Latest / Daniel and Kelly’s Extraordinary Universe / Which force(s) power the human senses?

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Which force(s) power the human senses? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Katie, pain me a picture of where you are.
• 0:11
  Speaker 1: Tell me what you're seeing right now?
• 0:13
  Speaker 2: Okay, Well, I'm seeing sort of the corner of my
• 0:17
  Speaker 2: microphone because it's very close to my face. I'm seeing
• 0:20
  Speaker 2: a wall, my computer, some plants. Shall I go on?
• 0:26
  Speaker 1: No, now, let's add to the picture. Tell me what
• 0:28
  Speaker 1: sounds there are around you?
• 0:30
  Speaker 2: Well, sort of a very faint humming sound, your voice
• 0:36
  Speaker 2: in my ear, and I think the little footsteps of
• 0:40
  Speaker 2: my dog pacing outside waiting for me to be done
• 0:43
  Speaker 2: with this podcast.
• 0:44
  Speaker 1: And how about the smells in your sensorium?
• 0:47
  Speaker 2: Well, I smell my microphone, which does have a smell.
• 0:50
  Speaker 2: It's not gross, it's just, you know, microphone smell. I
• 0:53
  Speaker 2: think my husband is cooking something chicken maybe, or a
• 0:58
  Speaker 2: chicken like protein.
• 1:00
  Speaker 1: Does your microphone not smell like chicken? I thought everything
• 1:02
  Speaker 1: smells like chicken.
• 1:03
  Speaker 2: Hang on, let me see. I mean, if I really
• 1:05
  Speaker 2: think about chicken while smelling my microphone, I can make
• 1:08
  Speaker 2: that connection. Sure, all right?
• 1:10
  Speaker 1: And then the last sense is touch. What is your
• 1:13
  Speaker 1: sense of touch telling you?
• 1:15
  Speaker 2: Well, the sense of touch in my butt is telling
• 1:19
  Speaker 2: me that I should have invested in a much more
• 1:22
  Speaker 2: expensive ergonomic podcasting chair.
• 1:26
  Speaker 1: All right, So is that all I need to know
• 1:28
  Speaker 1: about what it's like to be you right now? To
• 1:30
  Speaker 1: pilot the meat machine that you call, Katie.
• 1:32
  Speaker 2: Golden, Well, there's little grimlins in my ear whispering things
• 1:36
  Speaker 2: at me. But other than that, yeah.
• 1:39
  Speaker 1: Those aren't gremlins, Katie, that's just me.
• 1:41
  Speaker 2: It's just a physicist. I don't know what to be
• 1:44
  Speaker 2: more afraid of the grimlins or a physicist physics grimlins.
• 2:04
  Speaker 3: Hi.
• 2:04
  Speaker 1: I'm Daniel. I'm a particle physicist and a professor at
• 2:07
  Speaker 1: UC Irvine, and I wonder what the world beyond my
• 2:10
  Speaker 1: senses is really like.
• 2:12
  Speaker 2: I'm Katie Golden. I host the podcast Creature Feature, which
• 2:16
  Speaker 2: is all about animal behavior and human behavior, and I
• 2:21
  Speaker 2: like to try to imagine what it's like to be
• 2:24
  Speaker 2: my dog by smelling other people's butts.
• 2:29
  Speaker 1: And how does that go over? I mean, I've been
• 2:31
  Speaker 1: Italy in a while, but I imagine that's still not a
• 2:34
  Speaker 1: typical kind of activity for.
• 2:35
  Speaker 2: Saying Hello, it's not I'm in jail.
• 2:41
  Speaker 1: You're doing everything you can to improve the reputations of
• 2:43
  Speaker 1: Americans abroad, right exactly, and welcome to the podcast. Daniel
• 2:48
  Speaker 1: and Jorge explain the universe in which we explore everything
• 2:52
  Speaker 1: that's out there in the universe, what people's butts smell like,
• 2:56
  Speaker 1: what the night sky looks like, what's actually out there
• 2:58
  Speaker 1: in deep space, how all the particles between our toes
• 3:02
  Speaker 1: are working to weave themselves together into our reality, and
• 3:05
  Speaker 1: how we sense experience and maybe even understand all of it.
• 3:10
  Speaker 1: My friend and co host Jorge can't be with us today,
• 3:12
  Speaker 1: but I'm very excited to have Katie Golden, one of
• 3:15
  Speaker 1: our regular and favorite guest hosts, to be with us
• 3:17
  Speaker 1: here today. Thanks Katie for joining us.
• 3:19
  Speaker 2: It feels good to be here.
• 3:23
  Speaker 1: And now I'm wondering if I ever do meet you
• 3:25
  Speaker 1: in person, Katie, if you're going to do more than
• 3:27
  Speaker 1: just shake my hand, if you're gonna.
• 3:28
  Speaker 2: Smell me up, like There's a lot you can tell
• 3:32
  Speaker 2: about a person just by huffing.
• 3:34
  Speaker 1: In that sense, you'll probably tell that I have dogs
• 3:37
  Speaker 1: and I have kids based on the random hairs on
• 3:39
  Speaker 1: my body.
• 3:40
  Speaker 2: The feel of the stickiness quotient is how I measure
• 3:44
  Speaker 2: whether someone has kids, Like, is there sticky patches on
• 3:47
  Speaker 2: your shirt? That's right, is in the shape of a
• 3:51
  Speaker 2: very small, curious little hand.
• 3:53
  Speaker 1: Do you have dried cheerios stuck to the side of
• 3:55
  Speaker 1: your shorts. If so, you have a toddler. But we're
• 4:00
  Speaker 1: not just interested in sensing other people. We are interested
• 4:03
  Speaker 1: in sensing the world. Everything we do in physics in
• 4:06
  Speaker 1: the end relies on these little data streams that we
• 4:09
  Speaker 1: get from the external universe that in the end we're
• 4:12
  Speaker 1: just assuming exists. We have a model for what's out there,
• 4:15
  Speaker 1: how it bangs around and creates information that we can
• 4:19
  Speaker 1: then perceive filter down into our minds and unravel into
• 4:23
  Speaker 1: a mathematical model in our heads that tries to explain
• 4:26
  Speaker 1: everything that we think is out there. But it seems
• 4:29
  Speaker 1: like kind of a long, complicated chain of events from
• 4:32
  Speaker 1: supernova explodes to somebody on Earth goes ooh, I think
• 4:36
  Speaker 1: I understand it. So on this podcast we try to
• 4:39
  Speaker 1: unravel all of those tricky, complicated things and make sure
• 4:42
  Speaker 1: you understand all of them.
• 4:44
  Speaker 2: It's so interesting to me that every sense we have
• 4:47
  Speaker 2: right is the direct result of physical interaction with the world,
• 4:54
  Speaker 2: because it feels strange since our mind seems very internal,
• 4:58
  Speaker 2: it seems very ice like, well, what I'm seeing is
• 5:02
  Speaker 2: kind of happening in my mind, But everything I'm seeing
• 5:05
  Speaker 2: like there's a direct sort of physics based interaction that's
• 5:09
  Speaker 2: happening between me and the world, and I don't know.
• 5:12
  Speaker 2: That makes me feel good. It makes me feel less
• 5:15
  Speaker 2: isolated in my own brain.
• 5:18
  Speaker 1: It really does a great job of reminding you that
• 5:20
  Speaker 1: information is physical, and that all observation is active. There's
• 5:25
  Speaker 1: no like passive just looking at the world. You are
• 5:28
  Speaker 1: absorbing it, you are consuming it, you are interacting with it.
• 5:31
  Speaker 1: When you see something, it's because photons are hitting your eye.
• 5:35
  Speaker 1: You're not just like passively observing it. And that of
• 5:37
  Speaker 1: course changes the way you feel about the universe and
• 5:39
  Speaker 1: has big philosophical implications for like quantum mechanics and what
• 5:42
  Speaker 1: happens when we collapse wave functions. But it also has
• 5:45
  Speaker 1: real consequences for what it means to like smell something nasty.
• 5:48
  Speaker 1: I mean, you're walking down the street and you're like,
• 5:50
  Speaker 1: m somebody didn't clean up after their dog. You know
• 5:53
  Speaker 1: that means poop molecules are hitting your nose.
• 5:55
  Speaker 2: When I have that realization, I think I was in
• 5:58
  Speaker 2: high school. It ruined my life world. I have never
• 6:01
  Speaker 2: gotten over that that like poopy smells, It's like, well,
• 6:04
  Speaker 2: the poopy particles are interacting with my nasal membranes in
• 6:08
  Speaker 2: some way. I don't like that and it is. Yeah,
• 6:12
  Speaker 2: it's a realization that ruined my life, and I'm glad
• 6:14
  Speaker 2: we can spread it to others.
• 6:16
  Speaker 1: And as we're going to learn later on, the sense
• 6:18
  Speaker 1: of smell the sense of taste are very closely intertwined,
• 6:22
  Speaker 1: and most of your experience of taste really is smell,
• 6:25
  Speaker 1: which means you're not just smelling that dog poop, you're
• 6:28
  Speaker 1: really tasting it delicious And we are excited to understand
• 6:33
  Speaker 1: this entire, delicious and disgusting universe in all of its glory.
• 6:37
  Speaker 1: And so today on the podcast, we're going to be
• 6:39
  Speaker 1: digging into the physics of this mechanism, how exactly information
• 6:43
  Speaker 1: gets banged around and propagated through all these amazing systems
• 6:48
  Speaker 1: into your brain so that you can experience the wonderful
• 6:51
  Speaker 1: smells of chicken cooking and the less wonderful smells of
• 6:55
  Speaker 1: dog residue.
• 6:56
  Speaker 2: I have smelled both today.
• 6:59
  Speaker 1: And so today on the podcast, we'll be answering the
• 7:01
  Speaker 1: question which forces power the human senses?
• 7:11
  Speaker 2: That sounds so cool. I'm imagining sort of my eyes
• 7:14
  Speaker 2: being powered by some kind of like futuristic technology.
• 7:21
  Speaker 1: Yeah, I guess power there can be confusing. It's not
• 7:23
  Speaker 1: like you have little coal power plants in your eyeballs
• 7:26
  Speaker 1: that are like making it all work in some sort
• 7:28
  Speaker 1: of steampunk version of your senses.
• 7:30
  Speaker 2: Now, I mean, as we all know, it's tiny grimlins
• 7:33
  Speaker 2: in there, running little projectors, the.
• 7:36
  Speaker 1: Little physics grimlins all the way down. Now, the idea
• 7:40
  Speaker 1: I think is to understand everything from a physics point
• 7:42
  Speaker 1: of view. I mean, you can zoom out to biology
• 7:44
  Speaker 1: and say, oh, yeah, we understand this bit and that
• 7:46
  Speaker 1: sell and they send signals or whatever. But I always
• 7:49
  Speaker 1: wonder from a microphysics point of view, like, what's really
• 7:52
  Speaker 1: happening at the lowest level. If in the end reductionism works,
• 7:56
  Speaker 1: and we can understand the whole universe in terms of
• 7:59
  Speaker 1: a few partsarticles and their interactions, and we should be
• 8:02
  Speaker 1: able to explain everything from human consciousness to supernova to
• 8:06
  Speaker 1: black holes to the evolution of the entire universe with
• 8:10
  Speaker 1: those fundamental laws. Of course, most of that is beyond
• 8:13
  Speaker 1: our ability currently, and the complex nature of these interactions
• 8:17
  Speaker 1: requires too much chaos for us to be able to compute.
• 8:20
  Speaker 1: But in some cases we can actually complete the thread.
• 8:23
  Speaker 1: We can't drill down and understand what is happening when
• 8:26
  Speaker 1: that chicken dinner enters your nose. How are you actually
• 8:29
  Speaker 1: seeing those things? What is the mechanism by which you
• 8:32
  Speaker 1: feel pain? In terms of the fundamental physics that we
• 8:36
  Speaker 1: do understand in our universe. So that's what we want
• 8:40
  Speaker 1: to dig into today.
• 8:41
  Speaker 2: I mean, it is really interesting because when you look
• 8:43
  Speaker 2: at biological processes like the smaller you get, you have
• 8:48
  Speaker 2: a very extensive, basically Rube Goldberg machine happening inside your
• 8:53
  Speaker 2: body on a tiny scale every time you sense something,
• 8:57
  Speaker 2: and then you zoom out and there's another Rube Goldberg
• 8:59
  Speaker 2: machine happening on a slightly larger scale. And I feel
• 9:03
  Speaker 2: like that's not too dissimilar to physics, although Goldberg machines
• 9:09
  Speaker 2: are operated by physics of force, which is not the
• 9:13
  Speaker 2: only kind of like physics we're talking about here, but
• 9:15
  Speaker 2: it's still it's still interesting that, you know, when you
• 9:19
  Speaker 2: have this whole complex process, domino effective physical phenomenon happening,
• 9:25
  Speaker 2: and then once it gets to your body and it
• 9:28
  Speaker 2: triggers an event, then you have a whole other complex
• 9:31
  Speaker 2: system of things that happens. There's so much just for
• 9:34
  Speaker 2: you to look at like a wadded up tissue. There's
• 9:38
  Speaker 2: so many things that have to happen so much.
• 9:40
  Speaker 1: Glorious physics in that experience of the watered up tissue.
• 9:44
  Speaker 1: But you know, I'm wondering how biologists feel about these machines,
• 9:47
  Speaker 1: these Rube Goldberg machines, because that's not exactly a compliment.
• 9:51
  Speaker 1: Like if I designed the machine to do something and
• 9:54
  Speaker 1: you said, wow, Daniel, that's kind of a Rube Goldberg machine,
• 9:56
  Speaker 1: I take it as like that's broke and overly complicated,
• 10:00
  Speaker 1: likely to fail, and could be better engineered. On the
• 10:03
  Speaker 1: other hand, I often hear biologists exclaiming that the wonders
• 10:05
  Speaker 1: of nature and the amazing things that evolution has been
• 10:08
  Speaker 1: able to engineer. So do you feel some pride in
• 10:12
  Speaker 1: evolution as an engineer or do you feel like embarrassed, like,
• 10:15
  Speaker 1: oh my gosh, this is ridiculous.
• 10:17
  Speaker 2: I think it could be both things, honestly. I mean,
• 10:20
  Speaker 2: I've heard of our immune systems being described as like
• 10:24
  Speaker 2: this amazing complicated ballet and dance, and that's true. But
• 10:28
  Speaker 2: then sometimes our immune system can act like an insane
• 10:32
  Speaker 2: traffic jam, just a horrible traffic snarl. And I think
• 10:36
  Speaker 2: these kinds of things happen in biold you or we
• 10:39
  Speaker 2: look at things like, you know, like the eyeball is incredible.
• 10:43
  Speaker 2: It's one of those things that make people question whether
• 10:46
  Speaker 2: evolution can be real. Of course, once you look at
• 10:49
  Speaker 2: the way in which ees develop over long periods of time,
• 10:53
  Speaker 2: you can see how it. You know, just after millions
• 10:56
  Speaker 2: of years you can get an eyeball. It's such an
• 10:58
  Speaker 2: elegant thing. And then on the other hand, we've got
• 11:01
  Speaker 2: some kind of weird uh things that happen in evolution,
• 11:05
  Speaker 2: you know, like these are called spandrels, where you have
• 11:07
  Speaker 2: an evolutionary trait that doesn't really have a purpose anymore,
• 11:12
  Speaker 2: or doesn't have any like a parent purpose, but it's
• 11:15
  Speaker 2: there because there's some other structural thing that occurred. And
• 11:20
  Speaker 2: then you just happen to have this thing because it
• 11:23
  Speaker 2: is a byproduct of other necessary structures. So it's not
• 11:28
  Speaker 2: meant to be necessarily elegant. It's just like what works works,
• 11:32
  Speaker 2: and sometimes it's elegant and sometimes it's not.
• 11:35
  Speaker 1: That's what you get when you leave the job up
• 11:37
  Speaker 1: to biology gremlins. All right, well, let's hear about what
• 11:40
  Speaker 1: some other gremlins had to say on this topic. I
• 11:42
  Speaker 1: reached out to listeners of the podcast to hear what
• 11:45
  Speaker 1: their thoughts were on the question. So before you hear
• 11:48
  Speaker 1: these answers, think to yourself, do you know which forces
• 11:52
  Speaker 1: power of the human senses. Here's what people had to say.
• 11:56
  Speaker 4: I'm going with the electromagnetic force, as I think all
• 12:00
  Speaker 4: of our sensors rely on that to send the signals
• 12:03
  Speaker 4: to our brain where we interpret them internally.
• 12:05
  Speaker 5: I suppose this would be the same as the forces
• 12:08
  Speaker 5: driving other metabolic processes. So ultimately the breakdown of ATP
• 12:11
  Speaker 5: to power some protein or enzyme that's involved in the
• 12:14
  Speaker 5: sensing signal transaction pathway, and then externally there would be
• 12:17
  Speaker 5: the force of the thing itself that's being sensed. Particularly exposed,
• 12:21
  Speaker 5: with the light, you'd have the photons striking rods or cones,
• 12:25
  Speaker 5: or in the case of sound, you'd have the vibrational
• 12:27
  Speaker 5: energy being sensed by the hairs. I guess with chemical
• 12:31
  Speaker 5: sensing it would be slightly more subtle, but there might
• 12:33
  Speaker 5: be some analogous process.
• 12:35
  Speaker 3: Well. I understand that the human senses are a collection
• 12:39
  Speaker 3: of receptors of very quantum phenomena such as light and
• 12:43
  Speaker 3: microscopic smell molecules. So I think that at the very end,
• 12:48
  Speaker 3: the fundamental forces such as electromagnetism and strong forces are
• 12:54
  Speaker 3: involved in somehow.
• 12:55
  Speaker 4: If you count equilibrium as a sense, then gravity would
• 12:58
  Speaker 4: affect that. Then touch, smell, here, and taste are all
• 13:01
  Speaker 4: physical contact ultimately, which is the interaction of molecules held
• 13:04
  Speaker 4: together by electromagnetism. And then vision is directly sensing the
• 13:07
  Speaker 4: electromagnetic spectrum. Ultimately everything is nerve impulses, which are electrochemicals.
• 13:12
  Speaker 4: So it seems like electromagnetism is the big winner.
• 13:14
  Speaker 1: I'd say the electromagnetic force is mostly responsible for powering
• 13:18
  Speaker 1: the human sensus.
• 13:19
  Speaker 3: Our entire nervous system basically works out in elecricity and
• 13:23
  Speaker 3: says our senses.
• 13:24
  Speaker 1: Are part of that. I'd say that's our usual suspect.
• 13:27
  Speaker 1: All right, We've got a lot of electromagnetism, but also
• 13:30
  Speaker 1: some gravity and chemistry and quantum mechanics mixed up in there.
• 13:35
  Speaker 2: I mean, I can't really disagree with this if we
• 13:39
  Speaker 2: blend all these answers together in sort of a stew
• 13:42
  Speaker 2: because as far as I understand it, like there's a
• 13:45
  Speaker 2: lot of different elements in terms of our ability to
• 13:50
  Speaker 2: perceive things. It's not always electromagnetic force, but that is
• 13:55
  Speaker 2: a major force and a lot of our sort of
• 13:58
  Speaker 2: the chain of events that occur that allow us to
• 14:01
  Speaker 2: perceive things. It's just there's so many different elements that
• 14:05
  Speaker 2: are happening all at once, or not all at once,
• 14:08
  Speaker 2: but in a sort of very quick rapid succession of events.
• 14:13
  Speaker 1: There are a lot of pieces at play. But one
• 14:15
  Speaker 1: of the things I love about the story we're telling
• 14:17
  Speaker 1: today is the eventual unity. How we achieve this sort
• 14:21
  Speaker 1: of physics goal of pulling everything together into one thing.
• 14:25
  Speaker 1: So I'm excited to get into that and take the
• 14:27
  Speaker 1: listeners on that saga and talk about what the fundamental
• 14:30
  Speaker 1: forces are that undergird the human senses.
• 14:34
  Speaker 2: So I understand fairly well the human senses and non
• 14:40
  Speaker 2: human senses, but I feel like I could use a
• 14:43
  Speaker 2: refresher on the main forces that exist in the physical
• 14:49
  Speaker 2: world that we can perceive, or at least something could perceive,
• 14:55
  Speaker 2: even if it's not a human.
• 14:56
  Speaker 1: Yeah, exactly. So we're going to map the human senses
• 14:58
  Speaker 1: to the fundamental forces. But are the fundamental forces? What
• 15:02
  Speaker 1: is the sort of target? What is the menu of options?
• 15:05
  Speaker 1: We have to describe stuff? So physics is all about
• 15:08
  Speaker 1: describing the universe, and humans have been observing stuff for
• 15:11
  Speaker 1: thousands of years and trying to describe it, And every
• 15:14
  Speaker 1: time we see something move in an unexplained way, get accelerated,
• 15:18
  Speaker 1: get a force applied to it, we come up with
• 15:21
  Speaker 1: a new force. We say, okay, well there must be
• 15:22
  Speaker 1: a new force that pushes things in this way. But
• 15:25
  Speaker 1: over thousands of years, we've worked to coalesce these things
• 15:28
  Speaker 1: into sort of the shortest list possible to say, oh,
• 15:31
  Speaker 1: the thing that does lightning is probably the same that
• 15:33
  Speaker 1: does that static electricity that zaps me. So we have
• 15:36
  Speaker 1: a list of the fundamental forces, the sort of basic
• 15:39
  Speaker 1: things that the universe can do, and that current list
• 15:43
  Speaker 1: has five things on it. So number one top of
• 15:47
  Speaker 1: the list is electricity, right, something humans have definitely known
• 15:51
  Speaker 1: about four thousands of years and a very important thing
• 15:54
  Speaker 1: in our lives. I mean, I drive an ev Electricity
• 15:57
  Speaker 1: is powering my entire life. You're listening to this device
• 16:00
  Speaker 1: using electricity. It's everywhere in our world. Hard to imagine
• 16:03
  Speaker 1: a universe without electricity.
• 16:05
  Speaker 2: How did we know about electricity before we had socks
• 16:08
  Speaker 2: and carpet.
• 16:09
  Speaker 1: Though Ben Franklin actually invented socks and carpets just to
• 16:13
  Speaker 1: do that experiment. Not a well known story, And we've
• 16:16
  Speaker 1: had sort of colloquial folk understanding of electricity for thousands
• 16:19
  Speaker 1: of years. But in the last couple of hundreds of years,
• 16:22
  Speaker 1: people doing experiments with literally like rags and glass rods
• 16:25
  Speaker 1: and all sorts of weird experiments have figured out that
• 16:28
  Speaker 1: we have charged particles, and those charge particles have these
• 16:31
  Speaker 1: electric fields that can push and pull on each other.
• 16:34
  Speaker 1: So you have two electrons, for example, they each have
• 16:37
  Speaker 1: an electric field and their electric fields can push on
• 16:40
  Speaker 1: other charged particles, and so that's the fundamental electrical force.
• 16:44
  Speaker 2: So can electrons because I know that electrons are often
• 16:48
  Speaker 2: a part of an atom or an atomic structure. Can
• 16:53
  Speaker 2: electrons just be out by themselves?
• 16:55
  Speaker 1: Oh? Yeah, Electrons do not have a curfew. They can
• 16:58
  Speaker 1: just be out there in the universe, and the Sun
• 17:00
  Speaker 1: produces a huge number of electrons shoots them out into
• 17:04
  Speaker 1: the universe. So if you take a spaceship through interstellar space,
• 17:07
  Speaker 1: you'll be swimming through a sea of electrons and protons
• 17:10
  Speaker 1: and all sorts of other particles. It's only when things
• 17:13
  Speaker 1: are cool, when these particles don't have enough velocity to escape,
• 17:16
  Speaker 1: that they're trapped into bonds. But the formation of the
• 17:19
  Speaker 1: atom is also electrical. Is the electrical force between the
• 17:23
  Speaker 1: proton and the electron that builds the atom. That's why
• 17:26
  Speaker 1: they bind together into hydrogen, and that's why atoms link
• 17:30
  Speaker 1: together into more complex molecules. So the structure of the
• 17:32
  Speaker 1: atom itself, and basically all of chemistry, the foundation of
• 17:36
  Speaker 1: that is electricity. It's all the forces of electrons on
• 17:40
  Speaker 1: each other and on nuclei.
• 17:41
  Speaker 2: So can you use electricity to facilitate chemical reactions in chemistry?
• 17:46
  Speaker 1: I mean, I think if you dig up a corpse
• 17:48
  Speaker 1: and lay them on a table and zap them with
• 17:50
  Speaker 1: lightning they come back to life, is that count as chemistry?
• 17:53
  Speaker 1: I think I saw that experiment somewhere.
• 17:56
  Speaker 2: That's true. I have seen muscle tissue. If you pour
• 18:00
  Speaker 2: like soy sauce or salt on it, it reacts like
• 18:04
  Speaker 2: the sort of electrical activity resumes, even though it's clearly
• 18:09
  Speaker 2: a dead thing. It can be a chunk of flesh.
• 18:11
  Speaker 2: And I think it's because of the sodium in the
• 18:15
  Speaker 2: salt or in the soy sauce, kind of like activating
• 18:17
  Speaker 2: these sodium channels and creating some kind of difference in
• 18:22
  Speaker 2: electrical voltage that allows there to be sort of this
• 18:25
  Speaker 2: twitching that happens. So if you see a video of
• 18:28
  Speaker 2: a fish or some meat on a plate kind of
• 18:30
  Speaker 2: twitching after you apply like soy sauce. It's not undead.
• 18:34
  Speaker 2: It's just a be re animated by the soy sauce.
• 18:38
  Speaker 3: Right.
• 18:38
  Speaker 1: But to give a serious answer to your question, yes, absolutely,
• 18:41
  Speaker 1: if you apply electricity or voltage or current to something,
• 18:44
  Speaker 1: youur depositing energy and that can definitely catalyze chemical reactions.
• 18:49
  Speaker 1: But you bring up another really important point, which is
• 18:51
  Speaker 1: how signaling happens. We know, of course, we can use
• 18:54
  Speaker 1: electrical signals to send information. You're listening to this podcast
• 18:57
  Speaker 1: with electrical signals, digital signals from computer to computer, and they're
• 19:01
  Speaker 1: probably analog signals and the speakers that are actually making
• 19:03
  Speaker 1: the sound that get to your ear. But also inside
• 19:06
  Speaker 1: our body, our nervous system uses these ionic channels, uses
• 19:10
  Speaker 1: charged particles and electrical forces two senden signals up and
• 19:13
  Speaker 1: down your nerves, which is why they move at almost
• 19:16
  Speaker 1: the speed of light.
• 19:17
  Speaker 2: Yeah, it's really fascinating because it's another thing is you
• 19:20
  Speaker 2: really can't chug soy sauce. It's bad for you. I'm
• 19:24
  Speaker 2: being silly, but it's also not a joke. If you
• 19:26
  Speaker 2: chug soy sauce, it's very dangerous because it interferes with
• 19:29
  Speaker 2: the ion channels in your brain, and it can actually
• 19:33
  Speaker 2: make it difficult for those electrical signals to occur in
• 19:37
  Speaker 2: your brain, and that's very dangerous. That can result in
• 19:40
  Speaker 2: coma or even death. So, you know, it's really interesting
• 19:43
  Speaker 2: how chemistry, right, like even basic chemistry, like the way
• 19:46
  Speaker 2: that sodium ions work and electricity, the tiny electrical impulses
• 19:52
  Speaker 2: in your brain work together and can be messed up
• 19:55
  Speaker 2: by soy sauce. Soy sauce is just so dangerous, you guys.
• 19:59
  Speaker 1: It's brewed up by soy goblins. I think they're quite
• 20:01
  Speaker 1: so dangerous.
• 20:02
  Speaker 2: I love soy sauce in moderation.
• 20:04
  Speaker 1: But that gives you a really cool picture of the
• 20:06
  Speaker 1: sort of electrical map of your body. And it reminds
• 20:09
  Speaker 1: you that your body is not just mechanical structures, not
• 20:12
  Speaker 1: just like cells and membranes and bones, but there are
• 20:15
  Speaker 1: electrical structures. There are also things that can get messed
• 20:19
  Speaker 1: up if you pour the wrong number of positively or
• 20:21
  Speaker 1: negatively charged particles in the wrong place. Your body is
• 20:24
  Speaker 1: sort of like a computer. If you poured soy sauce
• 20:26
  Speaker 1: on your computer, you would not expect it to operate
• 20:29
  Speaker 1: very well either. And it makes you wonder sometimes philosophically,
• 20:31
  Speaker 1: like what is this thing we call electric charge? Where
• 20:34
  Speaker 1: does it come from? And that's a tricky rabbit hole
• 20:37
  Speaker 1: to fall down, because really, fundamentally, in physics, charge is
• 20:41
  Speaker 1: something we assign. We say that some particles react in
• 20:44
  Speaker 1: the presence of electric fields, and that means that they're charged.
• 20:48
  Speaker 1: That's what charge means. And as we'll talk about it
• 20:50
  Speaker 1: in a minute when we get to the other forces,
• 20:52
  Speaker 1: we have other kinds of charge. Also, if you feel
• 20:55
  Speaker 1: the other fundamental forces, you are charged for those forces.
• 20:59
  Speaker 1: So we're used to talking about charge for an electrical sense,
• 21:01
  Speaker 1: we don't really know philosophically what it means. Why the
• 21:04
  Speaker 1: electron has a charge, Why these other particles have charges.
• 21:07
  Speaker 1: Some particles don't have charges. It's just something we observe
• 21:10
  Speaker 1: and describe.
• 21:11
  Speaker 2: So like all electrons have some kind of charge, but
• 21:15
  Speaker 2: we really like when do we feel that?
• 21:17
  Speaker 3: Right?
• 21:18
  Speaker 2: Like when can we observe that charge? Because like you know,
• 21:22
  Speaker 2: you have your door handle in your socks and somehow
• 21:26
  Speaker 2: by rubbing your socks on the carpet, now when you
• 21:28
  Speaker 2: touch the door handle, you have a charge that you
• 21:31
  Speaker 2: can actually sense a little zap. So what happens to
• 21:35
  Speaker 2: these charges to make us actually notice them, like lightning happens.
• 21:39
  Speaker 2: We can notice that even though this charge can be
• 21:42
  Speaker 2: all around us at this like sub atomic level without
• 21:45
  Speaker 2: us noticing.
• 21:46
  Speaker 1: Yeah, great question. I mean fundamentally, we notice something is
• 21:49
  Speaker 1: charged when it's moved by an electrical field. And that's
• 21:52
  Speaker 1: the definition of charge. If you give me a new
• 21:55
  Speaker 1: particle I'd never seen before, one of the first things
• 21:57
  Speaker 1: I would do would be descended through an electric field
• 22:00
  Speaker 1: and see is it accelerated by the field? Is it
• 22:02
  Speaker 1: pushed around by the field. If so, then it has
• 22:05
  Speaker 1: an electric charge, because that's the definition of it. When
• 22:07
  Speaker 1: you rub a cloth onto a glass rod, you're stripping
• 22:10
  Speaker 1: some of those charged particles from one to the other.
• 22:12
  Speaker 1: You're creating an imbalance, which creates an electric field, which
• 22:16
  Speaker 1: is then can accelerate any charge particle across it, which
• 22:19
  Speaker 1: is why you get that zap when things come back
• 22:21
  Speaker 1: close enough for that field to break down the air
• 22:23
  Speaker 1: and let the electrons pass through the other direction and
• 22:26
  Speaker 1: create that spark. So in the end, really charge is
• 22:29
  Speaker 1: about being moved by an electric field, which feels a
• 22:32
  Speaker 1: little circular because we also define an electric field to
• 22:34
  Speaker 1: be something created by a charge, and so that gives
• 22:37
  Speaker 1: you a glimpse into how deeply we do and do
• 22:39
  Speaker 1: not understand the fundamental forces.
• 22:42
  Speaker 2: It's very interesting. So it's like you have to have
• 22:44
  Speaker 2: some kind of imbalance in charge in order for us
• 22:47
  Speaker 2: to kind of sense that charge.
• 22:49
  Speaker 1: Yeah, exactly. If everything is totally neutral, then there are
• 22:52
  Speaker 1: no forces.
• 22:53
  Speaker 2: So I'm going to test this theory out by rubbing
• 22:57
  Speaker 2: my socks against the carpet and zap my husband while
• 23:00
  Speaker 2: he's trying to cook chicken. So I'm going to go
• 23:03
  Speaker 2: do that and I will report my experiment back when
• 23:07
  Speaker 2: we return. So the experiment was an unqualified success. I
• 23:26
  Speaker 2: did zat my husband. He said, ouch, what are you doing.
• 23:30
  Speaker 2: I'm just trying to cook some chicken. So we have
• 23:34
  Speaker 2: talked about electrical forces, that they exist in your body,
• 23:39
  Speaker 2: they exist outside of your body. It is something that
• 23:43
  Speaker 2: we see in lightning, in you know, static electricity, and
• 23:48
  Speaker 2: in our own bodies, in our synapses, in our brain
• 23:52
  Speaker 2: and in our along these long nerve fibers on our
• 23:56
  Speaker 2: spinal cord. So what other forces are there in the
• 23:59
  Speaker 2: world that can affect us?
• 24:01
  Speaker 1: So we've seen other stuff, not just electricity to spark
• 24:04
  Speaker 1: our husbands and to fry trees in a lightning storm.
• 24:08
  Speaker 1: But like magnets, right, magnets are definitely a different thing
• 24:12
  Speaker 1: than electricity. These are things we've known about for thousands
• 24:15
  Speaker 1: of years, and a couple of hundred years ago, a
• 24:17
  Speaker 1: clever Scotsman helped us understand that magnetic fields, which are
• 24:21
  Speaker 1: very similar to electric fields, actually fit together with them
• 24:25
  Speaker 1: into a blended concept called electromagnetism. But that doesn't mean
• 24:29
  Speaker 1: that electricity and magnetism are the same thing. A lot
• 24:32
  Speaker 1: of people get confused and imagine that the union of
• 24:34
  Speaker 1: electricity and magnetism into one concept means that they are
• 24:38
  Speaker 1: the same thing. But it's more like how the union
• 24:41
  Speaker 1: of the front of an elephant and the back of
• 24:42
  Speaker 1: an elephant, and give you a whole elephant, doesn't mean
• 24:45
  Speaker 1: the front in the back are the same thing.
• 24:47
  Speaker 2: Yes, and you will learn that if you're an elephant
• 24:50
  Speaker 2: keeper and you're behind an elephant.
• 24:51
  Speaker 1: Go out and take some data. You will learn that
• 24:53
  Speaker 1: very quickly. Sort of how two sides of the coin
• 24:56
  Speaker 1: make more sense when you think of them together than
• 24:58
  Speaker 1: when you think about them separately. But heads does not
• 25:01
  Speaker 1: equal tails, So magnetism really is its own thing. It's
• 25:04
  Speaker 1: just like a different part of electromagnetism, and it's fascinating
• 25:08
  Speaker 1: because it's very similar to electricity, but it's also very different.
• 25:11
  Speaker 1: One way in which it's different is that there are
• 25:14
  Speaker 1: no particles out there with like magnetic charge. We have
• 25:18
  Speaker 1: particles like electrons that can give you electric fields, but
• 25:20
  Speaker 1: there are no particles that just sit there and give
• 25:23
  Speaker 1: you magnetic fields. Magnetic fields only come from the motion
• 25:27
  Speaker 1: of electric charges, like a current will give you a
• 25:30
  Speaker 1: magnetic field, or something rotating with a charge on it
• 25:32
  Speaker 1: will give you a magnetic field. There are no particles
• 25:34
  Speaker 1: out there with a pure magnetic charge, which makes it
• 25:37
  Speaker 1: pretty different from electricity.
• 25:38
  Speaker 2: Now, hang on, Daniel, you say that magnetism is from
• 25:42
  Speaker 2: sort of the movement of charged particles. But I have
• 25:47
  Speaker 2: two magnets. They look pretty motionless, and then I put
• 25:52
  Speaker 2: them next to each other, and they still either stick
• 25:56
  Speaker 2: together or push each other apart. What's happening with magnet
• 26:00
  Speaker 2: If this is something that can be produced by an
• 26:05
  Speaker 2: electrical field, like something that is moving, the magnets themselves
• 26:08
  Speaker 2: do not, to my eyes, appear to be moving unless
• 26:12
  Speaker 2: I'm actually forcing them together through magnetism.
• 26:15
  Speaker 1: And you probably are not running an electric current through it.
• 26:17
  Speaker 1: So you're wondering, like, where's the motion of the charges
• 26:20
  Speaker 1: that's giving me these magnetic fields, And it's the electrons spinning,
• 26:24
  Speaker 1: and these little quantum particles electrons and protons whatever, they
• 26:27
  Speaker 1: have a property called quantum spin, which is not physical spin.
• 26:31
  Speaker 1: It's not like they're actually little balls that are literally spinning.
• 26:34
  Speaker 1: It's a different kind of quantum mechanical property. Check out
• 26:36
  Speaker 1: our podcast episode about what is quantum spin. But it
• 26:40
  Speaker 1: is definitely a kind of spin. It carries angular momentum
• 26:43
  Speaker 1: for sure, and it does generate a magnetic field. So
• 26:47
  Speaker 1: a charged particle with quantum spin has also a little
• 26:50
  Speaker 1: magnetic field to it, and enough of these particles line
• 26:54
  Speaker 1: up in your little blob of metal and it becomes
• 26:56
  Speaker 1: a permanent magnet. So that's how a fridge magnet works.
• 26:59
  Speaker 1: There really is a kind of motion inside of it
• 27:01
  Speaker 1: that's creating a magnetic field. And you might think, hold on,
• 27:04
  Speaker 1: doesn't that contradict what Daniel just said about how there
• 27:06
  Speaker 1: are no like objects just that have magnetic fields. Well,
• 27:09
  Speaker 1: the fridge magnet doesn't just have a magnetic field the
• 27:11
  Speaker 1: way an electron has an electric field. It has a
• 27:14
  Speaker 1: dipole field. It has a north and a south. Overall,
• 27:18
  Speaker 1: there's no net magnetic field because it's a north and
• 27:21
  Speaker 1: a south. They cancel each other out. There's no particle
• 27:23
  Speaker 1: out there that just has like a north or just
• 27:25
  Speaker 1: has a south. That would be something we call a monopole. Though,
• 27:29
  Speaker 1: when an electron can just have like a negative field
• 27:31
  Speaker 1: and a proton can have a positive field. In magnetism,
• 27:34
  Speaker 1: you can only have the north and south together because
• 27:37
  Speaker 1: it's generated by the motion of an electric charge.
• 27:40
  Speaker 2: It's interesting. So it's like if you're sort of in
• 27:42
  Speaker 2: a pool, like you're a little electron and you're moving
• 27:45
  Speaker 2: back and forth, there's always gonna be waves behind you
• 27:48
  Speaker 2: and in front of you. There's no such thing as
• 27:51
  Speaker 2: like if you're moving back and forth, it's not just
• 27:53
  Speaker 2: going to generate waves in front of you and not
• 27:56
  Speaker 2: behind you exactly.
• 27:57
  Speaker 1: It's always in balance. There's no over a magnetic charge
• 28:01
  Speaker 1: in the universe. It's just fascinating because it's a stark asymmetry.
• 28:04
  Speaker 1: On one hand, magnetism works exactly the same way as electricity.
• 28:08
  Speaker 1: You write down the equations, they're all the same equations,
• 28:11
  Speaker 1: except for this one key difference that there are no
• 28:14
  Speaker 1: pure sources of magnetism in the universe that we know about.
• 28:18
  Speaker 1: Check out our podcast episode on magnetic monopoles and the
• 28:22
  Speaker 1: Hunt for them. But it means that magnetism is a
• 28:24
  Speaker 1: sort of weird shadow version of electricity, and together the
• 28:28
  Speaker 1: two can do this incredible dance. The electric fields and
• 28:31
  Speaker 1: the magnetic fields can oscillate together. The electromagnetic oscillation is
• 28:36
  Speaker 1: something we call light. Photons are oscillations in the electromagnetic
• 28:42
  Speaker 1: field as it slashes back and forth between electricity and magnetism.
• 28:46
  Speaker 2: That's really interesting. I've never seen light occur just with magnets,
• 28:52
  Speaker 2: but I have seen light, you know, occur from electricity.
• 28:55
  Speaker 2: Natural sort of occurring plasma from a light is very bright,
• 29:01
  Speaker 2: So it's interesting that electromagnetism is like, is there like
• 29:06
  Speaker 2: a magnetic field around lightning?
• 29:09
  Speaker 1: There are definitely magnetic fields around lightning, absolutely, because you
• 29:12
  Speaker 1: have lots of very highly charged particles moving at very
• 29:15
  Speaker 1: high speed. So you could definitely detect lightning using a compass.
• 29:19
  Speaker 2: So is that a safe way to predict whether you're
• 29:22
  Speaker 2: gonna get hit by lightning? If you hold a compass
• 29:24
  Speaker 2: out and it starts going crazy.
• 29:26
  Speaker 1: I think compasses will definitely go crazy in a lightning storm.
• 29:29
  Speaker 1: So if you see your compass going crazy, it means
• 29:31
  Speaker 1: either aliens are arriving or you might be about to
• 29:35
  Speaker 1: get zapped. Either way, you might get zapped.
• 29:37
  Speaker 2: I'm gonna believe in the aliens option. Have you ever
• 29:41
  Speaker 2: wondered what would happen if you put like a giant
• 29:45
  Speaker 2: magnet next to your brain.
• 29:48
  Speaker 1: I've done that. Actually, I've had an MRI that's basically
• 29:50
  Speaker 1: a giant magnet next to your brain.
• 29:52
  Speaker 2: That is true. That's why you can't bring metal into
• 29:55
  Speaker 2: an MRI room, otherwise it's going to cause a big
• 29:59
  Speaker 2: problem problem.
• 30:00
  Speaker 1: And for our particle accelerators, we have huge magnets in
• 30:03
  Speaker 1: these facilities underground to bend charge particles. And sometimes you
• 30:07
  Speaker 1: go down there when the magnet's on and they tell you,
• 30:09
  Speaker 1: like take off everything. You know, screwdrivers can become weapons.
• 30:13
  Speaker 1: I once saw a woman who forgot to take off
• 30:14
  Speaker 1: her earrings and her ear lobes were tugged very very stiffly.
• 30:19
  Speaker 2: Ooh ah, that is that's like some final destination stuff
• 30:24
  Speaker 2: right there. So, like you can use electromagnetic forces to
• 30:29
  Speaker 2: impact the brain and actually kind of selectively shut off
• 30:34
  Speaker 2: parts of the brain. It's a reversible process. That's done
• 30:38
  Speaker 2: sometimes in research, sometimes in a clinical setting where you're
• 30:42
  Speaker 2: either stimulating or sort of shutting down parts of the
• 30:46
  Speaker 2: brain using electromagnetic forces. It is very creepy to me.
• 30:51
  Speaker 2: I'd be very interested to see what it feels like
• 30:54
  Speaker 2: to have like parts of your brain shut off, but
• 30:56
  Speaker 2: it's also scares me a little bit. I don't know
• 31:00
  Speaker 2: if I'd ever want to sign up for a study that.
• 31:02
  Speaker 1: Is terrifying, especially if it's computer controlled, which means eventually
• 31:05
  Speaker 1: there'll be an app for that where you can like
• 31:07
  Speaker 1: shut off parts of your brain.
• 31:08
  Speaker 2: This is how the AI win.
• 31:13
  Speaker 1: The computer gremlins.
• 31:14
  Speaker 2: So we've talked about electricity, We've talked about magnetism and
• 31:18
  Speaker 2: the way the two are like different sides of the
• 31:21
  Speaker 2: same coin. Are there other forces out there that you
• 31:25
  Speaker 2: know I could taste or touch or smell or know about.
• 31:30
  Speaker 1: Yeah, there are. The sort of next natural one on
• 31:32
  Speaker 1: the list is the weak nuclear force. This is the
• 31:34
  Speaker 1: force that lets us see neutrinos, which for example, have
• 31:38
  Speaker 1: no electric charge, no magnetic field, cannot be seen at
• 31:41
  Speaker 1: all with electromagnetism, but neutrinos carry a weak charge, a
• 31:46
  Speaker 1: different kind of charge, not electrical charge, but a weak charge,
• 31:50
  Speaker 1: so they interact via the weak force, which is a
• 31:53
  Speaker 1: very different kind of force. It doesn't use photons to interact.
• 31:56
  Speaker 1: That has wn z bosons, and it's called the weak force.
• 32:00
  Speaker 1: It's not nearly as powerful as electromagnetism. It's much much weaker,
• 32:04
  Speaker 1: but it does have an impact on our life and universe.
• 32:07
  Speaker 1: For example, is the cause of most nuclear decay as
• 32:11
  Speaker 1: neutrons turn into protons, for example, via beta decay, which
• 32:15
  Speaker 1: is a weak process. So a lot of radioactivity is
• 32:19
  Speaker 1: due to the weak force.
• 32:20
  Speaker 2: Now you say it is a weak force, and then you,
• 32:24
  Speaker 2: in the same sentence say radioactivity, which to me is
• 32:28
  Speaker 2: something that is powerful and scary. How can a weak
• 32:32
  Speaker 2: force be behind something like something being radioactive, which can
• 32:36
  Speaker 2: really mess with you.
• 32:37
  Speaker 1: Yeah, it's a great question. By week, we really don't
• 32:40
  Speaker 1: mean that it's not capable of giving particles high speed.
• 32:44
  Speaker 1: That it doesn't mean that it can't give particles a kick.
• 32:46
  Speaker 1: It means that it's less likely to wake up and
• 32:49
  Speaker 1: do its thing, like if you shoot a nutrino through
• 32:52
  Speaker 1: a wall, it will mostly ignore those other particles because
• 32:55
  Speaker 1: it has a very low probability of interacting. So the
• 32:58
  Speaker 1: weakness is really about a chances of it happening, not
• 33:02
  Speaker 1: about the force that it can apply. That's why neutrinos
• 33:04
  Speaker 1: can pass through like a light year of lead without
• 33:07
  Speaker 1: kicking into any particle. But if they do, if one
• 33:10
  Speaker 1: of those particles rolls the right number on the many
• 33:12
  Speaker 1: billion sided die and actually does interact with that neutrino,
• 33:16
  Speaker 1: it can get a substantial kick. You can have fairly
• 33:19
  Speaker 1: high energy interactions using the weak force. It's more about
• 33:23
  Speaker 1: the chances of it happening than the power that it
• 33:25
  Speaker 1: can transmit.
• 33:26
  Speaker 2: I feel like you guys should have named this the
• 33:29
  Speaker 2: shy forces then, because that neutrino is just shy, but
• 33:33
  Speaker 2: when you get to know it be pretty powerful.
• 33:36
  Speaker 1: Yeah, exactly.
• 33:37
  Speaker 2: So if there are weak forces, can I guess that
• 33:41
  Speaker 2: there are also strong forces.
• 33:43
  Speaker 1: Yes, this is one place in which maybe particle physics
• 33:46
  Speaker 1: has done a good job, because there is the force.
• 33:49
  Speaker 1: We call these strong nuclear force. This affects particles that
• 33:52
  Speaker 1: have a strong nuclear charge, which we also call color.
• 33:56
  Speaker 1: To be extra confusing, so some particles like quarks, for example,
• 34:00
  Speaker 1: have color.
• 34:01
  Speaker 2: Get your own word.
• 34:02
  Speaker 1: Wait a minute, there's red, green, and blue quarks. Any
• 34:06
  Speaker 1: particle that has color will feel the strong nuclear force.
• 34:10
  Speaker 1: The strong nuclear force super duper powerful, lots of energy,
• 34:14
  Speaker 1: and very likely to interact. Basically, almost always does interact,
• 34:18
  Speaker 1: and so quarks are never seen by themselves. They are
• 34:21
  Speaker 1: always busy interacting with each other and forming bound states
• 34:24
  Speaker 1: like protons and neutrons, which are just collections of quarks
• 34:29
  Speaker 1: wrapped together into a blob. So the strong nuclear force
• 34:31
  Speaker 1: is very, very powerful and fundamental to the way our
• 34:34
  Speaker 1: whole universe works because it's built the proton, which is
• 34:37
  Speaker 1: really the building block of the atom, which is pretty
• 34:39
  Speaker 1: important when you're making a chicken dinner.
• 34:41
  Speaker 2: All. Let my husband know to not forget the atoms
• 34:45
  Speaker 2: in the chicken dinner. So, because this is such a
• 34:47
  Speaker 2: strong force, is that why you know splitting an atom
• 34:51
  Speaker 2: causes such a huge effect?
• 34:54
  Speaker 1: Yes, exactly. And this can be a little confusing because
• 34:57
  Speaker 1: we think of the strong force as holding a proton
• 34:59
  Speaker 1: together or holding a neutron together, and technically those objects
• 35:03
  Speaker 1: are color neutral, they don't have an overall strong charge
• 35:06
  Speaker 1: to them. But the strong force is also capable of
• 35:09
  Speaker 1: holding those protons and neutrons together into the nucleus because
• 35:13
  Speaker 1: while overall the proton is not charged and the neutron
• 35:16
  Speaker 1: is not charged, there is a little bit of residual charge,
• 35:20
  Speaker 1: because these quarks are not all on top of each other,
• 35:22
  Speaker 1: they're in different places inside the protons, So like one
• 35:25
  Speaker 1: side of a proton will have a little bit of
• 35:27
  Speaker 1: color charge and the other side will have a little
• 35:29
  Speaker 1: bit of color charge, and that's enough to stick the
• 35:31
  Speaker 1: protons and neutrons together. And then when you split the atom,
• 35:34
  Speaker 1: you're breaking those bonds and releasing energy. So even just
• 35:38
  Speaker 1: this little extra residual bit of the strong force is
• 35:41
  Speaker 1: powerful enough to power nuclear weapons and nuclear reactors and
• 35:44
  Speaker 1: all sorts of crazy stuff. It's a very strong force.
• 35:47
  Speaker 2: It makes me think of two velcrow balls. Like the
• 35:51
  Speaker 2: balls themselves don't necessarily have any attraction to each other,
• 35:56
  Speaker 2: but the velcrow little individual hooks and tiny tiny loops
• 36:01
  Speaker 2: do have some attraction to each other. Well, it's not
• 36:04
  Speaker 2: a great metaphor because we're talking about velcrow versus quarks,
• 36:08
  Speaker 2: but like the quirks that make up the proton and
• 36:11
  Speaker 2: neutrons are attracted to each other, have a force pulling
• 36:14
  Speaker 2: them together. So they're like the parts are greater than
• 36:18
  Speaker 2: the sum of the parts, which is the opposite of
• 36:20
  Speaker 2: what it usually is.
• 36:22
  Speaker 1: Yeah, exactly. It's fascinating and it's complicated. We don't really
• 36:25
  Speaker 1: understand how the nucleus holds together. In some cases, you
• 36:28
  Speaker 1: have all these protons which are being pushed apart by
• 36:30
  Speaker 1: their electrical charges but being held together by the nuclear force.
• 36:34
  Speaker 1: As you add more neutrons in there, it helps keep
• 36:36
  Speaker 1: the protons further apart, so it makes it more stable.
• 36:39
  Speaker 1: There's a whole field of nuclear physics about understanding how
• 36:42
  Speaker 1: big a nucleus you can make, and which ones are
• 36:44
  Speaker 1: stable and which ones are not. Not something we understand.
• 36:46
  Speaker 1: Because the strong force is also really really hard to
• 36:49
  Speaker 1: do calculations with because it's so powerful, little changes in
• 36:53
  Speaker 1: position can totally throw off your calculation.
• 36:56
  Speaker 2: I mean that seems like it puts you in a
• 36:58
  Speaker 2: very difficult position as particle physicists and being able to
• 37:02
  Speaker 2: measure strong nuclear forces.
• 37:05
  Speaker 1: It is indeed very difficult. It's difficult to do the
• 37:07
  Speaker 1: theoretical calculations and difficult to make the measurements, which is
• 37:10
  Speaker 1: why the strong force is an enduring mystery in particle physics.
• 37:13
  Speaker 2: Well figure it out, you guys. What are we paying
• 37:16
  Speaker 2: you for? So is that it? Are there any other
• 37:19
  Speaker 2: forces that I should know about?
• 37:21
  Speaker 1: There's one more force which may not even be a force,
• 37:24
  Speaker 1: and that's gravity. Gravity is something we often think about
• 37:27
  Speaker 1: as a force colloquially, though in relativity we describe it
• 37:31
  Speaker 1: instead as the impact of the curvature of space time
• 37:35
  Speaker 1: changing the way things move and changing the relative distances
• 37:38
  Speaker 1: between things. But in our daily life and our experience,
• 37:41
  Speaker 1: we still sort of see it as a force because
• 37:43
  Speaker 1: we can't see that curvature of space time directly. Instead,
• 37:46
  Speaker 1: we just experience it as if there was a force there.
• 37:50
  Speaker 1: And gravity is very powerful in terms of building the universe,
• 37:53
  Speaker 1: like the Earth is held together because of gravity. The
• 37:55
  Speaker 1: whole structure of the universe is because of gravity. But
• 37:59
  Speaker 1: it's also dooper weak, Like you can overcome the gravity
• 38:03
  Speaker 1: of the Earth using the power of your muscles. Right
• 38:05
  Speaker 1: every time you leap off the surface of the Earth,
• 38:08
  Speaker 1: you were defeating an entire planet size gravitational field with
• 38:12
  Speaker 1: just your impressive quads.
• 38:14
  Speaker 2: Yeah, take that Earth.
• 38:17
  Speaker 1: But we don't know fundamentally if gravity is just the
• 38:20
  Speaker 1: curvature of space time or if it's a quantum force
• 38:22
  Speaker 1: like the other ones. There's a whole group of people
• 38:24
  Speaker 1: working on quantum gravity try to understand how to unify
• 38:27
  Speaker 1: gravity with the other forces for which we have quantum theories.
• 38:31
  Speaker 2: Yeah, and it's interesting because we can kind of feel gravity,
• 38:35
  Speaker 2: and I don't just mean like when you've impacted on
• 38:38
  Speaker 2: the ground, because you're just sort of feeling the ground
• 38:40
  Speaker 2: at that point, but like when you're weightless, if you've
• 38:43
  Speaker 2: ever been on a roller coaster or you feel kind
• 38:46
  Speaker 2: of weightless, it's not so much maybe that we're feeling
• 38:49
  Speaker 2: the gravity, but we're feeling acceleration or the lack thereof
• 38:53
  Speaker 2: when we're expecting it. But there's definitely sort of some
• 38:56
  Speaker 2: senses that we have that gravity definitely impacts.
• 39:00
  Speaker 1: Yeah, and we'll dig into that in a minute. And then,
• 39:03
  Speaker 1: of course there are forces we don't yet know about.
• 39:06
  Speaker 1: These are the ones we've experienced and categorized and described,
• 39:09
  Speaker 1: but there could be other forces out there in the universe.
• 39:11
  Speaker 1: Remember that most of the matter in the universe is
• 39:14
  Speaker 1: not the kind of matter that makes us up and
• 39:15
  Speaker 1: that we experience. It's dark matter, and dark matter might
• 39:19
  Speaker 1: have some other kind of forces that it uses to
• 39:21
  Speaker 1: obeying against itself that we have never experienced.
• 39:25
  Speaker 2: So you're saying there are like physics gremlins that we
• 39:28
  Speaker 2: just don't really know about.
• 39:31
  Speaker 1: Maybe the aliens are physics gremlins.
• 39:34
  Speaker 2: So we've talked about physics forces. Now I want to
• 39:36
  Speaker 2: talk about biology a little bit. I want to talk
• 39:39
  Speaker 2: about how physics interacts with our bodies.
• 39:42
  Speaker 1: Absolutely, let's talk about what we can sense and how
• 39:46
  Speaker 1: that works, how we map that to these fundamental forces.
• 39:49
  Speaker 1: And I think we should start with vision because to me,
• 39:50
  Speaker 1: it's one of the most fundamental senses. You know, it's
• 39:52
  Speaker 1: the way that we sort of build our model of
• 39:55
  Speaker 1: the world out there by looking around us and imagining
• 39:57
  Speaker 1: where stuff is.
• 39:58
  Speaker 2: Yeah, humans are interests because we are very vision focused,
• 40:05
  Speaker 2: I think. So vision is something that's very important to
• 40:09
  Speaker 2: us in terms of our socialization and our societies. And
• 40:14
  Speaker 2: you know, of course, like there are people who operate
• 40:17
  Speaker 2: without vision and they make it work, but sort of
• 40:20
  Speaker 2: evolutionarily speaking, vision is a very sort of fundamental sense
• 40:26
  Speaker 2: for human beings and how our socialization has developed, like
• 40:31
  Speaker 2: in terms of being able to see each other's faces,
• 40:34
  Speaker 2: understand each other's emotions, kind of these maps we have
• 40:37
  Speaker 2: in our brains of what a face should look like.
• 40:41
  Speaker 2: So it's really it's an interesting thing because there are
• 40:43
  Speaker 2: a lot of animals, There are a lot of creatures
• 40:45
  Speaker 2: in the world that are not as visually dependent as
• 40:48
  Speaker 2: humans are in terms of their sort of survival strategies.
• 40:52
  Speaker 1: Yeah, it's incredible sort of how we build our mental
• 40:55
  Speaker 1: maps of the world and how that's informed by what
• 40:57
  Speaker 1: we see what we don't see. But let's break it
• 40:59
  Speaker 1: down and think about like the journey of a photon
• 41:01
  Speaker 1: in terms of the fundamental physics. Of course, the photon itself,
• 41:05
  Speaker 1: the thing that you're seeing is a little ripple in
• 41:07
  Speaker 1: an electromagnetic field. It's created by an electron maybe that's
• 41:11
  Speaker 1: jumped down an energy level or whizzed around in the
• 41:14
  Speaker 1: universe and gotten bent by a field and had to
• 41:16
  Speaker 1: change directions. So given off a photon, that photon is
• 41:19
  Speaker 1: now a little pulse of energy in the electromagnetic field
• 41:22
  Speaker 1: wiggling through the universe at the speed of light. And
• 41:25
  Speaker 1: that is in the end, what we're trying to sense, right,
• 41:27
  Speaker 1: And so that photon then hits your eyeball, and there's
• 41:30
  Speaker 1: a lot of Rube Goldberg like mechanical bits that happen there.
• 41:34
  Speaker 1: When the photon hits your eyeball, you might say like, okay,
• 41:37
  Speaker 1: photon is electromagnetics, so therefore that's the force that powers it.
• 41:40
  Speaker 1: But you also have to dig into like how we
• 41:42
  Speaker 1: actually see the photon, not just what the photon itself
• 41:46
  Speaker 1: is made out of.
• 41:47
  Speaker 2: Yeah, exactly. So it's really interesting too, because our entire
• 41:51
  Speaker 2: eye is kind of one of the more elegant things
• 41:55
  Speaker 2: that evolution has produced, that there is all of these
• 42:00
  Speaker 2: structures that are specifically designed to be able to capture
• 42:07
  Speaker 2: and focus light. Of course, like we have the cornea,
• 42:11
  Speaker 2: which essentially like allows the light to pass through and
• 42:15
  Speaker 2: then it bends it and then it hits that lens
• 42:18
  Speaker 2: which can focus the light onto the back of the eye.
• 42:21
  Speaker 2: And the back of the eye is called the retina,
• 42:24
  Speaker 2: and the retina has all of these photoreceptors on it,
• 42:27
  Speaker 2: the rods and the cones. The iris is that colorful
• 42:33
  Speaker 2: ring around your pupil, and that focuses the constriction and
• 42:39
  Speaker 2: opening of the iris determines how much light is lit in.
• 42:44
  Speaker 2: And the pupil is not really a thing, it's the
• 42:46
  Speaker 2: absence of a thing. The pupil is just the hole
• 42:49
  Speaker 2: that leads into your eye.
• 42:52
  Speaker 1: Yes, you have this sort of squishy muscular sack that
• 42:55
  Speaker 1: controls where those photons go and how they get back
• 42:59
  Speaker 1: to the receptor, which is the part that's really doing
• 43:01
  Speaker 1: the sensing. But you can't just ignore the eyeball because
• 43:04
  Speaker 1: also it's a filter, right, It controls the amount of light,
• 43:07
  Speaker 1: so it rejects some photons. It also filters them by frequency.
• 43:11
  Speaker 1: Not all frequencies of light. See, the eyeball is equally transparent.
• 43:15
  Speaker 1: Some of them don't make it to the back of
• 43:16
  Speaker 1: the eyeball, and some of them do, which is why
• 43:19
  Speaker 1: you can and cannot see some frequencies of light.
• 43:22
  Speaker 2: That's right, Like, that's why we can't see UV light
• 43:25
  Speaker 2: generally because the cornea filters it out. That's why people
• 43:30
  Speaker 2: who have had surgery on their eyes where they're removing
• 43:33
  Speaker 2: a part of the cordia and replacing it with an
• 43:36
  Speaker 2: artificial cornea actually sometimes can see UV light because that
• 43:41
  Speaker 2: natural corneal filter is no longer there.
• 43:44
  Speaker 1: Wow, that's crazy, like a whole new window onto the universe.
• 43:47
  Speaker 1: But the actual sensing motion itself is amazing to mean,
• 43:50
  Speaker 1: because it's like a tiny little machine. I mean, you
• 43:53
  Speaker 1: imagine this whole thing is going to be electrical. They
• 43:55
  Speaker 1: have a pulse of electromagnetism which is then received and
• 43:58
  Speaker 1: turned into an electrical pulse. The nerves, et cetera, et cetera.
• 44:01
  Speaker 1: The whole thing's got to be electrical, right, But at
• 44:03
  Speaker 1: the heart of it is a little machine. These proteins,
• 44:06
  Speaker 1: which are fundamental building blocks of biology in the end,
• 44:09
  Speaker 1: are little molecular machines they like. And what a photoreceptor
• 44:12
  Speaker 1: fundamentally is is a protein that when a photon hits
• 44:15
  Speaker 1: it undergoes a conformational change. It's like it flips a
• 44:19
  Speaker 1: switch on this protein. It's kind of incredible to me
• 44:22
  Speaker 1: that the whole thing is so mechanical.
• 44:24
  Speaker 2: Yeah, it just kind of like snaps into place, and
• 44:28
  Speaker 2: that snapping is actually what causes the signal to be
• 44:33
  Speaker 2: sent to the nerve, and then that goes to the nerve.
• 44:37
  Speaker 2: Like all of these little smaller nerves collect into that
• 44:41
  Speaker 2: nerve bundle at the back of your eye. That's actually
• 44:44
  Speaker 2: where your blind spot is, and all of that goes
• 44:46
  Speaker 2: to the occipital lobe in your brain. But it all
• 44:49
  Speaker 2: starts with that snapping action of the photoreceptive cell.
• 44:55
  Speaker 1: It's incredible how important it is that things really move right.
• 44:59
  Speaker 1: We're used to thinking about solve state technology and hard
• 45:02
  Speaker 1: drives that don't spin is lasting longer, But in order
• 45:05
  Speaker 1: for you to see, you have to have these proteins
• 45:07
  Speaker 1: in your eye that flip back and forth. Right, they
• 45:10
  Speaker 1: flip when they get hit by a photon, and they
• 45:11
  Speaker 1: flip back quickly so you can see a new picture.
• 45:14
  Speaker 1: It's like having all these little mechanical shutters worrying inside
• 45:17
  Speaker 1: your eyeball at all times.
• 45:19
  Speaker 2: And depending on the type of cell, it responds to
• 45:23
  Speaker 2: the different wavelengths of light. So that's how we can
• 45:25
  Speaker 2: distinguish color, right, Like, if we didn't have that ability
• 45:30
  Speaker 2: to distinguish between wavelengths of light, we can only kind
• 45:33
  Speaker 2: of understand whether there's light or not. But because they
• 45:36
  Speaker 2: are specifically able to have that snapping movement to maybe
• 45:41
  Speaker 2: red light to green light, to blue light, or some
• 45:44
  Speaker 2: combination of that, like some sensitivity, it's usually on a spectrum.
• 45:48
  Speaker 2: That's how we are able to not only be able
• 45:51
  Speaker 2: to tell the difference between those types of wavelengths of light,
• 45:56
  Speaker 2: but to build a complex repertoire of a whole gray
• 46:00
  Speaker 2: of light, like we could in theory see like an
• 46:04
  Speaker 2: almost infinite combination of different types of wavelengths hitting our
• 46:09
  Speaker 2: eyes causing that reaction, and then our brain is the
• 46:13
  Speaker 2: thing that calculates like what we actually see, how we
• 46:16
  Speaker 2: actually interpret that color. But it's thanks to this mechanical
• 46:22
  Speaker 2: ability of those cells to respond differently to different wavelengths
• 46:26
  Speaker 2: of light. And so you'll have a cell that does
• 46:28
  Speaker 2: not respond to a longer wavelength of light, but that
• 46:33
  Speaker 2: same cell responds to a shorter wavelength of light, or
• 46:37
  Speaker 2: a different cell that only responds to longer wavelengths of light.
• 46:40
  Speaker 2: So it's that combination of those differentiated cells that allows
• 46:44
  Speaker 2: you to see complex color.
• 46:45
  Speaker 1: Yeah, it's sort of like frequency triangulation. You can figure
• 46:49
  Speaker 1: out by understanding how much each of them was triggered
• 46:51
  Speaker 1: where the real frequency was, which gives you the ability
• 46:54
  Speaker 1: to sense the infinite spectrum of photons. But even though
• 46:58
  Speaker 1: it is mechanical, even though you have all these little
• 47:00
  Speaker 1: machines worrying inside your eyeball all the time, which if
• 47:03
  Speaker 1: you're really quiet, maybe you could listen to and hear,
• 47:05
  Speaker 1: in the end, it is still electro mechanical because all
• 47:09
  Speaker 1: these things are chemical, like the protein structures and the
• 47:12
  Speaker 1: way the protein moves, the way a respond to the
• 47:15
  Speaker 1: photon is in the end, all because of the atomic bonds.
• 47:19
  Speaker 1: The way these proteins are built, the way they can
• 47:21
  Speaker 1: settle into various states, all come down to how the
• 47:23
  Speaker 1: atoms inside those protons are bonded with each other where
• 47:27
  Speaker 1: they like to be, where the lowest energy states are.
• 47:29
  Speaker 1: And that's all due to the atomic bonds which comes
• 47:32
  Speaker 1: from the electron the whizzing around between these nuclei. So
• 47:35
  Speaker 1: in the end, the entire chain here really is just
• 47:38
  Speaker 1: due to electromagnetism.
• 47:41
  Speaker 2: It's like an even tinier Roob Goldberg machine inside of
• 47:44
  Speaker 2: the tiny Roob Goldberg machine's Roob Goldberg machines all the
• 47:48
  Speaker 2: way down, which is a hard thing to say. The
• 47:51
  Speaker 2: words don't come out of my mouth very well.
• 47:53
  Speaker 1: So it's a pulso electromagnetism which then gets converted via
• 47:57
  Speaker 1: a little machine which is built on electromagnetism, into an
• 48:00
  Speaker 1: electromagnetic pulse in your nerves. So it's sort of like
• 48:02
  Speaker 1: a Rube Goldberg zapping machine, right.
• 48:05
  Speaker 2: And then once it hits your brain, of course, the
• 48:07
  Speaker 2: electromagnetic elements of the brain, it is the pattern of
• 48:11
  Speaker 2: the synapses firing. You have some kind of difference in
• 48:15
  Speaker 2: electrical potential between two neurons and then that causes firing
• 48:19
  Speaker 2: across the synapse of transfer neurotransmitters, and it's that pattern
• 48:24
  Speaker 2: of firing that gives you the conscious experience of the.
• 48:29
  Speaker 1: Color exactly, and your whole visual experience of the world
• 48:32
  Speaker 1: rests on electromagnetism. Without those electrons and their little magnetic properties,
• 48:37
  Speaker 1: you couldn't see anything.
• 48:39
  Speaker 2: I feel like this is a commercial for electromagnetism. Electromagnetism,
• 48:45
  Speaker 2: you couldn't do anything without it.
• 48:48
  Speaker 1: I am indeed a shill for big electron.
• 48:50
  Speaker 2: Well, we are going to take a quick break, but
• 48:53
  Speaker 2: you know what, we couldn't have taken a quick break
• 48:55
  Speaker 2: without electromagnetism. So here's a word from our sponsor, electromagnetism.
• 49:14
  Speaker 2: All right, so we are back. I hope you've all
• 49:17
  Speaker 2: purchased a big box of electromagnetism. I don't even know
• 49:21
  Speaker 2: what that would look like, a bunch of magnets and
• 49:24
  Speaker 2: light bulbs something. But yeah, let's talk about more senses
• 49:28
  Speaker 2: and how they work, how this complex dance between the
• 49:33
  Speaker 2: world of the physical and then our brains and our
• 49:36
  Speaker 2: sensory organs kind of interact.
• 49:39
  Speaker 1: Yeah, let's see if we can escape the little electromagnetic
• 49:41
  Speaker 1: grimlins and find out if other forces play important roles
• 49:45
  Speaker 1: in our senses in the universe. And maybe next we
• 49:47
  Speaker 1: should talk about the one that you're experiencing right now,
• 49:49
  Speaker 1: the one you're using to hear our voices. Sound. What
• 49:53
  Speaker 1: sound is and how we experience it. Sound waves are
• 49:56
  Speaker 1: just molecules bumping into each other. Soundwaves are not fun
• 50:00
  Speaker 1: mental properties of the universe. The way a photon is
• 50:02
  Speaker 1: a photon is a ripple in the electromagnetic field, a
• 50:05
  Speaker 1: sound wave is a ripple in something else that already
• 50:08
  Speaker 1: exists in the universe, matter in the universe. So if
• 50:11
  Speaker 1: you imagine like a table filled with ping pong balls
• 50:14
  Speaker 1: and you push on the ping pong balls on your side,
• 50:16
  Speaker 1: they're gonna push on the next set of ping pong ball,
• 50:18
  Speaker 1: to push on the next set, and eventually they'll fall
• 50:21
  Speaker 1: off the other side of the table. So sound is
• 50:23
  Speaker 1: really just like that. It's pressure waves in air or
• 50:26
  Speaker 1: in metal, or in water, or in any kind of
• 50:29
  Speaker 1: matter that squeeze together as bonded enough together for one
• 50:33
  Speaker 1: bit to push on another bit.
• 50:35
  Speaker 2: It's like a Newton's cradle and then the final ball
• 50:38
  Speaker 2: sor it's inside your ear, the little delicate organs that
• 50:43
  Speaker 2: help you experience sound.
• 50:44
  Speaker 1: And that's why sound requires some kind of matter medium. Right,
• 50:48
  Speaker 1: you can't have sound in a perfect vacuum because there's
• 50:50
  Speaker 1: nothing to push whereas you could have photons because photons
• 50:54
  Speaker 1: are ripples in the fundamental electromagnetic fields, which are always there,
• 50:58
  Speaker 1: no matter how much stuff you suck out of your chamber.
• 51:01
  Speaker 2: So when they say that there's no sound in space,
• 51:04
  Speaker 2: there's really no sound. Like It's not like if a
• 51:07
  Speaker 2: tree falls in a forest and no one's around, it's like, well,
• 51:10
  Speaker 2: it does make a sound because it is pushing the
• 51:14
  Speaker 2: air around it. So technically, if what we're calling sound
• 51:18
  Speaker 2: is the wave of molecules bonking into each other, it
• 51:22
  Speaker 2: does exist in a forest, but it really does not
• 51:25
  Speaker 2: exist in space.
• 51:26
  Speaker 1: Yeah, physics would say that pressure waves are created in
• 51:28
  Speaker 1: the air when a tree falls in the forest, but
• 51:31
  Speaker 1: it doesn't impact anybody's sensors. Is it really a sound
• 51:34
  Speaker 1: or is it just pressure waves? I think that's the
• 51:36
  Speaker 1: philosophical question, but the physics question for space. Actually, the
• 51:39
  Speaker 1: answer is that sound does exist in outer space because
• 51:42
  Speaker 1: space is not a vacuum. There are particles out there,
• 51:45
  Speaker 1: electrons and protons constantly whizzing around. Now much much lower density,
• 51:50
  Speaker 1: of course than anything we experience on Earth, but there
• 51:53
  Speaker 1: are particles out there, and you can push on them,
• 51:55
  Speaker 1: and you can make pressure waves in the solar wind,
• 51:59
  Speaker 1: for example, So technically there is sound in outer space,
• 52:02
  Speaker 1: so feel free to scream if you're attacked by the
• 52:04
  Speaker 1: electromagnetic gremlins on your next space voyage.
• 52:07
  Speaker 2: So did Star Wars lie to me or not?
• 52:10
  Speaker 1: The question? The answer to that is definitely yes. No
• 52:12
  Speaker 1: matter what we're talking about. Star Wars is a big lie.
• 52:16
  Speaker 1: We've got the force, we've got lightsabers, I mean, the
• 52:18
  Speaker 1: whole thing is just magical realism. I love it, of course,
• 52:21
  Speaker 1: but it's a big lie. So in terms of how
• 52:23
  Speaker 1: we perceive sound, right, we know sound are pressure waves
• 52:26
  Speaker 1: through the air, and we've developed these biomechanical abilities to
• 52:31
  Speaker 1: sense this. And the ear is basically like a complex
• 52:34
  Speaker 1: instrument for focusing and transmitting that energy into a mechanism
• 52:38
  Speaker 1: that your brain can perceive. And there's various parts of
• 52:41
  Speaker 1: the ear. It's really incredibly complicated. The outer ear focuses
• 52:45
  Speaker 1: the sound waves towards the ear drum, which then vibrates. Right,
• 52:48
  Speaker 1: you have this like literal drum inside your ear that's
• 52:51
  Speaker 1: vibrating at the same frequency as these pressure waves. And
• 52:54
  Speaker 1: you might think, oh, well, that's it. You have an
• 52:56
  Speaker 1: ear drum and it's vibrating, You're done. But that's just
• 52:59
  Speaker 1: like step one.
• 52:59
  Speaker 2: Right, And this is also why you do not use
• 53:02
  Speaker 2: Q tips in your ear, because it is a literal physical,
• 53:05
  Speaker 2: stretchy membrane, but it's very delicate, and it needs to
• 53:10
  Speaker 2: be very delicate to pick up on these very like
• 53:13
  Speaker 2: minute vibrations because we can hear soft sounds as well
• 53:17
  Speaker 2: as loud sounds, so it's got to be sensitive to that.
• 53:20
  Speaker 1: So you should always clean your ear drum with a squeegee.
• 53:22
  Speaker 2: Right exactly, you shove a cue tip in too far,
• 53:26
  Speaker 2: you'll actually puncture that ear drum.
• 53:29
  Speaker 1: Oh please don't do that.
• 53:30
  Speaker 2: Yeah, please don't do that. Don't I'm saying not to
• 53:34
  Speaker 2: do that, And.
• 53:35
  Speaker 1: Yet you're giving me a mental image of it happening,
• 53:37
  Speaker 1: which is making me show.
• 53:40
  Speaker 2: So we've shrunk down real tiny, and we're inside your ears.
• 53:45
  Speaker 2: We've found the ear drum, Like what else are we
• 53:48
  Speaker 2: going to find in here?
• 53:49
  Speaker 1: So then in the middle ear, we have these three
• 53:51
  Speaker 1: tiny little bones which basically help transmit those vibrations from
• 53:56
  Speaker 1: the outer ear to the inner ear. And this is
• 53:59
  Speaker 1: a little bit of an engineering called impedance matching. If
• 54:02
  Speaker 1: you want a signal to get transmitted across different kinds
• 54:05
  Speaker 1: of materials without complicated reflections. Then you have to be
• 54:09
  Speaker 1: really careful about how that interface happens so you don't
• 54:11
  Speaker 1: get all sorts of lostiness and reflections which you can
• 54:14
  Speaker 1: echo back on each other. So these are engineered to
• 54:16
  Speaker 1: sort of transform the waves from the ear drum into
• 54:20
  Speaker 1: the inner ear, which has this little tube filled with
• 54:23
  Speaker 1: fluid which can then vibrate. So it's really complicated process
• 54:27
  Speaker 1: with these ear drum and then these three tiny bones,
• 54:30
  Speaker 1: and then finally in the end it's this little spiral,
• 54:32
  Speaker 1: fluid filled tube that you want to vibrate so that
• 54:35
  Speaker 1: you can actually hear something.
• 54:37
  Speaker 2: That's so cool. I mean, in the complexity of the ear,
• 54:42
  Speaker 2: I think can also help us understand where a sound
• 54:46
  Speaker 2: is coming from, like is it coming from behind us?
• 54:49
  Speaker 2: Is it coming from right next to us. We have
• 54:52
  Speaker 2: not just a sense of sound, but a sense of
• 54:55
  Speaker 2: the location of the sound, which is really interesting. In fact,
• 55:00
  Speaker 2: in owls, they have a really unique thing where their
• 55:04
  Speaker 2: ear holes. They don't really have the external ears that
• 55:06
  Speaker 2: humans have, but they have ear holes and one ear
• 55:10
  Speaker 2: hole is actually lower than the other, so they're not symmetrical,
• 55:14
  Speaker 2: and that's to help them specifically be able to tell
• 55:18
  Speaker 2: where sound is coming from. When they are scanning for
• 55:21
  Speaker 2: a sound coming from the ground, because then the difference
• 55:27
  Speaker 2: in where the sound hits like their ear holes helps
• 55:30
  Speaker 2: them triangulate very specifically. Like if they hear a little
• 55:33
  Speaker 2: mouse in a field, they have to triangulate exactly where
• 55:36
  Speaker 2: that mouse is, and having that difference in locations of
• 55:40
  Speaker 2: the ear holes gives them yet another sort of mathematical
• 55:43
  Speaker 2: calculation that their brain can do of this difference of
• 55:46
  Speaker 2: the sound hitting each ear hole, and then they can
• 55:49
  Speaker 2: triangulate where the tasty mouse is and grab it.
• 55:52
  Speaker 1: Yeah, the key is always having different sensors with different
• 55:54
  Speaker 1: capacities allows you to triangulate, and that's fascinating. But every
• 55:57
  Speaker 1: time you say ear holes, it makes me wonder if
• 56:00
  Speaker 1: that's like a big insult that owls use on each other,
• 56:03
  Speaker 1: like they call each other ear holes.
• 56:05
  Speaker 2: You're a real ear hole, Frank.
• 56:07
  Speaker 1: You ate that little mouse and I totally called it.
• 56:12
  Speaker 1: So you have this little spiral, fluid filled tube which
• 56:15
  Speaker 1: is vibrating with the sounds which were created when Katie
• 56:18
  Speaker 1: screamed in space. How do you actually experience that in
• 56:22
  Speaker 1: your brain? Well, there's one more step, which is that
• 56:24
  Speaker 1: there are these little hairs that wiggle and the hairs
• 56:27
  Speaker 1: are in different places in this tube, and the tube
• 56:30
  Speaker 1: is designed so that the sound frequencies will resonate in
• 56:33
  Speaker 1: different parts of the tube. So a certain frequency, like
• 56:36
  Speaker 1: the really highest sounds in Katie's scream, will land in
• 56:40
  Speaker 1: a different place than this tube than the lower frequencies.
• 56:43
  Speaker 1: When she's like mostly given up, the ghost will land
• 56:45
  Speaker 1: in a different spot. And so different hairs get wiggled
• 56:48
  Speaker 1: by different frequencies, and then that sends signals to your brain.
• 56:52
  Speaker 1: The different hairs send different signals, and your brain is like, oh,
• 56:55
  Speaker 1: that was a lower frequency scream or a higher frequency scream.
• 56:58
  Speaker 2: Right, And the difference is ear structure based on what
• 57:02
  Speaker 2: animal you are determines whether you can hear higher or
• 57:06
  Speaker 2: lower frequency, Like elephants are really good at hearing really
• 57:10
  Speaker 2: low frequencies that we cannot hear with our dinky little
• 57:14
  Speaker 2: human ears, and dogs can hear higher frequencies that we
• 57:18
  Speaker 2: cannot hear with Like if you have a dog whistle
• 57:20
  Speaker 2: not talking about someone doing something naughty and pretending not
• 57:24
  Speaker 2: to it's like the very high frequency sound, your dog
• 57:28
  Speaker 2: will hear it and we won't. Younger people will hear
• 57:31
  Speaker 2: higher frequency than older people because older people after we
• 57:35
  Speaker 2: go to enough rock concerts, we start to become less
• 57:40
  Speaker 2: sensitive to high frequency sound because of damage we've actually
• 57:43
  Speaker 2: done to our ears.
• 57:44
  Speaker 1: It's sort of the opposite of what happens in a band.
• 57:47
  Speaker 1: Like the bigger instruments like the tuba can make deeper
• 57:50
  Speaker 1: sounds because they physically have to be larger to contain
• 57:53
  Speaker 1: the longer wavelength resonance modes there, and the little piccolo
• 57:57
  Speaker 1: like the mini flute, is super duper kind, so it
• 58:00
  Speaker 1: can get to those really high sounds which have shorter wavelengths.
• 58:04
  Speaker 1: In the same way, bigger ears can hear deeper sounds
• 58:07
  Speaker 1: lower wavelengths, and tiny ears can hear higher sounds at
• 58:10
  Speaker 1: higher frequencies. So these hairs wiggle and then they're transmitted
• 58:13
  Speaker 1: into nerve pulses, which is like the fundamental language of
• 58:15
  Speaker 1: how your brain works. So now we have the whole chain, right.
• 58:18
  Speaker 1: The scream happens in outer space, It creates a pressure
• 58:21
  Speaker 1: wave which then gets transformed into different kinds of pressure
• 58:24
  Speaker 1: waves in different parts of your ear, which eventually wiggle
• 58:27
  Speaker 1: those hairs and send a nervous pulse up to your brain.
• 58:30
  Speaker 1: And so in the end, it's all mechanical. Right. Sound
• 58:33
  Speaker 1: is mechanical all to the very very end when it
• 58:35
  Speaker 1: gets transformed into a nervous pulse. But that mechanical interaction
• 58:39
  Speaker 1: in the end is still electromagnetic because how does the
• 58:43
  Speaker 1: machine work. It's no different than those photoreceptors in your eyes,
• 58:46
  Speaker 1: which are little machines. They're built out of electrons, out
• 58:49
  Speaker 1: of atoms. The way they push against each other are
• 58:52
  Speaker 1: electrical forces. Like we started off talking about pingpong balls
• 58:55
  Speaker 1: pushing on each other, how does that happen? How does
• 58:58
  Speaker 1: one air molecule push against another air molecule. Their electrons
• 59:01
  Speaker 1: are repelling each other when they get too close. How
• 59:04
  Speaker 1: does your chair hold you up when you sit on it.
• 59:06
  Speaker 1: It's the mesh of electrical forces holding it together. So
• 59:10
  Speaker 1: the atomic structure which is used to build all of
• 59:13
  Speaker 1: these machines is the fundamental force that allows sound to
• 59:16
  Speaker 1: be transmitted through the universe into your ear holes.
• 59:20
  Speaker 2: So whether it's two ping pong balls hitting each other,
• 59:23
  Speaker 2: or molecules moving through the air and hitting this complex
• 59:27
  Speaker 2: structure inside of your ear, those are both things to
• 59:30
  Speaker 2: electromagnetic forces.
• 59:32
  Speaker 1: Absolutely, it's all electromagnetic forces that constructs the world that
• 59:35
  Speaker 1: we live in and allows machines to have a physical
• 59:39
  Speaker 1: extent and transmit forces to each other. And that's really
• 59:42
  Speaker 1: what sound is. All of mechanical engineering really is electrical.
• 59:45
  Speaker 2: Engineering, speaking of physical things bonking into each other. I
• 59:51
  Speaker 2: believe probably the same force might be behind what happens
• 59:56
  Speaker 2: in the inner ear in terms of your sense of
• 1:00:00
  Speaker 2: balance and acceleration and gravity. It's like why you get
• 1:00:04
  Speaker 2: motion sick, why you feel vertigo or a sense of
• 1:00:08
  Speaker 2: lack of balance, like when you feel slightly off balance.
• 1:00:11
  Speaker 2: Inside these fluid filled chambers in your ear, there's a liquid,
• 1:00:17
  Speaker 2: but suspended in the liquid are actually these tiny calcium
• 1:00:22
  Speaker 2: crystals that can When the movement of these crystals and
• 1:00:27
  Speaker 2: interaction with these tiny nerves, that information is sent to
• 1:00:32
  Speaker 2: your brain and it tells you like, hey, I'm moving,
• 1:00:35
  Speaker 2: I'm accelerating. I'm on a roller coaster. Oh no, i
• 1:00:39
  Speaker 2: hate roller coasters. So like, the ear not only is
• 1:00:42
  Speaker 2: a complex sound detector, it is also a movement kind
• 1:00:47
  Speaker 2: of like gravity and acceleration detector, which is really cool.
• 1:00:51
  Speaker 1: Yes, absolutely, the ear is capable of measuring acceleration right
• 1:00:55
  Speaker 1: as these crystals move to the liquid, or as the
• 1:00:57
  Speaker 1: liquid slashes around inside your ear and touches different parts
• 1:01:01
  Speaker 1: of it. Your brain can tell that you're being accelerator
• 1:01:03
  Speaker 1: or you're upside down. It's sort of like if you
• 1:01:05
  Speaker 1: had a ball inside the back of a truck. When
• 1:01:07
  Speaker 1: you hit the acceleration on the truck, then the ball
• 1:01:10
  Speaker 1: gets left behind, it hits the back of the truck.
• 1:01:12
  Speaker 1: When you hit the brakes on the truck, the ball
• 1:01:14
  Speaker 1: will roll towards the front of the truck bed. If
• 1:01:16
  Speaker 1: you're inside the bed of the truck, you can tell
• 1:01:18
  Speaker 1: when the gas is being pressed and when the brake
• 1:01:20
  Speaker 1: is being pressed just by watching the ball. In the
• 1:01:23
  Speaker 1: inner part of your ear basically works like that, and
• 1:01:25
  Speaker 1: it allows you to measure acceleration and gravity and what's
• 1:01:28
  Speaker 1: up and what's down. And that raised an interesting question
• 1:01:31
  Speaker 1: like what's the fundamental force involved there. We know there
• 1:01:33
  Speaker 1: are electromagnetic signals, and we know that the structure of
• 1:01:37
  Speaker 1: the inner ear and all the things that it works
• 1:01:39
  Speaker 1: on our little machines that are built with electromagnetic forces.
• 1:01:42
  Speaker 1: But in the end, it's sensing gravity, right, It's sensing
• 1:01:45
  Speaker 1: acceleration and motion, and so that's an interesting combination like
• 1:01:48
  Speaker 1: gravity I think really does play a role there. We're
• 1:01:51
  Speaker 1: using electromagnetics based sensors to observe gravity and acceleration.
• 1:01:56
  Speaker 2: Yeah, it's so interesting. It's that like, gravity is this
• 1:02:00
  Speaker 2: unique thing in the universe that may not even be
• 1:02:03
  Speaker 2: a force, and yet we still have an ability to
• 1:02:07
  Speaker 2: detect it with our ears. We've evolved this complex system
• 1:02:11
  Speaker 2: that is basically an accelerometer like inside of our heads.
• 1:02:16
  Speaker 1: It's amazing and very useful. And if it ever gets
• 1:02:19
  Speaker 1: messed up while the world feels like an unpleasant.
• 1:02:21
  Speaker 2: Place, yeah, that is like a dysfunction of those like
• 1:02:26
  Speaker 2: little ear crystals is thought to be behind disorders like vertigo.
• 1:02:30
  Speaker 2: I feel like we've covered the ears, not literally covered
• 1:02:33
  Speaker 2: the ears, because you still want to hear this podcast.
• 1:02:35
  Speaker 2: But let's talk a little bit about smell, because I'm
• 1:02:38
  Speaker 2: smelling that chicken. I do want to go to dinner,
• 1:02:41
  Speaker 2: but I first want to learn about how smell works.
• 1:02:45
  Speaker 1: Smell is super fascinating because in some ways it's much
• 1:02:48
  Speaker 1: more mechanical than the other senses, but it's also much
• 1:02:51
  Speaker 1: more complicated. Like sound and vision in the ends can
• 1:02:54
  Speaker 1: be expressed as observing different frequencies of the same thing,
• 1:02:58
  Speaker 1: So you can boil it down to information, right, like
• 1:03:01
  Speaker 1: what frequencies of light are you seeing? What frequencies of
• 1:03:03
  Speaker 1: sound are you hearing. You can look at the equalizer
• 1:03:06
  Speaker 1: on your stereo see like the fundamental building blocks of
• 1:03:08
  Speaker 1: the song that you're hearing, and so it can be
• 1:03:10
  Speaker 1: digitized and it can be transmitted. You can have like
• 1:03:12
  Speaker 1: electronic vision and hearing right microphones and cameras and screens
• 1:03:17
  Speaker 1: and all that stuff. The same is not true for
• 1:03:19
  Speaker 1: smell because it's much more complex. It's not just a
• 1:03:22
  Speaker 1: single frequency spectrum along which every smell sits. It's a
• 1:03:26
  Speaker 1: super high dimensional space. Essentially, smell is detecting individual molecules
• 1:03:32
  Speaker 1: of different kinds. You know, you're smelling a poop molecule,
• 1:03:35
  Speaker 1: you're smelling a chicken molecule, you're smelling molecules from flowers. Really,
• 1:03:39
  Speaker 1: smell is detecting super dilute presence of specific molecules in
• 1:03:43
  Speaker 1: the air. It's really incredible that it works at all.
• 1:03:46
  Speaker 2: This is one of the things that like, it's so
• 1:03:49
  Speaker 2: hard for me to understand, and I think it's also
• 1:03:52
  Speaker 2: just hard for experts to understand how smell works, because
• 1:03:56
  Speaker 2: it is one of these things where it's like we
• 1:03:58
  Speaker 2: have just a bunch of receptors and they kind there's
• 1:04:04
  Speaker 2: some sort of lock and key mechanism that happens with
• 1:04:07
  Speaker 2: these molecules and it sends a signal to the brain
• 1:04:11
  Speaker 2: and then we experience that smell and it can be
• 1:04:15
  Speaker 2: way more complicated, even in say like a dog, who
• 1:04:20
  Speaker 2: is able to distinguish massive amount of smells. In fact,
• 1:04:24
  Speaker 2: I would say like a dog's world is probably more
• 1:04:27
  Speaker 2: smell focused than it is vision focused. Of course they
• 1:04:31
  Speaker 2: can see, but smell is probably their primary way they
• 1:04:35
  Speaker 2: experience the world, which is very different from humans.
• 1:04:38
  Speaker 1: Yeah, dogs can be blind and they're like whatever, no
• 1:04:40
  Speaker 1: big deal. As long as I can still smell, I
• 1:04:42
  Speaker 1: can tell who's there and what they're doing, what they
• 1:04:44
  Speaker 1: ate for dinner, like three weeks ago is incredible. And
• 1:04:47
  Speaker 1: it all comes down to these super powerful lock and
• 1:04:50
  Speaker 1: key mechanisms. Basically to detect which molecules are out there,
• 1:04:54
  Speaker 1: what you need is some way to say, like, okay,
• 1:04:56
  Speaker 1: here's a little chicken molecule, or here's a little molecule
• 1:04:58
  Speaker 1: of pasta or whatever. I always want to understand these
• 1:05:01
  Speaker 1: things from the microphysics point of view, like zoom in
• 1:05:03
  Speaker 1: what is really happening? How do you have a sensor
• 1:05:06
  Speaker 1: which reacts to only one kind of molecule and not
• 1:05:08
  Speaker 1: another kind of molecule. So I talked to my wife
• 1:05:11
  Speaker 1: about this, who's a biochemist. She has a pretty deep
• 1:05:13
  Speaker 1: understanding of the fundamental mechanism. And essentially, you have these
• 1:05:16
  Speaker 1: cells in your nose that have membranes in them, like
• 1:05:18
  Speaker 1: every cell does, but you have these proteins which go
• 1:05:21
  Speaker 1: across the membrane. They have some bits that stick out
• 1:05:24
  Speaker 1: on the outside of the cell, and some bits on
• 1:05:26
  Speaker 1: the stick on the inside of the cell, and the
• 1:05:28
  Speaker 1: bits that stick on the outside all have funny, weird shapes,
• 1:05:31
  Speaker 1: so they're basically like the lock that the molecule fits
• 1:05:34
  Speaker 1: into like a key, so they trigger it. So if
• 1:05:37
  Speaker 1: the right molecule comes along and fits into these little
• 1:05:39
  Speaker 1: bits of the protein that stick out past the edge
• 1:05:42
  Speaker 1: of the cell and interacts with it, it can then
• 1:05:44
  Speaker 1: transmit a signal through the cell membrane into the inside
• 1:05:47
  Speaker 1: of the cell and make something happen, and that's how
• 1:05:50
  Speaker 1: you detect it. And then of course you have like
• 1:05:52
  Speaker 1: hundreds or thousands or maybe even more kinds of receptors
• 1:05:56
  Speaker 1: in your nose, so you can smell different kinds of stuff,
• 1:06:00
  Speaker 1: just like a spectrum from red light to green light
• 1:06:02
  Speaker 1: to blue light. It's like a huge list of individual
• 1:06:05
  Speaker 1: different kinds of receptors that can all detect different kinds
• 1:06:08
  Speaker 1: of molecules.
• 1:06:09
  Speaker 2: I mean, it actually kind of reminds me of how
• 1:06:11
  Speaker 2: the immune system works. It's a very similar lock and
• 1:06:13
  Speaker 2: key mechanism, where you have immune cells and they have
• 1:06:18
  Speaker 2: all sorts of surface receptors and they will be able
• 1:06:21
  Speaker 2: to fit with like different kinds of antigens. Like that's
• 1:06:26
  Speaker 2: like the key, and then the surface cell is like
• 1:06:28
  Speaker 2: the lock, and then they fit together. And then once
• 1:06:30
  Speaker 2: that happens, you have a basically chemical chain reaction that
• 1:06:35
  Speaker 2: happens across the membrane and into the cell. So like
• 1:06:38
  Speaker 2: that lock and key mechanism is so important in biology,
• 1:06:42
  Speaker 2: and it's found sort of in all sorts of biological processes,
• 1:06:45
  Speaker 2: including our sense of smell. Like those poop molecules are
• 1:06:49
  Speaker 2: getting real intimate with your cells.
• 1:06:51
  Speaker 1: They're unlocking something deep inside you. But it's even more
• 1:06:55
  Speaker 1: complicated than just a lock and a key, which gives
• 1:06:56
  Speaker 1: you the sense of like a mechanical thing. You might
• 1:06:58
  Speaker 1: be wondering, like, well, who's turn earning the lock? Right,
• 1:07:01
  Speaker 1: It's more complicated than just having the piece fit into
• 1:07:03
  Speaker 1: the right slot. There are electric fields there, right, because
• 1:07:06
  Speaker 1: these atoms have electrons whizzing around. That all has to
• 1:07:10
  Speaker 1: fit in just perfectly so that the atoms like to
• 1:07:12
  Speaker 1: hang out with each other. And then you have to
• 1:07:14
  Speaker 1: have like the right hydrophobic properties. Maybe together the lock
• 1:07:17
  Speaker 1: and the key element like to dispel water, They like
• 1:07:19
  Speaker 1: to push water out, so they fit together really snugly.
• 1:07:22
  Speaker 1: And these bits of these things which are squishy and
• 1:07:24
  Speaker 1: have to have like the right squishiness to click together
• 1:07:26
  Speaker 1: in the right way. And the end, what you're doing
• 1:07:29
  Speaker 1: is transmitting some energy from the molecule into the receptor,
• 1:07:33
  Speaker 1: and that either happens by coming in and hitting it
• 1:07:35
  Speaker 1: or interacting it with it in some way. But it's
• 1:07:37
  Speaker 1: not a deep bond. It's not like the lock and
• 1:07:39
  Speaker 1: the key are forming some new macromolecule through covalent bonding.
• 1:07:43
  Speaker 1: It's more like they're pushing up against each other. But
• 1:07:46
  Speaker 1: as you say, Katy, it's not something we actually understand
• 1:07:48
  Speaker 1: very well. There are all sorts of theories about how
• 1:07:51
  Speaker 1: that energy gets transmitted. There's lock and key mechanism, where
• 1:07:54
  Speaker 1: sort of mechanical transmission of energy is one of them.
• 1:07:56
  Speaker 1: But there's another theory called vibration theory that the molecule
• 1:07:59
  Speaker 1: that comes along is actually emitting a low energy photon
• 1:08:03
  Speaker 1: like an infrared photon as it transitions from one state
• 1:08:06
  Speaker 1: to another, and then that triggers the change of state
• 1:08:09
  Speaker 1: by the receptor, which is moving from one state to
• 1:08:12
  Speaker 1: another by absorbing this photon and doing it through quantum tunneling.
• 1:08:16
  Speaker 1: There's two states. It couldn't otherwise get from one to
• 1:08:19
  Speaker 1: the other. It needs a little bit of boost of energy,
• 1:08:21
  Speaker 1: but doesn't actually have enough energy to go over the hump,
• 1:08:24
  Speaker 1: so it tunnels through that barrier. We have, of course,
• 1:08:26
  Speaker 1: have a whole podcast episode on quantum tunneling. But fundamentally
• 1:08:30
  Speaker 1: the physics involved in smell is not something that we understand,
• 1:08:34
  Speaker 1: which is incredible that it's still an open mystery, right,
• 1:08:37
  Speaker 1: such basic questions of the human experience still not understood
• 1:08:40
  Speaker 1: in terms of the fundamental physics.
• 1:08:42
  Speaker 2: Well right, because I mean fundamental physics are not fully understood,
• 1:08:46
  Speaker 2: and fundamental physics are fundamental to understanding how it interacts
• 1:08:51
  Speaker 2: with biologies. I mean, I think it's just a humbling
• 1:08:54
  Speaker 2: thing to remember that, hey, biology, it is completely linked
• 1:08:57
  Speaker 2: with particle physics, like have a full understanding of biology,
• 1:09:02
  Speaker 2: like we would need to have a full understanding of
• 1:09:05
  Speaker 2: particle physics, so you know, hurry up, you guys figure
• 1:09:08
  Speaker 2: it out.
• 1:09:09
  Speaker 1: And there's so many questions still open about how smell
• 1:09:11
  Speaker 1: works and how these receptors work. My wife Katrina was
• 1:09:14
  Speaker 1: telling me that they find these receptors not just in
• 1:09:16
  Speaker 1: your nose and of course in the back of your mouth,
• 1:09:18
  Speaker 1: but all over your body, like on the palms of
• 1:09:21
  Speaker 1: your hands, inside your body, like in your guts. There
• 1:09:24
  Speaker 1: are these same kinds of receptors, which is like, are
• 1:09:26
  Speaker 1: we smelling our own poop inside our body? Are you
• 1:09:30
  Speaker 1: can smell a flour with your palm when you're holding it.
• 1:09:33
  Speaker 1: These reactions are happening, we just don't always sense them.
• 1:09:36
  Speaker 1: They don't always get converted by our brain into the
• 1:09:40
  Speaker 1: smell sensation.
• 1:09:42
  Speaker 2: Yeah, the gut thing is really interesting because there's definitely
• 1:09:44
  Speaker 2: a lot of information that's sent from your gut to
• 1:09:47
  Speaker 2: your brain and back and forth, and a lot of nerves,
• 1:09:50
  Speaker 2: a lot of neural activity that actually happens in your gut.
• 1:09:53
  Speaker 2: That's why things like ibs or like if you're anxious,
• 1:09:57
  Speaker 2: that can impact your guts functioning and vice versa. But yeah,
• 1:10:01
  Speaker 2: it's I mean, I don't think we know exactly what
• 1:10:04
  Speaker 2: those essentially like smell and taste receptors inside your gut does,
• 1:10:09
  Speaker 2: but it may have something to do with like how
• 1:10:11
  Speaker 2: our bodies regulate our guts, like how much blood are
• 1:10:14
  Speaker 2: we sending down to help speed up metabolism things like that.
• 1:10:18
  Speaker 1: Yeah, it's sort of like a subconscious smelling, like it's
• 1:10:21
  Speaker 1: a sensation of the presence of these molecules in a
• 1:10:24
  Speaker 1: way you're not consciously experiencing.
• 1:10:26
  Speaker 2: And thank goodness for that.
• 1:10:29
  Speaker 1: And also a lot of these receptors trigger molecules we
• 1:10:32
  Speaker 1: don't know, but we don't understand. It's not easy to
• 1:10:34
  Speaker 1: look at a receptor and say, oh, this one obviously
• 1:10:36
  Speaker 1: senses ketchup and this one's sense is mustard. And there's
• 1:10:39
  Speaker 1: lots of receptors we like, well what is this one sense?
• 1:10:41
  Speaker 1: We don't know, and they're all over the place, so
• 1:10:44
  Speaker 1: we have a lot to learn. And then there's a
• 1:10:47
  Speaker 1: lot of fascinating wrinkles on like how you actually experience
• 1:10:50
  Speaker 1: that smell. And one of my favorite tidbits comes from rats.
• 1:10:53
  Speaker 1: It turns out that in rodents is a very close
• 1:10:55
  Speaker 1: connection between smell and sound, which means that like if
• 1:11:00
  Speaker 1: they smell something, they smell it differently. If certain sounds
• 1:11:03
  Speaker 1: are playing. So in rodent science, they call this neural
• 1:11:06
  Speaker 1: convergence a new kind of perception called smound, which is
• 1:11:10
  Speaker 1: a combination of smell and sound.
• 1:11:13
  Speaker 2: Right, that is so interesting. I mean I think that
• 1:11:17
  Speaker 2: very rarely can happen in humans if you are affected
• 1:11:22
  Speaker 2: by something called synesthesia, which is when you're getting all
• 1:11:27
  Speaker 2: your sensory information as one typically would, but then in
• 1:11:30
  Speaker 2: your brain it is actually kind of mixing and matching
• 1:11:35
  Speaker 2: your sensory experience. So like you'll smell something and you
• 1:11:39
  Speaker 2: feel like that smell is a color, or you feel
• 1:11:43
  Speaker 2: like a number is a certain kind of color or feeling,
• 1:11:47
  Speaker 2: and it's very interesting. So like, I feel like this
• 1:11:50
  Speaker 2: is one of the things, like it's usually difficult to know,
• 1:11:54
  Speaker 2: like as humans, what it would be like to be
• 1:11:56
  Speaker 2: an animal. But I bet if you ask someone with
• 1:12:00
  Speaker 2: an esthesia, they could maybe give you something of an
• 1:12:03
  Speaker 2: idea of this experience of the rats where they have
• 1:12:06
  Speaker 2: this mound.
• 1:12:08
  Speaker 1: Makes me wonder, like what music pairings we should be
• 1:12:11
  Speaker 1: playing in fine restaurants, you know, because maybe your food
• 1:12:14
  Speaker 1: smounds good with Mozart, but doesn't smeund good with Black
• 1:12:18
  Speaker 1: Sabbath or whatever.
• 1:12:20
  Speaker 2: I feel like Mozart would be good with like a kianti,
• 1:12:24
  Speaker 2: whereas black Sabbath would be good with I don't know,
• 1:12:27
  Speaker 2: red bull.
• 1:12:28
  Speaker 1: There you go. Well, there's all sorts of fascinating biology
• 1:12:32
  Speaker 1: and wrinkles. The experience of smell we don't have time
• 1:12:34
  Speaker 1: to get into. You know, how dogs have like hundreds
• 1:12:37
  Speaker 1: or tens of thousands of times more acute senses. The
• 1:12:40
  Speaker 1: grizzly bears have even stronger senses than the bloodhound. How
• 1:12:44
  Speaker 1: people can sometimes smell like whether they're related to somebody
• 1:12:48
  Speaker 1: based on their body odor. It's really incredible, it really is.
• 1:12:53
  Speaker 2: The Only thing I'll say is that if you want
• 1:12:55
  Speaker 2: to make your dog happy, let them smell stuff like
• 1:12:57
  Speaker 2: that is, if you let your dogs smell, smell all
• 1:13:00
  Speaker 2: the smells, they'll be so happy. It's like them going
• 1:13:03
  Speaker 2: to the movies or to a museum. Smells are a
• 1:13:05
  Speaker 2: dog's whole world.
• 1:13:07
  Speaker 1: And in the end, all of this smell, in terms
• 1:13:09
  Speaker 1: of the fundamental physics, is chemistry.
• 1:13:11
  Speaker 3: Right.
• 1:13:11
  Speaker 1: We're talking about the interactions of molecules with each other, mechanical, electrostatic,
• 1:13:17
  Speaker 1: but fundamentally it's all chemistry. It's all electromagnetic. Everything involved
• 1:13:22
  Speaker 1: in smell is electromagnetic interactions of big complex molecules with
• 1:13:26
  Speaker 1: other complex molecules, whether that's mechanical which again is built
• 1:13:29
  Speaker 1: on the electromagnetic force, or literal electrostatic interactions between these molecules.
• 1:13:35
  Speaker 1: It's all electromagnetism.
• 1:13:37
  Speaker 2: So let me guess is touch also electromagnetism.
• 1:13:42
  Speaker 1: Touch also seems to be electromagnetism. The way you sense
• 1:13:46
  Speaker 1: touch is through various kinds of sensors in your skin.
• 1:13:49
  Speaker 1: Some sense pressure, some sense temperature, some sense damage. Right,
• 1:13:54
  Speaker 1: each one has a special kind of mechano receptor to
• 1:13:57
  Speaker 1: tell like are you being squeezed or are you being
• 1:14:00
  Speaker 1: heat it up? And then they send their signals up
• 1:14:02
  Speaker 1: to your brain using of course electromagnetic pulses.
• 1:14:07
  Speaker 2: That is so interesting. So like when I'm zamped with
• 1:14:09
  Speaker 2: some static electricity, I'm having electromagnetism zap me, but then
• 1:14:15
  Speaker 2: also electromagnetism telling my brain ouch I got zapped exactly.
• 1:14:22
  Speaker 1: And then the last sense, taste is very closely connected
• 1:14:24
  Speaker 1: to the sense of smell, as we talked about. Of course,
• 1:14:28
  Speaker 1: of course your mouth is different from your nose, and
• 1:14:30
  Speaker 1: you have a tongue with taste receptors on it, but
• 1:14:32
  Speaker 1: taste receptors are not nearly as complicated or as varied
• 1:14:36
  Speaker 1: as smell receptors. You have a few thousand of them
• 1:14:39
  Speaker 1: on your tongue, which can sense basic things about classes
• 1:14:42
  Speaker 1: of molecules, so you have like sweet, sweet, sour, salt, bitter, savory,
• 1:14:47
  Speaker 1: or sometimes people call it umami. Each of these are
• 1:14:50
  Speaker 1: like receptors in your nose, except they're more coarse. They
• 1:14:53
  Speaker 1: like detect certain classes of molecules that they can trigger.
• 1:14:56
  Speaker 1: They're not like one of a kind molecule receptors the
• 1:14:59
  Speaker 1: way your nose, which is why most of your sense
• 1:15:02
  Speaker 1: of taste actually comes from your nose. Your mouth contributes
• 1:15:05
  Speaker 1: to it, and your tongue helps. But if you last
• 1:15:07
  Speaker 1: time you've had a cold, for example, and you couldn't
• 1:15:09
  Speaker 1: smell anything, you might notice that things sort of taste cardboardy.
• 1:15:13
  Speaker 1: And that's because the tongue can only distinguish like five
• 1:15:16
  Speaker 1: different senses, and your nose can distinguish like hundreds and
• 1:15:19
  Speaker 1: hundreds of different senses. It's much more complex.
• 1:15:23
  Speaker 2: That's why you hold your nose when you're taking cough
• 1:15:25
  Speaker 2: medicine and makes it taste less bad.
• 1:15:28
  Speaker 1: And I thought this was fascinating. It turns out that
• 1:15:31
  Speaker 1: most of smell's contribution to flavor occurs when you exhale,
• 1:15:35
  Speaker 1: as opposed to with smell. When you smell something, that's
• 1:15:37
  Speaker 1: during inhalation, right, you're breathing it in across those receptors.
• 1:15:40
  Speaker 1: But when you eat something, it's when you breathe out
• 1:15:43
  Speaker 1: that smell contributes to that sense of taste. It's really
• 1:15:47
  Speaker 1: sort of incredible how closely linked they are.
• 1:15:49
  Speaker 2: I'm sorry to keep bringing it back to dogs, but
• 1:15:51
  Speaker 2: it reminds me of how like with thugs, when they exhale,
• 1:15:55
  Speaker 2: they're getting a ton more information from the smell, like
• 1:15:59
  Speaker 2: in their nose, like a specific channels in their nose
• 1:16:02
  Speaker 2: that allows them to experience more, which you know, you
• 1:16:05
  Speaker 2: always think that like when you're breathing in, you're breathing
• 1:16:08
  Speaker 2: in a smell like that's where you're getting the biggest experience.
• 1:16:11
  Speaker 2: But exhaling can give us, maybe not in terms of
• 1:16:15
  Speaker 2: identifying smells like with dogs, but for us it gives
• 1:16:18
  Speaker 2: us this much grander experience with flavor m M.
• 1:16:22
  Speaker 1: And in the end, in terms of the fundamental physics,
• 1:16:25
  Speaker 1: all this again is chemistry. It's the interactions of molecules,
• 1:16:28
  Speaker 1: which is determined by their structure, which is based on
• 1:16:31
  Speaker 1: their atomic bonds, which is electromagnetism and their electrostatic propulsion
• 1:16:35
  Speaker 1: of each other. So in the end, this sense is
• 1:16:38
  Speaker 1: also electromagnetism.
• 1:16:40
  Speaker 2: So has everything we've talked about been electromagnetism except for
• 1:16:45
  Speaker 2: that inner ear sort of accelerometer.
• 1:16:49
  Speaker 1: Yes, it turns out that electromagnetism is really the fundamental
• 1:16:52
  Speaker 1: force we use to experience the universe, with the exception
• 1:16:55
  Speaker 1: of this sense of balance, which also is connected to electromagnetism.
• 1:16:59
  Speaker 1: Of course, because it's built out of these pieces that
• 1:17:02
  Speaker 1: use electromagnetic structures. Everything really is fundamentally due to electromagnetism.
• 1:17:07
  Speaker 1: We don't rely on the weak force or the strong
• 1:17:09
  Speaker 1: force in order to interact with the universe. Though of
• 1:17:13
  Speaker 1: course without the strong force you couldn't have these molecules,
• 1:17:17
  Speaker 1: and so you might argue that the core structure of
• 1:17:19
  Speaker 1: the atom is due to the strong force, but doesn't
• 1:17:22
  Speaker 1: really play a deep role in how those things interact.
• 1:17:25
  Speaker 1: That's really due to the electromagnetic interactions of the atoms,
• 1:17:28
  Speaker 1: how they bond together. So yeah, underlying everything is electromagnetism.
• 1:17:33
  Speaker 2: It's kind of a particle chicken before the particle egg
• 1:17:36
  Speaker 2: kind of question one for philosophers.
• 1:17:38
  Speaker 1: Yeah, although there's another side of the story, which is
• 1:17:42
  Speaker 1: that maybe all these forces are more closely connected than
• 1:17:44
  Speaker 1: we initially described. I told you about how electricity and
• 1:17:47
  Speaker 1: magnetism are really just two sides of the same coin.
• 1:17:51
  Speaker 1: About fifty years ago we discovered that the weak force
• 1:17:53
  Speaker 1: is actually linked to electricity and magnetism in a very
• 1:17:56
  Speaker 1: similar way. You put them together into something we call electroweak,
• 1:18:00
  Speaker 1: which is actually a much prettier and much more sensible object,
• 1:18:03
  Speaker 1: has more symmetries, it's linked together. It's really this coin
• 1:18:06
  Speaker 1: has three sides. It turns out.
• 1:18:08
  Speaker 2: Wow, you just blew my mind. I can't picture a
• 1:18:11
  Speaker 2: coin with three sides. I guess it technical. Wait, a
• 1:18:14
  Speaker 2: coin does have three sides, because you got the head,
• 1:18:16
  Speaker 2: you got the tails, and then you got the little
• 1:18:18
  Speaker 2: rim around it.
• 1:18:19
  Speaker 1: The weak force is the rim around the coin of
• 1:18:21
  Speaker 1: electricity and magnetism. So in the end, the weak force
• 1:18:24
  Speaker 1: is also playing a role in your sensus because it's
• 1:18:27
  Speaker 1: part of the electra weak force, which really fundamentally is
• 1:18:30
  Speaker 1: the thing that lets you interact with the universe. Lots
• 1:18:33
  Speaker 1: of people are working on grand unified theories which would
• 1:18:35
  Speaker 1: combine the strong force with the electroweek into one single
• 1:18:39
  Speaker 1: unified force to describe all of these quantum interactions. And
• 1:18:43
  Speaker 1: so if that is successful, maybe one day we will
• 1:18:45
  Speaker 1: say that there's just one force out there that lets
• 1:18:48
  Speaker 1: us experience the universe.
• 1:18:50
  Speaker 2: Daniel, you told me Star Wars was lying to me
• 1:18:53
  Speaker 2: about the force.
• 1:18:56
  Speaker 1: In the end, it's all midichlorians. Those are the fundamental
• 1:19:00
  Speaker 1: little gremlins of the universe.
• 1:19:02
  Speaker 2: And we've done it. We've jumped the shark.
• 1:19:06
  Speaker 1: So an important way that we see the universe is
• 1:19:08
  Speaker 1: literally by seeing photons. But it turns out that electromagnetism
• 1:19:12
  Speaker 1: is deeply rooted in every kind of sense we have
• 1:19:15
  Speaker 1: of the universe, which gives us a rich and very
• 1:19:17
  Speaker 1: picture of what's out there, but also limits us in
• 1:19:20
  Speaker 1: what we can do and what we can experience. There's
• 1:19:22
  Speaker 1: lots of stuff out there in the universe that doesn't
• 1:19:24
  Speaker 1: experience electromagnetism, like dark matter, and so our electromagnetic based
• 1:19:28
  Speaker 1: senses might be missing out on the bigger picture.
• 1:19:31
  Speaker 2: Electromagnetism made me new friends and made me prettier too,
• 1:19:36
  Speaker 2: So get your electromagnetism today, call now.
• 1:19:42
  Speaker 1: This podcast is sponsored by Big Electron. Thanks everybody for
• 1:19:45
  Speaker 1: listening and tune in next time. Thanks for listening, and
• 1:19:56
  Speaker 1: remember that Daniel and Jorge explain the Universe is a
• 1:19:58
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• 1:20:03
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• 1:20:07
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