Your brain may be as blind to reality as a grasshopper is to calculus | Michelle Thaller

0:00 You have to have this humility and remind

0:02 yourself that it's possible that the human

0:04 brain is just as far away from perceiving the way the universe really is,

0:08 as a grasshopper is perceiving quantum mechanics.

0:11 We are not some be-all and end-all of perception.

0:15 The universe was not designed, not built,

0:18 to be comprehensible to the human mind.

0:20 We only see a little bit of it through the filter

0:23 of what our minds can ingest and how they do it.

0:26 And so we think that there really is such a thing as space and time.

0:29 You know, we actually think that there is a past,

0:33 present, and a future when in fact there may not be.

0:37 [Announcer] Our cosmic origins and the edge of our knowledge.

0:41 It's a fascinating question whether you could use a compass in space.

0:45 So let's talk first about compasses,

0:47 and then maybe talk a bit more about the idea

0:49 of how we locate ourselves in space in general.

0:52 A compass is something that responds to a magnetic field.

0:56 So the reason a compass always points north is

0:58 that it's responding to the magnetic field of the Earth.

1:01 Our planet has this wonderful core of molten metal,

1:04 that metal moves around inside the Earth,

1:06 and it generates a magnetic field that has two poles,

1:09 a north pole and a south pole.

1:10 When you make a compass,

1:12 you make it out of something metal that can respond to that magnetic field,

1:15 and it points to the magnetic pole of the Earth,

1:18 which is very close to our North Pole.

1:20 A magnetic field directs compasses.

1:22 Obviously, if you go away from the Earth far away from our planet,

1:27 it's no longer gonna be able to feel our magnetic field.

1:29 So a compass will not point to the North Pole of the Earth if,

1:33 say, you're out by Saturn.

1:34 Saturn and Jupiter are separate planets

1:36 and they have magnetic fields of their own.

1:38 So certainly, if you were actually close to Jupiter,

1:40 Jupiter has a magnetic field much stronger than the Earth's magnetic field.

1:44 Your compass would definitely point to the north pole

1:46 of Jupiter if you were actually around Jupiter now.

1:49 But what if you get farther out?

1:51 What if you actually go farther from there?

1:54 Is there any magnetic field out in space itself?

1:56 Well, actually it turns out that there are,

1:58 that our galaxy does have a magnetic field as a whole too.

2:01 This magnetic field might be hard to detect.

2:03 You might need a very, very sensitive compass.

2:05 But say you had it, you would actually see that our galaxy

2:09 does have sort of a magnetic north and south pole,

2:12 and that magnetic field permeates our whole galaxy.

2:15 With compasses, you could actually at least find out

2:18 where the north and south pole of another planet is,

2:20 the north and south pole of a star, a star has a magnetic field too,

2:24 even the north and south pole of a galaxy.

2:26 That's responding to a local magnetic field.

2:28 But then it kind of begs the question, how do you find your direction in space

2:33 that doesn't involve a magnetic field out between the galaxies,

2:36 where really there's no detectable magnetic field at all?

2:39 Everything is moving.

2:40 There's nothing to say this point is still,

2:42 and this is the reference point we're gonna use,

2:45 and everything moves according to that point.

2:47 We are moving around the sun at about 66,000 miles an hour right now.

2:53 The sun is moving around the galaxy,

2:54 around the core of the galaxy at about half a million miles an hour.

2:58 We are actually falling gravitationally into the center of a cluster

3:02 of galaxies at about a million and a half miles an hour.

3:05 That's just when we say relative to what?

3:08 Relative to the sun, relative to this group of galaxies.

3:11 There is no absolute standard of reference in the universe.

3:15 There is one thing that is perhaps the best

3:18 way of navigating your way around the universe,

3:20 and that's something called the microwave background radiation.

3:23 That's the farthest radiation we can possibly see.

3:26 That's radiation that's coming everywhere in the universe

3:29 from a time about 400,000 years after the Big Bang,

3:33 and it fills all of space with this gentle microwave radiation.

3:38 And it's pretty much the same in every direction.

3:40 In fact, if you had an old style

3:43 television that used to have an antenna decades ago,

3:45 a lot of static that you would see

3:47 on the screen was actually microwaves from this background radiation.

3:50 And one of the things we can measure

3:53 is our motion relative to this bath of radiation, the microwave background.

3:57 So if you were trying to navigate with a compass in space,

4:01 just remember that compass is going to respond

4:03 to the strongest and closest magnetic field.

4:05 It will point north, north to the pole of a planet, north to the pole of a star,

4:10 even to the north and south magnetic poles of our galaxy.

4:13 But what you're reading is a magnetic field, that's what a compass does,

4:16 and that's pretty much all I can tell you.

4:18 Well, this is the thing about the power of astronomy that kind

4:21 of really does blow my mind is how much we actually do know.

4:25 There's all kinds of things that we don't know, and astronomers,

4:28 scientists in general, tend to really focus on what we don't know,

4:31 because that's what we're working on, that's our jobs,

4:33 that's how we get, you know, the grant money to sustain ourselves,

4:37 is trying to answer the questions that we don't know yet.

4:40 But the things that we do know, in some ways,

4:43 just how recently we know them really kind of blow my mind.

4:47 You think about what are stars made of, right?

4:50 I mean, you've probably heard that stars are

4:52 mainly made of hydrogen and helium, you know,

4:54 they're these big sort of balls of gas,

4:56 you know, very, very hot, dense, burning balls of gas.

4:59 But how long ago did we know that, it was actually really not until, you know,

5:03 times like the '20s or '30s that a young

5:05 woman named Cecilia Payne working at Harvard,

5:08 wrote a PhD dissertation pretty much proving

5:10 they had to be made out of hydrogen.

5:11 It was a graduate student, a woman graduate student.

5:14 At the time, the idea was that the sun

5:16 was probably something very much like the Earth, it was like a big rock.

5:20 And if you have a rock that big, and this is true,

5:23 there would be so much gravity pushing it together,

5:26 that the temperature of the rock would be very hot.

5:29 So, you know, the temperature of the surface

5:31 of the sun is round about 10,000 degrees.

5:34 And if you had a rock that big with that much gravity pushing it together,

5:38 it would be that hot.

5:40 But it would only be that hot for probably a couple million years.

5:43 And the neat thing was, you know,

5:45 round about the late 1800s, was Charles Darwin,

5:48 who had been looking at things like evolution,

5:51 the strata of rock, like the Grand Canyon.

5:53 And he sort of had this feeling that millions

5:56 of years certainly was a long amount of time,

5:58 but he didn't think it was long enough

6:01 for the changes that he saw in the Earth itself.

6:03 The prevailing idea, and this was a problem,

6:06 is that the sun was basically a big Earth,

6:09 just the contraction of gravity was making it hot,

6:12 it would take millions of years to cool off.

6:15 It turns out that wasn't it at all.

6:17 It was actually made of hydrogen, the lightest substance in the universe.

6:21 But now, you have so much gravity crushing together the hydrogen,

6:25 making the interior very hot,

6:27 millions of degrees hot, hot enough actually to start a nuclear fusion reaction.

6:31 And that can last billions of years.

6:34 Certainly one of the biggest misconceptions is that people think

6:38 that scientists feel that the Big Bang came out of nothing, right?

6:41 I mean, how did all of this energy

6:42 and all of this matter that made up the universe,

6:44 you're saying it just came out of nothing?

6:47 No, I don't think any scientist actually believes that.

6:50 The problem is, when you think about the condition

6:53 the universe was in at that point where, I mean, take our observable universe,

6:58 right, I mean, you can look from one side of the universe to the other back,

7:01 you know, 13.5 billion light years or more.

7:04 All of the stuff that we see was

7:06 actually compressed into a space smaller than an atom,

7:09 volume smaller than an atom.

7:11 We don't have the physics that describes how that would work.

7:14 That is so much mass, so much energy and so little volume, I mean,

7:18 at this point there wasn't even mass, just basically pure energy,

7:22 that right now our physics doesn't go there.

7:24 As we get a better idea about

7:27 how gravity works under very extreme circumstances, your huge energy densities,

7:31 we may have some idea what set off the Big Bang,

7:35 and possibly what came before the Big Bang.

7:37 And even that word is a little bit

7:39 difficult when you start talking about the Big Bang.

7:42 Because the Big Bang, we believe, was the creation,

7:45 not just of space, but of time.

7:47 Whatever state the universe was in before the Big

7:50 Bang probably didn't have time as we perceive it either.

7:53 Space and time appear to be some kind of a consequence of the later expansion.

7:58 So how do you describe something that doesn't have space and time,

8:01 that has huge amounts of energy and tiny little volumes,

8:04 we don't have the physics.

8:05 It's not that we will never know this, but right now,

8:09 we don't have any way to describe it.

8:11 Now, another major misconception about the Big Bang is

8:13 that the universe before the Big Bang was small.

8:15 Okay, now, didn't I just say that everything

8:17 we see in the universe was probably contained,

8:19 you know, less than the volume of an atom?

8:21 Didn't I just say that?

8:22 Well, the thing is, I know every scientist understands

8:26 that we cannot see the entire universe right now,

8:30 and that's because there's such a thing

8:32 that we quantify as the observable universe.

8:34 The universe has existed, we think,

8:37 since the Big Bang, about, say, 13.8 billion years.

8:40 So as you look farther and farther out into space,

8:44 you necessarily have to look back in time.

8:47 If something is a million light years away from you,

8:49 like the Andromeda Galaxy is about two million light years away.

8:52 The light that you see through binoculars tonight

8:54 as you look up at the Andromeda Galaxy,

8:56 left two million years ago, you're seeing the Andromeda Galaxy as it was.

9:00 So today, we actually have telescopes that are so powerful,

9:03 they can see back to a time about 400,000 years after the Big Bang.

9:07 That's amazing, we can see so far away in space

9:09 that the light has taken that long to get to us,

9:12 you know, nearly 13.8 billion years.

9:14 And when we look back to that time, the universe looks very different.

9:19 For one thing, it's very hot.

9:20 It's actually about as hot as the surface of the sun.

9:24 And it's so dense and hot that we actually can't see any farther.

9:29 Literally, in any direction you look around the sky,

9:31 anywhere you look, if you look to that distance,

9:34 you see the universe as it was at that time,

9:37 400,000 years after the Big Bang, and everything becomes just hot hydrogen gas.

9:41 So I know this is kind of a strange way to put it,

9:44 because we're talking about before the Big Bang there may not

9:47 have been space and time the way we think they are today.

9:49 But whatever it was before the Big Bang,

9:51 whatever was there, there was a tiny little part of it,

9:54 a tiny little volume that expanded to become the universe we see today.

9:58 But that little bit wasn't the whole universe.

10:01 We don't know yet how big the original universe was, all of it,

10:06 before the Big Bang happened,

10:08 before something changed to make it expand and completely change its form.

10:12 So the universe before the Big Bang didn't have to be necessarily tiny.

10:16 It actually could be infinitely large.

10:18 Because of that, we have no idea how big the universe is, what shape it has.

10:23 All we can see is a tiny little bit of it.

10:25 Think about my arm being the universe before the Big Bang, you know,

10:29 in some kind of state that we can't even describe through modern physics.

10:33 The entire observable universe that we can see

10:36 now used to be a tiny volume of it, maybe an atom in my arm.

10:41 One atom expanded and became the entire observable universe that we see.

10:46 But that's not the whole universe.

10:49 There are trillions of atoms in my arm.

10:51 Each one of those could expand

10:53 to actually be its own entirely observable universe.

10:56 So we can't tell yet how big the universe was before the Big Bang,

11:02 or even what shape the universe is,

11:04 because all we're seeing is a tiny little bit

11:06 of it that expanded to become everything that we see.

11:10 But that's not the whole universe, that's our observable universe.

11:14 There's far more out there than what we can see.

11:17 One of the most common questions that I'm getting from the public these days is,

11:21 "Is our universe a simulation?" I think that one

11:24 of the things people are thinking about is they've heard the term,

11:28 the "holographic universe", and this is indeed a very powerful

11:32 and increasingly popular idea in modern physics.

11:34 But it's a little bit unfortunately named,

11:37 and let me sort of take you through this.

11:40 This all started a couple decades ago when people like Stephen Hawking

11:43 and others were trying to figure out how a black hole really works.

11:46 We know black holes exist.

11:48 We actually observe them from a distance very routinely.

11:51 But the physics of how they work never quite worked.

11:54 They appeared to violate some pretty important laws of physics.

11:58 The universe doesn't like to lose information.

12:00 A particle has a charge, it has a spin.

12:03 There are all kinds of things you can say about an elementary particle.

12:07 But when it falls into a black hole,

12:09 the only thing that seems to exist anymore is mass,

12:12 the gravity that that particle had.

12:14 What happened to the information about its charge?

12:16 Can you ever get that back?

12:18 As people began to do the mathematics of it,

12:22 they noticed something very intriguing that everything seemed to work

12:25 much better if you assume the black hole was two-dimensional.

12:29 Now, black holes are actually three-dimensional objects.

12:31 You know, a lot of times they're portrayed kind of as things going down a drain.

12:35 But basically, you have a sphere, which is the point of no return.

12:38 Gravity is so intense around a black hole that if you get anywhere this close,

12:42 you never come back out.

12:43 That's the event horizon of a black hole.

12:46 So instead of assuming that it is a sphere around the black hole,

12:49 it all started to act like it was a two-dimensional surface.

12:53 Something that was three-dimensional became much

12:56 more understandable if it was two-dimensional.

12:58 And as scientists do, they thought, "Well, okay, if this works for a black hole,

13:02 is it telling us something about the rest of the universe?"

13:05 And this may be one of the most important new revolutions in modern physics,

13:09 that the laws of physics might work a lot better,

13:13 might actually work out together if you

13:15 assume that our reality is really two-dimensional.

13:17 You look around, there seems to be more

13:20 than two dimensions in space and there's time, how would that work?

13:24 The example of a hologram came up.

13:27 You know, I still remember being at a hologram museum back in the 1980s,

13:32 and the holograms were really new and really exciting.

13:35 The idea that a hologram is made out of just

13:38 a two-dimensional block of film or a block of glass,

13:41 but it seems to be three-dimensional when you look into it.

13:44 And even more than that, I remember

13:46 this one hologram that was put on a pedestal,

13:49 and as you walked around the hologram,

13:51 somebody appeared to move inside and wave at you.

13:53 If you were looking at the hologram, there appeared to be motion and even time,

13:58 all embedded in just this two-dimensional surface.

14:00 That's what they mean when they say holographic principle.

14:03 It doesn't imply that anybody made a hologram,

14:06 or that we are part of a projection that somebody,

14:09 some evil genius, is projecting reality on us.

14:11 What the holographic principle really is,

14:13 is the universe may store energy in a way

14:16 and information in a way similar to a hologram.

14:19 If that's true, and we really are embedded in this two-dimensional universe,

14:23 that has some pretty amazing repercussions.

14:26 It probably means that every point in time exists at once, that you know,

14:32 our idea that things are changing and that I'm moving right now,

14:36 and time is flowing in one direction,

14:38 that's probably the same as somebody just walking by a hologram

14:41 and having the perception that the image is moving.

14:44 It's probably not real.

14:46 The amazing idea is that the extension of space itself,

14:51 and time actually flowing, may not be real intrinsic parts of the universe.

14:56 There may be some way that we perceive it with the human brain,

15:00 but in fact, there's an underlying reality where that is not true.

15:04 We say that these are emergent properties, it's not the real story.

15:08 A hologram doesn't really move, a hologram is not really three-dimensional.

15:12 But it seems so through our perception.

15:15 That's an amazing idea that the entire universe exists

15:19 all at once as some kind of surface of information.

15:22 That's the holographic principle, it's working quite well right now.

15:25 I can't tell you whether it's true or not,

15:27 whether there really is some real two-dimensional

15:30 thing that we think of as the universe.

15:33 So stay tuned.

15:34 At the time that Darwin was doing this, I think there was sort of this argument

15:37 between like biblical people that said

15:38 the Earth was a couple thousand years old,

15:40 and then the scientists said, "Oh, no, no,

15:42 it must be millions of years old." One of the things

15:44 about being an astronomer is you throw around very,

15:46 very large numbers all the time.

15:48 I mean, some of them are just kind of, you know, stupidly large.

15:51 But even things like how many is a million, right?

15:54 How many is a billion?

15:55 The the human brain, I don't perceive that really any better than anybody else,

16:00 the human brain just doesn't go there.

16:02 Instead, you kind of find yourself getting

16:03 used to swimming in an environment where

16:05 your mind can't really grasp all the way around a concept, it just can't.

16:11 You know, I can't tell you how far away a light year is,

16:15 I mean, one light year, you know,

16:16 the distance light travels in one year at 186,000 miles per second,

16:21 that's up close to about six trillion miles.

16:24 I don't have the ability to actually visualize that or feel it.

16:28 And yet to me, a light gear seems very familiar and actually quite close.

16:32 So maybe that's one of the reasons astronomers are almost kind of predisposed

16:37 to being able to let go of sort of your common sense.

16:42 When people say things like the inside of a neutron star, you know,

16:46 is so dense that a single teaspoonful, you know,

16:49 of that material would have as much mass as Mount Everest.

16:52 It's like okay, the laws of physics pretty much require that.

16:55 Or when people say, "What was the temperature of the universe just, you know,

16:59 three seconds after the Big Bang?" Does

17:02 our physics really does work to predict that.

17:05 So I think that when you start swimming just in these big numbers and you begin

17:08 to kind of let go of the idea that the human mind is the be-all and end-all,

17:13 you know, we have these tools to start attacking larger problems,

17:16 to start asking bigger questions,

17:18 all of a sudden it comes very natural to say things like, "Oh yeah, you know,

17:22 gravity is actually a bending of space and time." The amazing

17:25 thing about that is that started out to be completely theoretical.

17:29 You know, people thought that Einstein's theories were very useful.

17:32 I mean, they made extremely accurate predictions about how the planet's move,

17:37 about how the universe works.

17:38 But was there any really reality to the fact that space and time could bend?

17:42 I mean, literally the space in front of me, the space and time around me,

17:47 can change and bend, even have a direction to it.

17:50 It turns out that, you know, our theories,

17:53 for the most part, do lead us to something really physically true.

17:57 And you know, right now people ask me questions like,

18:00 "Are there multiple universes?" "What's the shape of the universe,

18:03 you know, the larger universe?" All of these things are wonderful questions,

18:06 and we don't know the answer to them yet.

18:09 But I have a feeling that it's not just wasting time.

18:12 You know, I think some of these stranger

18:14 theories will bear themselves out over time, we just need to wait.

18:17 Right now, I think it's a little bit too soon

18:20 to follow them all the way into the rabbit hole.

18:22 Let's say that there were many,

18:23 many multiple realities: Well, how would physics work?

18:25 How would this work?

18:26 It's still too much conjecture for me to invest a huge amount in it.

18:30 You know, I still remember, you know, 2,000 years ago,

18:33 unless you had people like Aristotle who were brilliant,

18:37 and they came up with this idea that all the planets

18:40 had to follow perfect spherical orbits around the Earth in the middle,

18:43 and they were on these crystal spheres that somehow moved.

18:46 And, you know, people all the way up into the Renaissance were trying

18:48 to figure out how those crystal spheres

18:49 could have worked and how they were supported.

18:52 Well, it turns out there weren't any crystal spheres.

18:54 There's always a bit of me as an observational scientist that says,

18:57 you know, take everything with the grain of salt for now.

19:00 Oh, I mean, Aristotle had this elegant, wonderful system.

19:02 I mean, people loved it until the Renaissance, right?

19:05 Mm-hmm!

19:05 It's just that our observations didn't bear up with it,

19:09 and it was so beautiful, people hated to let it go.

19:12 But unfortunately, that's not how the solar system works.

19:15 Definitely pursue these questions, but I'm not sure I'm ready to dive all

19:19 the way into any of those rabbit holes quite yet.

19:21 I love to think about them, but I think it's probably a little too soon

19:25 to follow them ultimately to where they might go.

19:28 So people today have all these wonderful

19:30 questions that modern physics is leading us to.

19:32 Questions like, "Are the way we perceive space

19:34 and time real?" That's even 100 years old,

19:37 Albert Einstein said that space and time could be bent, time itself could stop.

19:41 Then there are things like the holographic principle.

19:44 Is it possible that our whole universe is some

19:46 sort of embedded information structure on a two-dimensional surface?

19:50 These are amazing ideas,

19:52 and they may turn out to actually have some physical truth to them,

19:54 we're not really sure yet.

19:56 But sometimes people say, "Well,

19:58 are you scientists just absolutely crazy?" "How is it that you

20:02 so blithely get rid of the idea that time has a direction

20:06 or that space is real?" One of the things you have

20:10 to very deeply accept to be a scientist is that your senses,

20:14 the human brain, is just not the best

20:17 instrument to perceive the entirety of the universe.

20:19 I mean, let's take a simple example.

20:22 There are many, many colors of light,

20:25 energies of light, that our eyes are not sensitive to.

20:28 There are things like gamma rays and X-rays, ultraviolet light, radio waves.

20:32 Those are all just different colors that our eyes don't see.

20:35 The universe has colors that just weren't built for the human body to perceive.

20:39 And when it comes to a mind, a brain,

20:42 think about some of the incredible creatures all around us.

20:46 I mean, you know, think about a grasshopper, a marvel of evolution.

20:50 It has a brain, it has a central nervous system.

20:54 But could you teach a grasshopper quantum mechanics or general relativity?

20:57 You know, could it compose a symphony or write a novel?

21:01 It just can't.

21:01 I mean, a grasshopper's brain just doesn't have the complexity to do that.

21:06 A grasshopper doesn't perceive those things.

21:08 What about a bacterium?

21:09 A bacterium doesn't even have a brain, but of course,

21:12 the majority of life on Earth by mass is still bacteria.

21:15 You know, when Galileo was around the idea that the Earth had to be the center,

21:20 God made it so, God must have put the Earth in the center.

21:23 But then it became proven that the Earth went around a larger object, the sun.

21:28 And I think almost more beautifully, one of my favorite observations of Galileo

21:31 is that when he invented his little telescope,

21:34 he looked at the sky and he realized that there were stars in the sky,

21:38 you couldn't see with just the unaided human eye.

21:40 There were stars up there that we were

21:42 unable to see unless you looked through a telescope, a piece of technology.

21:46 And the question was,

21:48 "Why would the universe do that if the universe was designed for us

21:51 to see and us to perceive?" "Why would there be things too far

21:55 away and too dim for us to see?" "Why are parts of the universe

21:59 so strange and so incomprehensible and make so little common sense?" Honestly,

22:04 why should it be any other way?

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