, should have produced equal amounts of matter and antimatter.
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Speaker 1: When matter and antimatter meet, they annihilate. If the balance
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Speaker 1: had been perfect, the universe would have destroyed itself in
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Speaker 1: its first moments, leaving nothing behind but a faint glow
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Speaker 1: of radiation. Instead, there are galaxies, there are stars, there
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Speaker 1: are planets and oceans and people asking questions about the
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Speaker 1: early universe. Something tipped the scale. one extra particle of
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Speaker 1: matter for every billion matter-antimatter pairs was enough to leave
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Speaker 1: everything we see. The Standard Model does allow for a
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Speaker 1: small imbalance between matter and antimatter. Physicists call it CP violation,
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Speaker 1: and this has been observed in certain particle decays. But
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Speaker 1: the amount the model allows is far too small to
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Speaker 1: account for the universe that actually exists. Something else caused
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Speaker 1: the asymmetry. The standard model does not say what. All
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Speaker 1: of this was known before the Large Hadron Collider ran
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Speaker 1: its first collision. None of it is new. What changed
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Speaker 1: over the course of three runs at CERN was not
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Speaker 1: the discovery that the model was incomplete. That was already clear.
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Speaker 1: What changed was where, specifically, the data started pulling away
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Speaker 1: from the predictions. the cracks began to have addresses. Physicists
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Speaker 1: had known for decades that the Standard Model was incomplete.
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Speaker 1: They just did not know exactly where the cracks would
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Speaker 1: start to show. On July 4th 2012, two independent experiments
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Speaker 1: at CERN announced simultaneously that they had found it, the
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Speaker 1: particle that physicists have been hunting for nearly half a century.
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Speaker 1: The auditorium at CERN filled with applause Peter Higgs, the
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Speaker 1: theorist who had proposed the particle's existence back in 1964,
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Speaker 1: was sitting in the front rows. He wiped his eyes.
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Speaker 1: Around the world, physicists who had spent careers building toward
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Speaker 1: this moment stopped what they were doing. Some of them wept.
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Speaker 1: This was not a small result. This was the last
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Speaker 1: missing piece of the Standard Model. The particle that the
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Speaker 1: entire theoretical architecture had predicted must exist, and which nobody
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Speaker 1: had been able to confirm for 48 years. To understand
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Speaker 1: why 2012 felt like a culmination, you have to understand
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Speaker 1: what the Higgs boson actually does. The Standard Model describes
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Speaker 1: particles and forces with remarkable precision, but there was a
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Speaker 1: problem buried in its early versions. The mathematics worked only
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Speaker 1: if certain particles had no mass at all. Photons fit
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Speaker 1: that description, but electrons, quarks, and the W and Z
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Speaker 1: bosons clearly do have mass. Something was giving them mass,
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Speaker 1: and the theory had no mechanism to explain it. In 1964,
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Speaker 1: Peter Higgs and several other physicists independently proposed a solution.
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Speaker 1: They suggested that space itself is filled with a field
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Speaker 1: now called the Higgs field, and that particles acquire mass
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Speaker 1: by interacting with it. The stronger a particle's interaction with
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Speaker 1: the Higgs field, the heavier it becomes. A particle with
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Speaker 1: no interaction at all, like the photon, passes straight through
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Speaker 1: without gaining any mass. The Higgs boson is the ripple
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Speaker 1: in that field. It is what you detect when you
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Speaker 1: disturb the field enough. For decades this was theoretical machinery, elegant, necessary,
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Speaker 1: but unconfirmed. The Higgs boson was predicted to be heavy,
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Speaker 1: somewhere above 100 billion electron volts in mass, which meant
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Speaker 1: it required a machine powerful enough to produce it in collisions.
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Speaker 1: The Large Hadron Collider was built, in large part, to
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Speaker 1: find it. When the ATLAS and CMS detectors both registered
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Speaker 1: a new particle at around 125 billion electron volts in
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Speaker 1: the summer of 2012, the statistical significance was beyond any
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Speaker 1: reasonable doubt. Five sigma from ATLAS, five sigma from CMS,
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Speaker 1: two independent detectors, two independent teams, the same result. The
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Speaker 1: Higgs boson was real. The mechanism was confirmed. The field
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Speaker 1: that fills all of space and grants mass to matter
19:41
Speaker 1: had been proven to exist. Physicists celebrated, and they had
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Speaker 1: every right to. This was a genuine triumph. The Standard
19:51
Speaker 1: Model had predicted the Higgs boson before the technology to
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Speaker 1: find it even existed, and the prediction was correct. That
19:59
Speaker 1: kind of success is rare in science. The theory had
20:03
Speaker 1: been vindicated at its deepest level. For a brief period,
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Speaker 1: It felt like the book might be closing on a
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Speaker 1: chapter of physics that had begun in the 1960s. Then
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Speaker 1: physicists started measuring the Higgs boson in detail. And the
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Speaker 1: questions started. The first thing researchers wanted to know was
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Speaker 1: whether the Higgs boson behaved exactly as the standard model predicted.
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Speaker 1: The theory is specific. It says how often the Higgs
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Speaker 1: should decay into each type of particle. and in what proportions.
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Speaker 1: It says how strongly the Higgs should couple to fermions
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Speaker 1: of different generations. Measuring these properties was not just a formality,
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Speaker 1: it was a test. Any deviation from the predictions, even
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Speaker 1: a small one, would be evidence that something beyond the
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Speaker 1: standard model was influencing the Higgs behind the scenes. One
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Speaker 1: decay mode drew particular attention. The Higgs boson can decay
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Speaker 1: into a pair of muons. Muons are second generation particles,
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Speaker 1: heavier cousins of the electron, but still relatively light compared
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Speaker 1: to the top quark or the bottom quark. The standard
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Speaker 1: model predicts that this decay should happen roughly once in
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Speaker 1: every 5,000 Higgs decays. That is extraordinarily rare. Collecting enough
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Speaker 1: of these events to say anything statistically meaningful requires enormous
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Speaker 1: data sets and years of running time. Scientists at the
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Speaker 1: ATLAS experiment eventually found compelling evidence that this decay was occurring.
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Speaker 1: The numbers, roughly, match the prediction. But roughly is doing
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Speaker 1: a lot of work in that sentence. The reason this
21:54
Speaker 1: particular decay matters so much is what it probes. The
21:59
Speaker 1: Higgs boson interacts most strongly with the heaviest particles. Its
22:04
Speaker 1: coupling to the top quark, the heaviest particle in the
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Speaker 1: standard model, is enormous. Its coupling to the bottom quark
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Speaker 1: is large enough to measure without much difficulty. But the
22:16
Speaker 1: muon is a second generation particle, much lighter, and its
22:21
Speaker 1: coupling to the Higgs is far weaker. Measuring that coupling
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Speaker 1: tests whether the Higgs field interacts with different generations of
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Speaker 1: matter in exactly the way the theory requires. Any deviation,
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Speaker 1: even a subtle one, could mean that the Higgs is
22:38
Speaker 1: not quite the particle the standard model describes. It could
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Speaker 1: mean something else is participating in the mass generation process.
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Speaker 1: It could mean the theory is missing a layer. So far,
22:51
Speaker 1: the muon coupling measurement is consistent with the standard model.
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Speaker 1: But consistent is not the same as confirmed. The uncertainty
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Speaker 1: on that measurement is still large enough to hide significant deviations.
23:06
Speaker 1: As the LHC collected more data through run 3, the
23:10
Speaker 1: error bars on this number shrank. They have not yet
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Speaker 1: shrunk enough to make a definitive statement. That work continues.
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Speaker 1: Then there is the question of Higgs self-coupling. This is
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Speaker 1: where the physics becomes genuinely unsettling. The standard model predicts
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Speaker 1: not just how the Higgs interacts with other particles, but
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Speaker 1: how it interacts with itself. The Higgs field has a
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Speaker 1: specific shape. Physicists call it the shape of the Higgs potential,
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Speaker 1: and that shape determines the structure of the field that
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Speaker 1: fills all of space. The self-coupling constant determines whether that
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Speaker 1: potential looks the way the theory predicts. Measuring it requires
23:53
Speaker 1: observing two Higgs bosons produced together in the same collision,
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Speaker 1: which is extraordinarily rare, far rarer than even the muon decay.
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Speaker 1: The LHC has been collecting these events, but the statistics
24:08
Speaker 1: are still thin. The measurement has not yet been made
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Speaker 1: with precision. What physicists have established is a range. The
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Speaker 1: self-coupling is somewhere within a factor of a few of
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Speaker 1: the standard model value. That is not good enough to
24:24
Speaker 1: confirm the theory. It is not good enough to break
24:27
Speaker 1: it either. Why does this matter? Because the shape of
24:31
Speaker 1: the Higgs potential is not just a detail. It describes
24:35
Speaker 1: how the Higgs field settled into its current state after
24:39
Speaker 1: the Big Bang. In the very early universe, the field
24:43
Speaker 1: was in a different configuration. As the universe cooled, it
24:48
Speaker 1: transitioned to its current state, giving mass to particles in
24:52
Speaker 1: the process. The precise shape of that potential determines whether
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Speaker 1: this transition happened smoothly or violently, and whether the conditions
25:02
Speaker 1: in the very early universe were capable of producing the
25:05
Speaker 1: matter-antimatter asymmetry that allowed the universe to survive. If the
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Speaker 1: self coupling deviates from the standard model prediction, it changes
25:16
Speaker 1: the picture of what happened in the first fractions of
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Speaker 1: a second after the Big Bang. This is not an
25:22
Speaker 1: abstract point. It connects the particle measured in a detector
25:27
Speaker 1: to the reason anything exists at all. There is one
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Speaker 1: more layer The Higgs boson is the only fundamental particle
25:36
Speaker 1: in the Standard Model with zero spin. Every other particle
25:40
Speaker 1: has some amount of angular momentum built into its quantum structure.
25:45
Speaker 1: The Higgs has none. It has no electric charge. It
25:50
Speaker 1: carries no colour charge, so the strong force ignores it.
25:55
Speaker 1: It is, in a sense, the quietest particle in the theory.
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Speaker 1: the one that sits at the center and connects everything
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Speaker 1: else by granting them mass while interacting as little as possible.
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Speaker 1: This uniqueness makes its properties especially sensitive to the presence
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Speaker 1: of new physics. Any additional particles or forces that couple
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Speaker 1: to the Higgs, even weakly, would leave fingerprints on its
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Speaker 1: decay rates and coupling strengths. The Higgs is, in this way,
26:26
Speaker 1: a precision instrument for detecting what the Standard Model cannot see.
26:32
Speaker 1: The decade following the 2012 discovery was not the quiet
26:36
Speaker 1: period of consolidation that some physicists expected. It was a
26:41
Speaker 1: decade of increasingly precise measurement, and each measurement sharpened the
26:46
Speaker 1: question of whether the Higgs was exactly what the theory said,
26:50
Speaker 1: or something slightly different. The answer, at the close of
26:55
Speaker 1: Run 3, that nothing is clearly broken but the precision
26:59
Speaker 1: required to make that statement keeps improving and the range
27:04
Speaker 1: of possible deviations keeps narrowing and within that narrowing range
27:09
Speaker 1: there is still room for something unexpected to be hiding
27:13
Speaker 1: the Higgs boson had been found confirmed and celebrated and
27:18
Speaker 1: then it started behaving in ways that raised more questions
27:21
Speaker 1: than it answered the word penguin does not belong in
27:25
Speaker 1: particle physics, and yet here we are. The name comes
27:29
Speaker 1: from a bar bet in the 1970s, a story too
27:34
Speaker 1: strange to be invented, involving a physicist who lost a
27:38
Speaker 1: wager and had to sign a paper with a penguin
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Speaker 1: drawn on it. The diagram he was illustrating at the time,
27:45
Speaker 1: a particular kind of particle interaction drawn on a whiteboard,
27:50
Speaker 1: happened to look vaguely like the bird if you tilted
27:54
Speaker 1: your head at the right angle. The name stuck. Particle
27:58
Speaker 1: physics has not looked back. And while the name sounds
28:02
Speaker 1: like something from a children's book, what it describes is
28:06
Speaker 1: one of the most precise and troubling discrepancies in modern science.
28:11
Speaker 1: To understand why penguin decays matter, you first have to
28:15
Speaker 1: understand what a B meson is. A meson is a
28:19
Speaker 1: particle made of exactly two quarks, one quark and one
28:24
Speaker 1: antiquark bound tightly together by the strong force. B mesons
28:29
Speaker 1: are a specific family within that category, and what makes
28:33
Speaker 1: them interesting is that they contain a bottom quark. Bottom
28:37
Speaker 1: quarks are heavy, they are unstable. Left to themselves, they decay,
28:43
Speaker 1: transforming into lighter quarks and releasing energy in the process.
28:48
Speaker 1: The B-maison is essentially a clock that is always winding down.
28:52
Speaker 1: In the detectors at CERN, a B-maison lives for roughly
28:56
Speaker 1: a trillionth of a second before it falls apart into
29:00
Speaker 1: other particles. That is enough time, given how fast these
29:04
Speaker 1: particles move, to leave a detectable track. Physicists catch the
29:10
Speaker 1: wreckage and work backward to figure out what happened. Most
29:14
Speaker 1: of the time, B mesons decay in fairly ordinary ways.
29:19
Speaker 1: The bottom quark changes into a charm quark, releasing a
29:23
Speaker 1: W boson that quickly decays into lighter particles. This is
29:28
Speaker 1: a straightforward charged current interaction, well understood, well measured. The
29:35
Speaker 1: standard model predicts it cleanly and the data matches. There
29:39
Speaker 1: is no mystery there but there is another class of
29:43
Speaker 1: B meson decay that is far rarer and far stranger
29:48
Speaker 1: in these decays the bottom quark transforms not into a
29:52
Speaker 1: charm quark but into a strange quark without emitting a
29:57
Speaker 1: W boson in the direct way Instead, the transformation happens
30:02
Speaker 1: through a quantum loop. The quark briefly emits and reabsorbs
30:07
Speaker 1: virtual particles, including a virtual top quark and a virtual
30:12
Speaker 1: W boson, before emerging as a strange quark. The loop
30:17
Speaker 1: itself releases a Z boson or a photon, which then
30:21
Speaker 1: decays into a pair of leptons, often two muons. This
30:26
Speaker 1: is the penguin decay. It is named for the shape
30:30
Speaker 1: of that loop diagram on paper, and it happens only
30:34
Speaker 1: once in roughly every million B meson decays. That rarity
30:39
Speaker 1: is precisely why it matters. In the standard model, this
30:44
Speaker 1: process is suppressed. It happens, but it happens rarely, because
30:49
Speaker 1: the loop structure carries what physicists call a flavor-changing neutral current,
30:55
Speaker 1: A type of transition that the standard model actively disfavors.
31:00
Speaker 1: The frequency and the angular distribution of the products are
31:03
Speaker 1: calculable in advance with high precision. When you measure the
31:08
Speaker 1: actual results in a detector and compare them to that calculation,
31:13
Speaker 1: the two numbers should match. If they do not match,
31:16
Speaker 1: something is interfering in that loop that the standard model
31:20
Speaker 1: does not account for. An undiscovered particle. an unknown force,
31:26
Speaker 1: something sitting in the quantum machinery of that decay that
31:30
Speaker 1: the current theory has no entry for. This is the
31:34
Speaker 1: thing that makes penguin decays so powerful as a probe.
31:38
Speaker 1: Because the standard model prediction is suppressed, any new physics
31:43
Speaker 1: that couples to these quarks stands out. The signal-to-noise ratio,
31:48
Speaker 1: in a sense, is favorable. You are looking for a
31:51
Speaker 1: ripple in quiet water. The LHCb experiment, built specifically to
31:57
Speaker 1: study B meson decays with extraordinary precision, has been collecting
32:02
Speaker 1: these events for over a decade. In runs spanning from
32:06
Speaker 1: 2011 through the end of run 3, the collaboration recorded
32:11
Speaker 1: hundreds of billions of B meson decays. The penguin decays,
32:16
Speaker 1: by contrast, are counted in the thousands or tens of
32:20
Speaker 1: thousands rare events pulled from an enormous flood of more
32:25
Speaker 1: common ones. Extracting them requires isolating specific final states, a kaon,
32:33
Speaker 1: a pion, two muons, each with a measurable momentum and angle.
32:38
Speaker 1: The analysis involves mapping the full angular distribution of the
32:43
Speaker 1: decay products across multiple variables simultaneously. It is not a
32:48
Speaker 1: single number, it is a shape. A pattern in many
32:52
Speaker 1: dimensions that the standard model predicts in detail and that
32:57
Speaker 1: the detector measures in detail. When researchers published their measurements,
33:02
Speaker 1: the shape did not match. Not dramatically, not in a
33:06
Speaker 1: way that rewrote textbooks overnight, but in a consistent and
33:11
Speaker 1: repeating way across multiple variables and multiple data sets. The
33:17
Speaker 1: observed angular distributions leaned away from the predictions. The rate
33:23
Speaker 1: of certain configurations appeared suppressed relative to what the model expected.
33:29
Speaker 1: Each individual deviation was modest. Taken together across all the
33:34
Speaker 1: variables and all the data, the disagreement was significant enough
33:39
Speaker 1: to draw serious attention. Early results pointed to tensions in
33:44
Speaker 1: the range of 2 to 3 standard deviations from the prediction.
33:49
Speaker 1: In particle physics, 3 sigma is considered evidence. 5 sigma
33:55
Speaker 1: is a discovery. 2 to 3 sigma means something is
33:59
Speaker 1: worth investigating very carefully. What followed was years of careful investigations.
34:06
Speaker 1: Because in physics, a disagreement between theory and measurement can
34:11
Speaker 1: mean several things. It can mean the measurement has a
34:15
Speaker 1: systematic error, a miscalibration of the detector, a background process
34:21
Speaker 1: being misidentified as signal. It can mean the theoretical prediction
34:25
Speaker 1: has an error. Hadronic effects, the messy influence of the
34:30
Speaker 1: strong force on these decays, are notoriously difficult to calculate.
34:35
Speaker 1: and introduce genuine uncertainty, or it can mean the standard
34:40
Speaker 1: model is wrong about what is happening in that loop.
34:43
Speaker 1: Ruling out the first two possibilities takes time and independent confirmation.
34:49
Speaker 1: Both take years. The hadronic uncertainty argument was taken seriously.
34:55
Speaker 1: Some theorists argued that strong force effects inside the B
34:59
Speaker 1: mesons Specifically, contributions from charm quarks running inside the loop
35:05
Speaker 1: in ways that are difficult to calculate precisely could shift
35:09
Speaker 1: the predictions enough to explain the discrepancy without new physics.
35:14
Speaker 1: This debate ran through the literature for several years. It
35:18
Speaker 1: has not been fully resolved, but the experimental side of
35:22
Speaker 1: the argument kept gaining weight. The LHCb collaboration updated their
35:28
Speaker 1: analysis with larger datasets. The measurements did not drift back
35:33
Speaker 1: toward the standard model prediction. They held. Other experiments running
35:38
Speaker 1: independently on different hardware with different systematic uncertainties looked at
35:44
Speaker 1: related observables. The discrepancies they found were consistent with what
35:49
Speaker 1: LHCb had seen. In 2022, The picture sharpened again. New
35:56
Speaker 1: electroweak penguin results from LHCb, using the full dataset from
36:02
Speaker 1: Run 2, showed deviations across a suite of angular observables.
36:08
Speaker 1: The combined tension had grown. Physicists who had been cautious
36:12
Speaker 1: began to speak more carefully about what the data was
36:15
Speaker 1: actually saying. The pattern of deviations across multiple observables was coherent.
36:22
Speaker 1: The same direction roughly the same magnitude in measurements that
36:27
Speaker 1: probe different combinations of the underlying physics. Random errors in
36:32
Speaker 1: a detector do not produce coherent deviations across many different
36:36
Speaker 1: observables at once. Hadronic effects, while real and uncertain, do
36:42
Speaker 1: not generally produce this kind of structured disagreement across so
36:46
Speaker 1: many independent measurements simultaneously. Something systematic in the underlying physics
36:53
Speaker 1: begins to look more plausible as an explanation. The theoretical
36:58
Speaker 1: frameworks for what that something might be have been accumulating
37:02
Speaker 1: for years. One popular class of models introduces a new
37:07
Speaker 1: particle called the Z-prime boson, a heavier cousin of the
37:11
Speaker 1: standard model Z-boson that couples preferentially to certain quarks and leptons.
37:18
Speaker 1: If a Z prime exists at a mass above what
37:21
Speaker 1: the LHC can produce directly, it would appear in these
37:25
Speaker 1: penguin loops as a virtual correction, subtly shifting the rates
37:30
Speaker 1: and distributions in exactly the pattern observed. The numbers from
37:35
Speaker 1: the B meson data, when used to constrain the properties
37:39
Speaker 1: of a hypothetical Z prime, point to a mass somewhere
37:43
Speaker 1: in the range of tens of ATV. far above the
37:47
Speaker 1: direct reach of RUM3, but potentially within the reach of
37:51
Speaker 1: future machines. Other frameworks invoke lepto-quarks, particles that carry both
37:58
Speaker 1: quark number and lepton number, and have no place in
38:02
Speaker 1: the current standard model. Some supersymmetric models generate the same
38:07
Speaker 1: kind of loop-level corrections through the exchange of virtual superpartners.
38:13
Speaker 1: No single theory fits perfectly. But the range of theories
38:17
Speaker 1: that can produce the observed deviations is significantly narrower than
38:22
Speaker 1: it was a decade ago, which is itself a result.
38:26
Speaker 1: What makes the penguin decay anomalies particularly compelling as a
38:30
Speaker 1: direction for new physics is that they appear in a
38:34
Speaker 1: part of the standard model that is genuinely calculable. The
38:38
Speaker 1: theory makes a precise prediction, not a rough estimate. The
38:43
Speaker 1: hadronic uncertainties, while real, are bounded by independent measurements and
38:49
Speaker 1: theoretical consistency checks. When the measurement sits outside that boundary,
38:54
Speaker 1: the argument for new physics in the loop becomes harder
38:58
Speaker 1: to dismiss. The data has been collected, recollected, cross-checked across experiments,
39:05
Speaker 1: and re-analysed with different methods. The numbers disagreed with the model,
39:10
Speaker 1: and the disagreement was too clean and too consistent to
39:14
Speaker 1: be a bad day in the data. The Big Bang
39:17
Speaker 1: created two kinds of matter in equal measure, and if
39:21
Speaker 1: physics had been perfectly symmetric that day, you would not exist,
39:26
Speaker 1: neither would anything else. No galaxies, no stars, no planets,
39:33
Speaker 1: no atoms floating in the cold dark between them. The
39:37
Speaker 1: universe would have produced equal quantities of matter and antimatter.
39:42
Speaker 1: Those two populations would have found each other. And in
39:46
Speaker 1: a cascade of mutual annihilation, Every particle would have been
39:50
Speaker 1: converted back into pure energy. What remains would be a
39:55
Speaker 1: featureless sea of photons, expanding forever through a universe that
40:01
Speaker 1: contains nothing. That is the logical endpoint of perfect symmetry.
40:07
Speaker 1: The fact that you are reading this means symmetry failed.
40:11
Speaker 1: Something went wrong. Or perhaps more precisely, something went right.
40:17
Speaker 1: at a scale so small it seems almost impossible. One
40:22
Speaker 1: extra particle of matter for every billion matter-antimatter pairs. That
40:28
Speaker 1: is the margin. Every galaxy you can see in the
40:31
Speaker 1: night sky, every cloud of gas, every rocky planet, every
40:37
Speaker 1: ocean and mountain range and living cell is the leftover
40:41
Speaker 1: from that tiny imbalance. The rest was annihilated in the
40:45
Speaker 1: first fractions of a second after the Big Bang. What
40:49
Speaker 1: we call the observable universe is a rounding error, and
40:53
Speaker 1: for decades, nobody could explain where that rounding error came from.
40:59
Speaker 1: The question has a name in physics. Actually, it has
41:03
Speaker 1: several names, but the one that matters here is baryogenesis.
41:08
Speaker 1: the process by which the early universe came to contain
41:11
Speaker 1: more baryons than antibaryons. Baryons are the heavy particles. Protons
41:18
Speaker 1: and neutrons are baryons. The atoms in your body are
41:22
Speaker 1: built from baryons. If baryogenesis had not happened, or had
41:28
Speaker 1: not happened asymmetrically, none of that exists. The Standard Model
41:33
Speaker 1: does acknowledge that such an asymmetry is required. What it
41:37
Speaker 1: cannot fully explain is how large that asymmetry should be,
41:42
Speaker 1: or whether the mechanisms it describes are powerful enough to
41:46
Speaker 1: account for the universe we actually observe. To produce a
41:50
Speaker 1: matter-dominated universe, three conditions have to be met simultaneously. The
41:57
Speaker 1: physicist Andrei Sakharov laid them out in 1967. One of
42:02
Speaker 1: those conditions is that matter and antimatter must behave differently
42:07
Speaker 1: under certain transformations. Not differently in a vague or approximate way,
42:13
Speaker 1: differently in a specific, measurable, precise way. Physicists call this
42:19
Speaker 1: CP violation, a breaking of the combined symmetry between charge
42:24
Speaker 1: and parity. If you reflect a particle interaction in a mirror,
42:29
Speaker 1: and swap every particle for its antiparticle, CP symmetry says
42:34
Speaker 1: the result should look identical. CP violation means it doesn't.
42:39
Speaker 1: The standard model does predict CP violation. It has been
42:43
Speaker 1: observed before, but the observations had been confined to a
42:47
Speaker 1: specific class of particles called mesons, composite particles made of
42:52
Speaker 1: one quark and one antiquark. Mesons are real and measurable,
42:57
Speaker 1: but they are not the building blocks of the visible universe.
43:00
Speaker 1: Protons and neutrons are. And protons and neutrons are baryons,
43:06
Speaker 1: not mesons. For years, CP violation had been confirmed in
43:11
Speaker 1: the meson sector without being directly confirmed in baryons. That
43:16
Speaker 1: distinction matters more than it might sound. Finding asymmetry in
43:21
Speaker 1: mesons is like finding asymmetry in the tools used to
43:24
Speaker 1: build a house. What you actually need to explain is
43:28
Speaker 1: the house. In 2019 and the years following, the LHCb
43:33
Speaker 1: experiment at CERN began producing results from a new analysis
43:38
Speaker 1: of baryon decays. The LHCb detector is built specifically to
43:43
Speaker 1: study particles containing beauty quarks, Its full name is the
43:47
Speaker 1: Large Hadron Collider Beauty Experiment, and it operates in the
43:52
Speaker 1: forward region of the collision zone, catching particles that fly
43:56
Speaker 1: out at shallow angles from the beam. That geometry gives
44:00
Speaker 1: it unusual sensitivity to the kinds of rare decays that
44:05
Speaker 1: carry signatures of CP violation. What the collaboration was hunting
44:11
Speaker 1: for was a difference in how baryons decay compared to
44:15
Speaker 1: how antibaryons decay. If matter and antimatter are truly symmetric,
44:21
Speaker 1: a baryon undergoing a particular decay should produce the same
44:26
Speaker 1: angular distribution of daughter particles as its antimatter counterpart. The
44:32
Speaker 1: same rates. The same patterns. Mirror images. CP violation means
44:39
Speaker 1: those mirrors are slightly distorted One set of decays happens
44:44
Speaker 1: just a little more often, or produces daughter particles at
44:48
Speaker 1: slightly different angles, or releases them with slightly different energies.
44:53
Speaker 1: The difference is small. Catching it requires enormous data sets
44:58
Speaker 1: and extremely precise detectors. The LHCb analysis combined data from
45:05
Speaker 1: multiple runs, studying hundreds of millions of baryon decays. The
45:11
Speaker 1: collaboration looked at how B-barians, particles containing a bottom quark
45:16
Speaker 1: bound with lighter quarks, broke apart into lighter particles. They
45:22
Speaker 1: measured the rates. They mapped the angular distributions. They compared
45:27
Speaker 1: matter to antimatter at each step. And they found it.
45:31
Speaker 1: The decays were not symmetric. Barians and antibarians were not
45:36
Speaker 1: behaving as mirrors of each other. The asymmetry was small,
45:41
Speaker 1: as expected, but it was there, and it was statistically robust.
45:46
Speaker 1: This was the first time CP violation had been confirmed
45:50
Speaker 1: in baryons with the statistical weight needed to call it
45:54
Speaker 1: an observation, rather than a hint. The precision of this
45:58
Speaker 1: measurement reflected the maturity of experimental particle physics. The LHCb
46:04
Speaker 1: team had to account for detector efficiencies backgrounds from competing processes,
46:11
Speaker 1: and the subtle ways particles interact with detector materials. They
46:16
Speaker 1: applied sophisticated statistical methods to extract genuine signals from noise.
46:23
Speaker 1: The analysis included exhaustive studies of systematic uncertainties, potential sources
46:30
Speaker 1: of bias that statistical methods alone cannot capture. Every major
46:35
Speaker 1: systematic had to be quantified and combined carefully. The collaboration
46:41
Speaker 1: produced auxiliary measurements to validate key assumptions. They cross-checked their
46:46
Speaker 1: findings using independent analysis strategies. Only when multiple approaches converged
46:54
Speaker 1: on the same answer could they claim confidence in the result.
46:58
Speaker 1: This is the standard modern particle physics demands before calling
47:03
Speaker 1: anything an observation. The significance of that result goes beyond
47:08
Speaker 1: adding a new entry to a catalogue. This is the
47:11
Speaker 1: first demonstration that the fundamental building blocks of atomic matter,
47:16
Speaker 1: the particles from which every proton and neutron is assembled,
47:21
Speaker 1: do not treat matter and antimatter identically. The universe is
47:26
Speaker 1: not symmetric at the level of baryons. That is not
47:30
Speaker 1: a minor finding. It is a confirmation that one of
47:33
Speaker 1: Sakharov's three conditions is physically real in the particle class
47:38
Speaker 1: that matters most for the existence of the visible universe.
47:43
Speaker 1: What the result does not do is close the problem.
47:47
Speaker 1: This is where things become genuinely difficult. CP violation in
47:52
Speaker 1: baryons exists. But the amount of CP violation that the
47:57
Speaker 1: standard model predicts across all the processes where it appears
48:02
Speaker 1: is far too small. The calculations have been done many
48:06
Speaker 1: times by many independent groups. They all converge on the
48:11
Speaker 1: same conclusion. The observed asymmetry between matter and antimatter Even
48:17
Speaker 1: when you add up every source the Standard Model contains
48:21
Speaker 1: is insufficient by many orders of magnitude to produce a
48:25
Speaker 1: universe with as much matter as ours. The imbalance that
48:30
Speaker 1: gave rise to everything we see required far more asymmetry
48:34
Speaker 1: than the model can generate. That gap is one of
48:38
Speaker 1: the most significant open problems in all of physics. It
48:42
Speaker 1: means one of two things. Either there are additional sources
48:47
Speaker 1: of CP violation that the standard model does not account
48:51
Speaker 1: for new particles, new interactions, new mechanisms operating at energies
48:58
Speaker 1: the LHC has not yet been able to reach or
49:01
Speaker 1: the model is missing something more fundamental about how the
49:05
Speaker 1: early universe evolved. Neither answer is satisfying in the sense
49:10
Speaker 1: of being available. Both require physics that has not been
49:15
Speaker 1: discovered yet. The LHCb confirmation of baryon CPU violation is
49:21
Speaker 1: a piece of the puzzle and a significant one. But
49:24
Speaker 1: identifying that the asymmetry is real in baryons is not
49:29
Speaker 1: the same as identifying its origin. The detection tells you
49:33
Speaker 1: the behavior exists. It does not tell you what is
49:37
Speaker 1: generating it at a level sufficient to populate the universe
49:41
Speaker 1: with matter. The measurement sits alongside the penguin decay anomalies,
49:46
Speaker 1: the Higgs coupling results, and the other discrepancies accumulating in
49:51
Speaker 1: the LHC data, all pointing in the same direction, all
49:56
Speaker 1: stopping short of a definitive answer. There is something almost
50:00
Speaker 1: vertiginous about the scale of what this implies. one extra
50:05
Speaker 1: particle per billion. That is the margin by which matter won.
50:11
Speaker 1: Every star in every galaxy, every cubic centimeter of gas
50:16
Speaker 1: in the interstellar medium, every atom in every human body,
50:21
Speaker 1: all of it descended from that margin. The physics that
50:24
Speaker 1: generated it operated in the first microseconds of the universe's existence,
50:30
Speaker 1: temperatures and densities that no laboratory can fully replicate and
50:35
Speaker 1: no equation is completely captured. The LHCb result confirms that
50:41
Speaker 1: the asymmetry is built into baryons at a measurable level.
50:46
Speaker 1: It does not explain why the universe survived at the
50:49
Speaker 1: scale it did. The asymmetry is real, confirmed and sitting
50:54
Speaker 1: in the data and it is still not large enough
50:57
Speaker 1: to explain why the universe survived. In the 1950s, particle
51:02
Speaker 1: physicists had a problem they called the particle zoo, and
51:06
Speaker 1: for a while it looked like nature was taunting them.
51:09
Speaker 1: Every few months a new particle turned up in a
51:12
Speaker 1: detector somewhere. Pions, kaons, lambda particles, sigma particles, Xi particles,
51:20
Speaker 1: the list kept growing. Each one was real, each one
51:24
Speaker 1: had been measured carefully and confirmed. and none of them
51:28
Speaker 1: fit into any clean organising principle. Physicists had built machines
51:33
Speaker 1: to find the fundamental building blocks of matter, and instead
51:38
Speaker 1: they were finding an ever-expanding catalogue of particles that seemed
51:43
Speaker 1: almost deliberately random. Enrico Fermi reportedly said that if he
51:49
Speaker 1: had wanted to memorise the names of all these particles,
51:53
Speaker 1: he would have gone into botany, The joke landed because
51:56
Speaker 1: it was also a genuine expression of frustration. There was
52:01
Speaker 1: no map. There was no framework. Just more animals in
52:05
Speaker 1: the zoo. Then, in 1964, Murray Gell-Mann and George Zweig
52:12
Speaker 1: independently proposed that all these hadrons were not fundamental at all.
52:17
Speaker 1: They were combinations of smaller objects, quarks. Protons and neutrons
52:23
Speaker 1: were made of three quarks each. The lighter mesons were
52:27
Speaker 1: made of two, one quark and one antiquark. Once you
52:32
Speaker 1: accepted that, the particle zoo made sense. The hundreds of
52:38
Speaker 1: strange particles were not random. They were predictable combinations of
52:43
Speaker 1: a small set of building blocks, following a small set
52:47
Speaker 1: of rules. The framework that eventually emerged from this insight
52:52
Speaker 1: became quantum chromodynamics. or QCD, the theory of how quarks
52:58
Speaker 1: bind together through a force carried by particles called gluons.
53:03
Speaker 1: The zoo was tamed. Physicists congratulated themselves and moved on.
53:09
Speaker 1: What they did not fully settle, even then, was whether
53:13
Speaker 1: quarks could only combine in groups of two or three.
53:17
Speaker 1: The theory did not strictly forbid larger combinations. A particle
53:22
Speaker 1: built from four quarks a tetraquark, was mathematically allowed. So
53:28
Speaker 1: was a five-quark particle, a pentaquark. Theorists pointed this out
53:34
Speaker 1: almost immediately after quarks were proposed. The prediction was made
53:39
Speaker 1: in the 1960s, sitting quietly in the literature for decades
53:44
Speaker 1: while experimental physics lacked the tools to confirm or rule
53:48
Speaker 1: it out. Finding a genuine tetraquark or pentaquark would require
53:54
Speaker 1: both enough collision energy to produce them and enough detector
53:58
Speaker 1: precision to identify them before they fell apart, which they
54:02
Speaker 1: do in extraordinarily short timescales, fractions of a fraction of
54:07
Speaker 1: a second. The exotic Hadron search occupied physicists for generations
54:13
Speaker 1: with limited success. The problem was fundamental. These particles are rare,
54:19
Speaker 1: fragile and fleeting. They materialize in the chaos of a
54:24
Speaker 1: collision and decay almost instantly into more stable products, leaving
54:29
Speaker 1: behind only traces that detectors must somehow reconstruct and disentangle
54:35
Speaker 1: from background noise. Creating the conditions for their birth and
54:40
Speaker 1: then catching their death requires extraordinary instrumental precision. The theoretical
54:46
Speaker 1: community remained interested, developing models and making predictions about what
54:52
Speaker 1: these exotic states should look like if they existed. But
54:56
Speaker 1: without experimental evidence, the field remained largely speculative, confined to
55:01
Speaker 1: the margins of particle physics research where ambitious ideas waited
55:06
Speaker 1: for technology to catch up. The first credible evidence for
55:10
Speaker 1: exotic hadrons only began appearing in the early 2000s, and
55:16
Speaker 1: even then the results were contested. Some signals appeared, then
55:21
Speaker 1: failed to replicate. The history of exotic hadron searches before
55:26
Speaker 1: the LHC is largely a history of false starts. Then
55:30
Speaker 1: the LHCb experiment came online, and the picture changed. LHCb
55:36
Speaker 1: was designed specifically to study particles containing bottom and charm quarks,
55:42
Speaker 1: the heavier members of the quark family. It was built
55:45
Speaker 1: with exceptional precision tracking. because the decays it was chasing
55:49
Speaker 1: happened close to the collision point and required careful reconstruction
55:54
Speaker 1: of particle trajectories. That combination of heavy quark production and
55:59
Speaker 1: precision tracking turned out to be exactly what was needed
56:03
Speaker 1: to find exotic hadrons. In 2014, LHCb announced the first
56:09
Speaker 1: unambiguous observation of a tetraquark. Then pentaquarks followed in 2015.
56:16
Speaker 1: And then the discoveries started accelerating. By 2022, the situation
56:22
Speaker 1: had become remarkable. In a single announcement, LHCb reported three
56:28
Speaker 1: new particles at once, a new kind of pentaquark and
56:33
Speaker 1: the first ever pair of tetraquarks observed together. The pentaquark
56:37
Speaker 1: was something physicists had not seen before. Designated PLPPSS 4338,
56:47
Speaker 1: It was the first pentaquark ever found to contain a
56:50
Speaker 1: strange quark alongside a charm quark and a charm antiquark.
56:56
Speaker 1: Most previous pentaquarks contained charm quarks but no strange quarks.
57:02
Speaker 1: This one did both. That combination had been predicted as
57:06
Speaker 1: theoretically possible, but confirming it required finding it in the data,
57:11
Speaker 1: separating it from background noise, and verifying that the signal
57:15
Speaker 1: was real. The statistical significance of that discovery was 15
57:20
Speaker 1: standard deviations. That number is worth pausing on. In particle physics,
57:26
Speaker 1: the threshold for claiming a discovery is 5 standard deviations,
57:31
Speaker 1: a level of confidence that means the probability of a
57:34
Speaker 1: statistical fluke producing the same result is roughly 1 in 3.5 million.
57:40
Speaker 1: 15 standard deviations is not close to the threshold. It
57:45
Speaker 1: is three times past it. The strange pentaquark was not
57:49
Speaker 1: a hint or an anomaly. It was a clean, overwhelming
57:53
Speaker 1: signal sitting in the detector data like a neon sign.
57:57
Speaker 1: The two tetraquarks announced at the same time, tax zero, 2,900 zero,
58:05
Speaker 1: added something different to the picture. The doubly charged version
58:09
Speaker 1: was notable because its charge was unusual. Standard mesons carry
58:14
Speaker 1: one unit of charge at most. A tetraquark carrying two
58:19
Speaker 1: units of positive charge cannot be explained as a quark-antiquark
58:23
Speaker 1: pair under any interpretation. Its charge alone was proof that
58:29
Speaker 1: it contained at least four quarks. There was no ambiguity
58:33
Speaker 1: about its exotic nature. The particle's properties forced that conclusion
58:38
Speaker 1: before any deeper analysis was needed. What made the 2022
58:44
Speaker 1: announcements significant beyond the discoveries themselves was what they implied
58:49
Speaker 1: about the particle zoo now repeating. The LHC, across its
58:54
Speaker 1: first three runs, found more than 85 new hadrons in total.
59:00
Speaker 1: 23 of them were confirmed exotic states, 5 pentaquarks and
59:05
Speaker 1: 18 tetraquarks, each one containing at least one charm quark.
59:10
Speaker 1: That number is growing, and the pace has not slowed.
59:14
Speaker 1: History was not just echoing, it was replaying at higher resolution,
59:20
Speaker 1: with more sophisticated instruments and more particles than the 1950s
59:25
Speaker 1: physicists had encountered. The question that follows all of this
59:30
Speaker 1: is the one that matters most. What is it actually
59:33
Speaker 1: telling us? Finding new hadrons is interesting. Finding dozens of
59:39
Speaker 1: exotic hadrons is something else. It means the strong force,
59:44
Speaker 1: the fundamental interaction that holds quarks together inside protons and neutrons,
59:50
Speaker 1: is richer and stranger than the standard picture assumed. QCD
59:55
Speaker 1: permits these exotic combinations in principle, but the theory's predictions
1:00:01
Speaker 1: about how they form, how stable they are, and what
1:00:05
Speaker 1: internal structure they have are genuinely difficult to calculate. The
1:00:10
Speaker 1: strong force does not yield to simple mathematics the way
1:00:14
Speaker 1: electromagnetism does. Its equations are notoriously hard to solve at
1:00:20
Speaker 1: low energies. which is precisely the energy range where hadrons
1:00:24
Speaker 1: form and decay. Each new exotic particle is a test case.
1:00:30
Speaker 1: Its mass, its decay products, its lifetime. These are measurements
1:00:35
Speaker 1: that can be compared against theoretical predictions. When the predictions match,
1:00:41
Speaker 1: QCD gets validated in a new corner of its parameter space.
1:00:45
Speaker 1: When they do not match, something in the theoretical framework
1:00:49
Speaker 1: needs adjusting. The strange pentaquark, the doubly charged tetraquark, they
1:00:55
Speaker 1: are not just entries in a catalogue, they are probes
1:00:59
Speaker 1: into how the strong force actually behaves when quarks are
1:01:03
Speaker 1: arranged in configurations that protons and neutrons never encounter. Two
1:01:08
Speaker 1: charm quarks sitting inside a five quark system create a
1:01:13
Speaker 1: very different dynamic than two light quarks in a proton.
1:01:18
Speaker 1: The interaction strengths are different. The spatial distributions are different.
1:01:24
Speaker 1: The binding mechanisms may be different in ways that current
1:01:27
Speaker 1: models handle only approximately. Some theorists believe these exotic hadrons
1:01:34
Speaker 1: are genuinely compact objects. Four or five quarks tightly bound
1:01:39
Speaker 1: together the way quarks are bound in a proton. Others
1:01:43
Speaker 1: believe they are molecular states. Two ordinary hadrons orbiting each
1:01:48
Speaker 1: other loosely. held together by residual strong force interactions the
1:01:53
Speaker 1: way hydrogen atoms bind into H2 molecules. The distinction matters.
1:01:59
Speaker 1: Compact tetraquarks and molecular tetraquarks would test different aspects of QCD.
1:02:07
Speaker 1: Figuring out which interpretation is correct requires more data, higher
1:02:12
Speaker 1: precision measurements, and theoretical tools that are still being developed.
1:02:18
Speaker 1: A problem of this scale naturally mobilizes entire generations of
1:02:23
Speaker 1: theorists to work together on the same fundamental questions. The
1:02:28
Speaker 1: experimental results are outrunning the theory's ability to fully explain them,
1:02:33
Speaker 1: which is exactly the situation that drives physics forward. In
1:02:38
Speaker 1: the 1950s, the particle zoo looked like chaos until quarks
1:02:43
Speaker 1: gave its structure. Now the zoo has grown again. And
1:02:48
Speaker 1: the structure that explains it is not yet fully written.
1:02:52
Speaker 1: More than 85 new hadrons discovered across three LHC runs.
1:02:58
Speaker 1: And the theory that is supposed to explain all of
1:03:00
Speaker 1: them is still catching up. Protons have been around since
1:03:04
Speaker 1: the first moments after the Big Bang. Physicists have been
1:03:09
Speaker 1: studying them for almost a century. That makes it strange
1:03:13
Speaker 1: that a particle four times heavier than a proton made
1:03:17
Speaker 1: of a similar arrangement of quarks, went unconfirmed until 2017.
1:03:24
Speaker 1: The particle is called the Kexi-CC nums, pronounced roughly as
1:03:29
Speaker 1: XICC +. And its discovery by the LHCb experiment at
1:03:35
Speaker 1: CERN was not a surprise in the sense that theorists
1:03:38
Speaker 1: had been predicting something like it for decades. It was
1:03:42
Speaker 1: a surprise in the sense that theorists had been predicting
1:03:46
Speaker 1: something like it for decades. It was a surprise in
1:03:50
Speaker 1: the sense that theorists had been predicting something like it
1:03:54
Speaker 1: for decades. To understand why this particle matters, you need
1:03:59
Speaker 1: a picture of what it actually is. A proton contains
1:04:04
Speaker 1: three quarks. Two of them are up quarks. One is
1:04:08
Speaker 1: a down quark. These are the lightest quarks in existence,
1:04:12
Speaker 1: essentially massless by the standards of particle physics. The strong
1:04:17
Speaker 1: force holds them together. Because the quarks are so light,
1:04:22
Speaker 1: they move at speeds close to the speed of light
1:04:25
Speaker 1: inside the proton. The whole system is chaotic. The quarks
1:04:30
Speaker 1: themselves contribute almost nothing to the proton's mass. Nearly all
1:04:35
Speaker 1: of that mass comes from the energy of the gluons
1:04:38
Speaker 1: and the constant motion inside, a fact strange enough to
1:04:42
Speaker 1: deserve its own pause. The XKCC nuff has a different structure.
1:04:48
Speaker 1: It contains two charm quarks and one down quark. Charm
1:04:53
Speaker 1: quarks are heavy. Each one carries roughly 1,200 times the
1:04:57
Speaker 1: mass of an up quark. Put two of them in
1:04:59
Speaker 1: the same particle, And the result is something with a
1:05:06
Speaker 1: total mass around three 620 mega electron volts, about four
1:05:12
Speaker 1: times the mass of a proton. The down quark rides
1:05:16
Speaker 1: along almost as a passenger, contributing comparatively little to the total.
1:05:22
Speaker 1: This is a fundamentally different kind of hadron than anything
1:05:26
Speaker 1: in an ordinary nucleus. Here is why physicists care. The
1:05:31
Speaker 1: strong force which binds quarks together is described by a
1:05:36
Speaker 1: theory called quantum chromodynamics. It is one of the most
1:05:40
Speaker 1: precisely tested theories in all of physics. But quantum chromodynamics
1:05:46
Speaker 1: has a peculiar property. It behaves very differently depending on
1:05:50
Speaker 1: the energy scale at which it is operating. At high energies,
1:05:55
Speaker 1: the strong force weakens. Quarks inside high energy collisions barely interact.
1:06:02
Speaker 1: At low energies, the force becomes so strong that quarks
1:06:06
Speaker 1: cannot be separated at all. Pull two quarks apart and
1:06:10
Speaker 1: the energy you spend just creates new quarks rather than
1:06:14
Speaker 1: freeing the original ones. This behavior is called confinement. It
1:06:20
Speaker 1: is one of the strangest features of nature at the
1:06:22
Speaker 1: subatomic level. The problem is that the low energy regime
1:06:26
Speaker 1: of quantum chromodynamics The regime where ordinary protons and neutrons
1:06:32
Speaker 1: live is extraordinarily difficult to calculate. The mathematics becomes intractable.
1:06:40
Speaker 1: Physicists have to use approximation methods, numerical simulations, educated guesses
1:06:47
Speaker 1: to work out what the theory actually predicts for bound
1:06:50
Speaker 1: states of light quarks. There is a gap between the
1:06:54
Speaker 1: elegance of the equations and the ability to solve them
1:06:58
Speaker 1: precisely in ordinary matter. This is where the XKCC num
1:07:03
Speaker 1: becomes a tool rather than just a curiosity. When both
1:07:07
Speaker 1: quarks in a system are heavy, the physics changes in
1:07:11
Speaker 1: a useful way. Heavy quarks move slowly relative to the
1:07:15
Speaker 1: speed of light, even inside a bound particle. The system
1:07:19
Speaker 1: becomes more ordered, more calculable. It is somewhat like the
1:07:23
Speaker 1: difference between trying to describe the behavior of a chaotic
1:07:27
Speaker 1: gas and describing the motion of two heavy planets in
1:07:31
Speaker 1: a gravitational orbit. The heavy system yields to mathematics in
1:07:36
Speaker 1: a way the light system does not. Physicists call this
1:07:40
Speaker 1: the heavy quark limit. It has been exploited with great
1:07:44
Speaker 1: success in systems containing a single charm quark or a
1:07:48
Speaker 1: single bottom quark. The CLICCCC nub pushes into territory that
1:07:54
Speaker 1: had never been experimentally confirmed before, a system where two
1:07:59
Speaker 1: heavy quarks are bound together simultaneously, with the third, lighter
1:08:05
Speaker 1: quark orbiting the pair. Theorists have predicted that the two
1:08:09
Speaker 1: charm quarks would form a tight inner system, almost like
1:08:13
Speaker 1: a tiny nucleus of their own, with the down quarks
1:08:17
Speaker 1: circling around them at a much larger distance. The whole
1:08:21
Speaker 1: object would resemble in a rough structural sense, a hydrogen atom,
1:08:26
Speaker 1: with the charm-charm core playing the role of the nucleus
1:08:30
Speaker 1: and the down quark playing the role of the electron.
1:08:33
Speaker 1: This analogy has limits, as all analogies in particle physics do,
1:08:39
Speaker 1: but the two-layer structure was a genuine theoretical prediction waiting
1:08:44
Speaker 1: for experimental verification. When LHCb confirmed the XACC nub in 2017,
1:08:52
Speaker 1: It did more than add a name to a list.
1:08:55
Speaker 1: It gave theorists an actual measurement to test against. The
1:08:59
Speaker 1: mass came in at 3621.4 megalectron volts. That number could
1:09:07
Speaker 1: be compared directly to predictions from quantum chromodynamic simulations. The
1:09:12
Speaker 1: comparison revealed something important. The theoretical calculations had gotten the
1:09:18
Speaker 1: structure roughly right, but the fine details required adjustment. The
1:09:24
Speaker 1: measurements placed pressure on the models in a way that
1:09:27
Speaker 1: decades of studying ordinary protons simply could not. This was
1:09:32
Speaker 1: because ordinary protons are too tangled, too light, too relativistic
1:09:38
Speaker 1: to serve as clean tests of the theory's predictions. There
1:09:42
Speaker 1: is also the question of what the strong force is
1:09:45
Speaker 1: actually doing when it holds two heavy quarks together. In
1:09:49
Speaker 1: a proton, the three light quarks are so mobile and
1:09:53
Speaker 1: the gluon field so energetic that describing the binding in
1:09:58
Speaker 1: simple terms is nearly impossible. In a double charm system,
1:10:03
Speaker 1: the binding between the two charm quarks can be studied
1:10:07
Speaker 1: more directly. It behaves, in some respects, like a miniaturized
1:10:12
Speaker 1: version of the force that holds atomic nuclei together, operating
1:10:17
Speaker 1: at a far smaller scale. The similarity is not coincidental.
1:10:23
Speaker 1: Both arise from the same underlying theory. But the double
1:10:27
Speaker 1: charm system lets physicists study the mechanism with a clarity
1:10:31
Speaker 1: that nuclear physics, Operating at larger scales and with more
1:10:35
Speaker 1: complicated many-body interactions cannot provide. What makes this particularly striking
1:10:42
Speaker 1: is that the XKCC Nung is unstable. Its lifetime is
1:10:48
Speaker 1: measured in fractions of a second, so small the number
1:10:51
Speaker 1: itself is difficult to write in a way that means
1:10:55
Speaker 1: anything to ordinary intuition. It exists long enough to travel
1:11:00
Speaker 1: a few millimeters inside a detector. a track that the
1:11:04
Speaker 1: LHCb could reconstruct from the particles it decays into. That
1:11:09
Speaker 1: brief existence is enough to measure its mass, its decay modes,
1:11:15
Speaker 1: the properties of its internal structure. The measurement is precise.
1:11:20
Speaker 1: The implications for understanding the strong force are significant. Physicists
1:11:26
Speaker 1: expect that the discovery of the X-carc-CC scene is not
1:11:30
Speaker 1: the end of this line of investigation, but the beginning.
1:11:34
Speaker 1: There are other double heavy particles predicted by quantum chromodynamics,
1:11:40
Speaker 1: systems involving bottom quarks, or combinations of charm and bottom
1:11:45
Speaker 1: quarks that have not yet been observed. Each one would
1:11:50
Speaker 1: probe a slightly different corner of the theory, testing calculations
1:11:55
Speaker 1: that cannot be checked any other way. The LHCb was
1:11:59
Speaker 1: built with the sensitivity to find these particles if they exist.
1:12:04
Speaker 1: The datasets from Run 3 contain collisions that may already
1:12:08
Speaker 1: hold the evidence, waiting to be extracted through careful analysis.
1:12:13
Speaker 1: Two charm quarks in the same particle turn out to
1:12:16
Speaker 1: behave nothing like two light quarks would. That difference is
1:12:20
Speaker 1: exactly the kind of thing that forces theorists back to
1:12:23
Speaker 1: their equations. For a tiny fraction of a second after
1:12:28
Speaker 1: the Big Bang, less than a millionth of a second,
1:12:32
Speaker 1: the entire universe existed as a single churning soup of
1:12:37
Speaker 1: quarks and gluons, with no protons, no neutrons, no atoms,
1:12:43
Speaker 1: nothing organised at all. Every particle that would eventually become stars,
1:12:49
Speaker 1: planets and people was dissolved into this primordial broth. moving
1:12:54
Speaker 1: too fast and packed too tightly to form anything stable.
1:12:59
Speaker 1: Then the universe cooled. Quarks clumped into hadrons. Structure began.
1:13:06
Speaker 1: The soup became a world. That transition happened once, nearly
1:13:11
Speaker 1: 14 billion years ago, and for most of scientific history
1:13:15
Speaker 1: there was no way to study it directly. The only
1:13:19
Speaker 1: record it left behind was the universe itself. Physicists call
1:13:24
Speaker 1: that original state quark-gluon plasma. The name is descriptive. In
1:13:30
Speaker 1: ordinary matter, quarks are locked inside protons and neutrons, bound
1:13:36
Speaker 1: together so tightly that pulling them apart requires more energy
1:13:40
Speaker 1: than it takes to simply create new quarks. They are
1:13:44
Speaker 1: never free. But at temperatures and densities high enough, that
1:13:49
Speaker 1: confinement breaks down. The boundaries dissolve. Quarks and gluons stop
1:13:55
Speaker 1: belonging to any particular particle and become part of a
1:13:59
Speaker 1: collective state, a fluid of fundamental constituents with no internal
1:14:05
Speaker 1: structure above them. This is what the universe was in
1:14:09
Speaker 1: its first microsecond. Not a gas of particles. Not empty
1:14:14
Speaker 1: space punctuated by atoms. A single undifferentiated plasma stretching in
1:14:21
Speaker 1: every direction. The LHC recreates this state by abandoning protons
1:14:27
Speaker 1: entirely and switching to lead ions. A lead nucleus contains
1:14:33
Speaker 1: 82 protons and 126 neutrons, packed into a sphere roughly
1:14:40
Speaker 1: 14 femtometers across. When two of these nuclei are accelerated
1:14:46
Speaker 1: to nearly the speed of light and aimed directly at
1:14:49
Speaker 1: each other, the collision is not a simple impact. It
1:14:53
Speaker 1: is more like two dense crowds running through each other
1:14:57
Speaker 1: at full speed. The nuclei overlap for an instant so
1:15:01
Speaker 1: brief it is measured in yoctoseconds, and in that instant
1:15:05
Speaker 1: the energy density at the collision point reaches temperatures around
1:15:10
Speaker 1: 5 trillion degrees Celsius. For context, the core of the
1:15:15
Speaker 1: Sun sits at roughly 15 million degrees, The LHC heavy
1:15:20
Speaker 1: ion collisions are more than 300,000 times hotter than that.
1:15:25
Speaker 1: At those temperatures, protons and neutrons cannot hold themselves together.
1:15:30
Speaker 1: Quarks break free. Quark-gluon plasma forms, lasting for perhaps 10
1:15:36
Speaker 1: yoctoseconds before the system cools and hadrons reassemble. The entire
1:15:43
Speaker 1: event is over before light can cross a single proton
1:15:47
Speaker 1: Physicists had a clear prediction for what this plasma would
1:15:51
Speaker 1: look like. The quarks and gluons, freed from confinement, would
1:15:56
Speaker 1: behave like a gas, particles moving independently, rarely interacting, spreading
1:16:02
Speaker 1: outward in roughly straight lines from the collision point. This
1:16:06
Speaker 1: was a reasonable assumption. Plasma states in ordinary matter, like
1:16:11
Speaker 1: ionized gas in a star's atmosphere, behave this way. The
1:16:16
Speaker 1: particles are free, and free particles tend not to cooperate.
1:16:21
Speaker 1: When the R-Reich C collider at Brookhaven National Laboratory first
1:16:25
Speaker 1: produced quark-gluon plasma in 2005, and the LHC later studied
1:16:31
Speaker 1: it in far greater detail, the results contradicted that picture
1:16:36
Speaker 1: almost completely. The plasma was not behaving like a gas.
1:16:41
Speaker 1: It was flowing. When the lead nuclei collide off-centre rather
1:16:46
Speaker 1: than head-on, The overlap region is not a perfect sphere,
1:16:50
Speaker 1: but an almond shape, elongated in one direction. A gas
1:16:55
Speaker 1: expanding from that shape would simply spread outward uniformly, erasing
1:17:00
Speaker 1: the geometry almost immediately. Instead, the particles emerging from LHC
1:17:07
Speaker 1: heavy ion collisions preserved that almond geometry in their outward flow,
1:17:12
Speaker 1: more particles coming out along the long axis than the
1:17:16
Speaker 1: short one. This is what a liquid does. A liquid
1:17:20
Speaker 1: has internal pressure gradients. It flows collectively, with each part
1:17:26
Speaker 1: of the fluid responding to what the rest is doing.
1:17:30
Speaker 1: The quark-gluon plasma was not a collection of independent particles.
1:17:35
Speaker 1: It was a collective fluid, and it remembered its initial
1:17:39
Speaker 1: shape as it expanded. The technical term physicists use is
1:17:44
Speaker 1: a nearly perfect liquid. The measure of a fluid's resistance
1:17:48
Speaker 1: to flow is viscosity. Water has relatively low viscosity. Hummy
1:17:54
Speaker 1: has high viscosity. The quark-gluon plasma produced at the LHC
1:18:00
Speaker 1: has a viscosity so close to zero that it approaches
1:18:04
Speaker 1: the theoretical minimum allowed by quantum mechanics. There is a
1:18:08
Speaker 1: lower bound on viscosity set by the uncertainty principle, a
1:18:13
Speaker 1: floor below which no fluid can go. The quark-gluon plasma
1:18:18
Speaker 1: sits just above that floor, making it the least viscous
1:18:22
Speaker 1: fluid ever observed. It flows more freely than superfluid helium.
1:18:29
Speaker 1: It flows more freely than anything else scientists have ever measured.
1:18:33
Speaker 1: This was not expected. Strongly interacting particles, which quarks and
1:18:39
Speaker 1: gluons certainly are, were supposed to produce a messy, high-viscosity medium.
1:18:46
Speaker 1: when liberated. Instead, they produce something almost frictionless. The reason
1:18:52
Speaker 1: has to do with the coupling between the particles at
1:18:55
Speaker 1: those extreme temperatures. Counterintuitively, the strong force that normally confines
1:19:01
Speaker 1: quarks does not simply vanish when they are freed. The
1:19:05
Speaker 1: quarks remain strongly coupled to each other even in the
1:19:08
Speaker 1: plasma phase. just without the confinement that strong coupling is
1:19:13
Speaker 1: what produces the collective behavior the plasma flows together because
1:19:19
Speaker 1: its constituents are still constantly talking to each other through
1:19:23
Speaker 1: blue on exchange reacting and adjusting in concert the fluid
1:19:29
Speaker 1: is strongly interacting and strongly interacting fluids can have extraordinarily
1:19:35
Speaker 1: low viscosity under the right conditions The ALICE experiment at
1:19:40
Speaker 1: the LHC was built specifically to study this state of matter.
1:19:45
Speaker 1: It tracked tens of thousands of particles produced in a
1:19:49
Speaker 1: single heavy ion collision, measuring their momenta, their angles, their identities.
1:19:56
Speaker 1: From those measurements, physicists reconstructed the flow patterns of the plasma,
1:20:02
Speaker 1: mapped its collective behavior, and began building a detailed picture
1:20:07
Speaker 1: of what the early universe actually looked like in its
1:20:11
Speaker 1: first moments. The data from Run 3 added precision to
1:20:15
Speaker 1: that picture. New measurements of the plasma's expansion velocity, its
1:20:21
Speaker 1: temperature gradients, and its response to the geometry of different
1:20:25
Speaker 1: collisions confirmed and extended what earlier runs had suggested. What
1:20:31
Speaker 1: this tells us about the early universe is both specific
1:20:35
Speaker 1: and unsettling. The standard picture of the Big Bang's first
1:20:39
Speaker 1: microsecond had assumed the universe was a hot, relatively simple
1:20:44
Speaker 1: medium that expanded and cooled until quarks condensed into hadrons.
1:20:50
Speaker 1: The plasma turns out to be far more structured than that.
1:20:53
Speaker 1: It has collective modes. It has flow. It has memory
1:20:58
Speaker 1: of its initial geometry. The early universe was not an
1:21:02
Speaker 1: undifferentiated chaos, but something with internal dynamics, internal correlations, behaving
1:21:09
Speaker 1: more like a coherent fluid than a random explosion. That
1:21:14
Speaker 1: changes how physicists model the transition from plasma to hadrons,
1:21:20
Speaker 1: and it changes what assumptions are safe to make about
1:21:23
Speaker 1: conditions even earlier. In the first instance before quark-luon plasma
1:21:29
Speaker 1: itself formed, the early universe was not a gas, it
1:21:34
Speaker 1: was a liquid, and that single fact has forced a
1:21:37
Speaker 1: rewrite of the first chapter of cosmic history. Every galaxy
1:21:42
Speaker 1: we have ever observed is spinning too fast, not slightly fast,
1:21:49
Speaker 1: not by a margin that could be explained away with
1:21:51
Speaker 1: better measurements or a rounding error in the math. The
1:21:55
Speaker 1: stars at the outer edges of galaxies are moving at
1:21:59
Speaker 1: velocities that should, according to every gravitational calculation based on
1:22:04
Speaker 1: visible matter, fling them out into the void. A spiral
1:22:10
Speaker 1: galaxy rotating at those speeds, held together only by the
1:22:14
Speaker 1: gravity of its visible stars and gas and dust, should
1:22:19
Speaker 1: be tearing itself apart. It is not. None of them are.
1:22:25
Speaker 1: Every galaxy we have pointed a telescope at holds together,
1:22:29
Speaker 1: and the visible matter inside them is nowhere near enough
1:22:33
Speaker 1: to explain why. The first person to take this problem
1:22:37
Speaker 1: seriously was an astronomer named Vera Rubin, working in the 1970s.
1:22:43
Speaker 1: She measured the rotation curves of spiral galaxies, essentially how
1:22:48
Speaker 1: fast stars move at different distances from the galactic centre.
1:22:55
Speaker 1: based on Newtonian gravity and the distribution of visible mass,
1:22:59
Speaker 1: was clear. Stars farther from the centre should orbit more slowly,
1:23:04
Speaker 1: the same way the outer planets of our solar system
1:23:07
Speaker 1: move more slowly than the inner ones. What she found
1:23:11
Speaker 1: instead was flat curves. Stars far from the centre moved
1:23:17
Speaker 1: at nearly the same speed as stars close in. The
1:23:21
Speaker 1: curve did not drop Something was adding mass that nobody
1:23:25
Speaker 1: could see. Rubin's data was careful. Her methods were sound,
1:23:31
Speaker 1: and the conclusion was unavoidable. Either the laws of gravity
1:23:35
Speaker 1: were wrong at galactic scales, or there was a vast
1:23:39
Speaker 1: quantity of invisible matter wrapped around every galaxy in the universe,
1:23:44
Speaker 1: providing the extra gravitational pull needed to keep stars in orbit.
1:23:49
Speaker 1: Physicists eventually settled on the second explanation. The invisible matter
1:23:55
Speaker 1: got a name, dark matter. It does not emit light.
1:23:59
Speaker 1: It does not absorb light. It does not interact with
1:24:03
Speaker 1: the electromagnetic force at all, which is why no telescope
1:24:07
Speaker 1: can detect it directly. Its only confirmed interaction with ordinary
1:24:13
Speaker 1: matter is gravitational, and there is an enormous amount of it.
1:24:18
Speaker 1: Current measurements put dark matter at roughly 27% of the
1:24:23
Speaker 1: total energy content of the universe. Ordinary matter, atoms, stars, gas,
1:24:31
Speaker 1: everything the standard model describes, accounts for about 5%. Dark
1:24:37
Speaker 1: matter outweighs everything we have ever seen or touched by
1:24:40
Speaker 1: more than 5 to 1. The standard model has no
1:24:44
Speaker 1: candidate for it. Not a single particle in the entire
1:24:48
Speaker 1: framework of known physics matches the description. This is not
1:24:53
Speaker 1: a minor gap in an otherwise complete theory. The most
1:24:57
Speaker 1: successful theory in the history of science says nothing about
1:25:01
Speaker 1: the dominant form of matter in the universe. Physicists have
1:25:06
Speaker 1: spent decades proposing candidates. The most popular class for many
1:25:11
Speaker 1: years was called WIMPs, Weakly Interacting Massive Particles. The idea
1:25:17
Speaker 1: was that dark matter consists of particles with masses in
1:25:20
Speaker 1: the range of a few GeV to a few TeV,
1:25:24
Speaker 1: interacting through the weak nuclear force. WIMPs were attractive because
1:25:29
Speaker 1: they arose naturally in certain extensions of the Standard Model,
1:25:33
Speaker 1: particularly supersymmetry, and because the predicted relic abundance from the
1:25:38
Speaker 1: early universe matched the observed dark matter density. This coincidence
1:25:44
Speaker 1: had a name, the WIMP miracle. The Large Hadron Collider
1:25:48
Speaker 1: was well positioned to find WIMPs, if they existed. At
1:25:53
Speaker 1: the energies the LHC reaches, the weak force operates at
1:25:57
Speaker 1: full strength, and WIMPs, if they are real, should be
1:26:01
Speaker 1: producible in proton-proton collisions. The experimental signature is distinctive. A
1:26:08
Speaker 1: WIMP would escape the detector entirely, carrying energy away invisibly.
1:26:15
Speaker 1: But the total energy going into a collision is known precisely,
1:26:19
Speaker 1: so a wimp leaving the detector would show up as
1:26:22
Speaker 1: a mismatch, energy going in that does not come out
1:26:26
Speaker 1: the other side. Physicists call this missing transverse energy, and
1:26:32
Speaker 1: it is one of the cleanest signals in the business.
1:26:35
Speaker 1: Atlas and CMS spent years hunting for it. Run 1
1:26:40
Speaker 1: found nothing. Run 2 found nothing. Run 3 pushed the
1:26:45
Speaker 1: search deeper, with higher collision energies and better detector resolution,
1:26:50
Speaker 1: and the answer was the same. No WIMPs appeared. The
1:26:54
Speaker 1: WIMP miracle is looking less miraculous with each passing year.
1:26:59
Speaker 1: This does not mean dark matter does not exist. It
1:27:03
Speaker 1: means WIMPs of the type that the Standard Model's extensions
1:27:07
Speaker 1: predicted most confidently are probably not the answer. And ruling
1:27:12
Speaker 1: that out, while frustrating, is genuinely useful. Every dead end
1:27:18
Speaker 1: in physics narrows the map. The territory that remains is
1:27:22
Speaker 1: still large, but it is smaller than it was before
1:27:25
Speaker 1: the LHC ran its first collision. CERN researchers shifted focus
1:27:30
Speaker 1: toward lighter candidates. The MeV to GV range of dark matter,
1:27:36
Speaker 1: sometimes called light dark matter, offers a different set of
1:27:40
Speaker 1: signatures and a different set of production mechanisms. In this picture,
1:27:46
Speaker 1: dark matter particles are too light to produce missing energy
1:27:50
Speaker 1: signals at the LHC in the conventional sense, but they
1:27:53
Speaker 1: might still be produced if there are mediator particles that
1:27:57
Speaker 1: bridge the dark sector and the visible sector. These mediators
1:28:02
Speaker 1: would be particles carrying force between ordinary matter and dark matter,
1:28:08
Speaker 1: detectable through their decay products even if the dark matter
1:28:12
Speaker 1: itself escapes. The LHCb experiment, with its forward geometry and
1:28:18
Speaker 1: sensitivity to lower mass particles, became particularly useful here. Searches
1:28:25
Speaker 1: for dark photons, hypothetical mediators that mix weakly with ordinary photons,
1:28:32
Speaker 1: were conducted across multiple run periods. Again, nothing definitive appeared.
1:28:38
Speaker 1: The hunt also turned out to be a success. toward
1:28:40
Speaker 1: particles that barely interact at all with ordinary matter, but
1:28:45
Speaker 1: could be produced in the enormous flux of particles generated
1:28:49
Speaker 1: by the LHC's beams. Some theories predict that dark matter
1:28:54
Speaker 1: annihilates into standard model particles through new forces, at rates
1:28:59
Speaker 1: that depend on the collision energy in ways that accelerator
1:29:03
Speaker 1: experiments can probe directly. The advantage of this approach is
1:29:08
Speaker 1: that it does not depend heavily on assumptions about dark
1:29:11
Speaker 1: matter's specific nature. If the dark sector connects to the
1:29:16
Speaker 1: visible sector through any new force, the LHC should see
1:29:20
Speaker 1: some trace of that connection in the decay products of
1:29:24
Speaker 1: the mediators. No such trace has emerged cleanly enough to
1:29:28
Speaker 1: cross the threshold of a confirmed detection. What CERN has
1:29:33
Speaker 1: produced is an extraordinarily detailed map of what dark matter
1:29:38
Speaker 1: is probably not. Supersymmetric partners of standard model particles, once
1:29:44
Speaker 1: the leading theoretical candidates, have been pushed to masses so
1:29:49
Speaker 1: high that they would require energies beyond the LHC's reach
1:29:53
Speaker 1: to produce, Certain classes of extradimensional theories predicted dark matter
1:29:59
Speaker 1: candidates at accessible mass ranges. Those ranges are now ruled out. Axions,
1:30:06
Speaker 1: a class of light particles originally proposed to solve a
1:30:10
Speaker 1: different problem in particle physics, but later recognized as viable
1:30:14
Speaker 1: dark matter candidates, fall outside the LHC's primary detection sensitivity
1:30:21
Speaker 1: and require dedicated experiments to search for. Each exclusion result
1:30:26
Speaker 1: from the LHC's three runs represents real scientific progress, even
1:30:32
Speaker 1: when it delivers no discovery. The honest position, after more
1:30:37
Speaker 1: than a decade of searching with the most powerful collider
1:30:42
Speaker 1: ever operated, is this. The evidence for dark matter from
1:30:46
Speaker 1: astrophysical observations is overwhelming. Gravitational lensing maps of galaxy clusters
1:30:53
Speaker 1: show it bending light in regions containing no visible matter.
1:30:58
Speaker 1: The large-scale structure of the universe, the way galaxies cluster
1:31:03
Speaker 1: into filaments and voids over billions of light years, cannot
1:31:07
Speaker 1: be reproduced in simulations without it. The cosmic microwave background,
1:31:13
Speaker 1: the oldest light in the universe, carries an imprint of
1:31:17
Speaker 1: dark matter's influence from less than 400,000 years after the
1:31:22
Speaker 1: Big Bang. Something is there. The LHC has narrowed the
1:31:27
Speaker 1: search considerably, ruling out large swaths of parameter space. But
1:31:33
Speaker 1: whatever dark matter is, it has not yet shown its
1:31:36
Speaker 1: face inside a detector. In 2025, The Breakthrough Prize Foundation
1:31:43
Speaker 1: gave its top award in fundamental physics to four experiments
1:31:47
Speaker 1: at CERN. Not because they had finished the job, but
1:31:51
Speaker 1: because of how much they had found while doing it.
1:31:54
Speaker 1: The prize went to ATLAS, CMS, ALIS and LHCb. Four collaborations.
1:32:02
Speaker 1: Thousands of physicists spread across dozens of countries. Each experiment
1:32:08
Speaker 1: built around a different set of questions. Each one aimed
1:32:12
Speaker 1: at a different corner of what the standard model either
1:32:15
Speaker 1: predicts or fails to predict. The Breakthrough Prize Foundation cited
1:32:20
Speaker 1: precision measurements of the Higgs boson, probes of rare particle interactions,
1:32:27
Speaker 1: studies of exotic states of matter, and the discovery of
1:32:31
Speaker 1: more than 72 new hadrons. They also cited something less obvious.
1:32:38
Speaker 1: The careful, painstaking measurement of subtle differences between matter and antimatter.
1:32:44
Speaker 1: That last item is not a solved problem. It is
1:32:48
Speaker 1: an open wound in the theory, and the prize recognised
1:32:52
Speaker 1: the people holding it open. Atlas and CMS are the
1:32:56
Speaker 1: two general purpose detectors, each the size of a cathedral,
1:33:01
Speaker 1: each built to catch the debris of proton collisions at
1:33:04
Speaker 1: energies no previous machine could reach. ATLAS confirmed the Higgs
1:33:09
Speaker 1: boson independently of CMS in 2012, and in the years since,
1:33:15
Speaker 1: both experiments have pushed deeper into the Higgs' properties, measuring
1:33:21
Speaker 1: how it decays, how often it decays, and whether those
1:33:25
Speaker 1: numbers match what the equations predict. Some of them do.
1:33:30
Speaker 1: Some of them sit in uncomfortable places just slightly off
1:33:34
Speaker 1: from where the theory puts them. not far enough to
1:33:37
Speaker 1: claim a discovery, far enough to keep theorists awake. ALICE
1:33:42
Speaker 1: is different. It is built not for proton collisions, but
1:33:47
Speaker 1: for heavy ion collisions. Lead smashed into lead at near
1:33:52
Speaker 1: light speed, briefly recreating the quark-gluon plasma of the early universe.
1:33:58
Speaker 1: What ALICE has contributed to the prize is a portrait
1:34:02
Speaker 1: of matter in a state that has not existed since
1:34:06
Speaker 1: the first microseconds after the Big Bang. That portrait turned
1:34:11
Speaker 1: out to be stranger than expected. The plasma behaves like
1:34:15
Speaker 1: a liquid, not a gas. It flows. It has viscosity.
1:34:21
Speaker 1: It is, by certain measures, the most perfect liquid ever observed.
1:34:27
Speaker 1: That finding does not fit comfortably into the picture physicists
1:34:31
Speaker 1: had before the LHC switched on. LHCb sits downstream from
1:34:36
Speaker 1: the main collision point and catches particles that fly forward
1:34:41
Speaker 1: at low angles, specifically the B mesons and baryons that
1:34:46
Speaker 1: carry the signatures of rare decays. It was LHCb that
1:34:51
Speaker 1: built the most precise map of CP violation in baryons.
1:34:56
Speaker 1: It was LHCb that measured the penguin decays that disagreed
1:35:00
Speaker 1: with standard model predictions. It was LHCb that found the
1:35:05
Speaker 1: strange pentaquark, the doubly charged tetraquark, and dozens of other
1:35:11
Speaker 1: exotic states. When the prize committee wrote about subtle differences
1:35:16
Speaker 1: between matter and antimatter, they were writing largely about work
1:35:21
Speaker 1: done inside that detector. But here is the thing about
1:35:25
Speaker 1: the prize that the headlines mostly missed. The breakthrough prize
1:35:30
Speaker 1: in fundamental physics is awarded for achievement. The citation lists
1:35:36
Speaker 1: discoveries and measurements and confirmations. What it does not say
1:35:40
Speaker 1: out loud, but what sits underneath the whole list, is
1:35:45
Speaker 1: that the most important thing these four experiments produced was
1:35:49
Speaker 1: not certainty. It was precision in the face of uncertainty.
1:35:54
Speaker 1: The measurements that matter most right now are the ones
1:35:57
Speaker 1: that almost fit the theory. The decay rates that are
1:36:01
Speaker 1: slightly off, the asymmetries that are larger than expected or smaller,
1:36:07
Speaker 1: the signals that are clean enough to be real and
1:36:11
Speaker 1: not quite large enough to be declared. This is where
1:36:14
Speaker 1: the concept of statistical significance becomes important. In particle physics,
1:36:21
Speaker 1: A result is not a discovery until it reaches 5 sigma.
1:36:26
Speaker 1: Sigma is a measure of standard deviation, a way of
1:36:30
Speaker 1: expressing how far a result sits from what random chance
1:36:34
Speaker 1: would produce. 1 sigma means the result could easily be noise.
1:36:39
Speaker 1: 3 sigma gets people interested. 5 sigma means there is
1:36:44
Speaker 1: roughly a 1 in 3.5 million chance that random fluctuation
1:36:49
Speaker 1: produced what you measured. That is the threshold. Below it,
1:36:54
Speaker 1: you report a hint. Above it, you call a press conference.
1:36:58
Speaker 1: Several of the results that contributed to the 2025 Breakthrough
1:37:03
Speaker 1: Prize were sitting at three sigma, three and a half,
1:37:06
Speaker 1: occasionally brushing four. The penguin decay anomalies. Certain Higgs coupling measurements.
1:37:15
Speaker 1: Some of the matter-antimatter asymmetry numbers. Not quite five. Not
1:37:21
Speaker 1: quite a discovery, but not going away either. This is
1:37:25
Speaker 1: a specific kind of scientific situation that does not map
1:37:29
Speaker 1: cleanly onto the way science is usually explained. The textbook
1:37:34
Speaker 1: version of physics says, you measure something, you compare it
1:37:38
Speaker 1: to the prediction. If it matches, the theory is confirmed.
1:37:42
Speaker 1: If it does not, the theory needs revision. The reality
1:37:46
Speaker 1: at the LHC is stranger. You measure something with extraordinary precision.
1:37:51
Speaker 1: The number you get is close to what the theory predicts,
1:37:54
Speaker 1: but it is not exactly the same. And the question
1:37:58
Speaker 1: is whether that gap is the beginning of something new,
1:38:02
Speaker 1: or simply the tail of a distribution that will shrink
1:38:05
Speaker 1: back towards the prediction when you collect more data. That
1:38:10
Speaker 1: ambiguity is not a failure of the experiments. It is
1:38:14
Speaker 1: the result of pushing precision to a level that was
1:38:17
Speaker 1: not possible before. Twenty years ago, you could not measure
1:38:21
Speaker 1: a B meson decay rate with enough accuracy to notice
1:38:26
Speaker 1: a 2% discrepancy with the standard model. Now you can.
1:38:30
Speaker 1: The discrepancy might dissolve, it might grow. The prize was
1:38:35
Speaker 1: given partly because these four experiments built machines and methods
1:38:41
Speaker 1: sensitive enough to find a 2% discrepancy in the first place.
1:38:46
Speaker 1: That sensitivity is itself an achievement. independent of what it
1:38:51
Speaker 1: eventually reveals. The most significant scientific results do not always
1:38:56
Speaker 1: come with clean answers attached. Sometimes a result matters because
1:39:01
Speaker 1: of the question it refuses to close. The 2025 Breakthrough
1:39:07
Speaker 1: Prize was awarded to four experiments that have spent over
1:39:11
Speaker 1: a decade generating exactly those results, precise enough to be meaningful.
1:39:17
Speaker 1: unresolved enough to demand more work, that is not a
1:39:21
Speaker 1: consolation prize for not finishing. That is a recognition that
1:39:25
Speaker 1: the most valuable thing you can do in science sometimes
1:39:29
Speaker 1: is to find the edge of what the theory can
1:39:31
Speaker 1: explain and hold it there, clearly, until the next generation
1:39:36
Speaker 1: of machines can push further. Five sigma is the threshold
1:39:41
Speaker 1: for a discovery. and several of the most interesting results
1:39:45
Speaker 1: from Run 3 are sitting just below it, which is
1:39:49
Speaker 1: either a sign of statistical moiz, or the most frustrating
1:39:53
Speaker 1: position in the history of physics to be in. The
1:39:56
Speaker 1: number 125.4 inverse femtobarns sounds like nothing until you work
1:40:03
Speaker 1: out what it represents in actual particle collisions. An inverse
1:40:08
Speaker 1: femtobarn is a unit of measurement for collision beta, a
1:40:12
Speaker 1: way of counting how many opportunities existed for a rare
1:40:16
Speaker 1: event to occur inside a detector. One inverse femtobarn corresponds
1:40:22
Speaker 1: to roughly 70 trillion proton-proton collisions. Multiply that by 125.4
1:40:28
Speaker 1: and you are looking at something close to 9 quadrillion
1:40:34
Speaker 1: collision events recorded across RUM3 alone. That is more data
1:40:39
Speaker 1: than the LHC had delivered in any previous single year
1:40:43
Speaker 1: of operation. It is a number that stops making intuitive
1:40:48
Speaker 1: sense almost immediately, which is part of why physicists use
1:40:52
Speaker 1: the shorthand. The collisions themselves happen fast. At full luminosity,
1:40:58
Speaker 1: the LHC produces around 600 million proton-proton collisions every second
1:41:05
Speaker 1: inside the main detectors. Most of those collisions are not interesting.
1:41:10
Speaker 1: Two protons glance off each other, scatter in ordinary ways,
1:41:15
Speaker 1: and produce nothing that wasn't already predicted by the standard
1:41:18
Speaker 1: model before the machine ever switched on. The detectors are
1:41:22
Speaker 1: not recording all of it. They cannot. The data would
1:41:27
Speaker 1: overwhelm every storage system on Earth within minutes. Instead, the
1:41:32
Speaker 1: experiments run trigger systems. layers of fast electronics and algorithms
1:41:39
Speaker 1: that evaluate each collision in microseconds and decide whether it
1:41:43
Speaker 1: is worth keeping. Only about one collision in a million
1:41:48
Speaker 1: passes these filters and gets written to disk. That is
1:41:53
Speaker 1: still an enormous archive, but it means the truly rare events,
1:41:58
Speaker 1: the ones that don't match expectations, have to survive a
1:42:03
Speaker 1: gauntlet of selection before a physicist ever sees them. What
1:42:08
Speaker 1: makes 125.4 inverse femto-barns significant is not just the raw volume,
1:42:16
Speaker 1: it is what that volume unlocks statistically. Rare processes are
1:42:21
Speaker 1: governed by probability. A decay that happens once in every
1:42:26
Speaker 1: billion collisions requires a billion collisions before you can expect
1:42:31
Speaker 1: to see it even once. To study it with any precision,
1:42:36
Speaker 1: to measure its properties, to compare the rate against theoretical predictions,
1:42:42
Speaker 1: to ask whether the numbers agree, you need to see
1:42:46
Speaker 1: it hundreds of times. Run-3 pushed several of the rarest
1:42:51
Speaker 1: processes in particle physics from the category of barely observed
1:42:55
Speaker 1: into the category of measurable. That distinction matters enormously. Observation
1:43:02
Speaker 1: tells you something exists. Measurement tells you how it behaves.
1:43:07
Speaker 1: The measurement of electroweak penguin decays is one example. By
1:43:12
Speaker 1: the end of Run 2, researchers had collected around 650
1:43:17
Speaker 1: billion B meson decays to work with. Run 3 tripled
1:43:22
Speaker 1: that sample. The additional data did not just improve the
1:43:26
Speaker 1: statistics on existing results. It allowed physicists to test new
1:43:32
Speaker 1: angular distributions. new decay products, new corners of the parameter
1:43:37
Speaker 1: space where the standard model makes precise predictions and where
1:43:42
Speaker 1: any unknown particle or force would leave a distinct fingerprint.
1:43:47
Speaker 1: The discrepancies that had been hovering around 3 and 4
1:43:50
Speaker 1: sigma at the end of RUM2, suggestive but not conclusive,
1:43:55
Speaker 1: got sharper. Whether they cross the discovery threshold is a
1:44:00
Speaker 1: question the collaboration is still working through. The people doing
1:44:04
Speaker 1: that work number in the thousands, the four main LHC experiments, ATLAS, CMS,
1:44:12
Speaker 1: ALIS and LHCb, collectively involve more than 10,000 scientists, engineers
1:44:19
Speaker 1: and students drawn from over 100 countries. A single physics
1:44:24
Speaker 1: paper from the ATLAS collaboration can carry more than 3,000 authors.
1:44:30
Speaker 1: That is not a vanity exercise. Every one of those
1:44:34
Speaker 1: people contributed something. Detector calibration, software development, data quality checks,
1:44:42
Speaker 1: statistical analysis, theoretical cross-checks, without which the result would not exist.
1:44:49
Speaker 1: The science at CERN is not done by a genius
1:44:52
Speaker 1: alone in a room. It is done by a civilization-scale
1:44:57
Speaker 1: collaboration running on shared infrastructure and decades of accumulated expertise.
1:45:03
Speaker 1: The organizational structure reflects this complexity. Different physicists focus on
1:45:09
Speaker 1: different aspects. Some optimize the trigger algorithms that separate signal
1:45:14
Speaker 1: from noise. Others concentrate on detector calibration. Still others develop
1:45:20
Speaker 1: the pattern recognition software that reconstructs what happened from raw
1:45:25
Speaker 1: detector signals. There is no single analysis strategy imposed from above. Instead,
1:45:33
Speaker 1: Teams form around physics questions and compete within bounds of courtesy.
1:45:39
Speaker 1: The collaboration moves forward through reasoned debate and accumulated evidence.
1:45:44
Speaker 1: This culture of healthy skepticism embedded in the peer review
1:45:49
Speaker 1: process prevents errors from hardening into published facts. The timeline
1:45:55
Speaker 1: between data collection and published result is longer than most
1:45:59
Speaker 1: people expect A collision event recorded in 2023 might not
1:46:05
Speaker 1: appear in a peer-reviewed paper until 2026 or 2027. The
1:46:11
Speaker 1: raw data has to be reconstructed, translated from detector signals
1:46:16
Speaker 1: into physical quantities like particle momenta and energies. That reconstruction
1:46:22
Speaker 1: requires calibrations that themselves take months to finalize. Once the
1:46:28
Speaker 1: reconstructed data is available, Analysts apply their selection criteria, run
1:46:34
Speaker 1: their statistical models, cross-check against simulation, and then submit to
1:46:40
Speaker 1: the collaboration's internal review process before anything goes public. For
1:46:46
Speaker 1: results touching on possible new physics, the internal review is
1:46:50
Speaker 1: particularly slow and rigorous. Nobody at CERN wants to announce
1:46:55
Speaker 1: a discovery that evaporates under scrutiny. Run-3 confirmed things that
1:47:01
Speaker 1: Run-1 and Run-2 had only sketched. The CP violation signal
1:47:07
Speaker 1: in baryons, the asymmetry between matter and antimatter in the
1:47:11
Speaker 1: particles that make up atomic nuclei, came through with enough
1:47:16
Speaker 1: statistical weight in the combined dataset to move from evidence
1:47:20
Speaker 1: to observation. The exotic Hadron catalogue grew substantially. Several tetraquark
1:47:28
Speaker 1: and pentaquark states that had been seen at marginal significance
1:47:32
Speaker 1: in earlier runs were confirmed at well above the 5-sigma
1:47:36
Speaker 1: threshold using the larger Run-3 sample. The properties of quark-gluon
1:47:42
Speaker 1: plasma were measured with a precision that earlier lead-iron runs
1:47:46
Speaker 1: could not reach. These are not incremental improvements. They represent
1:47:51
Speaker 1: the difference between knowing something exists and understanding how it behaves.
1:47:56
Speaker 1: Higgs boson measurements also advanced. The rare decay of the
1:48:01
Speaker 1: Higgs into two muons, one in every 5,000 Higgs decays,
1:48:06
Speaker 1: had been seen at the edge of observability at the
1:48:09
Speaker 1: end of Run 2. Run 3 moved that result into
1:48:13
Speaker 1: firmer territory, providing the clearest look yet at how the
1:48:17
Speaker 1: Higgs field couples to second-generation fermions. If that coupling deviates
1:48:23
Speaker 1: from the standard model's prediction, the deviation will show up
1:48:27
Speaker 1: in exactly this channel. The data from Run 3 is
1:48:31
Speaker 1: still being analyzed. The final word on whether those muon
1:48:35
Speaker 1: couplings agree with theory has not been written yet. That
1:48:39
Speaker 1: is the situation right now. The machine has gone quiet.
1:48:44
Speaker 1: The tunnels beneath the Swiss-French border are lit by construction equipment,
1:48:49
Speaker 1: not by proton beams. The detectors are being modified. But
1:48:53
Speaker 1: the data that RUN3 produced, nine quadrillion collision events, filtered
1:48:59
Speaker 1: down to the events worth keeping, stored on servers distributed
1:49:04
Speaker 1: across member institutions on multiple continents, That archive is still
1:49:09
Speaker 1: being worked through. Physicists are running analyses that will take
1:49:14
Speaker 1: years to complete. Some results from Run 3 will not
1:49:19
Speaker 1: be published until the High Luminosity LHC is already collecting
1:49:23
Speaker 1: its first new collisions. The gap between data and understanding
1:49:29
Speaker 1: is part of how this science works, and it is
1:49:32
Speaker 1: not a flaw. It is what rigor looks like at
1:49:36
Speaker 1: this scale. The last proton has already circled the ring.
1:49:41
Speaker 1: Now it is up to the data to finish what
1:49:43
Speaker 1: the machine started. Right now, several hundred meters beneath the
1:49:48
Speaker 1: Swiss-French border, workers are dismantling sections of the most complex
1:49:54
Speaker 1: machine ever built by human hands. The tunnel is cold
1:49:58
Speaker 1: and narrow. The equipment inside it cost decades and billions
1:50:03
Speaker 1: of dollars to build. and they are taking it apart
1:50:07
Speaker 1: on purpose. This is Long Shutdown 3, and it is
1:50:12
Speaker 1: not a pause. It is a transformation. The Large Hadron
1:50:17
Speaker 1: Collider that discovered the Higgs Boson, that found more than
1:50:22
Speaker 1: 85 new hadrons, that confirmed matter-antimatter asymmetry in the building
1:50:27
Speaker 1: blocks of atomic nuclei, that machine is being replaced by
1:50:32
Speaker 1: something significantly more powerful. The upgrade has a name, the
1:50:37
Speaker 1: High Luminosity LHC or HL-LHC. It is scheduled to begin
1:50:43
Speaker 1: colliding protons again around 2030. What it will do when
1:50:47
Speaker 1: it switches back on is, in the language of physics,
1:50:51
Speaker 1: almost hard to describe without reaching for numbers that sound invented.
1:50:56
Speaker 1: The key word is luminosity. In particle physics, Luminosity is
1:51:01
Speaker 1: a measure of how many collisions a machine can produce
1:51:05
Speaker 1: per second. More luminosity means more events, more data, more
1:51:10
Speaker 1: chances to catch something rare happening in real time. The
1:51:15
Speaker 1: original LHC was already extraordinary in this regard. The HL-LHC
1:51:21
Speaker 1: will deliver roughly 10 times the collision rate of the
1:51:25
Speaker 1: machine that ran through 2026 per year. it will accumulate
1:51:30
Speaker 1: approximately seven times more data than the accelerator produced during
1:51:36
Speaker 1: the era that gave us the Higgs discovery. The number
1:51:39
Speaker 1: of individual proton collisions the upgraded machine will generate over
1:51:44
Speaker 1: its lifetime is not a modest increase over what came before.
1:51:49
Speaker 1: It is a different order of magnitude entirely. To achieve this,
1:51:54
Speaker 1: engineers are replacing 1.2 kilometers of the accelerator's inner sections
1:52:00
Speaker 1: with new magnets made from a material called niobium tin.
1:52:05
Speaker 1: The magnets currently in place use niobium titanium. That was
1:52:10
Speaker 1: already pushing the boundaries of what superconducting technology could reliably do.
1:52:16
Speaker 1: Niobium tin can generate stronger magnetic fields. That means tighter
1:52:21
Speaker 1: beam focus. That means more protons occupying a smaller space
1:52:26
Speaker 1: when they cross paths, which means more collisions. The trade-off
1:52:31
Speaker 1: is that niobium tin is harder to work with, more brittle,
1:52:35
Speaker 1: more expensive to manufacture at the scale the upgrade requires.
1:52:39
Speaker 1: It took years to develop the production process. The magnets
1:52:43
Speaker 1: being installed now represent the leading edge of what superconducting
1:52:48
Speaker 1: engineering can currently produce. Alongside the new magnets, the upgrade
1:52:53
Speaker 1: is installing devices called crab cavities. The name sounds informal
1:52:58
Speaker 1: for equipment this precise. Crab cavities are radio frequency structures
1:53:04
Speaker 1: that tilt the proton beams slightly just before they collide,
1:53:08
Speaker 1: rotating them so their oval cross sections align face to
1:53:12
Speaker 1: face rather than edge to edge. The effect is that
1:53:16
Speaker 1: more of each beam overlaps with the opposing beam at
1:53:19
Speaker 1: the collision point. Without crab cavities, a significant fraction of
1:53:24
Speaker 1: each bunch of protons simply passes by without hitting anything.
1:53:29
Speaker 1: With them, the overlap, and therefore the collision rate, increases substantially.
1:53:35
Speaker 1: It is a small geometric adjustment with a large physical consequence.
1:53:40
Speaker 1: The detectors themselves are being rebuilt almost from scratch. The
1:53:44
Speaker 1: ATLAS and CMS experiments are receiving new silicon tracking systems
1:53:49
Speaker 1: designed to handle the far higher density of events the
1:53:53
Speaker 1: HL-LHC will produce, at 10 times the collision rate. The
1:53:58
Speaker 1: electronics that read out particle tracks have to work faster
1:54:03
Speaker 1: and sort through more simultaneous data without losing the rare
1:54:08
Speaker 1: signals buried inside it. New precision timing detectors will allow
1:54:13
Speaker 1: scientists to separate events that happen in the same nanosecond,
1:54:19
Speaker 1: but at slightly different positions along the beamline. A problem
1:54:23
Speaker 1: that barely existed at current collision rates, but becomes significant
1:54:28
Speaker 1: at the luminosities the HL-LHC will reach. These are not
1:54:33
Speaker 1: incremental adjustments to existing systems. They're new instruments. All of
1:54:39
Speaker 1: this matters because of where RUN3 left things. The penguin
1:54:43
Speaker 1: decay measurements showed a disagreement with standard model predictions, not
1:54:49
Speaker 1: a large enough disagreement to claim a discovery, but a
1:54:53
Speaker 1: clean one and a consistent one across multiple analyses. The
1:54:58
Speaker 1: matter-antimatter asymmetry results confirmed CP violation in baryons for the
1:55:04
Speaker 1: first time. But the size of the effect measured is
1:55:08
Speaker 1: still not enough to explain the universe's imbalance on its own.
1:55:13
Speaker 1: The Higgs boson's self-coupling, the way the Higgs field interacts
1:55:17
Speaker 1: with itself, the property that determined the shape of the
1:55:21
Speaker 1: universe in its earliest moments, has not been measured at all.
1:55:26
Speaker 1: It requires observing two Higgs bosons produced simultaneously in a
1:55:31
Speaker 1: single collision. An event so rare that the entire Run3
1:55:35
Speaker 1: dataset contained only a handful of candidates. None of these
1:55:40
Speaker 1: questions can be answered with the data already on hand.
1:55:44
Speaker 1: The HL-LHC was designed with exactly these questions in mind.
1:55:50
Speaker 1: At 10 times the luminosity, the penguin decay sample grows
1:55:55
Speaker 1: from hundreds of millions of events to billions. Statistical fluctuations
1:56:00
Speaker 1: that could mimic a real signal at current data volumes
1:56:04
Speaker 1: become visible for what they are. If the disagreement in
1:56:08
Speaker 1: B-maison decays is a genuine signature of an undiscovered particle
1:56:13
Speaker 1: interfering in the loop, more data will sharpen it into
1:56:17
Speaker 1: something that crosses the 5-sigma threshold. If it is noise,
1:56:22
Speaker 1: more data will wash it out. Either answer closes a
1:56:26
Speaker 1: chapter that Run 3 could not close. The same logic
1:56:30
Speaker 1: applies to the dark matter searches. The LHC hunts for
1:56:34
Speaker 1: dark matter by looking for collisions where momentum goes missing,
1:56:38
Speaker 1: where particles carry energy out of the detector without leaving
1:56:42
Speaker 1: any trace. The HL-LHC will produce enough collisions to probe
1:56:49
Speaker 1: production rates orders of magnitude smaller than anything the current
1:56:54
Speaker 1: machine could reach, into mass ranges and coupling strengths that
1:56:59
Speaker 1: were simply invisible before. The Higgs self-coupling measurement may be
1:57:04
Speaker 1: the most consequential single number the HLLHC is being built
1:57:10
Speaker 1: to find. In the standard model, that coupling has a
1:57:14
Speaker 1: specific predicted value. If the measured value matches the prediction,
1:57:20
Speaker 1: the Higgs sector is exactly what the theory says it is.
1:57:24
Speaker 1: If it deviates, even slightly, it points to new physics
1:57:29
Speaker 1: in the most fundamental part of the model, the mechanism
1:57:33
Speaker 1: that gives mass to everything. Observing enough Higgs pairs to
1:57:38
Speaker 1: measure the self-coupling precisely requires approximately the full data set
1:57:43
Speaker 1: the HL-LHC is expected to produce over its entire planned
1:57:48
Speaker 1: operational lifetime. It cannot be rushed. It cannot be done
1:57:53
Speaker 1: with a smaller machine. The four-year shutdown, the $ 1. 5 billion,
1:58:00
Speaker 1: the new magnets and crab cavities and detector systems, all
1:58:04
Speaker 1: of it is aimed in part at this single measurement.
1:58:08
Speaker 1: The scale of what is happening underground right now is
1:58:11
Speaker 1: easy to understate. Thousands of engineers, physicists, technicians across dozens
1:58:18
Speaker 1: of countries are coordinating a reconstruction project with tolerances measured
1:58:23
Speaker 1: in fractions of a millimetre and timelines measured in years.
1:58:27
Speaker 1: Every component being installed has to work at temperatures colder
1:58:32
Speaker 1: than deep space. Every new detector system has to integrate
1:58:37
Speaker 1: with software pipelines that will process more data per second
1:58:41
Speaker 1: than most scientific instruments generate in a year. The work
1:58:46
Speaker 1: is already underway. The expected restart is around 2030. The
1:58:50
Speaker 1: upgrade is a $ 1. 5 billion bet that the anomalies are real.
1:58:56
Speaker 1: that ten times more data will be enough to tell
1:58:59
Speaker 1: the difference between a fluctuation and a discovery. If even
1:59:04
Speaker 1: two or three of the current anomalies hold up under
1:59:07
Speaker 1: the scrutiny of the high luminosity LHC, the standard model
1:59:11
Speaker 1: as a complete description of nature is done. Not damaged,
1:59:16
Speaker 1: not patched, done. That is not an overstatement. It is
1:59:20
Speaker 1: what the logic demands. A theory that fails to predict
1:59:24
Speaker 1: what experiments repeatedly observe is not a complete theory, and
1:59:30
Speaker 1: the Standard Model has been failing in small, precise, consistent
1:59:34
Speaker 1: ways for long enough that the pattern is difficult to ignore.
1:59:40
Speaker 1: To understand what that actually means, it helps to be
1:59:43
Speaker 1: clear about what the Standard Model is and is not.
1:59:47
Speaker 1: It is not a guess. It is not a rough sketch.
1:59:51
Speaker 1: It is one of the most precisely tested frameworks in
1:59:55
Speaker 1: the history of science, confirmed across decades and across dozens
2:00:00
Speaker 1: of independent experiments on multiple continents. Its predictions for things
2:00:05
Speaker 1: like the magnetic moment of the electron match observations to
2:00:09
Speaker 1: 11 decimal places. 11. That is the kind of accuracy
2:00:15
Speaker 1: that earns a theory the right to be taken seriously.
2:00:19
Speaker 1: And yet, Underneath that extraordinary precision, the cracks are there.
2:00:26
Speaker 1: The penguin decay measurements that don't line up. The matter-antimatter
2:00:30
Speaker 1: asymmetry in baryons that exists but isn't large enough to
2:00:35
Speaker 1: explain the universe we live in. The 2,100-day cycle problem,
2:00:41
Speaker 1: in a different field, has a familiar shape, a clean
2:00:45
Speaker 1: repeating signal that none of the standard explanations can account for.
2:00:50
Speaker 1: In particle physics, several of those signals are stacking up
2:00:54
Speaker 1: at once. Here is what physicists actually mean when they
2:00:58
Speaker 1: talk about what comes next. If the anomalies are real,
2:01:03
Speaker 1: the first question is whether they point toward new particles,
2:01:07
Speaker 1: new forces, or new symmetries. And the answer matters, because
2:01:13
Speaker 1: each possibility points to a different kind of revolution. New
2:01:17
Speaker 1: particles alone would be significant but manageable. The standard model
2:01:23
Speaker 1: could potentially be extended. New forces would be a deeper disruption.
2:01:28
Speaker 1: The known forces, electromagnetism, the strong force, the weak force,
2:01:34
Speaker 1: are built into the architecture of the theory at a
2:01:37
Speaker 1: fundamental level. A fifth force, or a hidden sector of
2:01:41
Speaker 1: forces operating between dark matter particles, would require rewriting that
2:01:47
Speaker 1: architecture from the floor up. Then there is supersymmetry. For decades,
2:01:52
Speaker 1: this has been the leading candidate theory for what lies
2:01:55
Speaker 1: beyond the Standard Model. The basic idea is that every
2:01:59
Speaker 1: particle we know has a partner particle, heavier and not
2:02:04
Speaker 1: yet detected, related by a mathematical symmetry that connects fermions
2:02:09
Speaker 1: and bosons. Supersymmetry is not a fringe idea. it solves
2:02:15
Speaker 1: real problems. It provides a natural candidate for dark matter
2:02:20
Speaker 1: in the form of the lightest supersymmetric particle, which would
2:02:25
Speaker 1: be stable, massive and invisible to conventional detection. It helps
2:02:30
Speaker 1: resolve certain mathematical instabilities in the Higgs boson mass. It
2:02:36
Speaker 1: points toward a unification of forces at very high energies
2:02:40
Speaker 1: in a way that the standard model alone cannot achieve.
2:02:45
Speaker 1: The theory has a serious pedigree and serious supporters. The
2:02:49
Speaker 1: problem is that the LHC has not found any of it.
2:02:53
Speaker 1: Run 1, Run 2, and now Run 3 have pushed
2:02:57
Speaker 1: the lower bound on supersymmetric particle masses progressively higher than
2:03:02
Speaker 1: the most natural versions of the theory, the ones that
2:03:06
Speaker 1: predicted particles within reach of the LHC, are effectively ruled out.
2:03:12
Speaker 1: Supersymmetry is not dead. but it is considerably less comfortable
2:03:17
Speaker 1: than it was 15 years ago. Extra dimensions are a
2:03:21
Speaker 1: separate class of possibility. Some theoretical frameworks predict that space
2:03:27
Speaker 1: has more than three dimensions, but that the additional ones
2:03:31
Speaker 1: are curled up so tightly at such small scales that
2:03:36
Speaker 1: they are undetectable under ordinary conditions. At the energy scales
2:03:41
Speaker 1: the LHC reaches, These hidden dimensions might produce detectable effects,
2:03:47
Speaker 1: gravitons leaking into them, energy going missing in ways that
2:03:51
Speaker 1: don't match any known process. Nothing like that has been observed. Again,
2:03:57
Speaker 1: not ruled out entirely. But the easy versions of the
2:04:01
Speaker 1: idea are gone. Whatever new physics is out there, it
2:04:06
Speaker 1: is not sitting in the obvious places the theorists pointed
2:04:09
Speaker 1: to first. this is the honest position the standard model
2:04:15
Speaker 1: has cracks the most popular theories designed to explain those
2:04:19
Speaker 1: cracks have not shown up in the data that leaves
2:04:23
Speaker 1: physicists in an uncomfortable place the existing framework is clearly
2:04:28
Speaker 1: incomplete the proposed replacements are under serious pressure and the
2:04:33
Speaker 1: thing that actually replaces it may not have been written
2:04:37
Speaker 1: down yet physics has been in this situation before In
2:04:41
Speaker 1: the late 19th century classical mechanics was the most successful
2:04:46
Speaker 1: physical theory ever constructed and physicists believed they were close
2:04:51
Speaker 1: to a final description of nature. Then came the ultraviolet catastrophe,
2:04:56
Speaker 1: the photoelectric effect, the strange behavior of electrons in atoms.
2:05:02
Speaker 1: None of those anomalies fit the existing framework. The theory
2:05:07
Speaker 1: that resolved them, quantum mechanics, was not an extension of
2:05:12
Speaker 1: classical physics. It was a replacement, a different kind of
2:05:17
Speaker 1: logic operating underneath a surface that had looked smooth. The
2:05:22
Speaker 1: question now is whether the anomalies piling up at the
2:05:26
Speaker 1: LHC are the ultraviolet catastrophe of this era. The honest
2:05:31
Speaker 1: answer is that nobody knows. Physics has also been through
2:05:35
Speaker 1: periods where anomalies gathered, Theories proliferated, and then more data
2:05:41
Speaker 1: arrived and the anomalies dissolved. The 3.5 kV X-ray line
2:05:47
Speaker 1: that appeared in galaxy cluster spectra for years and generated
2:05:51
Speaker 1: enormous theoretical interest eventually faded as data quality improved. Anomalies
2:05:58
Speaker 1: in B meson decays that briefly looked like evidence of
2:06:02
Speaker 1: lepton universality violations. have been revised downward with better measurements.
2:06:09
Speaker 1: The history of particle physics is partly a history of
2:06:13
Speaker 1: phantom discoveries. This is not a criticism. It is how
2:06:17
Speaker 1: the process works. You take signals seriously, you test them harder,
2:06:23
Speaker 1: and you find out whether they were real. What is
2:06:26
Speaker 1: different now is precision. The penguin decay results are not
2:06:31
Speaker 1: a single anomaly from a single experiment in a single run.
2:06:35
Speaker 1: They are a pattern measured repeatedly across different decay channels
2:06:40
Speaker 1: with systematic uncertainties that have been carefully characterized. The matter-antimatter
2:06:46
Speaker 1: results in baryons represent the first observation of CP violation
2:06:52
Speaker 1: in that class of particles after years of dedicated searching.
2:06:57
Speaker 1: These are not flukes in noisy data. They are consistent,
2:07:01
Speaker 1: reproducible measurements that disagree with predictions in ways that grow
2:07:07
Speaker 1: harder to dismiss as statistics accumulate. When the high luminosity
2:07:12
Speaker 1: LHC delivers 10 times more data, those measurements will sharpen
2:07:17
Speaker 1: into either confirmations or contradictions. There will be no middle ground.
2:07:23
Speaker 1: Either the discrepancies hold and the standard model is fractured
2:07:27
Speaker 1: at its foundations, or they wash out and the model survives.
2:07:32
Speaker 1: battered but intact. The theoretical community is not waiting. Right now,
2:07:38
Speaker 1: papers are being written on lepto-quarks, particles that interact with
2:07:43
Speaker 1: both quarks and leptons, which the standard model forbids but
2:07:48
Speaker 1: which could naturally produce the patterns seen in certain B
2:07:52
Speaker 1: meson decays. Papers are being written on Z' prime bosons,
2:07:58
Speaker 1: hypothetical heavy cousins of the Z boson that could mediate
2:08:02
Speaker 1: new forces between standard model particles. Papers are being written
2:08:07
Speaker 1: on dark photons, on composite Higgs models, on extended gauge symmetries.
2:08:14
Speaker 1: Each of these frameworks makes predictions specific enough to be tested.
2:08:19
Speaker 1: Some of them predict particles that the high luminosity LHC
2:08:24
Speaker 1: should be able to produce if they exist at the
2:08:26
Speaker 1: right mass range. When Run-4 data starts coming in after 2030,
2:08:32
Speaker 1: these theories will either gain traction or lose it, and
2:08:36
Speaker 1: the field will start to converge. But here is what
2:08:40
Speaker 1: keeps the more careful theorists up at night. Every major
2:08:44
Speaker 1: revolution in physics arrived with a hint that the answer
2:08:48
Speaker 1: was something new. not just an extension of the existing vocabulary.
2:08:54
Speaker 1: Quantum mechanics did not look like corrected classical mechanics. Relativity
2:09:00
Speaker 1: did not look like corrected Newtonian gravity. They looked like
2:09:04
Speaker 1: different rules. The possibility that whatever is generating these anomalies
2:09:11
Speaker 1: follows a logic that physicists have not yet developed the
2:09:14
Speaker 1: language to describe is not a remote one. The LHC
2:09:20
Speaker 1: is finding things that don't fit. The theories designed to
2:09:24
Speaker 1: explain things that don't fit are themselves not fitting. That
2:09:29
Speaker 1: recursive problem is either a sign that the theorists haven't
2:09:33
Speaker 1: been creative enough yet, or a sign that the answer
2:09:37
Speaker 1: is going to require a new kind of creativity entirely.
2:09:41
Speaker 1: The history is clear on one point. Paradigm shifts in
2:09:46
Speaker 1: physics do not announce themselves in advance. They arrive through
2:09:51
Speaker 1: exactly this kind of process. Precise measurement, persistent anomaly, failure
2:09:58
Speaker 1: of existing frameworks to explain it, and then eventually a
2:10:02
Speaker 1: new idea that makes the anomaly obvious in retrospect. The
2:10:07
Speaker 1: measurement is already happening. The anomalies are already on the table.
2:10:12
Speaker 1: The most unsettling possibility is not that the new physics
2:10:16
Speaker 1: turns out to be supersymmetry or extra dimensions or any
2:10:20
Speaker 1: of the well-theorized candidates. It is that it turns out
2:10:24
Speaker 1: to be something nobody has written down yet. Step back
2:10:28
Speaker 1: from the individual discoveries and a stranger picture comes into focus.
2:10:34
Speaker 1: Every exotic particle, every anomalous decay, every measurement that sits
2:10:40
Speaker 1: in tension with the standard model. These have been the
2:10:43
Speaker 1: focus for the last several sections. They are genuinely important.
2:10:49
Speaker 1: But they are all operating inside a small corner of
2:10:52
Speaker 1: a much larger problem. Pull the camera back far enough
2:10:57
Speaker 1: and the real scale of what physics does not yet
2:11:00
Speaker 1: understand becomes almost difficult to hold in your head at once.
2:11:05
Speaker 1: The standard model accounts for roughly 5% of the universe.
2:11:10
Speaker 1: That is not a rough estimate or a figure that
2:11:13
Speaker 1: scientists expect to revise upwards slightly once they fill in
2:11:17
Speaker 1: a few gaps. It is a hard number, arrived at
2:11:21
Speaker 1: through decades of independent measurements from telescopes, cosmic microwave background surveys,
2:11:28
Speaker 1: and gravitational studies of galaxy clusters. The universe contains something.
2:11:34
Speaker 1: The Standard Model describes a fraction of it. The remaining
2:11:39
Speaker 1: 95% sits completely outside the theory's reach, not because physicists
2:11:45
Speaker 1: haven't looked, but because the model was never built to
2:11:49
Speaker 1: see it. Dark matter makes up about 27% of the
2:11:54
Speaker 1: universe's total energy content. It does not emit light. It
2:11:59
Speaker 1: does not absorb light. It does not interact with the
2:12:03
Speaker 1: electromagnetic force at all. which means every detector built around
2:12:08
Speaker 1: electromagnetic signals, which is most of them, is essentially blind
2:12:13
Speaker 1: to it. What dark matter does do is pull. Its
2:12:17
Speaker 1: gravitational influence shows up in the behavior of galaxies, in
2:12:22
Speaker 1: the way clusters of galaxies bend light from objects behind them,
2:12:27
Speaker 1: and in the large-scale structure of the universe itself. The
2:12:31
Speaker 1: maps of where matter is concentrated in the cosmos match
2:12:35
Speaker 1: a dark matter distribution with extraordinary precision. Something is there.
2:12:41
Speaker 1: It has mass. It shapes the universe. The Standard Model
2:12:46
Speaker 1: has no particle that fits this description. No field that
2:12:50
Speaker 1: produces it. No mechanism that generates it. It simply does
2:12:55
Speaker 1: not appear anywhere in the theory. Dark energy is stranger still.
2:13:01
Speaker 1: In 1998, Two independent teams of astronomers studying distant supernovae
2:13:07
Speaker 1: discovered that the expansion of the universe is not slowing down.
2:13:12
Speaker 1: It is speeding up. Space itself is accelerating outward, driven
2:13:17
Speaker 1: by something built into the fabric of the universe that
2:13:20
Speaker 1: pushes everything apart. This something, dark energy, makes up roughly
2:13:26
Speaker 1: 68% of the universe's total energy content. It is the
2:13:31
Speaker 1: dominant constituent of everything that exists. And like dark matter,
2:13:37
Speaker 1: it appears nowhere in the standard model. There is no particle,
2:13:42
Speaker 1: no force carrier, no field in the theory that corresponds
2:13:47
Speaker 1: to it. Some physicists associate dark energy with what Einstein
2:13:52
Speaker 1: called the cosmological constant, a term he added to his
2:13:56
Speaker 1: equations and later called his greatest mistake. and which turns
2:14:01
Speaker 1: out to describe reality more accurately than he was comfortable admitting.
2:14:06
Speaker 1: But connecting that constant to a physical mechanism remains one
2:14:10
Speaker 1: of the deepest unsolved problems in all of science. Add
2:14:14
Speaker 1: those numbers together, dark energy at 68%, dark matter at 27%,
2:14:18
Speaker 1: that accounts for 95% of the universe. The Standard Model,
2:14:27
Speaker 1: the most precisely tested theory in the history of science,
2:14:31
Speaker 1: confirmed to 11 decimal places in some of its predictions,
2:14:36
Speaker 1: describes the remaining 5%. This is not a small embarrassment.
2:14:42
Speaker 1: It is a fundamental statement about the limits of the theory.
2:14:46
Speaker 1: The thing physicists sometimes call the best theory ever written
2:14:51
Speaker 1: is a description of a thin slice of reality and
2:14:54
Speaker 1: the slice it misses is almost everything. Then there is gravity.
2:15:00
Speaker 1: The standard model describes three of the four fundamental forces.
2:15:05
Speaker 1: The strong force holds quarks together inside protons and neutrons.
2:15:10
Speaker 1: The weak force governs radioactive decay and certain particle transformations.
2:15:16
Speaker 1: Electromagnetism governs light, electricity, and the behavior of charged particles.
2:15:22
Speaker 1: Gravity is the fourth force. It is the one every
2:15:26
Speaker 1: person on Earth feels every moment of their life. It
2:15:30
Speaker 1: is the force that holds the Moon in orbit, collapses
2:15:34
Speaker 1: gas clouds into stars, and pulls galaxies into clusters. And
2:15:39
Speaker 1: it is completely absent from the Standard Model. Not poorly described,
2:15:45
Speaker 1: not approximately handled, absent. The mathematical framework of quantum field theory,
2:15:52
Speaker 1: on which the entire Standard Model is built, and the
2:15:55
Speaker 1: mathematical framework of general relativity, which describes gravity, are not compatible.
2:16:02
Speaker 1: They use different geometries, different assumptions, different mathematical languages. Every
2:16:09
Speaker 1: attempt to quantize gravity, to write down a theory of
2:16:13
Speaker 1: gravitons and gravitational fields in the same way the standard
2:16:17
Speaker 1: model describes photons and gluons, runs into infinities that cannot
2:16:22
Speaker 1: be removed. equations break, something about the way we understand space,
2:16:28
Speaker 1: time and quantum mechanics at the smallest scales is fundamentally wrong,
2:16:34
Speaker 1: or at least fundamentally incomplete. A truly unified theory would
2:16:39
Speaker 1: need to do something that no theory has yet managed.
2:16:44
Speaker 1: It would need to describe all four forces within a
2:16:47
Speaker 1: single mathematical framework, It would need to generate a dark
2:16:52
Speaker 1: matter candidate from first principles, a particle that has mass
2:16:58
Speaker 1: that interacts gravitationally and that does not couple to electromagnetism.
2:17:03
Speaker 1: It would need to explain why dark energy exists and
2:17:07
Speaker 1: why it has the value it has, rather than a
2:17:11
Speaker 1: value billions of times larger, which is what naive quantum
2:17:15
Speaker 1: calculations predict. It would need to explain the matter-antimatter asymmetry,
2:17:22
Speaker 1: why one extra particle of matter existed per billion pairs
2:17:26
Speaker 1: in the early universe. And it would need to do
2:17:30
Speaker 1: all of this while reproducing every successful prediction the Standard
2:17:35
Speaker 1: Model already makes, without disturbing any of the results that
2:17:40
Speaker 1: have been confirmed to extraordinary precision. That is an enormous
2:17:45
Speaker 1: set of requirements. theories exist that attempt to of it.
2:17:51
Speaker 1: Supersymmetry adds a partner particle to every known particle, and
2:17:56
Speaker 1: in some versions produces a dark matter candidate naturally. String
2:18:02
Speaker 1: theory attempts to unify gravity with the quantum forces by
2:18:06
Speaker 1: treating particles as vibrating strings in extra dimensions. Loop quantum
2:18:13
Speaker 1: gravity tries to quantize space-time itself. None of these has
2:18:19
Speaker 1: produced a confirmed experimental prediction that distinguishes it from the
2:18:24
Speaker 1: standard model. None has been tested and found to match
2:18:28
Speaker 1: observations in a way that compels physicists to accept it.
2:18:33
Speaker 1: They are frameworks, not yet confirmed theories, and the gap
2:18:38
Speaker 1: between a compelling mathematical structure and a tested physical theory
2:18:44
Speaker 1: is wider than it sometimes looks from the outside. Every
2:18:48
Speaker 1: discovery that has come out of CERN, the Higgs boson,
2:18:52
Speaker 1: the exotic hadrons, the CP violation in baryons, the anomalies
2:18:57
Speaker 1: in penguin decays, is real data about the 5% the
2:19:02
Speaker 1: standard model does cover. These are genuine advances. They sharpen
2:19:07
Speaker 1: our picture of how quarks behave, how the Higgs field operates,
2:19:12
Speaker 1: how matter and antimatter differ. But they are pieces of
2:19:15
Speaker 1: a puzzle where the majority of the image is still missing.
2:19:19
Speaker 1: The frame exists. The corner pieces are mostly in place.
2:19:24
Speaker 1: The section in the middle, the part that fills most
2:19:27
Speaker 1: of the board, has barely been started. What the next
2:19:32
Speaker 1: generation of experiments needs to do is find a way
2:19:35
Speaker 1: into that missing territory. The high luminosity LHC is not
2:19:41
Speaker 1: built to detect dark energy. It was not designed to
2:19:45
Speaker 1: solve quantum gravity, but it can search for particles that
2:19:49
Speaker 1: might hint at what dark matter is made of. It
2:19:52
Speaker 1: can measure the Higgs field's self-interaction with enough precision to
2:19:57
Speaker 1: look for deviations that point towards something beyond. It can
2:20:01
Speaker 1: confirm or rule out the anomalies that currently sit just
2:20:06
Speaker 1: below discovery threshold. Each of those results is another clue,
2:20:11
Speaker 1: and in a puzzle this large, every clue counts. The
2:20:16
Speaker 1: theory that scientists have spent 50 years building, testing and
2:20:21
Speaker 1: defending with extraordinary precision describes, at best, one twentieth of
2:20:28
Speaker 1: what the universe actually contains, and the other nineteen twentieths
2:20:33
Speaker 1: are still waiting to be explained. Every few years, someone
2:20:38
Speaker 1: with a reasonable question asks, Why billions of dollars are
2:20:42
Speaker 1: being spent to smash particles together in a tunnel under Switzerland?
2:20:47
Speaker 1: It is a fair question. The LHC cost roughly 10
2:20:52
Speaker 1: billion dollars to build and operates on an annual budget
2:20:56
Speaker 1: that could fund hospitals, schools or climate research. The people
2:21:01
Speaker 1: asking are not wrong to ask. The answer requires going
2:21:05
Speaker 1: back further than most people expect. In 1897, JJ Thompson
2:21:11
Speaker 1: discovered the electron. He was not trying to invent anything.
2:21:16
Speaker 1: He was trying to understand what cathode rays actually were.
2:21:21
Speaker 1: The practical applications of that discovery, every circuit board, every screen,
2:21:28
Speaker 1: every medical imaging device that uses electron beams, were completely
2:21:33
Speaker 1: invisible from where Thompson was standing. He had no way
2:21:37
Speaker 1: of knowing He was just following the question. The same
2:21:42
Speaker 1: pattern repeated with nuclear physics in the early 20th century.
2:21:46
Speaker 1: Rutherford and his colleagues mapped the structure of the atom
2:21:50
Speaker 1: without any intention of producing nuclear power or nuclear medicine.
2:21:55
Speaker 1: The applications emerged decades later as a consequence of understanding
2:22:01
Speaker 1: something fundamental. This is how foundational physics has always worked.
2:22:07
Speaker 1: You cannot see the application from the beginning, because the
2:22:11
Speaker 1: beginning is about understanding, not building. The World Wide Web
2:22:16
Speaker 1: was invented at CERN in 1989. Tim Berners-Lee was trying
2:22:21
Speaker 1: to solve a specific problem. How to share data between
2:22:25
Speaker 1: physicists spread across dozens of countries who needed access to
2:22:30
Speaker 1: the same experimental results. The solution he wrote was not
2:22:34
Speaker 1: designed to become the primary infrastructure of global communication and commerce.
2:22:40
Speaker 1: It was designed to help physicists talk to each other.
2:22:44
Speaker 1: The Internet, as most people experience it today, descended directly
2:22:49
Speaker 1: from a tool built to support particle physics research. Nobody
2:22:53
Speaker 1: planned that. It happened because the research required solving problems
2:22:58
Speaker 1: at a scale and complexity that drove engineering in directions
2:23:03
Speaker 1: it would not otherwise have gone. The same dynamic applies
2:23:07
Speaker 1: to medical imaging. MRI technology relies on the physics of
2:23:12
Speaker 1: nuclear magnetic resonance, a phenomenon that was studied purely for
2:23:17
Speaker 1: its scientific interest decades before anyone suggested it might be
2:23:22
Speaker 1: used to look inside a living body. Particle accelerators themselves
2:23:27
Speaker 1: are now used in cancer treatment. Proton therapy, which targets
2:23:33
Speaker 1: tumors with beams of protons, uses technology that is a
2:23:37
Speaker 1: direct descendant of accelerator physics developed at research institutions that
2:23:43
Speaker 1: were asking purely theoretical questions about atomic structure. These are
2:23:48
Speaker 1: not coincidences. are what happens when you fund the serious
2:23:53
Speaker 1: investigation of how nature works. The specific discoveries coming out
2:23:58
Speaker 1: of CERN carry their own long-range implications, even if they
2:24:03
Speaker 1: are harder to trace right now. Understanding the Higgs field,
2:24:07
Speaker 1: what it is, how it interacts with particles of different generations,
2:24:12
Speaker 1: whether its self-coupling matches predictions, matters because the Higgs field
2:24:18
Speaker 1: fills all of space. It is not a particle that
2:24:21
Speaker 1: exists in one place. It is a property of the
2:24:25
Speaker 1: universe itself, and the shape of that field determines why
2:24:29
Speaker 1: matter has mass at all. If the Higgs behaves differently
2:24:33
Speaker 1: than the Standard Model predicts, that difference is information about
2:24:37
Speaker 1: the structure of reality at its most basic level. What
2:24:41
Speaker 1: you do with that information is a question for later generations.
2:24:45
Speaker 1: The pattern suggests they will find something to do with it.
2:24:49
Speaker 1: the matter-antimatter asymmetry carries a more pointed implication. One extra
2:24:55
Speaker 1: particle of matter per billion pairs is what allowed the
2:24:59
Speaker 1: universe to exist. If the asymmetry had been slightly different,
2:25:04
Speaker 1: there would be no stars, no planets, no chemistry, no biology.
2:25:11
Speaker 1: Understanding exactly why the asymmetry exists What physical process tipped
2:25:17
Speaker 1: the scales in the first fraction of a second is
2:25:21
Speaker 1: not just an academic exercise. It is an attempt to
2:25:25
Speaker 1: explain the necessary condition for everything that followed. Whether that
2:25:30
Speaker 1: understanding ever translates into a practical technology is genuinely unknown.
2:25:35
Speaker 1: But the asymmetry is one of the deepest facts about
2:25:39
Speaker 1: why the universe is the way it is. and the
2:25:42
Speaker 1: LHCb results measuring CP violation in baryons moved the explanation
2:25:48
Speaker 1: one step closer. Dark matter is harder to connect to
2:25:53
Speaker 1: everyday life, but the reasoning holds. Roughly 27% of the
2:25:59
Speaker 1: universe is made of something that does not appear anywhere
2:26:03
Speaker 1: in the most successful theory of matter ever written. Galaxies
2:26:08
Speaker 1: could not hold their shape without it. The large-scale structure
2:26:13
Speaker 1: of the cosmos, the way galaxies cluster into filaments and walls,
2:26:18
Speaker 1: was shaped by dark matter's gravitational influence long before any
2:26:23
Speaker 1: stars formed. Whatever it turns out to be, it is
2:26:27
Speaker 1: not a minor addendum to physics. It is a dominant
2:26:31
Speaker 1: feature of reality. Finding it, naming it, understanding how it
2:26:37
Speaker 1: interacts even weakly with ordinary matter, would be among the
2:26:41
Speaker 1: largest scientific discoveries in history. And the search is ongoing
2:26:47
Speaker 1: at CERN and at detectors buried deep underground on multiple continents.
2:26:53
Speaker 1: There is also an argument that does not depend on
2:26:56
Speaker 1: future applications at all. The question of what the universe
2:27:01
Speaker 1: is made of and what rules it operates by is
2:27:05
Speaker 1: not a technical question that only specialists should care about.
2:27:09
Speaker 1: It is the oldest and most serious version of a
2:27:13
Speaker 1: question humans have been asking in every culture and every era.
2:27:17
Speaker 1: What is this place? What is it made of? Why
2:27:21
Speaker 1: does it behave the way it does? Particle physics is
2:27:25
Speaker 1: the most rigorous attempt to answer those questions with precision
2:27:29
Speaker 1: and evidence rather than assumption. The standard model is not
2:27:34
Speaker 1: a philosophy. It is a set of equations that have
2:27:37
Speaker 1: been tested to extraordinary accuracy and have held up against
2:27:42
Speaker 1: every experimental challenge thrown at them for 50 years. And
2:27:47
Speaker 1: it is still incomplete. The edge of what that model
2:27:51
Speaker 1: can explain is the current frontier of human understanding. The
2:27:55
Speaker 1: people working at CERN number in the thousands are They
2:27:59
Speaker 1: come from more than a hundred countries. They speak dozens
2:28:03
Speaker 1: of languages. They are united by a set of shared
2:28:07
Speaker 1: questions about particles and forces and fields that most of
2:28:12
Speaker 1: their families find difficult to understand at dinner. The research
2:28:16
Speaker 1: has no military application, no immediate commercial value, and no
2:28:22
Speaker 1: guaranteed payoff. It is funded by governments that have collectively
2:28:27
Speaker 1: decided the questions are worth asking. That decision reflects something
2:28:32
Speaker 1: about what science is actually for. Not only the production
2:28:36
Speaker 1: of useful technologies, but the systematic expansion of what humanity
2:28:41
Speaker 1: knows about the place it inhabits. The answer has always
2:28:45
Speaker 1: been the same, because the rules of reality are worth knowing,
2:28:49
Speaker 1: even before we know what to do with them. Around 2030,
2:28:54
Speaker 1: the first new proton beams will circulate through the upgraded machine,
2:29:00
Speaker 1: and the most sensitive particle physics experiment in history will begin.
2:29:05
Speaker 1: The high luminosity LHC will not be a different machine
2:29:09
Speaker 1: in name only. The niobium tin magnets being installed right
2:29:14
Speaker 1: now will push the magnetic fields beyond what the original
2:29:19
Speaker 1: superconducting coils could sustain. The crab cavities will tilt the
2:29:24
Speaker 1: proton bunches just before collision, squeezing more interactions into every crossing.
2:29:31
Speaker 1: The result is roughly 10 times the collision rate the
2:29:34
Speaker 1: original machine could achieve. That is not an incremental improvement.
2:29:40
Speaker 1: That is a different category of instrument. What that luminosity
2:29:45
Speaker 1: actually buys is specificity. The penguin decay anomalies that came
2:29:50
Speaker 1: out of Run 3 were measured across roughly 650 billion
2:29:56
Speaker 1: B meson events. The high luminosity era will produce datasets
2:30:01
Speaker 1: 15 times larger. The statistical significance of those deviations, the
2:30:08
Speaker 1: gap between what the standard model predicts and what the
2:30:11
Speaker 1: detectors recorded, will either grow or disappear. There is no
2:30:17
Speaker 1: middle outcome. If the anomaly was a fluctuation, More data
2:30:22
Speaker 1: will wash it out. If something real is interfering in
2:30:25
Speaker 1: those decays, something the standard model cannot account for, the
2:30:31
Speaker 1: signal will sharpen into a discovery. Physicists have been in
2:30:35
Speaker 1: this position before, watching a hint sit just below 5 sigma,
2:30:40
Speaker 1: not knowing whether to trust it. The HLLHC is being
2:30:45
Speaker 1: built to resolve exactly that uncertainty. The Higgs self-coupling measurement
2:30:51
Speaker 1: is in the same position. The strength with which the
2:30:54
Speaker 1: Higgs field interacts with itself is one of the most
2:30:57
Speaker 1: fundamental unmeasured quantities in particle physics. It sets the shape
2:31:03
Speaker 1: of the Higgs potential, the mathematical landscape that determines how
2:31:07
Speaker 1: the field behaves across all of space. In the early universe,
2:31:13
Speaker 1: that potential governed the transition out of the hot symmetric
2:31:17
Speaker 1: state and into the broken symmetry state we live in now.
2:31:21
Speaker 1: Whether that transition was smooth or violent, whether it created
2:31:26
Speaker 1: conditions favorable for the matter-antimatter imbalance, depends on that coupling.
2:31:32
Speaker 1: Run 3 could not measure it. The data set was
2:31:35
Speaker 1: too small. The HL-LHC will produce enough Higgs pair events,
2:31:42
Speaker 1: rare one in thousands of Higgs decays leading to a
2:31:45
Speaker 1: detectable pair, to pin down the self-coupling with real precision.
2:31:51
Speaker 1: What comes back from that measurement will either confirm the
2:31:54
Speaker 1: standard model's prediction or contradict it. Both outcomes matter. A
2:32:01
Speaker 1: contradiction would be the most significant result in particle physics
2:32:05
Speaker 1: in decades. The Higgs decay into muons is a similar case.
2:32:10
Speaker 1: One in 5,000 Higgs decays produces a muon pair. Run
2:32:15
Speaker 1: 3 found evidence of it. the HL-LHC will turn that
2:32:20
Speaker 1: evidence into a precise measurement, testing whether the Higgs couples
2:32:24
Speaker 1: to second-generation fermions exactly as the standard model says it should.
2:32:30
Speaker 1: Any deviation, even a few percent off the predicted rate,
2:32:35
Speaker 1: points toward new particles or forces operating behind the scenes.
2:32:41
Speaker 1: The new precision timing detectors and upgraded silicon trackers being
2:32:45
Speaker 1: installed during Long Shutdown 3 were designed specifically to catch
2:32:50
Speaker 1: these rare events cleanly, stripping away the background noise that
2:32:55
Speaker 1: made the measurement difficult before. Dark matter is the search
2:33:00
Speaker 1: that may take longest. The LHC has already ruled out
2:33:04
Speaker 1: the most popular theoretical candidates. certain supersymmetric particles that many
2:33:10
Speaker 1: physicists expected to find in the first run. They were
2:33:15
Speaker 1: not there. The HL-LHC will push into lower mass ranges,
2:33:20
Speaker 1: testing models where dark matter is lighter and interacts through
2:33:25
Speaker 1: mediator particles bridging the visible and dark sectors. If dark
2:33:31
Speaker 1: matter is produced in collisions, it will leave through the
2:33:35
Speaker 1: detector without triggering anything it shows up as missing energy.
2:33:40
Speaker 1: With 10 times more collisions, the statistical picture of what
2:33:45
Speaker 1: missing energy should look like under the standard model becomes
2:33:49
Speaker 1: precise enough that a genuine dark matter signal would stand
2:33:54
Speaker 1: out clearly against it. This is not guaranteed to work.
2:33:59
Speaker 1: The dark matter candidate could fall outside the LHC's reach entirely.
2:34:05
Speaker 1: but the search will be more thorough than anything that
2:34:07
Speaker 1: has been attempted before, and ruling out more of the
2:34:11
Speaker 1: parameter space is itself a result. What happens if several
2:34:17
Speaker 1: of these measurements come back wrong at once, not one anomaly,
2:34:21
Speaker 1: but three or four, each pointing away from the standard
2:34:26
Speaker 1: model in different directions? That is the scenario that rewrites physics.
2:34:32
Speaker 1: A single confirmed deviation at 5 sigma is a discovery.
2:34:38
Speaker 1: Multiple confirmed deviations would be a framework problem. They would
2:34:43
Speaker 1: suggest that the standard model, successful as it is, is
2:34:47
Speaker 1: a low-energy approximation of something deeper. The theoretical candidates are
2:34:53
Speaker 1: already waiting. Supersymmetry, extradimensions, new gauge symmetries, leptoquarks. None of
2:35:01
Speaker 1: them are confirmed. Each predicts specific signatures that the HL-LHC
2:35:07
Speaker 1: could detect if they are real. What follows a genuine
2:35:11
Speaker 1: discovery of new physics is not just a new particle
2:35:15
Speaker 1: added to the table, it is a new generation of
2:35:19
Speaker 1: experiments designed around whatever the new theory predicts. New colliders.
2:35:25
Speaker 1: New detectors. New questions asked at higher energies. probing shorter distances,
2:35:33
Speaker 1: looking for the next layer down. And if the HL-LHC
2:35:37
Speaker 1: finds nothing? If every anomaly fades, every measurement lands exactly
2:35:43
Speaker 1: where the standard model said it would? That outcome has
2:35:47
Speaker 1: its own weight. It would mean the theory survives at
2:35:51
Speaker 1: energies ten times more precisely probed than before. It would
2:35:56
Speaker 1: push the scale of new physics higher. making it harder
2:36:00
Speaker 1: to reach experimentally. It would sharpen the question of what
2:36:04
Speaker 1: kind of collider comes after this one. The conversation about
2:36:08
Speaker 1: a future circular collider, a machine with a circumference nearly
2:36:13
Speaker 1: four times larger than the LHC, reaching energies of 100
2:36:18
Speaker 1: tera-electron volts, is already underway at CERN. That proposal exists
2:36:25
Speaker 1: because physicists understand that if the HL-LHC does not crack
2:36:30
Speaker 1: the standard model open, the next machine will need to
2:36:34
Speaker 1: hit harder. The questions are on the table. The machine
2:36:39
Speaker 1: is being rebuilt to answer them. And somewhere in the
2:36:43
Speaker 1: data that will come out of the next decade, the
2:36:46
Speaker 1: rules of reality are going to look either more familiar
2:36:50
Speaker 1: or completely different. And there is no way to know
2:36:54
Speaker 1: which until the collisions begin.