Quantum Reality: Space, Time, and Entanglement

Quantum Reality: Space, Time, and Entanglement

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.

100 thoughts on “Quantum Reality: Space, Time, and Entanglement

  1. I wonder if this is evidence for the individual creator? My universe if I measure…your universe if you measure?

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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

  9. 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.

  10. 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

  11. how would you know a black holes gravity wene not knowing what gravity is or what causes it –

  12. 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.

  13. Why can't we say that the one particle is spinning up and down at the exact same time. Is this not true?

  14. 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?

  15. 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.

  16. 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.

  17. everything is connected, and nothing isn't absolutely nothing as nothing is always something a void is a something, much more than a nothing.

  18. 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.

  19. 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 ?

  20. 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..

  21. 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 😃

  22. 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.

  23. 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

  24. 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.

  25. 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.

  26. 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?

  27. 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

  28. 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?

  29. So if we can un entangle and entangle space we can build faster than light space tunnels and roads, basically control space-time? Fuck

  30. they do experiments in a vacuum, or are they bouncing on air particles? they tried lead plates to shield outside radiation, could be bouncing on charged particles. they real excited but never mention efforts to determine if any outside sources are influencing the tests.

  31. For someone who isn't a physicist, or scientist this gets a little hard to follow. I do have questions. What gives the particle the energy to spin? Are the only two things qantum computing and qantum levitation?

  32. FIRST MATTER: In every facet of the motion of all particles the light of Divine unity shines like the sun. For as is proved briefly in the First Indication of the Tenth Word and in detail in the Twenty-Second Word, if every particle is not an official of God acting with His permission and under His authority, and if it is not undergoing change within His knowledge and power, then every particle must have infinite knowledge and limitless power; it must have eyes that see everything, a face that looks to all things, and authority over all things. For every particle of the elements acts, or can act, in an orderly fashion in all animate beings. But the order within things and laws according to which they are formed differ from one thing to the next. If their order was not known to the particles, the particles could not act, or even if they could act, they could not act without error. In which case, the particles which are performing their duties in beings are either acting with the permission and at the command, and within the knowledge and at the will, of the owner of an all-encompassing knowledge, or they themselves must have such an all-encompassing knowledge and power. Yes, all particles of air can enter the bodies of all animate beings, the fruits of all flowers, and the structures of all leaves. They can act within them, although the way the beings are formed is all different and their order and systems quite distinct. As though the factory of a fig was a loom for weaving cloth and the factory of a pomegranate, a machine for producing sugar, and so on; the programmes of their structures and bodies all differ from each other. A particle of air, then, enters or can enter all of them. It takes up its position and acts in a wise and masterly fashion without error. And on completion of its duty it departs. A mobile particle of mobile air, therefore, either must know the forms, shapes, measures, and formations with which plants and animals, and even fruits and flowers, are clothed, or else it must be an official acting under the command and will of one who does know. Similarly with a stationary particle of stationary earth: since it has the ability to be the means and place of cultivation for all the seeds of all flowering plants and fruit-bearing trees, either there must be in the particle itself or in the handful of soil that is its little house immaterial machinery and factories in good working order to the number of the varieties of the trees and plants, and flowers and fruits in fact, it is in every single particle that there must be a factory peculiar to it and all the equipment and machinery necessary for the running of the factory or else it must have a miraculous knowledge that knows all things about all things and a miracle-working power that creates everything from nothing; or, those duties are performed at the command and with the permission of One Who is Knowing of All Things, and through the power and might of One Who is Absolutely Powerful over All Things. If an untrained and inexperienced, common, ordinary, and blind man was to go to Europe and in all the factories there to work at all the trades and crafts in perfect and masterly fashion, and if he was to display a wise and artistic skill to such a degree that it left everyone speechless with amazement, anyone with a grain of consciousness would know that the man was not acting on his own initiative, but that a master of all trades was teaching him and causing him to work. And if there was a blind and impotent man who lived in a simple little house and was unable even to rise from his place, and if small fragments of stone, and bits and pieces of material like bone and cotton were to enter his little house and then sacks of sugar, bales of cloth, crates of jewelry, finely-made clothes encrusted with jewels, and delicious foods were to emerge, would anyone with a grain of intelligence not say: "That man is a wretched doorkeeper or merely a latch on the door of the factory of a wondrous miracle-working being, which is the source of his miracles"? In exactly the same way, the motion and duties of particles of air in plants and trees, and blossom and fruit, all of which are missives of the Eternally Besought One, antique dominical works of art, miracles of power, and wonders of wisdom, indicate that the particles are acting under the command and at the will of an All-Wise and Glorious Maker, an All-Generous and Beauteous Creator. Particles of earth, also, since they are the source and means for the shoots and plants produced by seeds, each of which is a different factory and workbench, a different printing-press, treasury, and antique, a different manifesto proclaiming the Glorious Maker's Names and ode hymning His perfections, it is as definite as two plus two equalling four that the particles of earth are acting at the command, with the permission, and through the will and power of an All-Glorious Maker Who is Lord of the command of "Be!" and it is, {[*]: Qur'an, 36:82, etc.} and to Whose command everything is subjugated. In this we believe. Risale-i Nur Collection 572 – Bediüzzaman Said Nursi

  33. Greene is fantastic and I believe it and I more or less understand what he's saying but next time find 4 other people that all sound like Greene (without mumbling & accents). And the others could not explain how to find the front door of the building. And the others sound like they're explaining this for the first time. And they interrupt themselves with puns. And they interrupt each other. I'm listening/watching on a 27-inch Apple I-Mac with the volume set to 100% and same for the YouTube slider. What do folks with a hearing loss do? And there are many such folks. Next time make it 92 minutes of Brian Greene solo. Or team up with Dr. Tyson (he speaks clearly). Good work, Brian!!! PS: next time gradually sprinkle in a 20-word glossary of terms. Your new meanings of the word "information," for example.

  34. I would like to see the double slit experiment done using the particle beams but with two barriers on the back side just outside the two slits to see if some of the particle light waves hit the barriers or continue like was shown without the barriers ??

  35. i am having difficulty in understanding, let alone comprehending, why or how does an object appear to stand still at the event horizon (around 1:12:20),

    i understand that there are enormous time dilation which ultimately turns into infinite when an object reach event horizon, however it's the object's time, how does far away observer experience it (by seeing that the object stands still, never passing the horizon)? and if so, how come that a black hole's surface doesn't appear full of matters (gas, or whatever get sucked into it)?

    anyone care to explain in a simple manner? not even amateur physicists here, just physics enthusiast

    thanks in advance

  36. Did one of them just say that if they sent one photon through every 1.5 hours, it would still work? If so, that's another way this is blowing my mind. I'd like to see / understand HOW they're shooting light at the slits, how the direction is set per 'shot'. That part is pretty fuzzy.

  37. I spent some good few minutes looking for a good long video too fall asleep too. Not even in a mean way I just want something to listen to while eating or doing something simple

  38. Hey, before claiming that every reality is possible, please look into cantor diagonalization and see how infinity can miss a possibility. A reality in witch I "marry Kate Upton" may be unreachabeable and not not part of the infinitive realities possible. You need to be VERY careful about that. George Cantor tells us infinity is NOT what we think.

  39. Has anyone ever tried shifting the double slit experiment to see if the placement of particles is consistent with the shift or if where the particles lands shifts as well?

  40. Can someone please explain to me how exactly it is that observation causes the quantum probability to collapse into a single state? What degree of observation is necessary? Direct visual observation? Observing the particle through a tool like an electron microscope? Seeing a video feed of it taken by a tool? Would an animal doing the observation have the same effect? What this implies, if we know that there are stable single states in our universe (stars don't dramatically change states because nothing is observing them) then is there an observer for the universe? I'm not sure I understand this concept, please someone explain!

  41. As mentioned Einstein still has a point. Before we have more evidence, no one has still proved the information wasn’t there before the measurement. So often misunderstood Einstein was not against quantum mechanics, he just said , there are some issues we still need before we jump into conclusion how quantum mechanics works. But in quantum mechanics a singularity is not allowed. Therefore we have a kind of crisis in physics. Imagine if Einstein was around today, I think if anyone could solve this crisis, I would guess he would be a good candidate. We are coming so long since his general theory, which still hasn’t been proven wrong.

  42. They all got it wrong. Shrodinger equation is a result of our lack of ability of knowing exactly the particle trajectory of travelling, so instead, the best we can do is empirically collecting its statistical pattern.

  43. Quantum physics actually provided me with an explanation for my many unusual actual 😉 experiences throughout my lifetime! So wrapping my mind around these concepts is my normal!

  44. They steal and conceal Teslas solutions of frequency and vibration then try to brainwash us with this crap to distract us from achieving our potential. Classic media brainwashing, an hour of my life I'll never get back. You cant predict particle movement because we control the ones relevant to us from within ourselves. We are part of the spiral! Waves are an impossible method of measurement for forces influenced by so many overlapping factors spiraling together.

  45. Umm… Has anyone coined the term Van Raamsdonk Tunnels yet? 'Cuz I really want to have coined the term Van Raamsdonk Tunnels.

  46. so since you're firing electrons and photons could it be that when you fire it its reacting with the electrons of all the air molecules since they react in the same plain sort of how the water waves do because water is traveling along the same plain? has anyone done the double slit experiment inside a vacuum to see if it still produces the wave pattern or if it will do a double beam like with the pellets

  47. The wave function for many universes collapses to only one universe, if there is an all knowing god observing everything.

  48. When I travel space-time it's easier just to go around the black holes because waiting for triple a is a reality bummer… And at least I'm saving entropy that way🏞🍻⛥😎

  49. Around 46 minutes in, I don't think t'Hooft is just echoing Einstein. Einstein believed the "imprecision" that led to the superpositions had to do with the internal state of the individual quantum systems. I think t'Hooft was speaking much more broadly than that. He's saying that our quantum systems are entangled with portions of the universe that we are not considering, and therefore we arrive at superpositions. And that if we could properly take all those portions into account, our predictions would be much sharper.

    Einstein needed the answer to be completely pre-ordained by internal state of the particles. That's a fail – Bell showed us that. But t'Hooft is alluding to the fact that the particles can be entangled not only with one another, but also with the instruments, with the experimenters, with other things out in the universe, etc. Therefore there is no pre-ordained answer at any time – everything that happens to anything the particles are entangled with (including, potentially, the decisions of the experimenters) can affect the final measured outcomes. Bell's theorem does not preclude that sort of explanation of this situation.

    Therefore, quantum superpositions are a reflection of our ignorance. Not merely our ignorance of things that occur before the experiment begins, but rather of our ignorance of things that occur before the experiment ends. In theory the entire history of the universe up to the measurement can affect the outcome. So we will never be able to purge this uncertainty. Quantum theory is simply our mathematical toolbox for coping with it in a rational way.

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