Good to see all of you.You see a quote up

there by Niels Bohr, one of the founding figures of quantum mechanics: “Anyone who thinks

they can talk about quantum mechanics without getting dizzy hasn’t yet understood the

first word of it.” Now, why would that be? What did Niels Bohr mean by that? Well, basically he meant that we all have

a good intuition for classical physics. Right? And by that, I mean, you know, if I was to

take any little object, right, and give it a catch. Nice! Did a one-handed catch right there. Throw this a little bit further back. Here we go, two for two. Nope, we’re still one-for-two. They’re still back in the dark ages–here

we go. You have that one over there? Good. Right now, each one of the people who caught,

so that would be the two of you over here, is really an evolved human being. Now, you see, when we were out there in the

savannah trying to survive, we needed certain skills, we needed to be able to know where

to throw a spear or how to throw a rock to get the next meal. We needed to dodge some animal that was running

toward us. And therefore we learned the basic physics

of the everyday macroscopic so-called classical world. We learned that intuitively. And that’s why when I throw an object, you

don’t have to through some elaborate calculation to figure out the trajectory of that stuffed

animal. You just put out your hand and catch it. It’s built into our being. But that’s not the case when we go beyond

the world of the everyday. If we explore the world, say of the very small, which is what we are going to focus on here tonight, we don’t have experience in that

domain. We don’t have intuition in that domain. And in fact, were it the case that any of

our distant brethren way in the past, if they did have some quantum mechanical knowledge

and they sat down to think about electrons and probability waves and wave functions and

things of that sort, they got eaten! Their genes didn’t propagate, right? And therefore we have to use the power of

mathematics and experiment and observation to peer deeper into the true nature of reality

when things are beyond our direct sensory experience. And that’s what quantum mechanics is all

about. It’s trying to describe what happens in

the micro-world in a way that is both accurate and revealing. And the thing to bear in mind is that even

though our focus here tonight will really in some sense be in the microworld, the world

of particles, we are all a collection of particles. So any weirdness that we find down there in

the microworld, in some sense it has an impact even in the macroworld and maybe suppresses–we’ll

discuss. But it’s not like there’s a sharp divide

between the small and the big. We are big beings made of a lot of small things. So any weirdness about the small stuff really

does apply to us as well. And in this journey into the micro-world,

the world of quantum mechanics, we have some of the world leading experts to help us along,

to figure things out. And let me now bring them on stage. Joining us tonight is a professor of philosophy

at the University of Southern California who spent 22 years at the University of Oxford

as a student, researcher, and faculty member. He is the author of a book on the Everett

interpretation of quantum mechanics titled “The Emergent Multiverse.” Please welcome David Wallace. Also joining us tonight is a professor of

chemistry at the University of California, Berkeley, co-director of the Berkeley Quantum

Information and Computation Center and faculty scientist at the Lawrence Berkeley National

Laboratory. She’s a fellow of the American Physical

Society and recipient of awards from the Bergmann, Sloan, Alexander von Humboldt Foundations. Please welcome K. Birgitta Whaley. Our third participant is a professor of physics

at the Univeristy of British Columbia, a Simons Investigator and member of the Simons Foundation

“It from Qubit” collaboration. He was a Canada research chair and Sloan Foundation

fellow and was awarded the Canadian CAP medal for mathematical physics for 2014. Please welcome Mark Van Raamsdonk. Our final participant is a professor of theoretical

physics at Utrecht University in the Netherlands and winner of the 1999 Nobel Prize in Physics

for work in quantum field theory that laid the foundations for the standard model of

particle physics, one of the greatest minds of our era, please welcome Gerard ‘t Hooft. Alright, so the subject is quantum mechanics,

and part of the evening will involve some challenge to the conventional thinking about quantum mechanics. And so before we get into the details, I thought

I would just sort of take your temperature. Get a sense of where you stand on quantum

mechanics. Is it, in your mind, a done deal? It’s finished, we completely understand

it? Is it a provisional theory? Is it something which 100 years from now we’re

gonna look back on with a quaint smile? “How did they think that that’s how things

worked?” So, David, your view. Well I don’t think we fully understand it

yet. I think it has a lot of depth left to plumb,

and who knows it might turn out to be replaced. But right at the minute, I think we don’t

have either empirical or theoretical reason to think that anything will take its place. Good I think it’s here to stay. There maybe extensions, modifications, there

may be something more complete, but this will still be part of it, in my view. OK, Mark Yeah, so there’s a frontier in quantum mechanics

that I work in, and this is the frontier. It’s like the wild west of theoretical physics,

where we’re trying to combine quantum mechanics and gravity, and we need to do that to understand

black holes and hopefully eventually understand the big bang. And there’s a lot to do, and we don’t

know if we’re going to have to modify quantum mechanics, or it will all be the same quantum

mechanics all the way down. Now, Gerard, you have unusual views. Well yes, I could spend the rest of the evening

explaining them. But, to my mind, quantum mechanics is a tool,

a very important mathematical tool, to calculate what happens if you have some underlying equations. And telling us how particles and other small

things behave. We know the answer to that question–the answer

is quantum mechanics. But we don’t know the question, that’s

still something we’re trying to figure out. Good. So, sort of a jeopardy issue, if you know

the American reference. (Exactly.) Alright, so just a quick overview. We’re going to start with some of the basics

of quantum mechanics just to sort of make sure that all of us are more or less on the

same page. We’ll then turn to a section on something

called the “quantum measurement problem,” something weird, “quantum entanglement”

as in the title of the program. We’ll then turn to issues of black holes,

spacetime, and quantum computation, which will take us right through to the end. Alright, so just to get to the basics of quantum

mechanics. The story, of course, began more or less in

the way that I started. We understood the world using classical physics

in the early days, way back to the 1600s. And then something happened in the early part

of the 20th century, where people like–we started with Newton, of course, then we moved

on to people like Max Planck, Albert Einstein. What drove the initial move into quantum physics? David? I think it was really just pushing really

hard at classical mechanics as it went down into the scale of atoms and the structure

of atoms, and just finding that that structure snapped and broke. That trying to use classical mechanics to

understand how hot things got or how electrons went around atoms without collapsing into

the nucleus. In all those places, we had a series of hints

that something was amiss in our classical physics. And it took, I guess, most of 30 years for

those hints to coalesce into a coherent theory. But that coherent theory then became not really

just a single physical theory, but the language for writing physical theory, be it theories

of particles or fields, maybe someday even gravity. And that language was more or less sort of

solid by, I guess about 1930. Yup. Yeah and it’s actually quite remarkable

that it only took that number of years to develop a radically new way of thinking about

things. And Richard Feynman, who is of course a hero

of all of us, also known to the public, famously said that there was one experiment–we can

go through the whole history of everything you described, with the ultraviolet catastrophe

and photoelectric effect and all these beautiful experiments–but the Double Slit Experiment,

luckily for us, in having a relatively brief conversation, allows us to get to the heart

of this new idea, where it came from. This actually is the paper on, in some sense,

the Double Slit Experiment. The first version, Davisson and Germer. And I’ll draw your attention to one thing. You see the word “accident”? And this is just a footnote. But, in the old days, people would actually

describe the blind alleys that they went down in a scientific paper. But as science progressed, we were kind of

taught, “no no don’t ever say what went wrong. Only talk about what went right!” But here is an old paper, and indeed this

experiment emerged from an accident in the laboratory at Bell Labs. They were doing a version of this experiment,

they turned the intensity up too high, some glass tube shattered, and when they re-did

the experiment, unwittingly, they had changed the experiment to something that was actually

far more interesting than the experiment they were initially carrying out. So, just to talk about what this experiment

is in modern language, so David again, just, what’s the basic idea of the Double Slit

Experiment? So you take a source of, well of particles

of any kind, but let it be light, for instance. You shine that light as a narrow beam on a

screen–it has two gaps in it, and you look at the pattern of light behind the two gaps

in the screen (“two slits”) two slits, exactly, yes. So the slits are just literally gaps in a

black sheet of paper, in principle. The light’s going through. If light is a particle, you’d expect one

sort of result on the far side of the screen. If light is a wave, you might expect something

different as the light coming through one part of the slit interferes with the light

going through the other part of the slit. And the weird thing about the quantum two-slit

experiment is that it seems, in various ways, to be doing both of those things at the same

time. Good. So, Birgitta, if you can just take us through

a particle experiment to build up our intuition. So let’s say we carry out the experiment

the way we described, but we don’t start with photons or electrons, we start with pellets–bullets

or something. So I think we have a little animation that

you could take us through. So what would we expect to happen in this

experiment? Well so you have the source of the pellets

here in front of us, spitting out the pellets and some of them go through the holes, and

the ones that go through the holes basically travel rectilinear, straight ahead, as we

might expect from our classical intuition. And we get two bands at the back, indicating

the pellets that went through the right slit, on the right, and the left band is the pellets

that went through the left slit. Now, if I was–that’s completely intuitive

right? So this is the stuff that our forebears would

have known even on the savannah. Now, if we took the size of the pellets and

we dialed them down to a very small size, before going to your quantum intuition that

you have, what would you expect naively to happen if you simply dialed down the size? Would you expect there to be any different

if you were–this is a leading question, by the way. So, just follow me here. The answer is…would you expect anything

different? Would you expect anything different? (…obviously the same thing. No no not at all.) Good. Good. Naively not! Naively not. Exactly right. So here’s what you would naively expect

would happen. Again, you got the particles going through

the two slits. So Mark, tell us what exactly does happen–not

that I don’t think Birgitta could, just to give us all a little airtime. So it’s of course, while the place where

you would least expect to see something on that screen is exactly behind that big barrier

that’s in the middle. And somehow, when you actually do the experiment,

you see that actually, that’s where most of the particles end up. So, it’s always exactly the opposite. And you get this weird pattern with other

bands going out. And so you initially would stare at it and

shake your head and wonder what you’d actually have. So we’ll analyze what that means in just

a moment. But I, you know, we often, I don’t know,

probably most everyone in this audience has seen a still image or animation like this

in the discussion of quantum mechanics. And I thought it would be kind of nice to

show you that it, that this actually happens. It’s not just an animation that an artist

does. So we’re going to actually do the Double

Slit Experiment, for real, right now. And to do that, I’m going to invite a friend

of mine from Princeton University. Omalon, can you wheel out, if you would, the

Double Slit Experiment? Alright, so what we have here is a laser on

this far side. So this is our source. So actually we’re doing this in some sense

opposite to the orientation that we saw in the animation. And we’re going to fire this laser, which

is photons, in essence. And the photons are going to go through a

barrier that has two openings in it–it’s harder to see that of course mechanically,

but trust me there’s a barrier with two openings. And we’re going to take a look at the data

that falls on a detector screen, which in the modern age is a more complicated and somewhat

finicky piece of equipment. So we’re all sitting here, on shpilkes,

if you speak any Yiddish, you know exactly what I’m talking about right there. But hopefully this will work out. So, Omalon, why don’t we just actually see

ambient noise. Can we see a little bit of that first? Can we switch over to the input to the screen? Alright so this is the output from that device. And now, if we actually turn on the laser

and allow us to collect all the photons that land, over time. There, they’re building up. And there you see what actually happens. So this is the result of this very device

here. And you see it. You can see on the very far left, we see some

of the photons are landing. Then we get a dark region in between. Then a bright, a dark, a bright, a dark, a

bright, a dark, and a bright and a dark…even though this device over here really is a barrier

that has only 2 slits in it. So the animation that we showed you actually

does hold true in real experiments. And that then forces us to come to grips with

it, to try to understand what in the heck is actually going on. So, thank you Omalon. So there we have it. We have this situation in which we expected

to get two bands and we got more. What does that tell us? Where do we go from there? That there’s an existing bit of mathematics

that comes up with exactly that same pattern. But it has nothing to do with particles. It’s the mathematics that you use to describe

waves, water waves, or other kinds of waves. Yeah. So can we see the animation that has a single? So this is a warm-up to the problem, where

we have water going through a single opening. Just tell us what we see happening here. That’s right, so you’ve got sort of a

water wave, a wave front coming along, and then that slit acts as a bit of a source for

this rippling wave going out in a circular pattern. And you see it’s most wavy at the place

behind the slit on the wall. That’s indicated by the brightness there. Yeah. And then if we go on to a more relevant version for the actual Double Slit Experiment… Yeah, so now we’ve got that same wave front. But now there’s two slits, and it’s like

there’s two different sources of waves, like if you threw two different pebbles in

the pond at the same time. And what happens is they’re both, you’re

both creating waviness. But some places on the screen, the wave from

one is doing this, and the wave from the other is doing this, and they kind of cancel out. But right there in the middle, what’s happening

is that the wave from the one slit is going up right when the wave from the other slit

is going up, and then they do this, and then you get a big wave and that’s the bright

part. But, if you work out the mathematics, then

the places that have the big waves are exactly these bright ones, and that’s just like

we saw in the Double Slit for the particles. Right. So as Gerard was saying, as Mark was saying,

we now have a strange confluence of two things: the data that comes out of the Double Slit

Experiment when done with particles, and something that seems to have nothing to do with it,

where we just have waves going through a barrier with two openings. So, the conclusion then is that there is some

weird connection between particles and waves, that’s where that connection comes from. And, let’s push that further, so… Yeah. I mean let’s just drive home how weird it

should be that there is any kind of connection here. So imagine I do the Two Slit Experiment. I cover up one of the slits. The effect completely goes away. I get a bit of a spreading out of the particles, but I don’t get that interference. I don’t get those bands. Much as we saw with water going through a

single opening. Exactly, much as we see with water going through

the single slit, and much as we see with your classical intuition about particles. If I cover up the other slit, exactly the

same result. It’s only if I have both slits open at the

same time that the effect happens. So it seems to be, for all the whirls, if

somehow something’s going through the first slit, and something else is going through

the other slit, and between them they’re interacting to create this strange effect. And that’s why it matters so much, that

I can do this experiment with one particle at a time. If this was just a massive light going through,

no surprise. The sunlight’s going through the left slit,

the sunlight’s going through the right slit. The left-hand light, the right-hand light

interferes. But I can set this stuff up so that only one

photon goes through every hour and a half, I still see the effect. It doesn’t go down in its likeness. Yeah, can we see that? I think we have that– And then you might be thinking, well maybe

each individual particle breaks in half, and half of the particle goes through one slit,

and half of the particle goes through another slit. But again, then you’d think you could–look–then

you’d think you’d be seeing half-strength detections. But that’s not what you see. Whenever you look, each time you send a particle

through, if you look where it is, you see the particle in one place and one place only. So trying to reconcile those two accounts

of what’s going on makes your mind hurt. Yeah, exactly. So we’re forced into, as David was saying,

not just thinking that a large collection of particles behaves like a wave, which maybe

would not be that surprising because water waves are made of H2O molecules, particles,

and therefore they’re kind of wavy, but each individual particle somehow has a wave-like quality. And historically, people struggled to figure

out what wave, what kind of wave, what is it made of and what does it represent if you have a wave associated with a particle. A wave is spread out, a particle is at a point. And it was Max Born in the 1920’s who came up with the strange idea of what these waves are. So, Birgitta, what are these waves telling

us about? Well the waves, what we see is the probability

which, the square of the wave or the modulus of the wave, but— So here’s a wave behind you. So you said, “probability,” in essence— Yes. This is an amplitude, this is an amplitude

which will give us a probability. If we take this amplitude and look anywhere

here with some measuring device, we will find with some distinct probability, after measuring many times, we’ll find that there’s a definite probability of the particle being

there, just as in the double slit. After sending many particles through, we found

with a certain probability that they would all appear on the left, or all on the right. So, in some sense, vaguely, where the wave

is big, there’s a high likelihood you’re going to find the particle. Where the wave is near zero, there’s a very

small probability that you’re going to find the particle. But you can’t guarantee it. So any one particle could be in a place where

the wave is very very small. Now these are all just pictures. In the 1920s, physicists were able to make

this precise. So Schrodinger wrote down an equation, and

I think we can show you what the equation looks like. Obviously, you don’t need to know the math

to follow anything that we’re talking about here. But Gerard, you wanted to emphasize that there

is math behind this, because your experience has been that many people miss that point,

so feel free to emphasize. Absolutely. Quantum mechanics, when we talk about it,

there is a temptation to keep the discussion very fuzzy. And so I get very many letters by people who have their own ideas about what quantum mechanics is, and they are very good at reproducing

fuzzy arguments, but they come without the equations, or the equations are equally fuzzy

and meaningless. Whereas, the beauty of quantum mechanics is the fundamental mathematical coherence of these equations. You can prove that, if this equation describes

probabilities exactly as you said before, then actually the equations handle probabilities

exactly the way probabilities are supposed to be handled. Except, of course, when two waves reinforce

each other, the probabilities become four times as big rather than twice as big. But a lot of soft spots, the waves annihilate

the probabilities, and so the probabilities become zero where the waves are vanishing. So all this hangs together in a fantastically

beautiful mathematical matter. Now math is one thing. Experiment is another. So how would you test a theory that only gives rise to, Mark, probabilities of one outcome or another? How would you go about determining if it’s

right or if it’s wrong? Yeah, so it’s like if you gave me a coin,

and you said “this is a probabilistic thing. You flip it, it’s going to be heads half

the time and tails half the time.” And I want to check that, I don’t trust

you for–I don’t know why that would be, but– Don’t worry, I’m not insulted. So I just flip the coin, you know, a hundred

thousand times, or whatever. You have a lot of patience to test these things. The more sure I want to be, the more I flip

it. So maybe I do it 10 times and I get 4 and

6, and I’m like, “oh, maybe I’ll flip it a hundred times” and then I get 48 heads

and 52 tails. So I can basically just repeat the experiment

a whole bunch of times, and if I have a very precise prediction from those quantum mechanics

equations to tell me exactly how often I should expect to get one result versus another, So, I think we have, we can give a little

schematic, what are we seeing here? Have a look. Right, so we’re doing, there’s our wave

that’s describing the state of the particle, the thing without a definite location. Then we’re setting that up a whole bunch

of times, and measuring where the particle is each time. And these X’s are showing the results of

our measurement. That’s like flipping your coin and getting

a head or getting a tail. Exactly. So there’s all these possible locations. And what we see is that after a while, the

pattern of how often I get one place versus another place, it’s matching up to that

expectation given by the blue curve, by this wave, or wave function. That’s right, so we can’t predict the

outcome of any given run of the experiment, but over time, building up the statistics,

we believe the theory if they align with the probability profile given by this wave, whose

equation we showed you, and that is what works out the shape of the wave in any given situation. And just to bring this full circle, if we

look at the Double Slit Experiment in this wave-like language, now think of the electron

or the photon as a wave, it goes through, it interferes like water waves going through

the two openings, and therefore you have an interference pattern on the screen, which

is telling you where it’s bright, it is very likely that you’ll find the particles. Where it’s dark, it’s unlikely. Where it’s black, there’s zero chance

of finding the particle there, and therefore you run this experiment with a lot of particles,

and they’re going to primarily land in the bright regions. They’re going to land somewhat in the greyer regions, and they’re not going to land at all in the black region. And indeed, that’s exactly what we showed

in the experiment that we ran with the double slit just a moment ago. And that’s why we believe these ideas. So that’s, in some sense, really the basics

of quantum mechanics. Classical physics, particle motion, is the

intuitive one described by trajectories. And quantum physics, the particle motion is

somewhat fuzzier. It’s got this probabilistic wave-like character,

and the curious thing about a wave, as sort of a wave of probability, if the wave is spread

out, it means there’s a chance that the particle is here, a chance that it’s here,

a chance that it’s here. And therefore the wave embraces a whole distinct

collection of possibilities all at once. That, in some sense, is really the weirdness

of quantum mechanics. So that’s the basic structure. And now we’re going to move on to our next chapter where we’re going to dig a little bit deeper. We’ll talk about measurement, and also entanglement. And it’s a dead heat. They’re checking the electron microscope. And the winner is…number 3, in a quantum

finish! No fair! You change the outcome by measuring it! Now either we have a very sophisticated audience, or you just love Futurama, I’m not sure which. But this is part of the issue that we now

want to turn to. Which is, if we have a quantum setup, how

do you move from this probabilistic mathematics, saying that the electron say could be here

or here or here with different probabilities, to the definite reality that Mark was describing:

when you actually do an experiment, you find the electron here or here or here. You never find anything a mixture of results. We want to talk about how we navigate going

from the fuzzy probabilistic mathematical description to the single definite reality

of everyday experience. And this is something that many physicists

have contributed to over the years. Again, Niels Bohr, we had a quote from him

early on, and he’s certainly viewed as really one of the founding pioneers of the subject. But let’s now try to go a little bit further

with our understanding of going from the math to reality. And we’re going to follow in, for this part

of the program, really in Niels Bohr’s footsteps, in something called the Copenhagen approach

to quantum physics. So David, can you just begin to take us through,

what was the ideas of collapse of the wave function, in technical language, what are

those ideas all about? So look at it this way. I’ve got my probability wave, which is sort

of humped–let’s just say for one particle–it’s humped over here and it’s humped over here. So there’s kind of two ways I can think

about that. You might say there’s an “and” way and

an “or” way. So I could think of it as saying that the

particle is here and the particle is here. Or you could think of it as saying the particle

is here or the particle is here. And the problem is I kind of need to use both to make sense of quantum mechanics, or so it seems. So, if I try to explain the two-slit experiment, I have to think in the “and” way to start with. I have to think the particle is going

through this slit, “and” it’s going through this slit. Because if it’s just going through this

slit “or” it’s going through this slit, I can close one of the slits, and it wouldn’t

make any little difference. But then as soon as I look where the particle

is, suddenly the “and” way of talking stops making sense, because it doesn’t seem–we’ll

come back to this–but it doesn’t seem as if I see the particle here “and” the particle

here. It seems as if now, I need the “or” way

of thinking. So what came out of the ideas of Bohr and

Heisenberg and people of the 20’s and 30’s was, well there must be some new bit of physics,

some way in which that Schrodinger’s equation we saw earlier isn’t the whole story. So suddenly the wave function stops being

peaked here and here, and it jumps. It collapses. So let’s see a quick picture of that collapse. So if we have a probability wave here, and

this is the “and” description in your language, it could be in these variety of

different locations. And I now undertake a measurement, and I take

that measurement, and it collapses to the “or” way. It’s only at one of those locations. Yeah. Suddenly it’s here, and the rest of the

wave function is gone. And now if I turn away, and I stop measuring,

it melts back into the probabilistic description, and we’re back to a language that feels

quite unfamiliar with the particle, is in some sense, at all of these locations simultaneously. Now, the issue that it raised is that you

said, “look, we’re going to have to have some other math to make this happen.” So, first, if we just use the Schrodinger

equation, this beautiful equation that was written down, would that be enough to cause

a wave to undergo that kind of transformation? Nice and spread out. And now, collapses to one location, where

the particle is found. Can the Schrodinger equation do that for us? Birgitta? No. No. No. No. No. [to ‘T HOOFT] That means no, right? It means yes? OK So, like I said, Gerard has distinct views

which are spectacularly interesting. We are going to come to those in just a moment. But let’s now follow the history of the

subject where we’re going to just follow our nose and we look at the equation that

we have and it doesn’t do it. So what, then, do we do to get out of this

impasse? And to make this impasse even a little bit

more compelling, I’m going to take you through one version of this story that I hope will

make the conundrum as sharp as it can be, and then we’ll try to resolve it. So I’m going to take you through a little

example over here, where we have, say, a particle somewhere in Manhattan. And let’s imagine that the probability wave

makes the particle location peak at the Belvedere Castle in Central Park, just randomly chosen. What that would mean is if somehow I had some

measuring device that could work out where the particle is experimentally, observationally,

indeed it would reveal that the particle is at that location. The wave is sharply peaked at that spot, and therefore all the probability is focused right there. That’s quite a straightforward situation. Imagine we do the experiment again, and the

probability wave has a different footprint. Let’s say it’s way down there at Union

Square. If you follow the same experimental measurement procedure, and you go about figuring out through your observation where the particle is, you find, indeed, there it is, Union Square. The conundrum is the issue that David was

speaking to, where we now have a situation where we don’t have one peak, but two. Now it’s sort of like the particle is at

the Belvedere Castle AND in Union Square. And that’s puzzling, because if you go about looking at the observation, what do you think will happen here? Well the naive thing is, your detector kind

of doesn’t know what to do. It’s sort of caught between the particle

is at Belvedere Castle and it’s at Union Square. But the thing is, nobody has ever found a

detector–well, I should say nobody who is sober has ever found a detector that does

this. Right? This is not what we experience in the real

world. So this is the issue that we have to sort

out. Because that naive picture is not borne out

by experience. And I think many people here and many people

in the community have thought about this. You in particular, David, believe that you

have the solution. It has a long historical lineage, but why

don’t you tell us a little about the approach that you think resolves this? OK. Let’s start by reminding ourselves, what’s

the problem with just saying the wave function suddenly jumps to being in Belvedere or Union

Square? And the problem is really just that we’d

have to modify the equations of physics at every level to handle that. So the Schrodinger Equation just does not

let that happen. And to put it mildly, we’ve got quite a

lot of evidence for that structure of physics, and for a whole bunch of reasons. Actually trying to change the physics to make that sudden collapse of the wave function physical, and not just, as Gerard was putting

it, not just as a sort of fuzzy talk, is a really, really difficult problem. But you could say that we have to do that,

because, like Brian was saying, it doesn’t seem we ever see a particle here and here

at the same time. And I think Brian’s joke is about right

to just what our intuition is about what it would be like to see a particle here and here

at the same time. It would be like being really drunk, like

seeing double. But here’s the thing, if you want to work

out what some physical process would be like, and my looking at a particle is just one more

physical process, it turns out intuition is not a very good way to predict what happens. So how do we ask, what would it really be

like to see a particle that’s here and here at the same time? Well, what does the physics say? I’m just one more measuring device. And the physics says something like this. If I saw the particle here, I’d go into

a state you might call a “seeing the particle here” state. If I look at the particle there, then I’d go into

what you’d call a “seeing the particle there” state. If it’s in both states at the same time,

then I go into both states at the same time. So, being a little loose for the minute, then

I’m now in the state “seeing the particle here” and “seeing the particle there.” And if I tell Brian where the particle is,

because I’m sure he’s fascinated, Brian’s now in the “David says it’s here, David

says it’s there.” And the whole audience would have to listen

to me say this. You’re all now in the “it’s here”

and “it’s there” states at the same time. And the reality is that, even if I don’t

tell you this, uncontrollable effects spread outward. And so, before you know, the whole planet

or the whole solar system is in a “particle was seen here and particle was seen here at

the same time” state. And those two states don’t interact with

each other. They’re way too complicated to do the sorts

of interference experiments we were doing with the two slits. You can’t do a two-slit experiment on the whole planet. And so for all intents and purposes, what

the quantum theory is now describing is two sets of goings on, each of which looks, for

all the world, like the particle being in a definite place. And that’s where the terminology of this

way of thinking about quantum mechanics comes about, the Many Worlds Theory. It was Hugh Everett who said, look, if you

just take quantum mechanics seriously, you’re led to this crazy sounding idea of there being

many parallel goings-on at the same time every time you make a quantum measurement. But the thing I want to stress here, is it’s

not that we say quantum mechanics is weird, but let’s bring in an even weirder idea

out of the realm of science fiction to make it even stranger. It’s, whatever it was saying, and what the

people who have pushed his idea since then have been trying to make precise, is the idea

that the quantum theory itself–that Schrodinger equation itself–when you take it very seriously,

tells you that, not at the fundamental level, not at the level of microscopic physics, but

at the level that we see around us in the everyday, then the physics is describing many

goings-on at the same time. The quantum probability wave carries on being

an “and” wave all the way up. So you’re talking about many universes? So this is where this idea of parallel universes

or many worlds comes from. So, in the example that we were looking at,

there would be, say, if you were undertaking this measurement, there would be “you seeing

the particle at Belvedere,” “you seeing it at Union Square,” and as you said, once

you articulate that, we’re all hearing it, and we’re all going along with you in one

universe and another. So that’s one approach to try to disambiguate

a situation in which the quantum mechanics has many possibilities. You’re saying, “no no, it’s not just

that one of them happens, they all happen. They all just happen to happen in distinct

universes.” And weirdly, that’s a conservative idea. Mathematically conservative. And that’s actually a vital point. So, and this is an idea that is hard to communicate

to a general audience. I’m sure many of you are technically trained,

but those who aren’t: if you stare at the equations of quantum mechanics and just take

them at face value, this seems to be where the math takes you. But does that convince–so are you guys convinced? Birgitta, you— There are alternative perspectives. But what about–why don’t you like this

one? I like it. I think it’s fascinating. I think it’s wonderful. But let’s bring in some information. So how much information are we going to keep? So this “many worlds” hypothesis would

say that we’re keeping every single piece of information. But if we–so we have a measuring device,

and then the measuring device is interacting with the environment. Then the environment of outside is also playing

a role, it’s also affecting the measuring device. And of these many many options, measurements

that can be recorded by the measuring device–if the environment, which is interacting with

that measuring device, is interacting with that measurement device and producing many

more outcomes, and yet then we throw–in producing much more information, but then we throw all

of that information of the environment away. Then we’re left with something which produces

just one of these options. So you’re talking technical language of

what’s called “decoherence”? Yes. I’m introducing this technical term that

the coherence of the wave function, the preservation of these… So your belief is that if we don’t focus

just on the simple particle itself, but take into account how it talks to and interacts

with the full environment, you feel like that’s enough to solve the conundrum? Well, I’m, there’s also mathematics to

justify this. So this is another perspective. I’m not saying we don’t know it, which

is one. But this is a very strong argument for saying

why we don’t actually experience many, many universes at once. What’s your view on the many— Yeah, I mean, I think it’s what you were

describing. It’s basically just going all in on the

Schrodinger equation, saying, OK, we’ve got this beautiful equation. It applies to the atomic world. Let’s take it seriously and just, if we

believe in it, then not only kind of understand through the mathematics there that at the

local level you would effectively get something like collapse if you look at just a part of

the description of the system. But then the only thing is that, in the end,

it’s a little bit disturbing philosophically that there’s maybe a part of the wave describing

the universe where, you know, I’m a football player, or then that question of well why,

why do, what is our experience in that picture of many worlds? Is there some way to understand, you know,

why is it that we’re just experiencing one thing and So Gerard, how about–now, I know that you

are going to take us somewhere else now. When you asked me about this question about

the wave function, you were nodding–I was supposed to nod “no,” and I nodded “yes.” And, I caught you off trap for a moment. And the point of this is that the quantum mechanics today is the best we have to do the calculation But the best we have doesn’t mean that the

calculation is extremely accurately correct. So, according to the equations, we get these

many worlds. I agree with that statement. But I don’t agree with the statement that

quantum mechanics is correct, so that we have to accept all these other universes for being

real. No, the calculation is incomplete. There is much more going on that we didn’t

take into account. And then again, you can mention the environment

and other things that you forgot. So, we are so used to physics that unimportant

secondary phenomena can be forgotten, it just leaves out everything taken for granted. But if you do that, you don’t get for certain

what universe you’re in, you get a superposition of different universes. It doesn’t mean that the real outcome that

was really happening is that the universe splits into a superposition of different universes. It means our calculation is inaccurate, and

it could be done better. And that doesn’t mean that our theory is

wrong, but that we made simplifications. We made lots of simplifications. Instead of describing the real world, we split

up the real world in what I call templates. All the particles we talk about are not real

particles, they are just mathematical abstractions of a real particle. We use that because it’s the best we can

do, which is perfect. It’s by far the best we can do. So, in practice, that is just fine. But you just have to be careful in interpreting

your result. The result does not mean that the universe

splits into many other universes. The result means, yes, this answer is the

best answer you can get. Now, look at the amplitude of the universes

that you get out. The one with the biggest amplitude, is most

likely the rightest answer. But, all the other answers could be correct

or could be wrong if we add more details, which we are unable to do. Today, and perhaps also tomorrow. We will also, we will be unable to do it exactly

precisely correctly. So we will have to do with what we’ve got

today. And what we got today is an incomplete theory. We should know better, but unfortunately we

are not given the information that we need to do a more precise calculation. That precise calculation will show wave functions

that do not peak at different points at the same time, like you had in Manhattan at this

address or that address and we are at a superposition. No, in the real world, we are never in a superposition,

because the real world takes every single phenomenon into account, and you cannot ignore

what happens in the environment and so on. If you ignore that, then you get all this

case superposition phenomena. If you were to do the calculation with infinite

precision, which nobody can do, if you calculate everything that happens in this room and way

beyond and take everything into account, you would find a wave function which doesn’t

do that. You would find one which peaks only at the

right answer and gives a zero at the wrong answer. Now, this view… But the theory is so unstable, that the most

minute incorrectness in your calculation gives you these phony signals that say, maybe the universe did this, maybe the universe did that, maybe it did that. Only if you do it precisely correctly, then

you only get one answer. Yeah. Now that resonates obviously with an idea

that goes all the way back to Einstein, that quantum mechanics was incomplete– Yes, this is. Yes, I think Einstein would agree with such— Yeah, I think that he would too. Maybe he would have his own ideas. But anyway, to me it sounds like an Einsteinian

attitude. That, no, nature’s absolute. God doesn’t gamble. The gamble is in our calculation, because

we can’t do any better. So let’s take a step back and see why Einstein

came to this conclusion that quantum mechanics is incomplete, which takes us to the next

strangeness of quantum mechanics, which is something called quantum entanglement. So, this is an idea that has a long history

in physics. “I would not call”–entanglement, which

we are about to talk about–”one but rather the characteristic trait of quantum mechanics,

the one that enforces its entire departure from classical lines of thought.” So here’s again one of the founding pioneers

of the theory who thought about this notion that we’re about to describe as the key

element that distinguishes it from our intuition, our classical way of thinking. And as we’ll see, it quickly, in the hands

of Einstein, takes us to a viewpoint that aligns really with what Gerard was saying. And that comes most forcefully in a paper

from 1935, a date that’s good to keep in mind, because we’re going to come back to

it in just a little bit, where these folks write a paper, Einstein, Podolsky, and Rosen. And we can just, this is actually a New York

Times article on it, and you see that they call the theory “not complete,” much as

Gerard was describing. And it’s good to get a feel for why it is

that they came to this conclusion. And it involves this idea of entanglement,

and I’d like us to walk through that, just some of the key steps. And it’s good to do it in the context of

an example. It’s not the example that Einstein and his

colleagues actually used. But it’s an example having to do with a

quality of particles called spin. So just to set it up and then I’ll let the

panelists take it from there. When we talk about a particle, say, like an

electron, it turns out that has a characteristic called spin. You could think of it almost like a top that’s

spinning around. And roughly speaking, using classical language

to get a feel for it, if the spin, say, is counterclockwise, you say it’s spinning

up. If it’s clockwise, you say it’s spinning

down. And weirdly, a particle can be in a mixture

of being both up and down, using your language of the “and.” And only when you measure the particle, you

find that it snaps out of that mixture, and is at–in the case of the particle in Manhattan,

it was either at one location or another–here it’s one spin or another. It’s spinning down or up, but it’s definite

after you do the measurement. You never find it in between. Again, you can do a second measurement, and

say it snaps out of this fuzzy haze and it’s spinning up. And that’s a quality of a single particle

that’s well known in quantum physics. But entanglement arises when you don’t have

one particle, but rather when you have two of them And here’s the weirdness that happens. If you do a measurement in this situation,

even though each particle is 50% up or 50% down, you’d think they’re completely independent,

but you can set these up in such a way that if you do a measurement, it’s always the

case that if the one on the left is up, the one on the right is down. They never are both up or both down. And we can go back to this story again, do

another measurement, and they can be as far apart as you want, and you measure it, and

find, say that the left one is down and the right one is up. So they’re kind of locked together by a

quantum connection–quantum entanglement–which is graphically what we’re representing by

this yellow line over here. Now, Gerard was talking about incompleteness

of quantum mechanics. What was Einstein’s view of what was going

on here? Well, Einstein’s view was that, really,

what’s going on here is, if you have particles that the math says are both spinning up and

spinning down at the same time, if you could look deeper to the deeper structure that Gerard

was referencing, you’d find that these particles always have a definite spin. They’re not actually going up and down;

that’s just mathematics. They actually have a definite spin and therefore

if you measure them and find that one is up and the other is down, they were already like

that. It’s not as though there was some long distance

connection or communication going on. And this is what’s known as quantum entanglement. And when I describe this to a general audience,

people often get the phenomenon. Yeah, you measure it here, it’s down, you

measure it there, it’s up. But then they always come back to me and say,

“but what’s really going on?” You know, like, but just, “tell me, explain

to me.” I say, “I just did explain to you what’s

going on. That’s all there is–” “No, no,” they

say, “please tell me, how could this be?” So how should we interpret this result? So Einstein says the way you interpret it

is, it was like this the whole time, nothing surprising. But then we try to do experiments and see

if that’s the case and what happens? So there’s a famous person that comes into

the story, who, John Bell. So what is, Mark, what does Bell do for us? I mean, basically, to put it simply, he finds

that any kind of simplistic, Einstein-like description where the thing had the definite

configuration before we did that measurement, it can’t explain the results. So it just…you can’t… When you say the results you are talking about

observational results. That’s right. Yeah, so he writes this famous paper. What year, is this 1964? I think this…I think it’s like 1964. He writes this famous paper where he surprisingly

is able to get at an experimental consequence of an Einsteinian view, that things are definitely

up or down before you look, it’s just the mathematics that’s giving this weird superposition

quality. And then people go out and ultimately starting,

say, with John Clauser in the, this must be the ‘70s then into the ‘80s with Alain

Aspect. They carry out the measurement, and they find,

as Mark was saying, that the Einsteinian picture doesn’t describe the actual data. So if Einstein were here, I think he’d have

to conclude that, not necessarily that quantum mechanics is complete, but the chink in the

armor that he thought he found isn’t actually correct. So, Gerard, what’s your–because you’re

coming at it from an Einsteinian view–how do you deal with, let’s say this very experiment? May I just add one point of interest? You can think of a classical experiment as

very simple, but not strange at all. Think of–I take two marbles in a black box. One marble is red, the other one is green. Now, I shake the marbles as much as I want. I put–blindfolded, I put one marble in one

box and another marble in the other box. And now I bring these boxes as lightly as

away from each other. As soon as somebody who sits–or say one on

Earth and one on Mars. So somebody on Earth opens this box, and at

the same time the guy on Mars opens his box. Before they opened the box, they didn’t

know what kind of marble they had in there in the box. Was it the red one, was it the green one,

you don’t know. As soon as the one on Earth opens the box

and says I have the red marble, instantly, the guy on Mars knows he has the green marble. That information went much faster than light. But you also know all this is nonsense, because

they knew it in advance. I had one red, and one green marble. So what’s the big issue? No problem, right? So, the Bell experiment is fundamentally different

from this situation, in the sense that– So what you described, you described sort

of the Einsteinian picture. Einstein would say, don’t get worked up

about entanglement. It’s just like having a green marble or

red marble. Einsteinian picture would work perfectly well

for the box with the red marble and green marble. No sweat, no difficulty. We understand this situation. No miracle at all. But for the Bell Lab experiment with the spinning

particle, you’re using the fact that the particle is a quantum spinning particle, and

a spinning particle is something very, very strange. It can either spin up or spin down. But then someone asked, what about spinning

sideways? Why not rotate the particle 45 degrees or

90 degrees, and they would say “yes, but that’s a quantum superposition.” But, now if the one person on Earth looks

at the particle spinning up, the one on Mars is spinning down, but then when the person

on Earth sees the particle spinning sideways, the guy on Mars sees the particle spinning

sideways in the other direction, and sees it either spinning up or spinning down, we

still don’t know. But when they both look at the sideways direction,

they again see the spin opposite. That is the miracle. That is a thing which is very very difficult

to understand classically. I maintain, but this is my private opinion,

that you can explain it, but it is– How? Because this is where Einstein failed… Because they both have the same origin. They both came eventually from an atom emitting

two spinning objects: two photons, or two electrons or something like that, which were

entangled. So the entanglement can be explained in terms

of correlations, so that the initial state was not that the particle could be doing just

anything. No, there are correlations all over the place. This is very, very difficult to explain, and

I even wouldn’t dare to try to go in depth, but the answer lies in correlations. Do you think there is a way out of this impasse? I think there is a way out. But it’s extremely non-trivial, and if you

don’t do it quite right, you end up mystified by the situation. It is actually also extremely hard to make

a model that works, that gives this strange-looking phenomenon. So yes, we have a problem, but now I think

the problem has an answer, but the answer is very difficult and you have to work very

hard to make it all hang together properly. That will be in the footnotes of tonight’s

program. You’ll receive it in your email. So David, your view on entanglement? Is there a mystery here, or…? There’s a kind of mystery, and it can link

to our earlier mysteries. Look at it this way. My wave–my probability wave for the two spinning

particles, you can kind of describe it as something like half is this–down up–and

half is this–up down. And again we can ask this–well do I want

to think about it as an “and” or an “or”? Do I want to say, well, it’s this “or”

it’s this, or do I somehow have to say it’s this “and” it’s this. Now if it’s this “or” this, that’s

Gerard’s case. That’s not mysterious at all. And that’s exactly what Einstein, Podolsky,

and Rosen hoped was the case. But what Bell’s results show us is that

the “this OR this” reading of entanglement, just like in some ways the “this slit OR

this slit” reading of the two-slit experiment would lead to experiment predictions that

don’t pan out. We can’t, at least straightforwardly, we

can’t make sense of the experiments without seeing the entangled system as being this

“and” this. And now we’re right back to the mystery,

because understanding how it can be this “and” this, which seems to imply some sort of deep

connection between the two systems, where somehow saying everything there is about this

side, and everything there is about this side separate doesn’t tell you anything. That weird reading seems compulsory. Right. So, Birgitta, your view on this? Should we fret about entanglement? Is it— I think Gerard raised a very important point. It’s that when one talks about entanglement,

one should not forget to say how the particles got entangled. And they get entangled through an interaction. And I think, to most physicists, entanglement

is not so mysterious if we think about it in those terms, even in just atomic or molecular

terms. So you take the two electrons in the helium

atom. In the ground state, the helium atom is–if

we were to separate the two electrons—we know we can’t do that, because they’re

sitting on top of each other. But were you able to take those two electrons

and pull them apart, they would be in a perfectly entangled pair. But we know how they got there, because they

had an interaction that put them into a particular electronic state. And so if you randomly just put two particles

together, they would not be entangled necessarily. Yeah. To my mind, though, the very fact that–I

don’t care how you set it up, the fact that you CAN set it up still makes me, in Niels

Bohr’s language, “dizzy.” But yes, I agree that does mitigate it to

some extent, but still, it’s so far outside of common experience that it’s still hard

to grasp. But for these purposes, let’s assume entanglement

is real. Because now we want to move on to think about

how it manifests itself in some unusual places like in the vicinity of a black hole. So that’s the next thing that we’re going

to turn to. And for that extent let’s move on to the

next section– “Quantum Mechanics and Black Holes.” And we’ll also begin with a little clip. Lisa, do you have a stray dog down there? Um, it’s a lot worse than a stray dog. Two stray dogs? It’s a black hole! That was going to be my next guess. Are you sure your next guess wasn’t “three

stray dogs”? Maybe. Alright, so black holes. I think most people here are quite familiar

with what they are. But just again, to get us on the same page,

Mark, just describe what is a black hole. Yeah, so it comes out of Einstein’s picture

of gravity and how the space we live in is not sort of a passive background, but it’s

dynamical, it can warp and bend and it does that kind of in response to the mass and energy

that’s in the universe. And the black hole is the situation where

you take that to the extreme. You have, so much matter–could be a gigantic

star at the end of it’s life when it has burned up it’s fuel and it starts to collapse. And as it’s getting denser and denser, warping

the space more and more, through Einstein’s picture. And at some point, you get this space–the

space time is warped so much, that you get the thing we call a horizon, you get the point

of no return where if you go past that, you can’t get out, you can’t send signals

out, light can’t get out, and that’s our basic notion of a black hole. Now there are many puzzles about black holes,

and some of them are right at the forefront of research. One in particular that I want to focus on

as it will bring together these ideas of entanglement and ultimately the structure of spacetime,

which is where we’ll get to in the next chapter, which is simply this–if something

falls into a black hole, what happens to the information it contained? Right? So to just be concrete, imagine if I was to

take out my wallet and throw it into a black hole. My wallet has all sorts of information, my

credit card information–oh, there it is. They took it out of my pocket, they throw

it into the black hole, it crosses over the horizon, the edge that Mark was referring

to. And at least in the non-quantum, the classical

description, it’s just gone, right? And then you can think that the information

is sort of, maybe still there, it’s just on the other side. We can’t get at it, unless we go in. But if we do that, there are consequences–we

can’t come back out with the information. You know, so that’s sort of the classical

story. This becomes a really big puzzle and a bigger

puzzle when we include quantum mechanics into the story, because of a result that was due

to a couple of very insightful physicists–one who you may not have heard of, one who you

will have heard of. So, back in the ‘70s, Jacob Bekenstein,

and also this fellow over here, Stephen Hawking. They began to apply quantum ideas to black

holes, and found a surprising result, which is that black holes are not actually completely

black. So anyone just jump in and–what is it that

that means? Or Mark, go ahead. So Hawking found, when you start to apply

quantum mechanics to the physics in the vicinity of a black hole, that there are quantum effects

that lead to the black hole seeming to emit particles out of it, as if– Yeah, I think we have a little picture that

can help. Yeah, so this sort of a quantum effect where

you have something happening right at the horizon of the black hole where what we would

call virtual particle and an antiparticle, they— The particle that is red, and the particle

that is blue– Virtual particle is red, and the antiparticle

is blue. This can happen in quantum mechanics, but

because of the black hole horizon, the particles end up going out, and so what it looks like– And their partners fell in, they went out. We don’t see those partners— Which would mean, from far away, if we look

at this situation… That’s right. So there we go. So the black hole looks like it’s emitting

stuff, and it’s actually losing some of its mass. So you see it’s getting smaller. Hawking did a detailed calculation to show

that it’s behaving like an object that’s getting hotter and hotter and hotter, and

sort of what you’d call evaporating more and more quickly, and ultimately disappearing. So all of this information that might have

been in the black hole, it’s now this heat, the thermal radiation going out into space. And all this is happening, if I understand–so

you got the edge of the black hole, you got this quantum process right at the edge that

we’re familiar with. Particle and anti-particle sort of pop out

of empty space. The difference is, now with the black hole

there, it can kind of pull on one member of the pair, get sucked in, the other just rushes

out, and that gives rise to radiation flying outward. And that’s what makes this puzzle sharp,

because if the wallet goes into the black hole, and then you have this radiation coming

out, ultimately, and perhaps the black hole even disappears through this. Everything that went in has come out, but

if the radiation itself doesn’t have an imprint of the wallet, doesn’t somehow embody

the information, the information would be lost. Hawking’s calculation showed that, it should

not matter what formed the black hole. You get the exactly the same radiation. But whether it’s my wallet or whether it’s

a refrigerator, chicken soup, it all would sort of come out the same. The information is lost. Now this disturbed Gerard deeply. Very much so. But the statement you just made was only about

the average Hawking particle. The Hawking particles form what you call a

thermal spectrum, which means that they come out in a completely fundamentally chaotic

way. But it doesn’t mean that they don’t know

in what way they come out. Again, it’s quantum mechanics, but again

there is a theory on the line of quantum mechanics which is more precise, and which we should

provide the missing information. And yes, there was missing information, and

yes your wallet does leave an imprint on the radiation coming out… So can we show–? …Because your wallet, yes, if you want to

have a moment, your wallet carries a gravitational field, even though it’s very light compared

to a planet or a star, it does have gravity. That gravity is sufficient to leave a very

minute imprint on the outgoing particles. And that’s enough… So we sort of see that imprint here of my

wallet on the edge of the black hole. The effect of this is that the information

gets stuck on the horizon of the black hole, ready to come out again in the form of the

Hawking particles. And this, in principle, you can compute. And you find that the culprit is the gravitational

field of your wallet, that many people forget to take into account. Then you get a tremendous problem. You don’t understand how can it be that

all those dollars in your–and those credit cards in your wallet, that information gets

out. Well, a normal person would never be able

to identify, to decompose Hawking radiation to get back your wallet. So surely, it’s a better shredder you’ll

never find anywhere, but even the shredder still contains the information. Right. So people won’t actually be able to do this

reconstruction, but in principle… No, in practice, of course you won’t. …just like with the shredder, in principle

they would be able to do that. So this is an idea that you developed also

with Lenny Susskind, which gives rise to what we call the holographic principle, the holographic

description. Again, because if information is stored on

a thin surface at the edge of the black hole, it sort of brings to mind a hologram, which

is a thin piece of plastic which has etchings on it. When you illuminate it correctly it yields

a three-dimensional entity. Here, you’ve got information on this thin

two-dimensional surface, which is able to reconstruct the object that went in. And that’s why this word “holography”

is used. So this is sort of a deep insight which has

been generalized. People, Gerard and Lenny and others, think

that perhaps the right way of thinking about the universe in any environment, even right

here on Earth, there’s a description where data exists on a thin two-dimensional bounding

surface, which would make us the holographic projections, using this language, of this

information that exists on a thin surface that you wouldn’t think would even have

the capacity to store enough information to make it adequate to describe all the comings

and goings in this three-dimensional realm. Yes, David? Yeah, I just want to sort of pin down for

a moment, like, why should we care in the first place that the information was lost? We’ve- but by assuming the information was

not being lost, we’ve made our way to remarkable new ideas in physics. And I think there’s a somewhat of a temptation

to think, “well yeah, maybe that’s the wrong lesson. Maybe what we should learn is information

disappears sometimes. Deal with it.” Which is what Hawking said. Which is what Hawking himself thought, exactly. And there’s still a minority of people in

physics who take that line. And I think the deeper reason to think why– But Hawking doesn’t take that line in the

end. Hawking changed his mind. Right. And I think the deeper reason to see why the

information being lost is such a problem is, it goes back to where we started, the idea

that black holes are hot, that everything else in the universe that we know is hot has

a story to tell about why it’s hot but basically says it can be in zillions and zillions

and zillions of states, and by statistically averaging over all those states, we get out

the hot behavior. That’s how thermodynamics is grounded in

microscopic physics for every other hot thing in the universe. If information is lost forever in black holes,

then black holes are hot for a fundamentally different reason than why everything else

in the universe is hot. And this whole story about holography and

about information being preserved is basically a bet, and it seems to me a very well-motivated

bet on the idea that black holes are hot for the same reason everything else is hot. Right. So, again, one way of saying that is, when

a black hole is radiating, it’s radiating because, in some sense, stuff is burning near

the edge, even though all the matter that fell in is compressed at the center. And that’s unfamiliar, because, when a star

burns, it’s burning at its surface, so the stuff responsible, the fuel, is burning right

where the radiation is emitted. But with a black hole, all of the fuel, the

mass, is here, whereas the radiation is coming out over here. And that distinction might suggest that it’s

a different kind of burning, but you’re absolutely right. We want all the usual ideas of physics

to work, it better be the same kind of burning. And that’s what the approach of holography

provides for us. And what I’d like to do now is if we can

jump actually to the next chapter, just because time is a little bit short. I want to take this idea of entanglement,

and Mark… Let me just introduce that a little bit. One of the things–you know, Hawking did his

calculation in an approximation, where he didn’t have a theory that actually combined

gravity and quantum mechanics. He was using bits of quantum mechanics and

Einstein’s theory and coming up with this result that you lose information. And if that were true, it would say that gravity

and quantum mechanics are incompatible. You have to change quantum mechanics somehow,

but in quantum mechanics, you never lose information. And so this is why this holographic insight

of Gerard and others is so important. It sort of has given us a way of avoiding

Hawking’s conclusions, and Hawking has accepted that. And so, this way–there’s now–it’s been

for the past 20 years, we’ve got a way of doing quantum gravity, of combining gravity

and quantum mechanics. And it uses this holographic idea in a completely

essential way. And it was like that picture of the Earth

with the data around it. It’s kind of like saying that our reality

that we experience, this gravitational universe that we’re in, there’s kind of an underlying

reality which you can think of as those bits, those 1’s and 0’s on the surface surrounding

us. And that’s what Brian was referring to as

the holograms. So somehow if you want to understand the quantum

mechanics of a system with, say, black holes and gravity, what you really want to do is

understand the quantum mechanics of that hologram, and not kind of directly trying to the calculations

like Hawking did of the black hole. So it’s a very powerful–we’ll come to

you in half a second to summarize that, but–it’s a very powerful dictionary, in some sense. You now have two ways of describing a given

physical system. You can describe it sort of in the conventional

way that we’ve always thought about it as a three-dimensional world that has comings

and goings. Or you have an alternative language if you

want to make use of it, which is the physics that takes place on this thin bounding surface. And sometimes, that latter description gives

you insights that are very difficult to obtain from the traditional description. And we’re going to come to a version of

that in just a moment. But yeah, Gerard. Yeah, I think you can make the picture a little

bit more clear perhaps by realizing that whenever you throw something into the black hole, when

you look at it from the outside, you will never actually see it pass through the horizon. It hangs around at the horizon. So it shouldn’t be too surprising that that

information also hangs around at the horizon. So can I just flesh it out for half a second? So what Gerard is saying is, if you look at

how a black hole affects the passage of time, you find that as a clock gets closer and closer

to the edge of a black hole, the clocks ticks off time ever more slowly. So if you’re watching this from very far

away, the object is starting to go in slow motion as it goes toward the edge of the black

hole. It doesn’t just immediately go over the

edge. In fact, it goes so slow that it would take

an infinite amount of time from your perspective for it to actually fall over the edge. So it hangs out there. The observers there would think that the clock

was standing still. But the clock is simply slowing the time that

the observer, who goes with the clock, sees that “oh, that’s time I’m going through

the horizon.” But, for the outside the observer, that’s

the eternal time, it never changes anymore. The other observation one could make is, it’s

a very elementary calculation to find out how much, how can it put other kinds of information

in such a box? Take a box with a certain radius–or let it

be spherical for simplicity. And ask, how much information can I put in

the box no matter what I do? So take a gas, or take a liquid, or take a

dictionary, throw anything in a box, when do I get the maximum amount of information? You can calculate that, and what you find

is, if you try to put more things in the box, that takes so much energy that those encyclopedias

that you try to put in this box will automatically make a black hole. And what is the object that contains the most

information that you could ever imagine? It’s the black hole. It always wins. So, the black hole is the maximum. There is no way, no matter what you put in

the box with a given radius, to get more information in that box than what fits on the surface. And that’s the holographic principle. Information is two-dimensional, not three-dimensional. And that is very strange, so that’s why

I call it holography. It is as if, you know, we have a three-dimensional

world, but you take a picture with the machinery of holography. I don’t really know. It is a camera which makes a picture, and

if you look at the picture from different angles it looks like reconstructing the three-dimensional

object. But it only exists on a two-dimensional surface. So did you doubt this idea, when you first,

or was it? Yeah, this is, in the discussion with Lenny

Susskind, the word “holography” came up. Right, but were you certain that this was

right when it popped out? Or was this so strange that you were…? Well, no, it is very strange, but this comes

out of the calculation, must be true. But it’s very counterintuitive. Yeah, yeah. It’s like saying our reality is not as real

as we think it is. Yeah, right, yeah, which for most of us is

pretty odd. So the question is, what happened to the rest

of the information. The three-dimensional information doesn’t

disappear, doesn’t get lost, this is the mysterious aspect of our space time. So let’s take this holographic idea, and

push it one step further, which, Mark, you have been pioneering. Yeah, I mean, so if we take it seriously then… But let me–before we get that, because there’s

one thing that we didn’t discuss that would be useful, and it’s right here, which is,

something else that happened in 1935, which is the idea of wormholes. So if you can just take us through what a

wormhole is, and then we can make the So the wormhole, if you set to solving Einstein’s

equations to figure out, well, what kind of geometries are possible for space time, then

there’s a weird thing that comes out where it’s like you have a black hole in an empty

universe. And then there’s this entirely separate

universe with another black hole in it. So the top and the bottom of this picture. Yeah, so that’s the space. The flat part is the space in one universe,

and then this is like a black hole. But you see it’s connected down to the flat

part, which is like the other universe, and there’s this physical, geometrical connection. So if one person jumped into one black hole,

and the other person jumped into the black hole at the bottom, they could potentially

meet up inside that wormhole, you know, before being annihilated by the black hole. So it’s sort of a tunnel connecting these

two things. That’s right. Are you volunteering? Uh, I’ll pass on that one. Alright, and who–so you may recall I said

remember the year 1935, that was that Einstein Podolsky Rosen, which was that entanglement

that we’ve been discussing. This is also 1935, where it’s Einstein and

Rosen–so again, 2 of the 3 folks involved. And in Einstein’s mind, I think it’s pretty

clear, and correct me if you think otherwise, I don’t think he thought there was any connection

between these two 1935 discoveries. Entanglement on one hand, coming from quantum

physics, wormholes coming from general relativity–completely separate subjects at the time, and some of

the work that you and various of our other colleagues have been pursuing is suggesting

that there’s actually a deep connection between these ideas. It’s truly amazing, so So, I think we’ll sort of step through that

now, if that works for you. So we have a little, you can sort of walk

us through what we’re having here So we’re looking at some kind of universe. There’s a black hole in this universe. And then what’s on the outside is this hologram;

this is the actual mathematical description in our modern way of understanding. So this red around the outside has all of

the information that is telling us what kind of geometry is in there– So that’s Gerard’s hologram. The information. That’s Gerard’s hologram. On the outside, you’ve got that hologram

in a particular kind of physical configuration. And that’s coding for the fact that there’s

this black hole, and maybe some stars in there in the spacetime. Yeah. And then if we go on and go to the second

black hole in the story. OK, so we show– Alright, now we’ve got two separate black

holes. And basically that’s going to be encoded

by some other information. So you change up the information and now you’ve

got two black holes. Yup, and then if we add to the story a certain

kind of entanglement, say, so… So here what we did was we turned that situation

into one where you have a wormhole connecting behind the two black holes. And the remarkable thing is, in order to do

that in the holographic set, in the holographic description, in the outside description, what

we actually, you know, we have to do something fundamentally quantum mechanical. What we had to do is actually add in a whole

bunch of entanglement between different parts of the hologram. And that was what achieved getting this, this

wormhole. So, just to summarize, because this is a deep

and utterly stunning idea, you’re saying that entanglement in the holographic description,

the red description, is, in the interior description, nothing but a wormhole connecting two black

holes. That’s right, which is, sort of a classical

thing that would have been covered by Einstein’s kind of classical understanding of gravity. It’s just a geometrical connection saying

you could get from here to here, and that property is entirely, according to this–or

according to our current understanding, due to quantum entanglement between different

parts of the hologram. And, moreover, if you find that you can actually

generalize this, that it actually even holds without a black hole in space. So take us from here. Yeah, so I–this was I guess 2009, I was thinking

about that. It seemed crazy, and then one of the things

that you realize if you start reading about entanglement and about just our description

in these theories of just empty space, is that even when you’re describing empty space,

you still have entanglement in the hologram. In the holographic description, there’s

lots of entanglement. And then you sort of ask yourself, well wait,

if that entanglement in the previous story was creating a connection between the two

black holes, could all of this entanglement there, in this picture–could that have something

to do with the fact that the space is sort of connected up into one nice smooth, empty

universe? That space has threads. In some sense, we call it the fabric of space,

is it’s somehow threaded in some manner. Could that be related to this entanglement? And then you were able to mathematically study

that by mathematically cutting the entanglement lines on the outside. Right. So it’s what we call a thought experiment. You just sort of take your math–your description

of this and you say, well what happens if I cut those threads of entanglement. What happens if–? So if we cut some of them— –I take the left half of the hologram and

the right half of the hologram, and I remove the entanglement between those two sides? There’s an effect. You remove entanglement in the hologram, and

then the spacetime starts splitting up, and it, you know, you could actually imagine even

more than this. So you’ve got a ball of clay, and you’re

pulling it apart, and it’s getting further and further apart, and the middle is pinching

off, and so you could keep doing that. You say, well what would happen if I took

away even more entanglement, and took away even more entanglement, and then in this model,

you know, now you’ve got your space and it’s split into four pieces. And I still got a little bit of entanglement,

but I’m going to take that away, and what happens in this description is that the big

nice empty universe that you thought you were describing just splits up into millions of

tiny bits. And once you’ve got no more entanglement

there in this description, you’ve got no more spacetime at all. And so you get to, you know, if this is all

right, you get to this incredibly dramatic conclusion that maybe you’ve just understood

what space actually is, and it’s actually fundamentally quantum mechanical that space

is somehow a manifestation of quantum entanglement in the underlying hologram system. So it’s this beautiful possibility that

we may actually get insight into what holds space itself together, and it may be entanglement

in this holographic description that’s actually threading it all together, which is, you know

I have to say, you know, as a graduate student, I, you know, as a, you have dreams of things

that you might one day gain insight into. Certainly when I was a graduate student, the

idea that we might somehow understand the fundamental structure of space itself, it

was one of those unattainable dreams. And the work that you guys are doing is starting

to reveal a possibility that we may actually get there. So I’m going to personally applaud right

here, because that is just, you know, an absolutely stunning insight which puts together all these

ideas–the ideas of entanglement, the ideas of holography, all put together to gain these

insights. So we’re sort of out there in the depths

of some pretty hefty ideas. We’re just going to spill over for a couple

of minutes, I hope that’s OK with you. Because I just want to sort of pull us back

a little bit to what quantum mechanics can actually do in the world around us that might

actually affect the future of how we do various things. So, Birgitta, you know, you work in the arena

of quantum computing. So, what are the possibilities of actually

harnessing these weird wonderful ideas in a manner that could actually have an impact

to, say, computing power? Well, over the last 30 years there’s been

a very rapid growth of the field of quantum information, which is really a marriage of

information science and quantum mechanics–and this is still the quantum mechanics from the

1930s, 1940s. You don’t even need relativistic effects

for this. And what we’ve seen is, in the mid-1990’s,

there was a very dramatic publication of an algorithm for doing a quantum–for doing a

calculation factoring large numbers. And this was an algorithm due to Peter Shor,

and this algorithm showed–could be run many, many orders of magnitudes faster if you had

a machine, a computer that was built on the principles of quantum mechanics, using superposition

states, using these wave functions–delocalized, highly delocalized wave functions over many

bits, and principles of entanglement. And then having, however, to maintain the

very delicate quantum nature of the system and not allowing interaction with the environment

to happen. But if you do this, then at the end, after

many procedures–quantum procedures, you would construct a very carefully designed measurement,

and ideally you’d want one measurement at the end and it would be the right measurement

that would give you the answer to your calculation. And are we going to read this? Yes, this was very important, because factoring

large numbers lies at the heart of most of our encryption schemes–the encryption of

your credit cards today, airline tickets, anything that you would think of. And so, from that moment on, the–in a sense

that sort of set the race to build such a quantum computer, and there’s been lots

of advances experimentally then, over the last 20 years. And we’re now at the point where we have

functioning devices with 9 or 10 quantum bits, the quantum analog of a classical bit. And in the quantum bit, so as we saw those

examples of the spinning electrons. So, classical bit will either be in a state

0 or 1, our digital universe, which we saw in outer space just now. But a quantum bit can be in a superposition–it

can be any arbitrary superposition of 0 and 1, which means it will be both 1 or 0, or,

and at the same time, 1 and 0. So it was just carrying this mystery along

with us. And so we now have devices that are functioning

with about 10 of these You say 10? Ten. Nine actually is the economical number right

now. But people are working furiously now to build

up to about 50, 60, and within a few years we should have somewhere close to 100. And then once we get close to about 100, that’s

a critical number because at that point, one starts to have real technical challenges in

maintaining the quantum nature of the states of these machines. And that brings in these issues of the environment,

decoherence, and also very, very delicate control. And as Gerard mentioned, then you really have

to know many, many many, many variables to really control every one of those variables,

and that’s a really big both physics and engineering problem, which is just starting

to be addressed now. And then after that, I think it’s impossible

to predict how long it would take after that, if at all possible to go up to about 1000

or so, and 1000 is about the number where one would really have a machine which would

do things that couldn’t be computed in the lifetime of a universe–on a classical machine. So that would be the real change for information

processing. Amazing. So we’re just about out of time, but I wanted

to end on bringing this even further down to Earth, because you sort of sort out with

the cosmos, black holes, wormholes, entanglement. There’s a wonderful demonstration in which

these quantum mechanical ideas does something that I find eye-popping no matter how many

times I’ve seen it. Maybe some of you have seen it before–we

have our fingers crossed. Omalon, can you come out one more time with

our–with quantum levitation, if you would, which is a stunning demonstration of again,

some of the strange ways in which quantum mechanics allows the world to work in ways

that, again, a classical intuition would not expect. And Omalon does this freehand. I’m going to stand back and–you want me

to actually touch this? But I’m going to wear a glove. He only wears it to look like he’s being

responsible–I see him do this bare hand all the time. You know, that’s just crazy, alright? That’s like 77 degrees or something? You know, Kelvin, which is cold. OK, so let’s just go right to the disk if

you would, and if you just put that there. And then I’m going to give this a little

bit of a push around. Can you see that, up on the–? Can you get a shot of that? This is actually just hovering–can I give

it a little bit more of a push? And what’s happening here, if you bring

up the final slide that we have here, it’s called quantum locking. It’s a wonderful application of quantum

ideas that originated with some Israeli physicists who demonstrated this once before. You’ve got magnetic lines that are penetrating

the superconducting disc. It’s cold–that allows it to be a superconductor. And the threads of these magnetic lines are

able to, in some sense, able to pin this object along this track. This track has uniform magnetic field, and

as long as you keep it cold and superconducting, they will hold it in place. Here’s another illustration of these ideas. Look at that, can you get a close-up of that

shot right there? Can you bring that up on the screen? There you go. So you see, that’s just hovering right there,

and there’s nothing in between there. And can we actually–can we flip this over

and show how that goes? Yeah, so we can take this guy…and do you

want…OK. And do you want a glove? No, you just want to do it by hand there. Yeah, OK. More fun that way, he says. OK, yeah. Wow, that’s insane. Now, can you get a shot of that underneath

there? It is now hovering underneath, which is a

fairly stunning and yes, right down to earth demonstration of quantum mechanics. Omalon, thank you. Totally cool. Appreciate that. And I want to thank the entire panel for what

I hope was an interesting journey. David Wallace, Birgitta Whaley, Mark Van Raamsdonk,

and Gerard ‘t Hooft. So thank you very much. Thank you.

After viewing 2 of these presentations I can see that there is a language issue. The issue is we are trying to explain function of a set of infinite potential quantum mechanisms with a language that is to primitive lol. It's like physicists want to bring infinite potential into a finite description so that our primitive minds can understand a set of snap shot functions the quantum realm. I'm not a physicist but I can tell that this is like looking through an open window at a limited viewing area. You look through the window but assume what's behind the walls is doing the same thing as what you are looking at…… the problem is that's not how it works, what you are looking at is a snapshot from that moment in our perception of time or flow of reality as is translated to us through our perception and information reception as we receive it. So as we look and analyze the area, this theory or concept…. the rest of the quantum realm is still functioning, moving, changing, flowing… as it is not governed by the same time flow restrictions as we are. Actually that same snap shot which we are looking at is already potentially different, because it has infinite potential. I can see these physicists on here struggling to put into language what they actually see in their minds…… translation for even a colleague seems laborious. Which makes Sense when you are trying to bring a higher function of existence into a finite perception. Perhaps we need to create a new language, stop bringing your information down…. and start bringing understanding and language up….. build a language in which these ideas can be expressed more easily…. mathematics is a good start but its incomplete, much like quantum mechanics and theories. If we don't address the foundation of concept and communication to elevate with higher understanding, understanding can never be achieved.

I'm sorry but David's voice I can't bear to listen. He makes it hard to follow his explanation. Over all, great discussion.

This explains why my wife doesn't allways agree with me; and yes, i allways spell things correctly.

Tried to watch this for knowledge but the total lack of testosterone drove me crazy.

What I see in entanglement is these group of scientists who believe that entanglement exists. What I see is that whenever in these method they produce two particles, with opposite positions or spins. There is miracle there. These miracle entanglement changes the whole universe if it was really true. Advanced Aliens would be communicating using entanglement and not relay on the electromagnetic spectrum which is much slower

So…double slit experiment, why is there a notion that quantum world doesnt behave like the normal world? Particles in the atomic scale act as waves when they are in a volume mass. And material resonance is a thing. Since light particles are tiny, in a continuous stream of light its like a wave since they all interact with each other scattering, within the medium of spacetime. So when going through the slits, who said they go through them perfectly straight? Light scatters, particles do not all travel in the same direction uniformly, so statistically some will bounce off the sides and create scattering. Since we are talking about real speed limit of the universe (that we can know so far), things behave differently at diff speeds, masses, volumes etc. Perhaps that the resonance of the particles ability do scatter uniformly? Even in the presentation it seems like the light doesnt exactly fall only into those 'lines' but there is plenty of spread between them.

Are there experiments with half the speed of light or a third etc?

You guys are tricking yourselves into thinking you know what you're talking about.

entanglement begins at 46.00

but its not a good discussion

HI PROF. GREENE

IF “ROBIN” NAVIGATES BY USING EARTH’S MAGNETIC FIELD – IS IT PERHAPS SO ABSURD TO BE ALSO PREOCCUPIED WITH PERFECTING A HUMAN WORN GADGET OF SOME SORT, MATCHING IF NOT BETTER THAN ROBIN’S RETINA DESIGN? IMHO, OUR LIMITED VISION, LET ALONE ALL OTHER SENSES LIMITATION SEEM TO BE LETTING US DOWN- LEAVING THE WHOLE QUANTUM ENTANGLEMENT EXERCISE COMPARABLE TO COMPREHENDING A BLACK HOLE’S EVENT HORIZON WITHOUT MATHEMATICS/OBJECTS THERMAL TELESCOPE DETECTOR. FORGIVE MY IGNORANCE, I MIGHT BE FAR OFF THE MARK.

GREETINGS FROM YOUR BROTHER THAT NEVER LEFT THE SAVANNAH

Wish they had spoken about delayed choice quantum eraser

If it apparently takes infinite time for something to fall into a black hole might it be possible that actually nothing is inside the depths of a black hole and that the black hole is a membrane of zero thickness that is closed upon itself, i.e. the perfect hologram?

Have you tried pulsing the laser to figure out a probility of where the particle may be oooooorrr where it may be comming from.

I agree with the Nobel Prize winner.

Very nice discussion.

My absolute favourite episode

Isn’t it odd how each person talks so damn weird?

Is this video a joke or is it for real…? 😂

David Wallace! Where is Michael Scott!?

Yes! Spacetime is made of entanglement

What holds all of reality together? Bullshit. What is the most prevalent substance in the entire universe? Stupidium. It's what was used primarily to make humans. I have proof! Read the comment right under what i just posted.

I'm sorry, but did he say Omolon? My brain automatically thought of the weapons manufacturers from Destiny.

30:00 suddenly this just made total sense to me. The photon is entangled with all possible locations. But when you measure it, that "triggers" that particular photon to instantly "flip" the state of all other entangled versions of itself into, what can only be described as non-existance. Like a Q-Bit, the photon IS in all places at once, but when you "flip the spin" or just measure it, all others it's entangled with flip to the opposite, the opposite of a "lit" photon. Perhaps that is dark energy or dark matter.

Or, it exists in all possible locations, but when you measure it, YOUR timeline collapses to where that particle is, while in parallel timelines it may be somewhere else, and in a timeline where nobody measured it yet, it's still "everywhere".

Perhaps this is what time IS, a saved "worldstate" of all quantum events that have thus far collapsed into one state.

Soooooooo…. can it be spacetime wavy and the probability wave just a product of spacetime interacting with the particle causing it to appear as if the particle is a wave when the movement of the particle causes ripples in spacetime?

(Thought on the perception problem and how measuring changes the reality as well so? Not sure if that ruins that hypothesis or not. How does measuring change how spacetime ripples via particle nature? Idk, so that's a problem)

Amazing, thank you!!!

Quantum Entanglement: i think there is no magic but simply linked to electromegnatism similar to North and South Poles, one will always be opposite to other,

How about doing the particle spin experiment with odd no. Of particle like 3;5,7 rather than in pair

That woman is making no sense to me so is a wave a probability or a particle…so obviously i have jumped down a you tube rabbit hole

Oh Lord please give me some different synaptic connections so i can understand this stuff.

I hate when Europeans discovery shit 🤦🏾♂️ they cant except that not everything has a measurement or concrete rational fucking explanation …

A 14 year old watching theories and facts about quantum physics……

I should look for some friends

Dumb white man

Is it normal that I can‘t understand parts of the video when I’m already 16?

Brian Greene is da man — the adult equivalent of Bill Nye the Science Guy. I am terminally math-impaired, yet deeply interested in both relativity's time/space counterintuitions, and quantum mechanics' weirdnesses; Greene seems to intuit workarounds for mathlexics like me, so that while I can't "math" it, I can indeed "picture" it.

And his moderation of this assemblage of heavyweights was, in addition to being pitch perfect, also a demonstration of his grasp of the cutting-edge boundaries of physics in general. "They also serve who stand and wait — and moderate."

The double slit experiment is an abomination. Materiality, protons, electrons, Atoms, Quarks, are not Quantum.

Quantum has no mass, is not measurable, has no relative numericle value, have a numerical value of Zero-0

"We have to use mathematics, experiment and observation to peer deeper into the true nature of reality" – this is a common error. Truth is not a correspondence between statements and reality, but rather the revealing that allowed the savanna dwellers the ability to sustain themselves. In the Heideggerian clearing approach, truth is taken from the average everydayness, not the exceptionally strange distant. Just saying.

At 55:15, "…correlations … to difficult to explain…" Oh no.

It was a major failure not to have included placing a measuring device to determine which slit the particle went through, revealing that we have two bands again. The Yoon Ho version 1999 involving backward causation was known at the time of this talk and yet was not introduced in the quantum entanglement section; a further major failure given the title.

at the end there that's what a future quantum fidget spinner's prototype lmao

you know, this is probably the best way of getting some crazy ideas that are legit from reputable sources

"He is responsible for the creation of the Standard Model" how the fuck have I never heard of this guy?

Double slit is flawed..fire a particle and it acts like a stone thru water so you would have a wave being created by the particle..so you would have two waves going thru and interference would take place..your firing particle thru superfluids…oh and there aint no cat either…its a bacteria..or omeoba..or…well you get the point..

Your particle is causing a wave before it goes thru the slit…air is a full superfluid…

It's all hogwash!

I wonder if this is evidence for the individual creator? My universe if I measure…your universe if you measure?

Show us how you do the measurements, don’t just bullshit.

I've come up with my own idea of how to communicate to any distance, and time with insteant response. First you to make up for distance, so to what we call 100 light years away concider the speed of your signal. Let's just say that it goes at light speed to make things easier. If the signal would normally take 100 light years to get to it's target, to make up for distance you would use a extremely powerfully liner, off range frenquences, or maybe even glitching the signal into space. The way to travel through time is speed, and we nor matter will ever to travel through time. If something we built went that fast it would get crushed. On the other hand radio signals can. So back to our signal push it all the way of 100 light years into the past, and it'll travel for 100 light years, to reach them, and get there the second you sent it. If say you wanted to communicate to 100 light years into the past now you would have to make up for distance and time. So push the signal 200 light years into to past it will travel 100 light years but had started 200 years ago. Now you've talked 100 light years a way 100 light years into the past. Now what about the future? At first going into past for some of it is glitching still into the past, but to the future. So if you went 50 light years and it travels for 100 light years starting 50 light years in the past that's 50 years into the future. If you sent it out with out boosting it it would take 100 light years, which is the future, further then that, you would some how slow the signal and talk further and further into the future. When you go up in frequency speed goes down, when you go down in frequency speed goes up. There is also the matter I just thought of, if you made it go fast enough to do that, you would some how do some adjusting. Leave comments, and thanks for reading. Peace out.

What use is any of this. Quantum Physics I mean. Has it actually been used to do anything new. Well, it is used to describe a lot of things. But so far everything that people say is a result of QP, has turned out to have been just ordinary physics. For instance, one guy told me that if it wasnt for QP we wouldnt have computers, as quantum tunneling is used for semiconductorsin CPU's. Well actually, semiconductors are a result of rigorous experimenting, basically, chemistry and physics. They didn't use any part of quantum theory to predict anything. And similar in other instantces. Please could anyone name something that QM is used to build. Im open to new ideas.

Where's Sheldon Cooper?

Quantum entanglement=Universal entanglement = Multiverse,

What if say, you could bend space, and put a whole in it, that would be a worm whole. It would move star systems a bit closer. If that was safe you would open and close the whole so they can't see you. Then you would leave space bent for further useage… At second thought if bending space is safe you could bend and unbend, but through time is still speed, not distance… What if you pointed a straight line to another Galaxy would that mean that it was a copy of our own Galaxy, and traveling through these worm wholes would take us there? What if you found an element that causes gravity and placed it on the front of the ship, like maybe a magnet or gold and it pulled space to you as you traveled to your destination, thus bunching up or wurping space in front of you, then opening the worm whole with super heated light waves, or some kind of hot beam.

Outcome of double-slit experiment with light (photons) or electrons in which both also proven without any doubt that photons and electrons are particles. Those lines (zero-order, first-order, second-order and so forth) with jagged edges that are constructs of pixels of electrons or photons that landed there. Especially those jagged edges are pretty much alive (dynamic) as they constantly changing depending on the photons or electrons that landed there. Precisely, outcome of double-slit experiment with photons or electrons has clearly showed that photons or electrons are particles. It is naïve in believing that electrons are waves. It's stupid in also believing photons are waves too. All electrons that emitted out from an electron-gun will be deflected to a single spot on a screen behind the cathode tube after interacting with a fixed external magnetic field. This clearly shows that there is only one type of electrons. If there are two types of electrons then there will be two spots on the screen behind the cathode tube after those emitted electrons from the electron-gun after they have interacting with a fixed external magnetic field. Black holes are not holes but a very dense "dark" celestial body that will transform other celestial bodies that have plunged onto it to preons, the finest elementary particles. If you are interested in real discoveries, I would recommend you to read my book, The Unification Theory – Volume One and you will be amazed with lots of new, interesting discoveries. In God I trust.

So smart but they have a hard time speaking..

Is this for real lol?

God energy is both, He controls all

44:50 I hope he's okay

i watched this entire thing SOMEHOW

the spooky things of sience fiction will desapear when this guys find that light spead multiplies by 10 each time that in a matter of an instant goes and comes to the edge of our universe and comes. no more atoms in any plase at same instant. ded or alive at same time, were reality is not real – Entanglement is never done in a flat space or put it black and white, it needs colors, flexibility on light not so ridged

entanglement is done in cross sections as dna does, have you seen alton arp intrinsic red shieft – there you find many diferent sistems and all them are cross sectional not a lasagnna italian food, but still he paid the price for let the publick know so did tesla and many more

wene you put to atoms togather they each one gains a side up or down and for ever stay the same – you will find it that earth north side go round one way and south the other and in the meddle one with both of them positive, neutral and negative from here all sistems are the same, as for exemple proton, neutron and electron, so is H-Li-He that make all tones

entanglement is real but never done flat.

not everything that shines is gold not every thing that is round and dark is a black hole – you must see on you tube: NEW EYES ON SPACE: JAMES, WEBB TELESCOPE DR MICHEL RESTLER at the time 6:00 on the left side a hole that goes through – there are actualy three of this on each side and in no way the angle could let a picture taken plus it should not emite light and all the sistems do.

the red and blue things wiil not exist wene found that electrisity multiplies by 10 at each time, matter kind of does the same cause by the end is light condensated state seen it as the serie PHI that is born and goes up so it must to fall

sometimes this guys are quanta none sence, if it evaporades so must fall.

anything that shood get in a black hole it becomes shet even the wallet

any shape of flat must to have positive, negative and a neutral no matter what.

how would you know a black holes gravity wene not knowing what gravity is or what causes it –

to strange things fricks me out – this guys are out of this world to strange to me.

their entanglement in no way could be on flat space, real entanglement is done cross section as pairs as on dna or the sun is.

Why can't we say that the one particle is spinning up and down at the exact same time. Is this not true?

One thing I want to know is…. if you have more than 2 particles that were "generated, interact, or share spatial proximity," then what do you get out of those "3" particles?

The photons in the double slit are not being shot through a vacuum. There are other light particles, or dark matter for that matter that those photons can cause a wave form in. Like a boat on the water, The water is one form or field, the boat is the photon. The boat can act singular but at the same time create a wave. If the boat was flying we wouldn't see the wave on the water but there would still be one only in the air, unless it's done in a vacuum we will never know.

How the only "antimatter" goes inside black holes and only "matter" got emitted

Mathematically, it will Always Grow exponentially

Stop limiting yourselves with circular thoughts

If you can't be proven wrong, it's not worth talking about.

min 12:57 – yeah, i would (naively) expect something different. the smaller the pallets the greater the chance to hit the lateral of the slit, the greater the angle of spreading. and further, the smaller so we have an angle so great that they interfere with the pallets from the other slit – creating a whole another pattern.

min 10 (cca) – in know the slit experiment for years but only now i regarded not as a wow source but as a real problem. first thought – the bombardment is composed (without our knowledge of course) by two elements – one wave one particles.

min 59:00 – novelistic idea. our very existence is based on an entanglement at conscience level (conscience – taken as in that one who is able a virus to have). so the fuzziness of our mind appear when we are trying to escape from the paradigm that give coherence to "our" reality. the (our (too)) mind evolved on top of the quantic polarized paradigma of a reality created by a master of consciousness (god) who polarized "this / the" world out of superposition in a specific certain position.

everything is connected, and nothing isn't absolutely nothing as nothing is always something a void is a something, much more than a nothing.

My bet has always been that all of this is because:

1) We are in a program. Whether you think of that as a simulation or not is irrelevant. It's a type of reality.

2) The universe is created through computations.

3) The quantum "randomness" you see is due to quantization and rounding errors in the program's execution.

4) Everything is quantized when output into our 4D Universe, but probably calculated with some other format inside the actual machinery. The translation from one format to the other during "rendering" of our Universe is what creates the quantum chaotic effects. All of the same effects as in Quantum Mechanics can be compared to similar artifacts in video games, MPEG compression, and so forth. The details are different, but that's just because the parameters are different. The underlying idea is the same though.

5) Entanglement is trivial. It only astonishes us because we are used to seeing large scale entanglement of trillions and trillions of atoms of matter. Your body is just a massive collection of quantum bits entangled together in a giant mass. You use Retrocausality to drive this clump of entangled bits around.

6) Retrocausality is the process by with the future writes the past. The rule is, to justify any present state, you must show a consistent set of steps to reach it. This is why we will keep discovering more and more detailed physics: because we are creating it in the future and justifying it in the past via agreed upon facts we decided. This is why I banned complaining (including internal complaining) from my life: everytime I complain, I'm cursing myself in the past and creating a consistent history going backwards to explain that sour moment in time. So now I instead express gratitude for my health, wealthy, growth, etc, so that I'm in the habit for the rest of my life, and later on, my habit will be the reason for the next X years of awesomeness.

Look for the artifacts.

I'm using "artifacts" in the technical sense of the term to mean, the imprint of engineering due to tradeoffs. Engineering is, at the end of the day, the art of using tradeoffs to create magic. So is programming. The universe is doing this and that's generating all the bizarreness we see.

This is a very good video. It helps me understand quantum reality, which I did not really understand before.

I was going to be a scientist. I failed the voice portion of the course.

What brings two quantum particles to entangle ? Just the fact that they were both part of the same "system" like two electrons from the same atom ? If so, particles from separate systems can't entangle ? Who can answer these questions ?

58:00 entanglement is like a car u split into two pieces. No matter how far apart they are they still fit together. Fitting together is a quality of duality to make a whole. Spin direction is just a different quality of duality to make a whole. They had a common origin, they are compliment half parts of a bigger whole that once was. Maybe everything "exists" because its fractured from a whole, entropy is just increasing chaos: energy spreading and diversifying giving rise to complexity and difference, even opposites..

crazy voice…lol mad scientist like

What a bunch of kindergarten… Every one knows the earth is flat and up top is the firmament where lights go around the earth just as the sun does from 3000km away 😃

random question what is the threshold in size of particles that reflect quantum behaviour.

Science has turned into a religion repetition of accepted theories and pushing of the status quo. Belief without proof and ridicule of of proven things because it doesn’t fit the narrative.

We would be so much farther along if free thinking was encouraged more and people with amazing ideas that go against the establishment were heard and not silenced and ruined ie Tesla ie dr berzynski and many many others

the thing is if we knew all there is to know about quantum mechanics. We could build food replicators teleportation devices , spaceships I could do a billion miles a second and time travel machines just to mention a few things.

Here's another thought I think Einstein was trying to slow the whole thing down.

the wave is caused by firing particles thru superfluid so will cause a wave in front like a boat would do in water….its not a wave and a particle.. That's just dumb.

Brian Greene is such a good speaker

Quantum mechanics has a fundamental problem and that is; Why does it only exist when it is observed. So another way of looking at the problem is does reality exist at all? Does the universe cease to exist once the observer has died? So quantum mechanics proves that reality doesn't exist at all. It only exists to those whom happen to be observing. So this problem exists but only while observed as well. That leaves the answer to quantum mechanics; is that once unobserved the problem is solved. Or to simplify; I flip a coin, but instead of looking for a heads or tails answer to the flip, I choose to say your prediction is right. Now if we both accept that answer then that answer is the correct one. Until the coin is observed. So quantum mechanics in itself is a absence of reality. Isn't that true?

Magnificent 😎

HEY, you know whats funny. Everyone is failing to realize the true power of the discovery and understanding of the quantum realm. If yall believe it, then accept it. Stop believing you will die. You are entangled always with your moments with life. How can death come.. Plus this ecience agrees with the bible. "God is one, God is eternal" be entangled in the oneness

not a science major but am always interested in these videos. Probably a dumb question just wondering if doing this double slit experiment in a vacuum would yield the same results? suppose there are no other forces interacting with the electron/photon would it still work? Or is gravitational wave (if it is continuous) would always affect its motion? Is there a reason to believe that gravitational waves suppose that happened both at the left and right of our galaxy and then travel to earth would that interfere even in a vacuum?

In a double slit experiment, what happens if the observer is drunk? Is there a fuzzy state of consciousness?

Great forum. The animations were explanatory to the layman. Science is simply fascinating. Love the WSF.

Bill Mahr of physics

So if we can un entangle and entangle space we can build faster than light space tunnels and roads, basically control space-time? Fuck

Holography….definition….it is a Ho's log that is in graphic nature….is that correct?