Is Time Emergent? Information, Entropy, and Reality

<v Speaker 1>Welcome to the quark Side. Quantum Physics podcast, an exploration
<v Speaker 1>of the fundamental structure of reality, where quantum laws govern matter, energy,
<v Speaker 1>and information. Here, uncertainty is a feature, not a flaw,
<v Speaker 1>and understanding begins at the smallest scales.
<v Speaker 2>I want you to just stop for a second, whatever
<v Speaker 2>you're doing, put down the phone, just listen. If it's
<v Speaker 2>quiet enough, maybe you can hear a clock or I
<v Speaker 2>don't know the hum of your computer. But even if
<v Speaker 2>it's dead silent, you feel it, don't you.
<v Speaker 3>Oh? Absolutely, that constant forward motion.
<v Speaker 2>Yeah, that relentless push. A second passes, then another. You
<v Speaker 2>can remember the coffee you had this morning, right, the taste,
<v Speaker 2>the warmth, but you can't remember the dinner you're going
<v Speaker 2>to have tonight.
<v Speaker 3>It's maybe the most fundamental part of being human. We're born,
<v Speaker 3>we age, it's one way street. It feels absolutely it
<v Speaker 3>feels like the bedrock of reality. Like if you took
<v Speaker 3>everything else so at, all the matter, all the energy, gravity, everything,
<v Speaker 3>you still feel like time would be there, just ticking away.
<v Speaker 2>In the dark, waiting for something to happen. Yeah.
<v Speaker 3>But yeah, and this is the idea that has been
<v Speaker 3>just completely messing with my head. For the past few days.
<v Speaker 3>What if that feeling is an illusion?
<v Speaker 2>Illusion is a strong word, maybe a secondary effect, a
<v Speaker 2>byproduct of something much much deeper. We've been going through
<v Speaker 2>some really fascinating, really dense material about what some are
<v Speaker 2>calling a quiet revolution in physics, and the headline claim
<v Speaker 2>is just staggering. Time is not fundamental, right.
<v Speaker 3>It's not the foundation. The proposal is that time is
<v Speaker 3>actually emerging from something.
<v Speaker 2>Else entirely, and that something else is information.
<v Speaker 3>Something we usually think of as abstract, you know, bits
<v Speaker 3>and bites, but physicists are starting to treat it as
<v Speaker 3>a real physical thing.
<v Speaker 2>The argument, if we hading it right, is that the
<v Speaker 2>universe is basically a giant recording device.
<v Speaker 3>In a manner of speaking, yes, and what we call
<v Speaker 3>time is just the act of that device recording, writing
<v Speaker 3>things into its own memory.
<v Speaker 2>Okay, we've got to unpack this very carefully, because time
<v Speaker 2>is memory. Sounds it sounds like.
<v Speaker 3>Poetry, it does, but the physics behind it is pretty serious.
<v Speaker 2>I want to start with the problem itself because I
<v Speaker 2>think most of us, myself included, kind of assume science
<v Speaker 2>has time figured out. We've got atomic clocks, GPS, we're
<v Speaker 2>pretty good at knowing what time it is.
<v Speaker 3>We know how to measure it. That's a very different
<v Speaker 3>thing from knowing what it is. And honestly, for over
<v Speaker 3>a century, physics has been well embarrassed.
<v Speaker 2>By n Rist. That's not a word I associate with physics.
<v Speaker 3>It's the only word that really fits. Because you see,
<v Speaker 3>we have two grand theories of the universe, two main
<v Speaker 3>rule books. On one side, you've got Aubert Einstein general relativity.
<v Speaker 2>The big stuff, planets, stars, galaxy, these gravity, the cosmic
<v Speaker 2>scale exactly.
<v Speaker 3>And in Einstein's world, time is not some universal clock
<v Speaker 3>taking the same for everyone. It's dynamic.
<v Speaker 2>It's a lack of into space right space.
<v Speaker 3>Time fabric, and it stretches and it squeezes. If you
<v Speaker 3>fly really fast in a spaceship, your clock takes slower
<v Speaker 3>than mine back here on Earth. If you hang out
<v Speaker 3>near a black hole, your.
<v Speaker 2>Clock slows to a crawl. The twin paradox precisely.
<v Speaker 3>So time is relative. It's a coordinate like left, right,
<v Speaker 3>er up down, but it's a bendi one. It's part
<v Speaker 3>of the geometry of the universe.
<v Speaker 2>Okay, so that's Rule book one. Time is a flexible
<v Speaker 2>personal dimension. What about Rule book two?
<v Speaker 3>Rule Book two is quantum mechanics, the laws for the
<v Speaker 3>very very small atoms, electrons, photons, all the tiny particles
<v Speaker 3>that make up you and me and everything else.
<v Speaker 2>And what does it say about time?
<v Speaker 3>It says the exact opposite. In standard quantum mechanics, time
<v Speaker 3>is rigid. It's absolute. How so, it's what physicists call
<v Speaker 3>an external parameter. Think of it like a metronome sitting
<v Speaker 3>outside the experiment, ticks away TikTok at a steady universal pace.
<v Speaker 2>And it doesn't care what the particles are doing.
<v Speaker 3>Not at all. It's a rigid background stage. The particles
<v Speaker 3>can dance and interact and do all their quantum weirdness,
<v Speaker 3>but the stage itself, the clock, is completely unaffected. It's
<v Speaker 3>just there.
<v Speaker 2>So Einstein says time is a participant in the dance.
<v Speaker 2>Quantum mechanics says it's the unchanging stage. The dance happens on.
<v Speaker 3>You've nailed it. That is the fundamental conflict, and it works.
<v Speaker 3>You know, it's fine as long as you keep them separate.
<v Speaker 3>You use Einstein for the cosmos, you use quantum mechanics
<v Speaker 3>for your phone's processor.
<v Speaker 2>But the universe doesn't keep them separate. The Big Bang
<v Speaker 2>was both incredibly massive and incredibly small.
<v Speaker 3>Exactly. The ultimate goal of physics, the holy grail, is
<v Speaker 3>to unite them a single theory that explains everything quantum gravity.
<v Speaker 2>And I'm guessing that when you try to write the
<v Speaker 2>equations for that time becomes the big problem.
<v Speaker 3>It becomes the problem when you try to merge the
<v Speaker 3>math of these two frameworks the equations, well, they break,
<v Speaker 3>and they break in a very specific and terrifying way.
<v Speaker 2>This is where that Wheeler DeWitt equation comes in, right.
<v Speaker 2>The source material really focused on this.
<v Speaker 3>It's the classic example. Back in the nineteen sixties, John
<v Speaker 3>Wheeler and Bryce DeWitt tried to write a single equation
<v Speaker 3>that describes the quantum state of the entire universe. They
<v Speaker 3>took Einstein's ideas about geometry and smashed them together with
<v Speaker 3>the rules of quantum mechanics. And what happened when they
<v Speaker 3>work through the math. When they simplified the equation the
<v Speaker 3>variable for time, the letter t yeah, it vanished.
<v Speaker 2>It is weird. It completely canceled out. The final equation
<v Speaker 2>basically says that the rate of change of the universe
<v Speaker 2>is zero.
<v Speaker 3>Wait wait, an equation to describe all of reality and
<v Speaker 3>the result is nothing ever happens. That's it. It describes
<v Speaker 3>a static, frozen universe, a block. It contains every possible
<v Speaker 3>arrangement of everything all at once, but there's no flow
<v Speaker 3>from one moment to the next.
<v Speaker 2>That's what they call the problem of time.
<v Speaker 3>That is the crisis. Our best attempt at a fundamental
<v Speaker 3>equation says change is an illusion. But we look around
<v Speaker 3>and my coffee is getting cold. Things are obviously changing.
<v Speaker 2>So the math is just wrong that right, I mean,
<v Speaker 2>how can you trust an equation that says I'm not
<v Speaker 2>getting older?
<v Speaker 3>And that is the terrifying part. We don't think the
<v Speaker 3>math is wrong individually. General relativity and quantum mechanics are
<v Speaker 3>the most precisely tested theories in the history of science.
<v Speaker 3>They work perfectly. It's only when they're combined that time
<v Speaker 3>goes away.
<v Speaker 2>So either our perception of time is a profound illusion, or.
<v Speaker 3>We are missing something fundamental about how time is generated.
<v Speaker 2>Which brings us to the let's call it the classic explanation.
<v Speaker 2>But what I learned in school, the bandage that physics
<v Speaker 2>has used for a century to explain the.
<v Speaker 3>Flow of time, entropy, the arrow of time.
<v Speaker 2>Right, the second law of thermodynamics can you just refresh
<v Speaker 2>us on that the shattered glass idea.
<v Speaker 3>Of course, the second law says that in an isolated system,
<v Speaker 3>disorder or entropy tends to increase.
<v Speaker 2>Over time, things get messier.
<v Speaker 3>Things get messier. If you drop a pristine ordered coffee mug,
<v Speaker 3>it shatters into a disordered pile of one hundred pieces.
<v Speaker 3>You will never ever see those hundred pieces spontaneously leap
<v Speaker 3>off the floor and reassemble themselves back into a perfect mug, because.
<v Speaker 2>There's only one way to be a perfect mug, but
<v Speaker 2>a billion ways to be a pile of broken shards.
<v Speaker 3>Precisely, the universe moves from unlikely ordered states to much
<v Speaker 3>more probable disordered states, and we just label that direction
<v Speaker 3>of increasing messinesses forward in time.
<v Speaker 2>This has always felt pretty intuitive to me. My desk
<v Speaker 2>gets cluttered, not cleaner. So if entropy explains the era
<v Speaker 2>of time, why are we even having this conversation? Why
<v Speaker 2>is this new information idea even necessary?
<v Speaker 3>Because entropy is more of a description of what happens,
<v Speaker 3>not a fundamental explanation for why time exists. And the
<v Speaker 3>source material points out two massive holes in the argument.
<v Speaker 2>Okay, what was the first one?
<v Speaker 3>The first is that the fundamental laws of physics themselves
<v Speaker 3>don't have a preferred direction in time. They are as
<v Speaker 3>we say, time symmetric.
<v Speaker 2>Meaning they work just as well forwards as they do backwards.
<v Speaker 3>Exactly, if you watch a video of two billiard balls colliding,
<v Speaker 3>you can't tell if I'm playing it forwards or in reverse.
<v Speaker 3>The physics is identical Schrodinger's equation Newton's laws. They don't
<v Speaker 3>care about past or future.
<v Speaker 2>So if the basic rules for the atoms don't have
<v Speaker 2>an arrow of time, how can the mug made of
<v Speaker 2>those atoms have one.
<v Speaker 3>You can't build a one way street out of two
<v Speaker 3>way birds. It feels like you're smuggling the conclusion in somewhere.
<v Speaker 2>Okay, that's a big hole. What's the second one?
<v Speaker 3>The second one is even bigger. It's called the past hypothesis.
<v Speaker 3>For the whole entropy argument to work, for the universe
<v Speaker 3>to be getting messier now, it must have started in
<v Speaker 3>a state of absurdly, unbelievably low entropy.
<v Speaker 2>The Big Bang had to be perfectly neat and tidy.
<v Speaker 3>Incredibly tidy, and statistically that's just bizarre. It's like walking
<v Speaker 3>down the beach and finding a billion grains of sand
<v Speaker 3>all lined up in a perfect row. You wouldn't think
<v Speaker 3>it just happened by chance.
<v Speaker 2>You'd assume someone or something set it.
<v Speaker 3>Up that way, right, But the entropy theory just says, well,
<v Speaker 3>it started out tidy. It doesn't explain why it relies
<v Speaker 3>on this one in a trillion initial condition as a given.
<v Speaker 3>It feels like a cheat.
<v Speaker 2>So to sum up the problem, our deepest math says
<v Speaker 2>time doesn't exist, and our best explanation for it relies
<v Speaker 2>on a cosmic coincidence that we can't explain.
<v Speaker 3>We need something deeper, and that's where this quiet revolution begins,
<v Speaker 3>the shift away from just thinking about matter and energy
<v Speaker 3>and towards thinking about information.
<v Speaker 2>This is where things really took a turn for me
<v Speaker 2>in the reading. We need to be very clear about
<v Speaker 2>what we mean by information, because normally I think of
<v Speaker 2>it as data, the words on a page. It's abstract,
<v Speaker 2>it feels abstract.
<v Speaker 3>But the sources we're looking at treat information as a
<v Speaker 3>physical quantity, as real as.
<v Speaker 2>A rock or a beam of light, as real as mass, not.
<v Speaker 3>Just as real in some sense equivalent to mass and energy.
<v Speaker 2>Hey, you got to explain that I can put a
<v Speaker 2>rock on a scale I can't weigh an idea.
<v Speaker 3>Well, this goes back to the nineteen sixties to a
<v Speaker 3>physicist at IBM named Ralph Landauer. He established a fundamental
<v Speaker 3>rule called Landauer's principle, and it's what connects the abstract
<v Speaker 3>world of bits and bytes to the physical world of thermodynamics.
<v Speaker 2>Is this related to that old thought experiment, Maxwell's Demon?
<v Speaker 3>It's the solution to Maxwell's demon.
<v Speaker 2>Yes.
<v Speaker 3>The demon was this imaginary creature that could sort hot
<v Speaker 3>and cold molecules, seemingly, violating the second law of thermodynamics
<v Speaker 3>by creating order from chaos.
<v Speaker 2>Right, it could make one side of a box hot
<v Speaker 2>and the other cold for free, seemingly.
<v Speaker 3>But Landauer realized the demon has to know which molecules
<v Speaker 3>are which it has to measure them. It has to
<v Speaker 3>store that information, even for a moment, and then to
<v Speaker 3>keep sorting, it has to forget the previous measurement to
<v Speaker 3>make room for the next one.
<v Speaker 2>So forgetting costs something.
<v Speaker 3>Erasing information has a physical cost. That was Landauer's great insight.
<v Speaker 3>He proved that to irreversibly erase one bit of information
<v Speaker 3>to resettle one to a zero, you must dissipate a
<v Speaker 3>tiny but non zero amount of heat into the environment.
<v Speaker 2>So deleting a file on my computer actually generated the
<v Speaker 2>tiny puff of.
<v Speaker 3>Heat, a truly infinitesimal amount. But yes, deletion is heat,
<v Speaker 3>and heat is a form of energy. We know from
<v Speaker 3>Einstein's famous equation E equals mc squared that energy and
<v Speaker 3>mass are two sides of the same coin.
<v Speaker 2>So information is tied to energy, which is tied to mass.
<v Speaker 3>It's physically tethered to the world. It's not a ghost
<v Speaker 3>in the machine. In a very real sense, it is
<v Speaker 3>part of the machine.
<v Speaker 2>Let me see if I've got this. If I have
<v Speaker 2>two identical hard drives and I fill one up with
<v Speaker 2>a complex movie and leave the other one blank, does
<v Speaker 2>the full one technically weigh more.
<v Speaker 3>In principle, yes, the difference would be smaller than the
<v Speaker 3>way of a single atom, But it is not zero.
<v Speaker 3>A drive full of complex high entropy data contains more
<v Speaker 3>energy than a formatted drive of all zeros.
<v Speaker 2>Okay, that grounds it for me. It's real, and this
<v Speaker 2>reality of information is where the new theory of time
<v Speaker 2>comes from.
<v Speaker 3>It's the key because once you accept that information is physical,
<v Speaker 3>you collide head on with the biggest puzzle in modern physics,
<v Speaker 3>the black hole. Information paradox.
<v Speaker 2>It always comes back to black holes, doesn't it.
<v Speaker 3>They're the ultimate laboratory there where gravity and quantum mechanics
<v Speaker 3>are both pushed to their absolute limits.
<v Speaker 2>So Stephen Honking he figured out that black holes aren't
<v Speaker 2>actually black.
<v Speaker 3>They leak, they radiate, they glow with what we now
<v Speaker 3>call Hawking radiation, and over immense time scales, they can
<v Speaker 3>completely evaporate and disappear.
<v Speaker 2>And this created a problem.
<v Speaker 3>A universe sized problem. Imagine you take a library of books,
<v Speaker 3>all that information, all those stories, and you dump it
<v Speaker 3>into a black hole. That information is now inside, but then,
<v Speaker 3>over trillions of years, the black hole evaporates into nothing
<v Speaker 3>but random thermal radiation.
<v Speaker 2>Where did the information in the books go?
<v Speaker 3>Exactly? If the black hole is gone and all that's
<v Speaker 3>left is random heat, the information seems to have been
<v Speaker 3>deleted from the universe, and that's not allowed. It's a
<v Speaker 3>cardinal sin. In quantum mechanics, there's a strict law called unitarity,
<v Speaker 3>which says that information can never ever be truly destroyed.
<v Speaker 3>You can scramble it, you can hide it, but you
<v Speaker 3>should always, in principle, be able to piece it back together.
<v Speaker 3>A black hole that deletes information breaks quantum mechanics.
<v Speaker 2>So who won hawking or quantum mechanics.
<v Speaker 3>In the end, almost everyone agrees that quantum mechanics has
<v Speaker 3>to win. The information must be preserved, It has to
<v Speaker 3>somehow be encoded in the radiation that leaks out.
<v Speaker 2>And this whole fight forced physicists to take information seriously.
<v Speaker 3>It forced them to see information not as something that
<v Speaker 3>describes reality, but as a fundamental ingredient of reality, maybe
<v Speaker 3>even more fundamental than space and time themselves.
<v Speaker 2>Okay, so let's make the pivot. If information is the
<v Speaker 2>real bedrock, how do you build what we feel as
<v Speaker 2>time on top of that foundation.
<v Speaker 3>This is the heart of the new model. The idea
<v Speaker 3>is to stop thinking of space time as a smooth, empty.
<v Speaker 2>Stage, an empty container. Right.
<v Speaker 3>Instead, you have to start thinking of it as a
<v Speaker 3>storage medium, a physical substrate like a cosmic card drivegy.
<v Speaker 3>The source material uses the idea of a space time
<v Speaker 3>lattice or spacetime cells. Imagine space isn't continuous. Imagine it's
<v Speaker 3>made of tiny, fundamental, discrete units pixels of reality.
<v Speaker 2>Okay, I'm with you.
<v Speaker 3>And these cells aren't just empty placeholders. They have a job.
<v Speaker 3>Their job is to record record what interactions every time
<v Speaker 3>two particles collide, every time a photon of light brounces
<v Speaker 3>off an electron, that's an event. The theory proposes that
<v Speaker 3>these events leave a physical mark, a trace, an imprint
<v Speaker 3>on the structure of the space time cells themselves.
<v Speaker 2>So the fabric of the universe is keeping a log book.
<v Speaker 3>It is the logbook. This is the crucial shift. The
<v Speaker 3>universe doesn't exist in time. It generates time by writing
<v Speaker 3>its own history into its own structure.
<v Speaker 2>I love that image, but what does it mean mechanically?
<v Speaker 2>How does writing a logbook create this feeling of a
<v Speaker 2>second passing and then another.
<v Speaker 3>It comes down to irreversibility. Think about the difference between
<v Speaker 3>the past and the future. In this moment. The past
<v Speaker 3>is what has already been written down. The future is
<v Speaker 3>the blank part.
<v Speaker 2>Of the page.
<v Speaker 3>Now, the key assumption is that you can't erase the ink.
<v Speaker 3>Once an interaction happens, the information about it, the entanglement,
<v Speaker 3>the correlations, leaks out and gets imprinted on the environment.
<v Speaker 3>On this space time lattice.
<v Speaker 2>You can't put the genie back in the bottle.
<v Speaker 3>You can't globally unwrite an event, and because of that,
<v Speaker 3>the record can only grow.
<v Speaker 2>The file size only gets bigger.
<v Speaker 3>Precisely, the arrow of time in this view isn't about
<v Speaker 3>entropy or things getting messy. It's about the amount of
<v Speaker 3>information in the universe increasing. We experience time moving forward
<v Speaker 3>for one simple reason. There's more information in the universe
<v Speaker 3>now than there was a nanosecond ago.
<v Speaker 2>So the present moment is just the leading edge of
<v Speaker 2>the recording head laying down a new track.
<v Speaker 3>That's a perfect way to put it. And this completely
<v Speaker 3>reframes our place in the cosmos. We aren't just passengers
<v Speaker 3>on a river of time that was already flowing.
<v Speaker 2>We're making the river.
<v Speaker 3>Flow our existence. Every single interaction between particles is what
<v Speaker 3>carves the channel. We are actively constructing space time by
<v Speaker 3>living in it.
<v Speaker 2>You just said something that I want to pause on
<v Speaker 2>constructing space time. Does this recording process actually change the
<v Speaker 2>physical geometry of space?
<v Speaker 3>According to the theory, Yes, And this is where it
<v Speaker 3>gets really exciting because it might just solve one of
<v Speaker 3>the biggest mysteries in astronomy dark matter. Dark matter.
<v Speaker 2>Okay, let's set the scene for this because it's a
<v Speaker 2>huge claim. The standard story of dark matter is that
<v Speaker 2>our galaxies are spinning too fast.
<v Speaker 3>Right, It's a simple observation. You look at a spiral galaxy,
<v Speaker 3>you measure the speed of the stars. You expect the
<v Speaker 3>stars on the outer edge to be moving much slower
<v Speaker 3>than the ones near the center, because gravity gets weaker
<v Speaker 3>with distance, just.
<v Speaker 2>Like in our solar system, Pluto moves way slower than Mercury.
<v Speaker 3>But that is not what we see when we look
<v Speaker 3>at galaxies. The rotation curve is flat. The stars on
<v Speaker 3>the very edge are whipping around almost as fast as
<v Speaker 3>the stars in.
<v Speaker 2>The middle, going so fast they should just fly off
<v Speaker 2>into space.
<v Speaker 3>They should be flung out. The gravity from all the
<v Speaker 3>stars in gas we can see isn't nearly strong enough
<v Speaker 3>to hold them in orbit. So for decades astronomers have
<v Speaker 3>assumed there must be some extra invisible stuff providing the
<v Speaker 3>extra gravitational glue.
<v Speaker 2>An invisible halo of dark matter.
<v Speaker 3>A mysterious particle that doesn't interact with light, that we
<v Speaker 3>can't see, but that has a lot of gravity. And
<v Speaker 3>we've spent half a century and billions or dollars building
<v Speaker 3>incredibly sensitive detectors deep underground trying to catch one of.
<v Speaker 2>These particles, and the result has been nothing.
<v Speaker 3>A complete blank, not a single confirmed detection.
<v Speaker 2>So how does this time is memory idea solve the
<v Speaker 2>problem without inventing a new particle.
<v Speaker 3>It offers a truly radical alternative. It says you don't
<v Speaker 3>need invisible matter. The extra gravity isn't coming from stuff,
<v Speaker 3>It's coming from the space time fabric itself.
<v Speaker 2>Wow.
<v Speaker 3>Remember Landauer's principle, information has an energy equivalent, and energy
<v Speaker 3>curves space time. That's just general relativity. Okay, So if
<v Speaker 3>space time is recording the history of interactions, then a
<v Speaker 3>region of space that has a lot of history, like
<v Speaker 3>a galaxy which has been around for billions of years,
<v Speaker 3>with stars forming and exploding and gas clouds colliding, is
<v Speaker 3>saturated with these records. It's heavy with information.
<v Speaker 2>The memory of the galaxy gives it extra mass.
<v Speaker 3>It creates an effective gravitational pull. The space time in
<v Speaker 3>and around a galaxy is different from the space time
<v Speaker 3>and the empty void between galaxies. It's been altered by
<v Speaker 3>its own past.
<v Speaker 2>So the stars on the edge are orbiting so fast
<v Speaker 2>not because of an invisible cloud of particles, but because
<v Speaker 2>they're moving through a space time that is dense with
<v Speaker 2>the memory of everything that happened before.
<v Speaker 3>That's the proposal. It's not ghost matter holding the galaxy together.
<v Speaker 3>It's the galaxy's own history that.
<v Speaker 2>Is profoundly elegant. It ties the quantum world of information
<v Speaker 2>directly to the cosmic scale of galaxies.
<v Speaker 3>It suggests that the arrow of time and the mystery
<v Speaker 3>of dark matter might not be too so problems. They
<v Speaker 3>could be two symptoms of the exact same underlying process,
<v Speaker 3>the universe accumulating a record of its own existence.
<v Speaker 2>I have to be the skeptic here, though it's a
<v Speaker 2>beautiful story. It ties up loose ends. But is it
<v Speaker 2>science or is it just a nice philosophy? Can you
<v Speaker 2>test it?
<v Speaker 3>That's the most important question, and the answer is yes.
<v Speaker 3>Unlike a lot of other ideas in quantum gravity, this
<v Speaker 3>one makes concrete, falsifiable predictions.
<v Speaker 2>Okay, how do you test if the universe is a
<v Speaker 2>hard drive?
<v Speaker 3>One place to look is again black holes in the
<v Speaker 3>standard picture. The Hawking radiation they emit is purely thermal.
<v Speaker 3>It's random. It's basically just heat, like the glow from
<v Speaker 3>a hot piece of coal, just noise exactly. But if
<v Speaker 3>this information theory is correct, and the information of things
<v Speaker 3>that fell in must be preserved, then that radiation can't
<v Speaker 3>be perfectly random.
<v Speaker 2>There has to be a signal hidden in the noise.
<v Speaker 3>There should be subtle correlations, patterns, a kind of structure
<v Speaker 3>hidden in the radiation that encodes the history of the
<v Speaker 3>black hole.
<v Speaker 2>Can we see that?
<v Speaker 3>Not yet. We need telescopes with far greater sensitivity than
<v Speaker 3>anything we have today. But it's a clear prediction. The
<v Speaker 3>theory says hawking radiation has structure. The old theory says
<v Speaker 3>it doesn't. One day we'll be able to look and
<v Speaker 3>see who's right.
<v Speaker 2>So that's a test for the future. Is there anything
<v Speaker 2>we can do now?
<v Speaker 3>There is.
<v Speaker 2>We can test it in the lab, on a tabletop.
<v Speaker 3>On a microchip using quantum computers.
<v Speaker 2>Ah.
<v Speaker 3>Of course, researchers can use quibits, the quantum equivalent of
<v Speaker 3>computer bits, to build tiny simulated universes. They can program
<v Speaker 3>a handful of these quibits to interact according to quantum rules.
<v Speaker 2>They create spacetime cells on a chip.
<v Speaker 3>Essentially, yes, and they can set up these systems to
<v Speaker 3>be perfectly reversible. In theory, you should be able to
<v Speaker 3>run the whole process backwards without any issue. There should
<v Speaker 3>be no inherent earrow of time.
<v Speaker 2>But what do they find.
<v Speaker 3>They find that as soon as the quibits interact the
<v Speaker 3>information about that interaction starts to spread out through the system,
<v Speaker 3>and this process of information spreading out of become correlated
<v Speaker 3>with the wider environment, creates an effective arrow of time.
<v Speaker 2>Even though the underlying laws are reversible.
<v Speaker 3>Yes, they can literally watch informational time emerge from the
<v Speaker 3>system's own processing. It shows on a small scale that
<v Speaker 3>you don't need a master clock to have time. You
<v Speaker 3>just need a system that records and spreads information.
<v Speaker 2>That is that's incredible. It's like building a little toy
<v Speaker 2>universe that learns to have it passed in a future
<v Speaker 2>all by itself.
<v Speaker 3>It's powerful evidence for the core mechanism of the theory.
<v Speaker 2>This whole thing is such a monumental shift in perspective.
<v Speaker 2>We tend to think of the laws of physics as
<v Speaker 2>being imposed on the universe from the outside, you know,
<v Speaker 2>like a cosmic rule book that was written before the
<v Speaker 2>game started.
<v Speaker 3>The platonic view of laws.
<v Speaker 2>Yes, but this theory suggests the rules, or at least
<v Speaker 2>some of them, like time and gravity, are actually emerging
<v Speaker 2>from the game as it's being played.
<v Speaker 3>That's a great way to describe it. It's the difference
<v Speaker 3>between a scripted play and an improv show. In the
<v Speaker 3>old block universe view, this script is already written, past, present, future,
<v Speaker 3>all there. We just read our lines.
<v Speaker 2>In this view, there is no script.
<v Speaker 3>There is no script. We are writing it line by
<v Speaker 3>line with every interaction, and once a line is spoken,
<v Speaker 3>it's part of the permanent record.
<v Speaker 2>It's canon, which leads me to something that's been bothering me.
<v Speaker 2>If the universe remembers everything, if every single thing that
<v Speaker 2>happens is etched into the geometry of space, does anything
<v Speaker 2>ever truly get lost?
<v Speaker 3>That's the deepest philosophical implication of this entire framework. In
<v Speaker 3>a universe where time is the accumulation of information, the
<v Speaker 3>concept of gone doesn't really mean anything.
<v Speaker 2>We think of the past as being gone. It's over.
<v Speaker 2>It exists in my memory, sure, but it's not physically
<v Speaker 2>here anymore.
<v Speaker 3>But if this theory is correct, that's wrong. The past
<v Speaker 3>is physically present. It's encoded in the current structure of
<v Speaker 3>the universe. The configuration of everything right now is the
<v Speaker 3>complete record of its history.
<v Speaker 2>So our lives aren't just a fleeting sequence of events.
<v Speaker 2>There are permanent con contribution to the structure of reality.
<v Speaker 3>You're not just passing through the universe, you are actively
<v Speaker 3>building it. Every choice you make, every word you say,
<v Speaker 3>every breath you take is adding a new, permanent piece
<v Speaker 3>of information to the cosmos. You are quite literally making
<v Speaker 3>the universe heavier with meaning.
<v Speaker 2>Let me bring it back to the beginning for a moment,
<v Speaker 2>the frozen universe from the Wheeler to Wit equation. Does
<v Speaker 2>this new theory solve that? Does it explain why we
<v Speaker 2>perceive flow if the fundamental equation is static?
<v Speaker 3>It does? It reconciles the two views from a god's
<v Speaker 3>eye perspective. Outside of everything, the universe might well be
<v Speaker 3>a single, static, four dimensional block of information, timeless.
<v Speaker 2>The frozen block still exists.
<v Speaker 3>But inside that block, for any observer living within it,
<v Speaker 3>the information is not distributed evenly. There's a gradient. The
<v Speaker 3>structure itself contains a sequence. It flows from states of
<v Speaker 3>less information the beginning to states of more information.
<v Speaker 2>So the block is static, but the pattern written on
<v Speaker 2>the block creates the appearance of a movie playing exactly.
<v Speaker 3>Time is the gradient of information, just like a hill
<v Speaker 3>is a gradient of elevation. The flow of time is
<v Speaker 3>just us experiencing that change from less complexity to more complexity.
<v Speaker 2>It really is a thermodynamics of time.
<v Speaker 3>Then that's the term for it in the same way
<v Speaker 3>that temperature isn't a fundamental property of a single atom,
<v Speaker 3>it's an average property of many atoms. Time isn't a
<v Speaker 3>fundamental property of the universe at the smallest scale. It's
<v Speaker 3>an emergent statistical property of information.
<v Speaker 2>So if I could zoom in all the way down
<v Speaker 2>to those space time cells, I wouldn't see a tiny
<v Speaker 2>clock ticking.
<v Speaker 3>No, you would just see a network of connections, a
<v Speaker 3>web of information. Time is the shadow cast by the
<v Speaker 3>processing happening on that web.
<v Speaker 2>What does this due to ideas like time travel? Because
<v Speaker 2>if time is just another dimension, sci Fi loves to
<v Speaker 2>talk about flying backwards along.
<v Speaker 3>It, Well, what makes time travel to the past profoundly difficult,
<v Speaker 3>if not logically impossible?
<v Speaker 2>So no going back to fix mystrakes.
<v Speaker 3>Think about it. If time is just a road, maybe
<v Speaker 3>you can turn your car around. But if time is
<v Speaker 3>the irreversible accumulation of a cosmic record, you can't go back.
<v Speaker 3>Why not to go back to yesterday? You would have
<v Speaker 3>to find a way to erase today's information from every
<v Speaker 3>single particle in the universe that it has touched. You'd
<v Speaker 3>have to undo every single quantum record that has been made.
<v Speaker 2>You would be fighting against the fundamental tendency of the
<v Speaker 2>universe to record things.
<v Speaker 3>You'd be fighting unitarity. You'd be fighting the second law
<v Speaker 3>of thermodynamics. On a cosmic scale. The past is locked
<v Speaker 3>because it's already been written. The future is open because
<v Speaker 3>the page is still blank.
<v Speaker 2>That at least feels right. It secures the past. You
<v Speaker 2>can't go back and create a paradox by killing your
<v Speaker 2>own grandfather.
<v Speaker 3>Because the information that your grandfather lived is already a
<v Speaker 3>structural component of the universe you inhabit. It's part of
<v Speaker 3>the geometry you're standing on.
<v Speaker 2>So we lose the DeLorean, but we get a universe
<v Speaker 2>that remembers us and an explanation for dark matter without
<v Speaker 2>needing magic particles.
<v Speaker 3>I call that a pretty good train. It's a much
<v Speaker 3>more elegant picture of the cosmos.
<v Speaker 2>Let's try to sum this all up. It's been a
<v Speaker 2>lot to process.
<v Speaker 3>It has okay, the big picture one. Our two best
<v Speaker 3>theories of physics, relativity and quantum mechanics, clash over the
<v Speaker 3>nature of time, leading to the problem of time where
<v Speaker 3>it vanishes from the math two.
<v Speaker 2>The old solution entropy explains the era of time as
<v Speaker 2>increasing disorder, but it has to assume the universe started
<v Speaker 2>in a bizarrely tidy state for no reason.
<v Speaker 3>Three, the new solution proposes that information is physical and
<v Speaker 3>that space time itself is a memory system that records
<v Speaker 3>every interaction that ever happens.
<v Speaker 2>Four, Time is the process of that record growing. The
<v Speaker 2>flow we feel is just the universe's memory getting larger
<v Speaker 2>and more complex.
<v Speaker 3>And five, this process of information accumulation actually has a
<v Speaker 3>gravitational effect, which might explain the mystery of dark matter
<v Speaker 3>without needing any new particles.
<v Speaker 2>And the big takeaway for us living.
<v Speaker 3>In it, we need to move from thinking about the
<v Speaker 3>universe as a passive stage for events to seeing it
<v Speaker 3>as an active system that is constant learning and remembering.
<v Speaker 3>It's a participant in its own story.
<v Speaker 2>You know, when we started, we talked about that gut
<v Speaker 2>feeling of time, and usually when physics comes along and
<v Speaker 2>explain something, it could feel like it's taking the magic away.
<v Speaker 2>You know, a rainbow is just light refraction. Love is
<v Speaker 2>just chemicals.
<v Speaker 3>It often feels reductive.
<v Speaker 2>Yes, but this, yes, this doesn't feel reductive to me.
<v Speaker 2>Time is memory. It feels significant. It feels like it
<v Speaker 2>gives a cosmic weight to our experience. It validates that
<v Speaker 2>feeling that the past isn't just gone, that it matters.
<v Speaker 3>It's built into the very foundation of the present. I agree,
<v Speaker 3>it gives a literal weight to history.
<v Speaker 2>So before we wrap up, I want to leave you
<v Speaker 2>with one last question to think about.
<v Speaker 3>Let's hear it.
<v Speaker 2>Okay, So the universe is a recording device. It's a
<v Speaker 2>library at everything that has ever happened written into the
<v Speaker 2>geometry of space. My question is who's reading it? That
<v Speaker 2>is the question? Isn't it is the writing of the
<v Speaker 2>book the whole point? Or is there a reader? And
<v Speaker 2>if the rec can never be fully raced, if every
<v Speaker 2>moment is permanently stored, does that mean, in a very
<v Speaker 2>real physical sense, that nothing ever truly ends, that were
<v Speaker 2>all just permanent features like mountains rivers on the landscape
<v Speaker 2>of space time.
<v Speaker 3>If the theory holds, the answer would have to be yes.
<v Speaker 3>Your existence is a permanent scar on the geometry of reality.
<v Speaker 2>Wow, I think I'm going to walk a little more
<v Speaker 2>deliberately today. I'm literally carving my path into the universe.
<v Speaker 3>Make it a good one.