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Sagittarius A* – The Monster at the Milky Way's Heart · Talking Science

0:00
So imagine you are standing outside on a properly
0:03
dark night, like, you know, somewhere way out
0:07
in the country, far enough from any city streetlights
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that the sky actually looks the way it looked
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to, well, basically every human being who lived
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before electricity. Oh, yeah. A truly dark sky
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is just a stunning sight. It really is. And if
0:21
you look up, you will see this pale, hazy band
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stretching completely from one horizon to the
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other. which is the Milky Way. Right. It's the
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edge -on view of our very own galaxy, just, you
0:33
know, seen from the inside. Exactly. And if you
0:35
trace that glowing kind of hazy band toward the
0:38
constellation Sagittarius, you're looking more
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or less straight at the very center of our galaxy.
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But, I mean, if you look there with the naked
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eye, you won't see anything unusual, right? It
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just looks like a particularly dense, glowing
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crowd of stars. Yeah, just a lot of stars. But
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sitting right in the middle of that cosmic crowd,
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completely invisible to any telescope that simply
0:57
looks for light, is one of the strangest, most
1:00
extreme objects known to science. It really is.
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It is a black hole, and not just any black hole.
1:05
This is a monster with a mass of around 4 million
1:08
suns. And here is the kicker. All of that mass
1:11
is squeezed into a space smaller than the orbit
1:14
of the planet Mercury. Yeah, trying to even visualize
1:17
that level of density genuinely strains the human
1:20
imagination. I mean astronomers call this object
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Sagittarius A, usually pronounced Sagittarius
1:26
A star. And that is our mission for today's deep
1:28
dive. We've got this massive stack of sources
1:31
on the table today, Nobel Prize citations, decades
1:34
of astrophysics research papers, and the incredible
1:38
data releases from the Event Horizon Telescope
1:40
team. Oh, there's so much amazing data. There
1:42
really is. We are going to explore Sagittarius
1:45
A, detailing exactly how scientists proved this
1:48
invisible giant exists without being able to
1:50
see it, how we miraculously managed to actually
1:53
photograph it, and why this terrifying, light
1:55
-bending... cosmic monster is actually shockingly
1:58
quiet and honestly a bit poorly fed. Yeah, to
2:02
really appreciate the monumental effort it took
2:04
to understand this object, we first need to establish
2:07
what exactly we are dealing with here. Because
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the term black hole gets thrown around in pop
2:12
culture a lot, usually as a synonym for like
2:15
a vacuum cleaner in space. Yeah, exactly. Just
2:18
sucking everything up. Right. But in astrophysics,
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it has a very precise meaning. So a black hole
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forms when an enormous amount of mass is compressed
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into a small enough space that its gravity becomes
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absolutely overwhelming. OK, let's unpack this
2:33
because gravity is everywhere, right? I mean,
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Earth has gravity. The sun has gravity. I'm anchored
2:38
to my chair by gravity right now. Thankfully,
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yes. Right. So what fundamentally separates a
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black hole's gravity from the gravity of just
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a really, really heavy star? Well, the defining
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feature of a black hole is a boundary called
2:50
the event horizon. Right. understand it, we have
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to talk about escape velocity. Okay. So if you
2:56
throw a baseball straight up in the air on Earth,
2:58
it comes back down. But if you could throw a
3:00
fast enough, which is about 11 kilometers per
3:03
second, it would completely break free of Earth's
3:06
gravity and fly into space. Wow. Okay. That is
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Earth's escape velocity. So the heavier and denser
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an object is, the higher its escape velocity.
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So the event horizon is like the exact distance
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from the center of the black hole where the escape
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velocity perfectly equals the speed of light.
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That is the absolute core of it, yes. And since
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a fundamental law of our universe is that absolutely
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nothing can travel faster than the speed of light,
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well, once you cross that invisible boundary,
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you are permanently trapped. Permanently. Permanently.
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No signal, no particle, no radio wave, literally
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no information of any kind can ever climb back
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up. I've always thought of it like, imagine you
3:48
are in a canoe, right? And you're rowing upstream
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toward a massive Oh, I like this analogy. It's
3:56
that invisible line in the water much further
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upstream where the current of the river simply
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becomes faster than your absolute top paddling
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speed. Yes. Once you cross that line, it doesn't
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matter how hard you paddle. The water is pulling
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you backward faster than you can move forward.
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You are going over. That is a brilliant way to
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picture the mechanics of it. Yeah. Once anything
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crosses that line, all of its mass is thought
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to be crushed down toward a single infinitely
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dense point right at the center, which we call
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the singularity. Singularity. Right. Though to
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be perfectly upfront, our best mathematical models
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of physics genuinely break down at that point.
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Yeah. I mean, nobody claims to fully understand
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what is actually happening at the singularity.
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It's basically the ultimate cosmic mystery box.
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It really is. But even if the center is, you
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know, a mathematical headache. We do know that
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the objects themselves are real and they come
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in different sizes. Right. You have your stellar
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mass black holes, which are born when a single
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massive star runs out of fuel and collapses at
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the end of its life. And those usually weigh
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between five and, say, a few dozen times the
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mass of our sun. Okay, so that's the smaller.
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Yeah. Then you have what Sagittarius A is, which
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is a supermassive black hole. Yeah, these are
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a completely different beast, weighing anywhere
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from hundreds of thousands to many billions of
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solar masses. Now, at 4 million solar masses,
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our local black hole actually sits toward the
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very small end of that supermassive range. Which
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is still incredibly massive. Absolutely. But
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that actually begs a structural question. We
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have stellar mass black holes that are a few
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times the mass of the sun and supermassive ones
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that are millions or billions of times the mass
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of the sun. What about the middle? Like, are
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there black holes that weigh, say, 10 ,000 suns?
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That is actually one of the biggest active mysteries
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in astrophysics right now. There is basically
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no well -established population of medium or
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intermediate mass black holes. Really? None?
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Pretty much none. We see the little ones, we
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see the absolute giants, but essentially nothing
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in between. We'll actually come back to why that
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missing middle is so puzzling when we look at
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how these supermassive objects might have formed
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later on. Okay, looking forward to that. But
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before we get to how it formed, I have a massive
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detective problem with this entire concept. Okay,
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what is it? If a black hole, by its very definition,
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traps all light and emits absolutely zero light
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of its own, how on earth do you even find it?
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I mean, you can't exactly aim a telescope at
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nothing. Right, you can't. Let alone weigh that
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nothing so accurately that you can confidently
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declare it weighs exactly 4 million solar masses.
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The answer to that is just one of the most elegant,
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patient pieces of detective work in modern astronomy.
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Because the trick to finding a black hole isn't
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to look for the darkness. It's to watch how the
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light around it behaves. Oh, okay. You don't
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look for the black hole. You watch the stars
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in its neighborhood. Wait, so scientists stared
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through the entire... dense disk of the Milky
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Way, like through cosmic dust and through Earth's
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incredibly blurry atmosphere, just to track individual
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dots of light circling a dark patch of sky. They
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did. For decades, actually. That's wild. Yeah.
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Starting in the early 1990s, two independent
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teams of astronomers, one in Germany led by Reinhard
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Genzel and one in the United States led by Andrea
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Ghez, they decided to use the largest telescopes
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on Earth to track individual stars at the very
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center of the galaxy. But as I mentioned, they
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faced those massive obstacles. Huge obstacles.
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First, the galactic center is shrouded in incredibly
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thick clouds of gas and dust. Visible light simply
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cannot penetrate it. So both teams had to shift
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their observations to infrared light. Oh, because
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it has longer wavelengths. Exactly. Those longer
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wavelengths can just slip right through that
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cosmic fog. Okay, but the second obstacle is
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just living on Earth. Right. Our atmosphere is
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constantly shifting and swirling. It's, you know,
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what makes stars twinkle to the naked eye. Right,
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the twinkling. Trying to take a precise measurement
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through that is like trying to read the date
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on a coin sitting at the bottom of a rushing
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swimming pool. That's a great way to put it.
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To solve the swimming pool problem, they utilize
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this wild piece of engineering called adaptive
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optics. Adaptive optics? How does that work?
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They shine a powerful laser high up into the
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atmosphere to create an artificial guide star.
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Computers then measure exactly how the atmosphere
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is blurring that laser, and then they use that
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data to physically deform a thin mirror inside
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the telescope. Wait, physically deform it? Yeah.
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It alters its shape thousands of times a second
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to perfectly cancel out the atmospheric distortion
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in real time. Wow, it's essentially noise -canceling
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headphones, but for light. That is a perfect
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analogy, yes. And all of that deeply complex
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engineering and patient observation paid off
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because they found something breathtaking. What
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did they see? They watched these stars at the
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galactic center trace out genuine closed elliptical
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orbits, just like planets orbiting the sun, but
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they were orbiting an entirely invisible point.
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And one star in particular became the absolute
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star of the show. Yes. From our research notes,
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this is the star cataloged as S2 by the European
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team or S02 by the American team. And its orbit
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is relatively short, right? Yeah, about 16 years.
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Right. So astronomers have actually watched it
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complete more than one full lap around the dark
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center. And we really need to pause and appreciate
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how fast S2 is moving here. Oh, it's flying.
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It really is. At its closest approach to the
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black hole, S2 swings past at 7 ,000 kilometers
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per second. Good grief. Which is over 2 % of
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the speed of light. And it passes within just
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17 light hours of the black hole. Which doesn't
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sound like a lot in space terms. It's not. To
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put that scale in perspective, 17 light hours
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is just a bit further out than Pluto's orbit
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around our sun. That speed is just staggering.
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But I want to make sure I understand how tracking
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a fast -moving star actually gives us the weight
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of the black hole. Well, it comes down to the
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exact same... basic Newtonian physics that Isaac
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Newton used to explain how planets orbit the
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sun. Okay. The rule is very straightforward.
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The heavier the central object is, the faster
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and tighter a star must orbit it to avoid falling
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in. So by measuring exactly how fast S2 was moving
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and exactly how tight its curve was, they proved
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mathematically that whatever S2 was orbiting
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had to possess the mass of 4 million suns. 4
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million suns packed into a space so small it
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couldn't possibly be an ordinary cluster of stars
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because, I mean, a cluster that dense would just
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collapse in on itself anyway. Exactly. So a supermassive
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black hole was literally the only physical explanation
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that fit the data. And that undeniable, decades
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-long body of work is what earned Genzel and
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Ghez a shared half of the 2020 Nobel Prize in
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Physics. Wow. And the other half went to theorist
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Roger Penrose, right? Yep, who decades earlier
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proved mathematically that black holes are an
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unavoidable prediction of Einstein's general
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relativity. The math is so elegant, and the indirect
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evidence of watching the stars dance is just
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rock solid. But human curiosity is demanding.
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It is. Knowing a monster is in the room isn't
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enough for us. want a picture of it. But if the
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event horizon is a boundary that traps all light,
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how do you photograph it? Well, you have to capture
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the silhouette. You look for the incredibly hot,
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glowing gas swirling just outside the event horizon,
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and you look for the dark shadow the black hole
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casts against it. Okay. But to see something
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that small from 26 ,000 light years away, you
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need to build an Earth -sized camera. Enter the
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Event Horizon Telescope, or the EHT. Yes. The
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EHT is an extraordinarily ambitious project,
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because in astronomy, there is a fundamental
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rule regarding resolution. The physically larger
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your telescope dish is, the sharper the details
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you can resolve. Right. But no single telescope
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dish you could possibly build on Earth is big
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enough to see the environment immediately surrounding
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a distant black hole. So rather than building
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a single impossible dish, they cheated in the
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best way possible. They totally did. They used
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a technique called very long baseline interferometry.
12:01
Let's explain how that actually works because
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it's a marvel. They took radio telescopes all
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over the planet from Hawaii to Chile to Spain.
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all the way down to the South Pole. And they
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pointed them all at Sagittarius A at the exact
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same time. At the exact same time. Yeah. And
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they used ultra -precise atomic clocks to timestamp
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every single incoming radio wave down to the
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microsecond. And then, this is my favorite part,
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they literally flew hard drives full of this
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data on airplanes back to supercomputers because
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the data files were simply too massive to send
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over the internet. Isn't that wild? Sneakernet
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on a global scale. It's amazing. So the supercomputers
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align those microscopic timestamps, effectively
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using the rotation of the Earth to sweep these
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separate dishes across the sky, stitching the
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data together to create a single virtual telescope
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the size of the entire planet. And in 2019, they
12:53
released their first triumph using this method,
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an image of a supermassive black hole in a distant
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galaxy called M87. Right. And then in 2022, they
13:05
finally released the image of our very own Sagittarius
13:08
A. Though we should refine what we are actually
13:11
looking at in that famous 2022 image because
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it shows a glowing, bright, slightly lopsided
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ring of hot gas. And right in the middle is a
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dark central shadow. Yes. Earlier we compared
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the event horizon to a bathtub drain, but I don't
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think that does the visual physics justice. A
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black hole isn't a literal hole you look down
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into. It's a spherical object in three -dimensional
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space. That is a crucial distinction. It's not
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a flat drain. So taking this picture is more
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like trying to see a perfectly transparent glass
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sphere. floating in a dark room, you can't see
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the glass sphere itself. But the room isn't totally
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dark because there is glowing dust blowing all
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around and behind that glass sphere. The gravity
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of the sphere bends the light from the glowing
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dust, trapping some of it. So what you end up
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seeing is the shadow the invisible sphere casts
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against the glowing environment around it. That's
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a really great way to visualize it. And what
14:02
makes that image so ironic and such a testament
14:04
to the scientists involved is that capturing
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the image of Sagittarius A was actually considerably
14:10
harder than getting the image of the distant
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M87 black hole. Wait, really? Yeah, even though
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ours is astronautically much closer to us. But
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wait, if ours is in our own galactic backyard,
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why would it be harder to photograph? Because
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our black hole is roughly a thousand times less
14:25
massive than M87's, so the physical space around
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it is much smaller, meaning the glowing material
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swirling around Sagittarius A completes an orbit
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in a matter of minutes. Oh, wow. Minutes. Exactly.
14:37
With M87, the material takes days to orbit. Ah.
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So M87 is like having your subject sit perfectly
14:44
still in a chair for an old -timey portrait,
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while Sagittarius A is like trying to take a
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crisp photo of a hyperactive toddler running
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in circles. Yes. It's a frustratingly blurry,
14:56
constantly moving target. The astronomers had
14:59
to develop entirely new algorithms to average
15:02
out those rapid minute -by -minute changes just
15:04
to get a clear image. That's incredible. But
15:06
seeing that glowing ring of gas brings up another
15:08
fascinating reality. Compared to other supermassive
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black holes in the universe, ours is shockingly
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dim. Oh yeah. If you dive into black hole research,
15:17
you inevitably hear about quasars or active galactic
15:20
nuclei. Right. These are supermassive black holes
15:22
in other galaxies that are eating so much material
15:25
so incredibly fast that the Friction heats the
15:28
gas up until it shines brighter than the entire
15:30
host galaxy combined. I mean, they can be seen
15:33
clear across the observable universe. But our
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black hole is absolutely not doing that. It emits
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a little bit of radiation, some x -rays, some
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radio waves, and occasionally it flares up briefly.
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But overall, it is remarkably faint and quiet.
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Here's where it gets really interesting. This
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implies that a black hole's terrifying power
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isn't an inherent trait of its size. Its visibility
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and destructive energy are entirely dependent
15:55
on its food supply. That's exactly it. A black
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hole does not glow on its own. The intense glow
16:01
comes entirely from the matter falling into it.
16:04
Right. As gas and dust spiral inward, they form
16:07
a flattened structure called an accretion disk.
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As the material gets closer to the event horizon,
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traffic jams form basically. The gas gets incredibly
16:16
compressed and friction heats it up to millions
16:19
of degrees. Millions of degrees. Yeah, and that
16:21
superheated disc is what actually glows. So an
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active quasar is just a black hole at an absolute
16:26
all -you -can -eat cosmic buffet pulling in massive
16:29
amounts of gas, maybe from like two galaxies
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colliding. Exactly. But Sagittarius A is on a
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very strict lean diet. There just isn't much
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gas available in its immediate surroundings for
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it to eat. It is less like a blazing furnace
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and more like a smoldering, mostly starved ember.
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Which is a primary reason it was so difficult
16:47
to detect and photograph in the first place.
16:50
And, you know, the faintness of it. actually
16:52
ties into the object's slightly odd name. Oh,
16:55
right. Let's talk about the asterisk. Where did
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that come from? So the broader region of the
16:59
galactic center, known as Sagittarius A, was
17:02
discovered as a bright source of radio waves
17:04
back in the 1950s. Okay. But in 1974, two American
17:09
astronomers, Bruce Bailick and Robert Brown,
17:12
found a particularly compact, unusually bright
17:15
point right at the center of that broader radio
17:18
region. And when they labeled it on their charts,
17:20
they borrowed a naming convention from atomic
17:23
physics, right? Exactly. In physics, when an
17:26
atom is in an excited or higher energy state,
17:28
you denote that by marking it with an asterisk.
17:31
Since this compact core was a very excited, distinctive
17:34
feature compared to the rest of the sky, they
17:36
playfully named it Sagittarius A. That's such
17:39
a great detail. Yeah, and it took decades for
17:42
Genzel and Ghez to ultimately confirm that the
17:44
excited asterisk was indeed a black hole. And
17:47
once we knew the mass was 4 million suns, we
17:50
could calculate its physical size. Every black
17:52
hole has what's called a Schwarzschild radius,
17:55
which is the mathematical boundary of the event
17:57
horizon. Okay, so for our 4 million sun monster,
17:59
that radius is about 12 million kilometers, which
18:03
honestly sounds huge until you remember the scale
18:06
of our solar system. Right, space is big. Yeah,
18:09
that means the entire event horizon would comfortably
18:12
fit inside the orbit of Mercury around our sun.
18:15
With millions of miles of room to spare, we essentially
18:18
squeezed 4 million suns into a space smaller
18:21
than Mercury's orbit. And that extreme compression
18:24
creates an environment with gravity so intense
18:26
that it becomes the ultimate pristine laboratory
18:29
to test our most fundamental laws of physics.
18:33
Specifically, Einstein's general theory of relativity.
18:36
We brought the star S2 back into the picture
18:39
for this, right? The one zooming around it at
18:41
2 % the speed of light. We did. Because S2 gets
18:44
so incredibly close to the black hole, it experiences
18:46
gravitational forces we simply cannot replicate
18:49
anywhere on Earth. In 2018, during S2's closest
18:53
approach, astronomers observed a phenomenon called
18:55
gravitational redshift. Gravitational redshift?
18:58
Yeah, and we need to explain why this happens,
19:00
because it proves Einstein was right about how
19:03
gravity affects light. Okay, so, when I throw
19:06
a baseball straight up... as it fights gravity,
19:08
it loses kinetic energy and slows down. Right.
19:11
But when light climbs out of an intense gravitational
19:14
well, It can't slow down because light fundamentally
19:17
must always move at the speed of light. So instead
19:20
of slowing down, it loses energy in a different
19:22
way. Exactly. The energy of a light wave is tied
19:25
to its frequency. So as the light from the star
19:28
S2 struggled to climb out of the black hole's
19:31
immense gravity, it lost energy by dropping in
19:33
frequency. Meaning the light waves physically
19:35
stretched out into longer, redder wavelengths.
19:38
Yep. Astronomers watched the star's light literally
19:41
turn redder as it swung past the black hole.
19:44
Newton's older theory of gravity couldn't predict
19:46
that. Only Einstein's did. And then, in 2020,
19:49
they observed something even wilder regarding
19:51
the orbit itself's short child precession. Oh,
19:54
this is so cool. Under basic Newtonian physics,
19:56
an elliptical orbit should be a closed loop.
19:59
The star should trace the exact same oval path
20:02
forever. But Einstein's theory says that extreme
20:05
mass actually warps the fabric of space itself.
20:09
Because space is warped near the black hole,
20:11
the orbit doesn't perfectly close its loop. Every
20:14
time S2 completes a lap, its oval path overshoots
20:18
just a tiny bit. Over decades, the entire elliptical
20:21
orbit slowly rotates, tracing out a shape that
20:24
looks like a spirograph pattern rather than a
20:27
single repeating oval. So we used a four million
20:29
sun cosmic monster to prove a highly abstract
20:33
math equation Einstein wrote a century ago on
20:35
a chalkboard. Pretty much. And the math held
20:37
up flawlessly. It did. But while Sagittarius
20:40
A is acting as a quiet, well -behaved physics
20:42
laboratory today, there is stark evidence hanging
20:45
over our galaxy that it wasn't always this peaceful.
20:48
The Fermi bubbles. Yes. Astronomers using space
20:51
telescopes have detected these enormous, symmetrical,
20:54
bubble -like structures extending far above and
20:56
far below the flat plane of the Milky Way. And
20:58
they blow, right? Yeah, they glow faintly in
21:01
high -energy gamma rays. The prevailing theory
21:03
is that these are the fading relics of a massive,
21:06
violent feeding outburst from our black hole
21:08
a few million years ago. So it wasn't always
21:11
a starving ember. A few million years ago, which
21:13
is practically yesterday in cosmic time, it was
21:16
feasting on a massive cloud of gas and blasting
21:19
out devastating amounts of energy. It's intense.
21:21
It really is. It just reminds you that a sleeping
21:24
giant is still a giant. Which brings us to the
21:28
most perplexing part of our deep dive. How did
21:32
a black hole this massive get there in the first
21:35
place? That is a genuinely unsettled area of
21:38
science right now. The logical assumption for
21:40
decades was that a supermassive black hole starts
21:43
as a normal stellar mass black hole. Over billions
21:46
of years, it just patiently eats gas and merges
21:49
with other black holes, slowly growing from a
21:51
few suns to 4 billion solar masses. But the James
21:55
Webb Space Telescope completely threw a wrench
21:57
in that timeline. It really did. Webb has been
21:59
looking back at the incredibly early universe,
22:01
very close to the Big Bang. And it is finding
22:04
fully formed supermassive black holes sitting
22:06
in early galaxies uncomfortably soon after the
22:09
universe began. Uncomfortably soon. Like way
22:12
too soon for them to have grown just by snacking
22:14
on gas bit by bit. Right. The cosmic timeline
22:16
simply doesn't allow for it. And remember that
22:18
missing middle we talked about earlier? The lack
22:20
of intermediate black holes? Yep. The missing
22:22
middle. That absence suggests these giants might
22:25
not be growing step by step. So astrophysicists
22:28
have two main competing theories to explain these
22:31
ancient monsters, right? Yes. The first is that
22:34
these early black holes started from unusually
22:36
massive stellar seeds. Basically, the very first
22:40
generation of stars in the universe might have
22:43
been gigantic, way bigger than any star forming
22:47
today, which would give their resulting black
22:49
holes a massive head start. Okay, that makes
22:52
sense. But the second theory is called direct
22:53
collapse. This idea proposes that in the extreme
22:56
dense conditions of the early universe, enormous
22:59
clouds of primordial gas could have collapsed
23:02
straight down under their own immense weight
23:04
into black holes weighing tens of thousands of
23:06
solar masses. So they would entirely skip the
23:09
process of ever igniting into a star. Exactly,
23:12
just bypassing the star phase entirely and going
23:14
straight from a gas cloud to a massive black
23:16
hole. Both ideas are fascinating, and I know
23:19
neither is fully confirmed yet. But hearing about
23:22
massive black holes forming and violent gamma
23:25
ray outbursts, it might naturally make you wonder,
23:28
is this thing a threat to us? Fortunately, no.
23:30
Oh, good. Yeah, at 26 ,000 light years away,
23:34
out here in the quiet suburbs of one of the Milky
23:36
Way's spiral arms, our solar system is completely
23:39
safe. The black hole's direct gravitational pull
23:43
on us is practically zero. That is a relief.
23:46
But if we connect this to the bigger picture,
23:48
though while it doesn't threaten us today, its
23:51
past outbursts likely influenced how our entire
23:54
galaxy formed. Oh, interesting. Yeah, many astronomers
23:57
now believe that supermassive black holes and
24:00
their social galaxies don't just meet by chance.
24:02
They grow up together in a deeply intertwined
24:04
relationship. When the black hole feeds and blasts
24:06
out radiation, it can heat up or blow away gas
24:09
in the wider galaxy, which directly controls
24:11
how and where new stars can actually form. What
24:15
does this all mean? We started by standing in
24:17
the dark, looking up at the hazy band of the
24:19
Milky Way. And what we found at its heart, hidden
24:22
behind dust and distance, is something utterly
24:25
alien. A place where time and space literally
24:28
break down and gravity traps light itself. Yet
24:31
it is also incredibly close to home. I mean,
24:34
in the most literal sense, it is the anchor our
24:37
entire solar system is quietly orbiting. There
24:40
is something so... profoundly poetic about the
24:43
fact that for decades this monster was entirely
24:45
invisible to us. We only learned it was there
24:48
by watching the stars around it dance to gravity's
24:50
tune, carefully tracking their speed to weigh
24:53
a ghost. It really makes you look at the night
24:54
sky entirely differently. It absolutely changes
24:57
your perspective on our place in the universe.
24:59
It really does. Which leaves us with one final
25:02
lingering question to ponder as we wrap up this
25:04
deep dive. If supermassive black holes and galaxies
25:08
really do grow up together and the wet telescope
25:11
is finding these massive black holes shockingly
25:13
early in the universe what actually came first
25:16
well the big question did a massive cloud of
25:18
gas form a sprawling galaxy which then slowly
25:21
funneled material inward to create a supermassive
25:24
black hole at its center or did the black hole
25:26
form first through direct collapse acting as
25:29
the ultimate gravitational seed that forced the
25:31
galaxy to build around it the chicken or the
25:33
egg on a cosmic scale think about that the next
25:36
time you look up at the stars