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Explores the nature of time, its symmetry in physics, and why we perceive time's flow despite fundamental laws being time-reversible.
Key Takeaways
- Fundamental physical laws are time-symmetric and do not inherently distinguish past from future.
- Our perception of time flowing forward is still a profound mystery in physics.
- Particles such as positrons can be understood as electrons moving backward in time.
- The block universe theory suggests all points in time exist simultaneously without a unique present.
- Understanding time's nature challenges both physics and human consciousness.
What the video covers
- The video discusses the concept of time symmetry in physics, where fundamental laws do not distinguish past from future.
- It explains how natural processes like atomic light emission and absorption exhibit time symmetry.
- The paradox of why we experience time flowing forward despite time-reversible laws is examined.
- The video introduces the idea that particles like positrons can be interpreted as electrons moving backward in time.
- It references notable physicists such as Stephen Hawking, Sean Carroll, Carlo Rovelli, and Richard Feynman on time's nature.
- The concept of the block universe or eternalism is presented, where all moments in time exist simultaneously.
- It highlights the mystery of the present moment and how our consciousness perceives 'now' despite physics denying its special status.
- The video touches on genetic information in DNA as a metaphor for time's presence within us.
- It discusses the challenges of reconciling everyday experience with the theoretical physics of time.
- The video also includes a brief promotion for a DNA testing service.
Full Transcript — Download SRT & Markdown
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Take a look at the screen and tell me, is there anything suspicious in this video? I’ll warn you right now: no matter how hard you look, you won't spot the trick. This video is flipped from left to right. And if you look at
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any natural object, it is generally impossible to tell from its image alone whether it is horizontally flipped or not. But why doesn't a universe that is literally turned inside out seem wrong to us? And that is only the beginning
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of the oddities. Nature often sees no difference between two directions. For example, atoms emit light. However, they also absorb it. Both of these processes are easily described by the same equations. An antenna for transmitting radio waves can also be
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used to receive them. Planets can move in their orbits in either direction. The list of such symmetries is huge, but the most amazing one is time symmetry.
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The laws of physics do not distinguish between the past and the future. Stephen Hawking, theoretical physicist, cosmologist.
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If you look at the building blocks that make up our world, for example, water molecules, you won't be able to tell if the recording of these molecules is playing forward or backward in time. No matter how hard you look, the concepts of past and
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future do not appear in the laws of physics at all. In the fundamental laws of physics, there is no distinction between one direction of time and another. Sean Carroll, theoretical physicist, cosmologist. It turns out that if you take something entirely
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made of these molecules, like water vapor, then, just like with a mirror reflection, if you reverse the footage in time by playing it backward, you won't notice a thing. Wait, no. What?
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Physics tells us some very strange things about the direction of time. Fundamental equations do not distinguish the past from the future. A direction of time does not emerge from them. Where, then, does the direction of time come from if it is not written
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into the fundamental grammar of the world? Carlo Rovelli, theoretical physicist, specialist in quantum gravity. The question of why time moves forward seems idiotic only until you start trying to answer it.
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Apparently, fundamental physical laws at the microscopic level are indeed completely time-reversible. Richard Feynman, physicist, Nobel Prize winner.
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But if nature is time-reversible at its most basic level, why has none of us ever seen movement into the past?
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Nothing can move backward in time, like in the movie Tenet. It can't, right? Take a transparent container with a cloth soaked in isopropyl alcohol and place it onto some dry ice. That’s it. You have a device on your table that
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lets you literally see the tracks of elementary particles flying through your room. It is a type of cloud chamber, for the creation of which Wilson himself received the Nobel Prize in 1927. By shining a flashlight into the chamber, you will see tracks of
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different particles. And if you are lucky, you will see the track of a positron. And according to quantum field theory, a positron is, in fact, an electron moving backward in time.
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This particle was born in the future and has returned to you. That is, in a cloud chamber, you can observe the trace of an event that has not yet occurred. What? First, if you decide to conduct this experiment, be careful
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with the dry ice. And second, here is what physicist Richard Feynman, who introduced and popularized this view of positrons, wrote. The example illustrates a strange but real possibility. An electron emits a photon, races backward in time to absorb a photon, and then
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flies forward in time again. The path taken by such an electron moving backward can be long enough to manifest in a real physical experiment in the laboratory. An electron moving backward is called a positron. This is a general
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phenomenon. Every particle in nature possesses an amplitude for moving backward in time. Feynman thought a lot about the idea of reverse time flow and often discussed it with his mentor, another great physicist, John Wheeler.
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By the way, the film "Tenet" refers directly to this duo. "You mean the reverse chronology?" Like the Wheeler-Feynman theory that a positron is an electron moving backward in time?
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Movement backward in time has long since become a standard tool, and many physicists use it daily. But despite all this, tell me, has anyone among you — not in experiments, not in Hollywood movies, but in ordinary life — ever observed time flowing backward?
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Water vapor always dissipates, broken eggs do not restore themselves, and we remember only the past, not the future.
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And if you can explain why, a Nobel Prize, a million dollars, and worldwide fame await you, for the laws verified with unthinkable precision, the laws upon which all of modern civilization stands, paint an absolutely wild picture.
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They say that all moments of time, including the infinitely distant past and the infinitely distant future, all these moments exist simultaneously. But most surprisingly, not one of these moments is special. That is, no present moment exists in physics.
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In other words, as strange as it may sound, as for what you are experiencing right now — the sensation of the passage of time — we have no idea what it is. This mystery has often surfaced in my videos, and every time, it
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completely baffled me. But it turned out that a possible answer to this riddle is capable of shocking us even more. I am captivated by the thought that the past and future are, right now, as if physically present within us,
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because there is something inside us that originated long before our birth and will likely continue to exist long after our death.
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I am talking about the genetic information written in our DNA — the instruction manual by which we were assembled. And it turns out that it can tell us much more about ourselves than we previously thought. More than a year ago, I took a DNA test at the Genotek
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company. I looked at the results and was sure that, well, that's it, now I know what's in my DNA. For instance, it turned out that I am not from Krypton after all. Most of my ancestors are from Dagestan. I also learned about a
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genetic predisposition to blood clotting. I started drinking more water and moving more often. I found out about my caffeine intolerance. I almost completely cut out coffee. And I no longer have that vague anxiety. And the dark circles under my eyes from
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constant insomnia have almost vanished. An increased risk of vitamin A and B9 deficiency was revealed. I started eating more carrots and beets. And I really do feel better. But it turned out that the results will be updated over time as new scientific data
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emerges. And if any risks raise questions, they can be discussed in a consultation with a doctor, which is already included in the cost of the test. Another interesting point: your DNA can also tell you something about your abilities and character. For
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example, I discovered a genetic predisposition to good visual memory, the analysis of numerical and textual information, as well as a penchant for risk. So, follow the link in the description, order your genetic profile, and see what your DNA can tell you
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about yourself. Moreover, the promo code Ali3 will give you a 72% discount. Why are physicists even willing to seriously discuss such madness as the simultaneous existence of all moments in time? Well, firstly, as I already said, because the theories from which
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this madness follows work brilliantly. And secondly, take, for example, the most famous formula in the world: E = mc². It's, damn it, even printed on T-shirts and mugs. But almost no one, except for physicists themselves, even remotely understands how ridiculous
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this formula is. You can't imagine how stupidly absurd it seemed when Einstein first formulated it. This formula sa
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In practice, this means absolute insanity. For instance, if you take just a liter of gasoline and extract all the energy from it, you could travel not 10 km, as with combustion, but 20 billion km. So, by a rough
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calculation, on one liter of gasoline, you could drive across all of Russia from one end to the other more than 2 million times.
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If that doesn't sound crazy enough to you, then how about this? Do you think that your body weight comes from the matter you are made of?
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Yes. But if you were to calculate the mass of all the elementary particles that make up your body, the mass of individual quarks and electrons, it would turn out that you should weigh only about 1 kg. So where does all the
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rest of the mass come from? According to the formula E = MC², 99%of your mass arises from the monstrous energy of the motion and interaction of that kilogram of elementary particles. It's roughly as if we took an empty
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refrigerator box and started stuffing light into it. until that box started to weigh 80 kg.
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You might ask, how much light would be needed for that? About as much as would be released by the explosion of thirty Tsar Bombas.
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For reference, the Tsar Bomba is the most powerful nuclear bomb ever tested in history, with a fireball diameter that reached 10 km, and a shockwave that blew out windows up to 800 km away . So, inside you is the equivalent of
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the explosion of about thirty such Tsar Bombas. It turns out that you are not so much matter as you are trapped energy. Therefore, please, keep yourself together.
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And if we are to take examples to the point of total absurdity, then from pure light alone, if concentrated enough, one could create a black hole. For such black holes, they even came up with a name: Kugelblitz, from the German for "ball lightning."
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In short, the idea that all moments of time are real and exist simultaneously, this idea may sound as crazy as you like. But, as we can see, physics has more than once forced us to accept and even normalize completely unhinged
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ideas. After the death of Michele Besso , Einstein's closest friend of 60 long years, Einstein wrote a letter to his family that ended with the following paragraph. Now he has departed from this strange world a little ahead of me
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, but that means nothing. For us, convinced physicists, the distinction between past, present, and future is nothing more than an illusion. Although a very persistent one, but how can this separation be an illusion? Very simply.
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Accelerate to this speed as a percentage of the speed of light, and for every second of your own time, you will zip 1,000 years into the future.
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Time travel into the future is an experimentally proven scientific fact of the theory of relativity, which many people know about. But the fact that the mathematics of this theory allows for such things with travel into the past, that is known to far fewer people
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. Electrons moving backward in time in a cloud chamber is certainly quite strange, but what about something much larger? In the 1960s, astronomers stumbled upon something absolutely abnormal. They discovered objects that were continuously ejecting as much energy into space as thousands of
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galaxies combined. These objects were named quasars. Physicists went through one hypothesis after another, but nothing fit. Not a single known physical process even came close to such frantic energy output.
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Then, some scientists suggested that— get this—perhaps quasars are time-reversed black holes, and therefore they don't absorb matter, but spit it out. Wait, wait, wait, wait, wait. Time-reversed black holes? What kind of heresy is that? I’ll explain.
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What is the main oddity of regular black holes? They say that at their center lies a point of infinite density , a so-called singularity. However, calling this point a "place" isn't quite right, because once you are inside a black hole, you can move in
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absolutely any direction, but regardless of the trajectory you choose, you will still end up in the singularity.
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That is to say, the singularity isn't exactly a place in space, but rather a moment in time—a moment in the future .
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And an attentive viewer might say, " Well, there's your designated direction of time." So, physics does distinguish between past and future after all, right? No. Like all other equations of fundamental physics, the equations of general relativity that predict the
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existence of black holes are completely time-symmetric. Consequently, the same equations, with the same rigor, predict the temporal antipodes of black holes, which physicists call white holes.
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It was white holes that became one of the possible candidates for quasars in the sixties. This is not a manifestation of some fundamental physical laws. General relativity is perfectly symmetric in time. For every spacetime that represents a solution to
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Einstein's equation, there exists another solution that is identical to the previous one but has the flow of time reversed. A black hole is one of the solutions to Einstein's equation, so there are also equivalent solutions that run in the other direction. White
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holes. Sean Carroll from the book "From Eternity to Here: The Quest for the Ultimate Theory of Time." Yes, today we know that quasars are most likely powered by regular black holes, accelerating matter to monstrous speeds with their gravity. But white holes
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haven't disappeared from the theory of relativity because of that. I emphasize once again, the theory generates them on its own, without us asking.
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There is very little popular information about white holes, and that is why people have a misconceptions about them.
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For example, you almost certainly think that white holes, unlike black holes, repel everything that approaches them.
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But that is a common myth. The confusion arises because a white hole is described as a black hole in reverse . But I repeat, "reverse" here does not mean an opposite force, but the opposite direction of time.
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And if you take an ordinary black hole and look at it in reverse, you’ll see that objects orbiting it don’t fly away, they simply start spinning in the opposite direction.
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Meaning that white holes, just like any other massive object, have gravity. And gravity, whether moving forward or backward in time, always acts as an attractive force.
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So what is the difference between a white hole and a black hole? Well, while with a black hole you can cross the event horizon inward but not outward—because from the moment you cross, no matter where you move, the
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singularity is always in your future— with a white hole, it’s the opposite. The singularity is always in your past, and the horizon can only be crossed outward, never inward.
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And it’s not that a white hole would repel you. No, it’s much stranger than that. The very geometry of spacetime won’t let you cross the horizon, because the universe simply contains no trajectories pointing into the future that would let you fly into
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a white hole. That probably didn't make it any clearer. I spent a long time coming up with an analogy, and here is what occurred to me. Imagine you are standing at the southernmost point of the South Pole.
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Can you go any further south? No. The geometry of the Earth simply doesn't allow for it. Being at the southernmost point of the South Pole, absolutely any direction for you will be north. Any future step you take will inevitably
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move you further from the South Pole. And not because some repulsive force is acting on you, but because at that point, in the geometry of the Earth itself, there are simply no other directions than away from the South
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Pole. Roughly speaking, the white hole’s horizon is a boundary that can only be crossed outward, not inward. Not because something is pushing you away, but simply due to the geometry of spacetime itself.
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As Sean Carroll writes, that is why it’s impossible to create a white hole, and they cannot arise naturally from processes like black holes.
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Since we exist in the external world, the singularity and event horizon of any white hole must necessarily remain in our past.
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In other words, according to Carroll, if we ever discover such an object, it would mean it has existed in the universe from the very beginning.
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However, that is not the only opinion. For example, in 2023, the renowned physicist Carlo Rovelli published a book titled "White Holes," where he proposed the idea that white holes emerge from black holes, and that the mysterious dark matter, which is five
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times more abundant in the universe than ordinary matter, is actually composed of countless white holes. At the very least, dark matter could partly consist of billions upon billions of these tiny, delicate white holes, reversing—though not entirely —the time of black holes and drifting
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easily through the universe like dandelion fluff, according to Rovelli. Dandelion fluff. Be careful if you decide to buy Rovelli's book. His hypothesis is truly curious.
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But if, looking at the title, you expect 200 pages about white holes, then, alas, out of 67 references in the book, my God, nearly a third are to Dante Alighieri's Divine Comedy.
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Oh, those Italians, there are much more exotic ideas as well. For example, that the Big Bang occurred as a result of the explosion of a supermassive white hole. In short, the equations of physics are clearly trying to tell us that not only electrons, but
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also supermassive objects can theoretically move into the past, which means the future and the past literally exist.
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But why then aren't we traveling back in time ourselves? And what makes you think we aren't?
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In 1949, the brilliant mathematician Kurt Gödel literally stunned Einstein with his calculations. He demonstrated that the mathematics of general relativity allows for travel into the past.
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In general relativity, the spacetime you are inside is not a static stage. It can theoretically be twisted into such a knot that, while moving forward along your path in time, you would return to your own past time and time
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again. Physicists call such temporal trajectories closed timelike curves. Time is not carved in marble. In general relativity, it is easy to find spacetimes—more than one—where closed timelike curves occur, says Sean Carroll. And do you know what life would feel like inside one of the
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simplest versions of such spacetime? About like in the movie Groundhog Day. Yes, a film in which the protagonist returns to the same day over and over is surprisingly similar to one of the exact solutions of Einstein's equations . But there are two terrifying nuances,
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because of which you would never want to be in the protagonist's shoes. First , all days would be exactly the same, including your actions, deeds, and even your thoughts.
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And second, and this is the most frightening part, it would be impossible to break out of this circle.
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It is a trap in which you will be stuck forever. And you won't even know about it, because each time, along with everything else, your memory will also return to its initial state. So you cannot be sure that you are not inside
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such a loop right now. And time loops are another indication of the absolute reality of all moments in time.
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Therefore, you should be much more careful with wishes for eternal life. Fortunately, such a prison is not, after all, the only model that the theory of relativity allows. You have probably noticed that almost every other video of mine is inspired by
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books that haven't been translated into Russian. I was a bit lucky. I attended a good gymnasium with an intensive English program. And that really helps now, because almost everything interesting in the world comes out in English first. If you were less lucky
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with your school, the online language school Skyeng can help fill that gap, because the main problem with learning a language is that sooner or later studying turns into torture: textbooks, exercises, lists of twenty words, and within a week you start feeling sick of
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it. That is exactly what they fight against at Skyeng. Here, you won't study the language through texts about the British royal family, but through things you are genuinely interested in: movies, music, travel, science, esports —yes, anything at all. As a child,
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you didn't start speaking your native language because you memorized grammar and rote-learned 10,000 words, but simply because you heard speech around you and tried to say something. This very principle lies at the heart of learning at Skyeng. You constantly use
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the language right during the lesson. You listen, read, speak, analyze new words, and immediately apply them in context. You can choose a teacher yourself with whom you will feel comfortable. And it doesn't have to be a Russian speaker. You can study with a
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teacher from another country and constantly hear live language. You can choose any class schedule you like.
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Furthermore, Skyeng has thematic speaking clubs where you can communicate with other students. Like I said, this is a true immersion in a language environment. It is very convenient that everything you need is gathered on one platform: homework, vocabulary, practice tools, and
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progress tracking. And Skyeng is not just English. You can study French, Spanish, German, Italian, Chinese, and other languages here. And until September 30th, there is a discount of up to 50%on lessons. Plus, Skyeng is giving away cool gifts. You can
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activate the discount for yourself via the link in the description or the QR code on the screen. Specially for this episode, Skyeng has prepared a free collection of a thousand most useful English words for travel, communicating with foreigners, and watching movies
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and series. Take a look at this photo of deep space . You might ask, "What is so unusual here?" Well, just a couple of galaxies.
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Maybe, or maybe it is the same galaxy that for some reason looks as if it were reflected in a cracked mirror, as if between us and this galaxy, in the very fabric of reality, there is a crack, a
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fissure that creates such a distorted image. Well, some astrophysicists are seriously considering this option.
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A crack in the fabric of reality sounds like the beginning of some horror movie .
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Let me explain. For example, when water freezes, it happens unevenly. Ice crystals begin to grow in different places. And when these growing boundaries collide, their patterns do not align, creating visible seams. That is why ice is almost never perfectly
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transparent. It looks more like a block glued together from shards. Well, in the early Universe, as the vacuum cooled, something similar could have happened, but with the very fabric of spacetime itself. And if so, then throughout space, such defects might be
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scattered here and there, one of which we might be seeing in this image. We were unlucky, and these hypothetical fractures were not given a cool name like "scars of being," but a boring one : cosmic strings. Cosmic strings, if
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they exist, do very strange things to spacetime. For example, if you fly around such a string, you will discover that you have covered less than 360 °.
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This means a sector has been cut out of the space around the string. Because of this, parallel lines can converge near a string. Triangles have a sum of angles less than 180 °, and light from distant objects can indeed travel along
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several paths at once, creating these double images. But how is this related to time at all?
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It is very related, because the real madness begins when two such strings move relative to each other. Under certain conditions, their combined influence on the geometry of spacetime can be so significant that spacetime closes in on itself, forming
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closed timelike curves. If you fly in a circle around these strings, as you finish your journey, you will run into yourself from the past, just beginning the flight. All these stories sound very wild, and it is not even the potential possibility
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of time travel, but simply the realization of the fact that the very fabric of reality can be twisted, turned, and literally folded.
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If you think about it for a long time, it instills a sort of primal anxiety, because in all of history, no living being has ever sensed spacetime fluctuations with their own senses. If, while on Earth, a bomb goes off at a
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relatively safe distance from you, the ground beneath your feet will tremble, you will feel the air vibrate with every cell of your body, and the roar of the explosion might even deafen you.
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But if you are in space and even the largest star explodes at a relatively safe distance, contrary to all your earthly intuition, it will happen in sterile silence. You will not feel it at all. And if you have your back to
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the star, you might not even notice the explosion because space lacks a medium that could transmit vibrations. For our biology, this is very unnatural, and therefore chilling.
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But believe me, you will be much more terrified if, while in the dead silence of deep space, you suddenly hear something after all. In the absence of an atmosphere, this can only mean one thing. Space-time itself is oscillating
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. And yes, you can actually hear it. Renowned American astrophysicist Janna Levin writes in her book "Black Hole Blues and Other Songs from Outer Space" that if space-time around you begins to vibrate powerfully, your entire body will alternately stretch and compress.
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Your eardrums will begin to resonate not with vibrations of the air, but with the vibrations of space-time itself. And your brain will start to interpret this as sound. Damn, that would be the most terrifying sound of your life. But from where, and how?
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What in heaven's name could disturb the very fabric of existence so violently, if even the explosion of the largest star isn't capable of it?
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You would look around with all your might, but you wouldn't see anything. And yet, this is what scientists around the world struggled to numerically simulate for nearly 30 years. And the simulation of which is right now before your eyes. It is the death dance of two
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black holes before their merger; two titanic masses orbiting each other at speeds approaching the speed of light.
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A cosmic-scale event, the peak power of which is comparable to the total luminosity of all stars in the observable universe.
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But it is an event that cannot be seen, because all this absurd energy does not go into emitting light, but into gravitational waves, that is, into the vibrations of space-time itself. Just realize that what you see here are the frantic pulsations of what
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seems to us absolutely immovable. Thus, although you cannot really see a black hole merger if there isn't something bright in the background, the merger can nevertheless be heard. And Janna Levin and her team were able to reconstruct this sound very accurately.
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Do you want to hear it? Protect your ears; it’s about to get unpleasant. If you hear this sound in space, be prepared. At any moment, you could be flung into the past because, as some mathematical models show, in such
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violently curved space-time, there are regions with closed timelike curves. I understand what you're thinking, that all this is some kind of extreme madness, but we are talking about the principle itself. It is unclear why we feel the flow of time at all if the
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equations show that all moments of time are equivalent and exist simultaneously . And in fact, mathematics does not necessarily require such extremes for traveling to the past. Literally a few months after Einstein formulated his theory of relativity, physicists began
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to parse its equations. And it very quickly became clear that these equations knew much more about the universe than their creator. Some wild stuff started coming out of these formulas that, frankly, no one was looking for.
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At first, the equations unexpectedly allowed for the existence of objects that would later be called black holes.
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Almost no one, including Einstein himself, believed that such objects could even exist. Then gravitational waves popped up, which also sounded like science fiction. Then the equations produced another extremely strange thing, which physicists have been unable to shake for over 100 years
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while trying to figure out if it even exists. And it is this very thing that became the basis for the most mathematically sound time machine—one that, in theory, could be built right here on Earth. Behold, the wormhole. A
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portal through space-time. You've seen wormholes in a million different works, from the legendary game Portal and comics to the movie Interstellar. But the first thing you need to understand is that wormholes are not sci-fi inventions, but an unexpected
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consequence of Einstein's equations. Although such portals in space-time seem like something very, very abstract , the physicist who coined the term " wormhole," John Wheeler, suggested they might not be rare exotic objects at all . Perhaps right now, the space around
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us is literally teeming with microscopic wormholes that are constantly appearing and disappearing. Where such wormholes could lead is unknown. Maybe somewhere nearby. Maybe to other galaxies, or perhaps even to other universes. For now, this is all just a realm of hypotheses.
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Wait. But a wormhole is just a tunnel through space, right? In Interstellar, where the wormhole was shown with the greatest mathematical accuracy, no one traveled through it into the past. So what does that have to do with time
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machines? It has to do with the fact that any traversable wormhole can easily be turned into a time tunnel.
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And this was demonstrated by the very scientist whose calculations were used in the movie Interstellar: Kip Thorne.
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In 1988, he and his colleagues wrote a paper with the telling title "Wormholes , Time Machines, and the Weak Energy Condition." The essence is simple. For example, if the wormholes from the game Portal existed in reality, if you were
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to open one mouth near Earth and another one higher up, a time desynchronization would immediately start to build up between the two mouths, since gravity makes time flow a little slower near Earth. And after some time, a paradoxical situation
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would arise. You would start exiting from the second mouth before you even entered the first. Wait. And what if I just change my mind about entering the upper mouth after that? Don't be silly, you won't be able to change your mind.
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You cannot change the future any more than you can change the past. Let me remind you: both the past and the future, all points in time already exist; they cannot be changed. This is perfectly demonstrated in the movie
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Tenet, where the time-inverted protagonist cannot resist stepping into a puddle because that event already exists and cannot be changed. If that’s not mind-bending enough, there are ways to make this effect absolutely colossal.
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For example, if you leave one end of a wormhole on Earth and send the other at near light speed to Proxima Centauri and back, due to relativistic time dilation, only about 10 hours will have passed for the traveling end, while a
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decade will have passed on Earth. As a result, a massive time shift emerges between the two ends. And by entering the returned end, you would emerge from the other nearly a decade before the moment you entered. Cosmic strings,
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black holes, wormholes. These are all different consequences of the theory of relativity, which tell us the same thing. The universe has no single, privileged "now." And that, in theory, you could travel along the timeline both forward and backward. However, the mathematics of
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the even more verified quantum theory says something even stranger: that time travel is actually happening to us all the time anyway. For instance, right now. Remember the double-slit experiment? Of course you do. Even though everyone is long since tired of
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hearing about this experiment, you still don't understand what kind of madness is really going on there.
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Richard Feynman said that the double-slit experiment contains the entire essence and the main mystery of quantum mechanics, which is impossible to explain. You probably remember that a fired electron passes through both slits simultaneously.
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Perhaps you've even heard that the electron doesn't just pass through both slits, but actually spreads out along every possible trajectory. However, almost no one understands that the phrase "all possible trajectories" literally means all possible trajectories.
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No, you still don't understand. To even believe what is going to be said next, you need someone with more authority than me.
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For example, Stephen Hawking, one of the greatest physicists of our time. In his book "The Grand Design," he writes, quote: "In the double-slit experiment, Feynman's ideas boil down to the fact that particles choose paths that lead either through one slit or the other.""
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Paths that lead through the first slit, then back through the second, and again back through the first." Paths leading to a restaurant that serves shrimp in curry sauce. Then to Jupiter, looping around it several times before returning, and even paths that lead
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across the universe and back. This, according to Feynman, explains how the particle gets information about which slits are open.
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Wait. What does time travel have to do with this? It has to do with the fact that the phrase "all possible trajectories" literally means all possible trajectories.
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Here is what Hawking writes in another of his popular books titled "The Universe in a Nutshell." If you apply Feynman's idea of a sum over histories to a single particle, you have to include histories in which the particle
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moves faster than light and even backward in time. In particular, there will be histories where a particle moves in circles along a closed loop in time and space. Like in the movie Groundhog Day, where a reporter relives the same day over and over again. And
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while everything inside you screams that this just cannot be, Hawking adds that the existence of such trajectories is proven experimentally. Particles with such closed-loop histories cannot be observed in accelerators. However, their side effects can be measured by observing a number of experimental
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effects. One of them is a slight shift in the radiation emitted by hydrogen atoms, caused by electrons moving in closed loops. Another is a small force acting between parallel metal plates, caused by the fact that slightly fewer closed loops fit between them than in
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the outer regions. This is another equivalent interpretation of the Casimir effect. Thus, the existence of closed-loop histories is confirmed by experiment.
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You might think this is just the electronic microworld, but there is no separate quantum physics for electrons.
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Everything you see obeys quantum laws. Therefore, when you throw a ball, strictly speaking, from the perspective of modern quantum theory, this ball also explores all trajectories. When a bird flies from branch to branch, its quantum path takes all possible
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trajectories into account. And even when you personally head from the living room to the kitchen, I think you get the idea. Yes, the contributions of all strange trajectories cancel each other out, and you get classical motion without trips to Jupiter or into the
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past. But you cannot exclude the crazy trajectories from your calculations, because the math stops working then.
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Feynman's path integral is one of the most accurate and successful methods in the history of physics, predicting experimental results with incredible precision. If you don't understand how this is possible, you are not alone. As Feynman himself cautioned his students,
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I think I can safely say that nobody understands quantum mechanics. So, don't take this lecture too seriously.
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Don't feel that you are obliged to understand what I am going to talk about within some kind of model. Just relax and enjoy it. Don't keep asking yourself: "How can this be?" Because otherwise you will go crazy and end up
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in a tight dead end from which no one has ever escaped. Nobody knows how this can be. Yes, I repeat, the contributions of all these strange trajectories cancel each other out, but still. What is the probability that one
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of us will actually travel into the past because of all these quantum oddities? Hawking jokingly estimated the probability of this for his friend Kip Thorne, the very one who showed how one can travel to the past through a
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wormhole. I estimated the probability that Kip Thorne would be able to travel into the past and kill his grandfather.
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It turned out to be less than one in ten to the power of a trillion trillion trillion trillion trillion. After all, travel to the past should really cause paradoxes. What happens if you step into a wormhole and actually kill your
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grandfather before your father is born? Wouldn't that lead to contradictions? Perhaps it wouldn't. When Kip Thorne and his colleagues published that very paper in 1988, "Wormhole Time Machines and the Weak Energy Condition," it caused a sensation. Previously, publishing articles on time travel in
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serious journals meant sideways glances from colleagues and ruined reputations. But Thorne changed everything. In his book "Black Holes and Time Warps ," Thorne recalls that right after the article's publication, his friend, the distinguished Soviet astrophysicist Igor Dmitrievich Novikov, called him in
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full delight. I quote: "I am so happy, Kip. You have broken the barrier. If you could publish a paper on time machines, then I can too." Two years later, Novikov and his colleagues published an article in a prestigious
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scientific journal on closed timelike curves, in which he gave a strict form to his famous self-consistency principle, one of the most elegant solutions to time travel paradoxes. Its essence is simple: history cannot be changed. Everything you do in the past
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was always part of that past. For example, if you try to kill your grandfather before your father is born, circumstances will inevitably conspire so that you fail. For instance, grandfather will be saved by a woman passing by. He will fall in love with
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her, and later it will turn out that she was your grandmother. In other words, you cannot do anything that would lead to temporal paradoxes.
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Honestly, I don't know why I'm making up examples, because the Novikov self-consistency principle is perfectly illustrated in the world-famous and scariest film of my childhood, the first Terminator. In the future, the rebellious artificial intelligence Skynet is losing the war to humans led
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by John Connor. So, Skynet sends a Terminator into the past to eliminate John Connor’s mother, Sarah, before she gives birth to her son. Thus, Skynet hopes to change history and avoid its own defeat. But that is precisely what triggers the birth of
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John Connor, because John Connor’s father turns out to be the soldier sent to protect Sarah from the Terminator.
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Studying the remains of the destroyed Terminator leads to the creation of Skynet itself, resulting in a self-consistent loop. And almost no one noticed how director James Cameron occasionally subtly shows the audience the self-consistency principle, hinting that fate is already written and cannot
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be changed. For example, here Sarah accidentally drops a bottle and reaches for it, which is why the Terminator doesn't notice her. Here, Sarah is protected from a bullet by a woman who happened to be behind her. Here, the Terminator
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runs out of ammo right before the decisive shot. And here, his machine gun suddenly jams. If you watch the movie closely, you'll see that the Terminator, an ideal killing machine, mows down everyone in its path yet can't seem to finish off one fragile
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girl. Each time, it is literally one step away from success, but every time, it fails. To those out of the loop, this looks like typical, lazy plot armor, but in reality, the universe simply prevents a contradiction from arising, because if Sarah dies, her son
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won't be born, and if he isn't born, Skynet won't send a Terminator back in time to kill Sarah. Which means Sarah will survive. This is a paradox, because Sarah cannot be both alive and dead at the same time. Or can she?
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Let’s be clear. Even if time travel leads to contradictions, who said that's a problem? Our current physical models already suggest that contradictions in the universe might be a completely mundane affair.
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Sarah Connor being alive and dead simultaneously sounds like nonsense, but a cat being alive and dead simultaneously sounds normal. You’ve heard about Schrödinger’s cat so many times. This story has become such a popular meme that everyone has long
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forgotten what monstrous things this thought experiment claims about our reality. In a nutshell, there is a tightly sealed lead box, completely isolated from the outside world. Inside the box is a cat, one radioactive atom, a radiation detector with a hammer, and
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a flask of poison. The probability of the atom decaying is 50%. If decay occurs, the detector triggers, the hammer breaks the flask, and the poison kills the cat. If there is no decay, the cat keeps living. Up to this point,
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everything sounds perfectly reasonable, but then things get absolutely bizarre. According to the mathematical framework of quantum mechanics, until a measurement is made, one cannot say that the atom has either decayed or not decayed. The atom is not in one of
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these states. It is in both at once. And since the laws of quantum mechanics are equally applicable to everything, not just an individual atom, this state inevitably spreads further: to the detector, the hammer, the flask of poison, and ultimately to the cat
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itself. This leads to the absolutely mind-bending conclusion that if you had such a closed box with a cat right now, you would be forced to answer the question of what is inside by saying there is a cat that is both alive and
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dead at the same time. Literally. It’s not that you just don't know whether the cat is alive or dead. No.
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Until the box is opened, the question of whether the cat is alive or dead fundamentally has no answer. Not because the answer is hidden, but because the very reality in which that answer already exists does not yet exist. Erwin Schrödinger didn't come
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up with this thought experiment to explain quantum mechanics to students, but to show his intelligent colleagues that there was something deeply wrong with it. But nearly 100 years later, we can confidently say that there is nothing wrong with it; it works
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perfectly. The absurdity of the Schrödinger's cat situation has never received a satisfactory explanation. How do modern physicists react to this ridiculous example? They don't. Schrödinger’s cat still bothers them today, if it happens to be brought up. But most of
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the time, physicists prefer to ignore the problem. Richard Muller is a physicist and professor emeritus at the University of California, Berkeley.
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And so many questions arise: what does it even mean to perform a measurement? How does a quantum system know you’ve opened the box and it needs to choose?
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What, in the end, does the cat feel while it is in two states simultaneously? Can a system be measured simply because a cat is looking at it, or does it require a human? As astonishing and unsettling as it may sound, the answer to all our
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questions is the same. We don't know. We chuckle when we tell students about Schrödinger's cat, but deep down we know this story is no laughing matter.
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When we are unable to answer students ' questions about the cat honestly, we avoid the answer. We simply follow Feynman's advice and avoid thinking about it for fear of going insane.
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Richard Muller. One might think the madness ends with the cat, but in 1961, physicist Eugene Wigner showed that this was just a harmless warm-up. Imagine that you opened the box and saw with your own eyes a live or dead cat. For you, the experiment is
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finished. Reality has been determined. But what if another person has been standing outside the lab door the whole time? They didn't see what was happening inside. For them, the lab is just as much a closed box as the box
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with the cat was for you earlier. Do you see? From the perspective of the person outside, you yourself are in two states simultaneously. There is you, who saw a live cat, and there is you, who saw a dead cat. And again, it’s
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not that the person outside simply doesn't know which of the two states you are in. Quantum mechanics requires us to say something much more unsettling. For the person outside, neither of these options physically exists yet.
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This raises the question: is there even a single objective reality for all observers? Because Wigner's experiment demonstrates the possibility of having different, contradictory facts at the same time.
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This is a profound question that suggests that facts in quantum mechanics, in quantum reality, may not be the same for everyone. There is no universally accepted solution to this paradox to this day. That’s how things are with quantum mechanics. But
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in the theory of relativity, the contradictions are just as insane. For instance, how do you like the fact that black holes don't actually exist?
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They don't exist, yet scientists say we have plenty of evidence for their existence. Well, yes, black holes exist, but not for everyone, and specifically not for us. If you throw a stone into a black hole, you will never see it cross the
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event horizon. From your perspective, the thrown stone will just keep slowing down until it stops completely. Right at the very edge of the horizon. In your frame of reference, the stone will freeze there forever. You would literally have to wait an infinite
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amount of time for that stone to cross the horizon. Yes, the stone’s silhouette will gradually fade and disappear, not because it crossed the horizon, but because its light stopped reaching your eyes. But in your frame of reference, the stone is still right
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there. Formally speaking, you would have an infinite amount of time to change your mind and pull the stone back. Think about what this implies. It implies that from the viewpoint of external observers, no object in the universe has yet managed to achieve the
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status of a true black hole. Because from an external observer's view, for a black hole to form, all the matter creating it must first overcome an infinite distance, spending an infinite amount of time to do so. But from the
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stone's own perspective, something completely different is happening. By its own clock, time is passing perfectly normally. It crosses the event horizon in finite time and very quickly finds itself inside a fully formed black hole. And most strangely, after crossing the horizon, from the
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stone's perspective, time in the outside universe approaches infinity and goes beyond it. What? Where does time go? Beyond infinity. Uh-huh. Well, that's absurd. Perhaps. However, in classical relativistic theory, that is the case. Richard Muller.
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Thus, common intuition tells us that we have two contradictory points of view. From our perspective, the stone falls for an infinite amount of time. From the stone's perspective, the fall time is finite.
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As we can see, formally, black holes exist only for what has fallen into them and do not exist for everything else. Such are the contradictions in the theory of relativity. And I haven't even mentioned that quantum mechanics, which describes the universe with
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maximum precision on microscopic scales , and the theory of relativity, which perfectly describes the universe on a cosmic scale, these two flawlessly working theories contradict each other at a fundamental level. A paradox is just a conflict between reality and
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your feeling of what reality should be. Richard Feynman. To sum up, potential time paradoxes would just be another set of paradoxes in physics. Anyway, that’s enough. What am I trying to say? The mathematics of our physical theories not only places no
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restrictions on moving freely along the timeline, but also actively suggests various ways this could be done.
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Mathematics truly demonstrates in every way that no moment in time—neither the past nor the future—possesses any special status. Mathematics. And what about in practice?
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In practice, the surrounding reality you observe almost completely ignores all of this. In practice, we have never seen water vapor, instead of dispersing , flow back into a pipe. In practice, you have never woken up in yesterday after today. You have never once in
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your life felt for a second that you were moving backward in time. None of us perceives all moments of the Universe simultaneously, like Dr.
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Manhattan from Watchmen. Why can no precision instrument tell you whether a recording of water molecules is playing forward or backward in time? So why does water vapor, which is literally made of those molecules, always move away from the pipe and never in the
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opposite direction? We are only interested in why the past is so strikingly different from the future.
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This would pose no mystery at all if not for the fact that the fundamental laws of physics are, in general, absolutely reversible. Sean Carroll. We have one common explanation, but it is very strange. I will explain it using a
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popular example. Take a standard deck of fifty-two cards and just shuffle it a little. That’s it. You are currently holding an order of cards that has never existed before. Not by any player, not by any magician, not in
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any casino in the entire history of humanity. And the point is not that people rarely or poorly shuffle cards, but that there are so many possible combinations of fifty-two cards that if we took every person who has ever lived
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on the planet—about 117 billion people—and made them shuffle decks since the Big Bang. And let's assume that every second every person got a new unique combination, then to this day, after 13.8 billion years, they would have only gone through this small
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percentage of all possible combinations of fifty-two cards. In practice, this number is indistinguishable from zero.
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It is the same as taking a single speck of dust and comparing its volume to the volume of the Sun and all the planets combined. So your shuffled deck is literally a unique signature of the universe that, likely, no one but you
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has ever held in their hands. And what's more, it is likely that no one will ever hold it again until the end of the history of the Universe. It belongs only to this moment. Enjoy it.
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And now look at this video and tell me, how does it seem to you, is it playing forward or backward? I bet you easily realized that this video is playing in reverse. But how did you guess? You didn’t see anything impossible here,
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did you? Not a single physical law was broken in the video. The answer lies in the fact that there is a vast number of possible states for a deck of cards, as we know, and you intuitively understand that only a tiny fraction of those
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states looks ordered. That is why the transition from order to chaos looks natural, while chaos to order looks incredible, even if it's not forbidden by the laws of physics. And if ordering just a few cards is nearly impossible,
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what can we say about water vapor, consisting of trillions of constantly shifting water molecules? For the steam to flow back into the pipe, all those molecules would have to simultaneously and orderly rush downwards. That is possible, but the probability of such an event is
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practically indistinguishable from zero . And many physicists believe that this is the whole secret. That time flows forward, not backward. Simply because more probable things happen more often than less probable ones.
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This is called the increase of entropy. Therefore, when there are only a few molecules or cards in the recording, it is impossible to determine the direction of time, since with such a small number of elements, any configuration is quite probable. But do
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you believe that time flows for this very reason? If we follow this logic, a rather strange thing happens. By changing entropy, we change the course of time. It turns out that inside your refrigerator time should slow down because cold makes molecules more
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ordered. And by a campfire, where energy dissipates, increasing chaos, time should move faster. Taking this logic to the limit, we would have to admit that if an improbable event occurred and all the steam molecules rushed down into the pipe for one
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second, it would mean that the time of that steam had locally wound back one second. But something tells me you would hardly agree that in such a case, time actually went backward. If, while shuffling a chaotic deck, you
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accidentally ended up with an ordered deck, like a fresh pack. You would hardly agree that the time of the deck had actually wound back. Such an explanation of the flow of time seems perverse. However, it is a very popular
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explanation. And, for example, it is precisely what was used in the film Tenet, which, for a moment, was directed by a filmmaker obsessed with the subject of time. In the film, time was reversed precisely through entropy inversion.
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Technology that inverts the entropy of objects. Ask a random physicist what makes time move forward. I don’t know how many physicists you know, but I know quite a few. And I’ve tried asking many of them this question. The answer was
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usually something like, "possibly entropy." Then the physicist would usually try to explain their answer. " I’m not sure it’s that way, but it seems to be all we have." Richard Muller. I suppose you also see that deep down there is a persistent feeling
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that the flow of time is a much greater mystery than simple laws of statistics.
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That time doesn't flow because entropy increases, but entropy increases because time flows. Let's just sum it up. At the moment, many, if not most physicists, are seriously considering the possibility that all moments in time exist simultaneously. If we try to
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visualize this somehow, it turns out that the Universe is a single, static, unchanging four-dimensional block. It is like a stack of three-dimensional snapshots arranged along the time axis.
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And the direction or arrow of time in this block is determined by the growth of entropy. This picture is called eternalism or the block universe concept. And we have seen why this picture is taken seriously, and not just in this video. I presented
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extremely weighty arguments, for example, right here. The block universe is a very well-founded philosophical concept with powerful arguments. It flows quite naturally from Einstein's theory of relativity, yet it almost totally contradicts how we perceive reality. Just think about it: if the
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universe is a dead, unchanging four-dimensional block, it means you exist simultaneously in every moment of your life from birth to death. In that case, why do we remember only the past and not the future? Why does the past
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seem irretrievably lost, and the future not yet existing? And in general, why then does your consciousness not perceive your whole life at once, in every single moment? Why instead does your consciousness, your attention in the static block, move unstoppably
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along the timeline and always reside in only one single mysterious moment we call "now"? And what even is this "now" ? Why does it specifically possess some special status if all moments in time are equally real? Finally, should we
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even consider our sensations in the physical picture of the world? Is everything we feel, in the words of Einstein, just a persistent illusion?
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Yes, the theory of relativity as a whole greatly contradicts our everyday experience. For example, when you stand up and start walking at a speed of just 5 km/h, in your frame of reference the entire observable universe ahead of you
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contracts by about 4.7 million km. That is about 12 times the distance from the Earth to the Moon. But as soon as you stop, the universe stretches back out by that same distance. In your own frame of reference, you can literally
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compress and stretch the entire universe by millions of kilometers. It is impossible to believe, but it is a measurable effect that has been experimentally confirmed many times.
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On the internet, there is a curious game called Velocity Raptor, in which you can actually experience most of the strange effects of relativity. However, no matter how strange these effects are , their strangeness alone does not prove anything. Quantum mechanics, as
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we have seen, also constantly forces us to abandon our most basic assumptions about how the world works.
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But with what we call the present moment, everything is completely different. Here the theory doesn't say that we fail to notice some strange aspects of reality, for example, that inside us is as much energy as in thirty-five Tsar Bombas. No, here the
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theory says something far more schizophrenic. It flatly states that, on the contrary, we permanently feel what we shouldn't feel, what doesn't exist in nature. The flow of time. The mystery of the flow of time stumped many of the greatest minds even before
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the theory of relativity. Aristotle devoted five chapters of his Physics to analyzing ideas about time and the present moment, and as a result, he ended up completely confused himself.
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Time either does not exist at all, or barely exists, being something obscure. Saint Augustine, in his Confessions, complained about his inability to understand what the flow of time is. If the present always remained present and did not pass into the past, then it
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would no longer be time, but eternity. If the present becomes time precisely because it passes into the past, then how can we say that it exists, if the reason for its existence is that it will cease to exist? And after the
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discovery of the theory of relativity, everything turned into some kind of extreme surrealism. Einstein himself was deeply disoriented by the attempt to understand what this mysterious "now " is. Einstein once said that he was seriously troubled by the problem of
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the "now." He explained that experiencing the present moment means something special for a person, something fundamentally different from the past and future, but that this important difference is not and cannot be in the realm of physics. The fact
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that science is unable to grasp this experience seemed to him only a cause for bitter humility. I noted that science can objectively describe everything that happens. On the one hand, physics describes the temporal sequence of events, and on the other,
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psychology can describe and explain the features of human perception of time, including its different attitude toward the past, present, and future. But Einstein felt that such descriptions might not satisfy our human needs, that there is something very important in
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the present moment that, however, lies beyond the reach of science, from the memoirs of Rudolf Carnap, philosopher and logician. Therefore, when I stumbled upon a book with the screaming title "Now" on the physics shelves of the Rostov Public Library, I
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immediately grabbed it and greedily devoured it with my eyes. Yes, you often find things here that you won't find on store shelves. It turns out the book was written in 2016 by world-renowned physicist Richard Muller , a man whose quotes have been flashing
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on and off for the last 10 minutes of the video. Mind-blowing ideas. Muller puts forward a theory that seems plausible at the same time. And, which is surprising for a book with formulas, the main idea of which one does not
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want to spoil in advance. Time Magazine . The uniqueness of this book is that it is the only book dedicated to the mystery of time written by an experimental physicist. Whose projects are directly connected to understanding the nature of time. Muller is blazing a
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new trail. I expect controversy. Saul Perlmutter, physicist, Nobel laureate. And if Muller's hypothesis turns out to be correct, the philosophical consequences of his idea would be so staggering that I get chills just thinking about it. But let's not get
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ahead of ourselves. A provocative, convincingly argued book about the fundamental nature of time. As a cosmologist and experimentalist who has initiated some of the most important experiments of our time, Muller is well aware of where the boundaries of
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science lie and keeps us engaged with his ability to work at the very edge of those frontiers. Lee Smolin, theoretical physicist. The book is called "Now." Certainly not by chance.
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As we have seen, modern physics says that an objective "now" does not exist. However, Muller provides excellent arguments that the "now" may actually be the most fundamental element of physical reality. Perhaps he is right, or maybe he is wrong. But along the way
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, Richard Muller gives you a masterclass on what time is and how and why we perceive it in exactly this way.
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Neil deGrasse Tyson, astrophysicist. And you know, something has been bothering me. What the hell did Einstein mean when he said that there is something very important about the present moment that lies outside the reach of science? How can something so
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important possibly lie outside the realm of science? Well, we certainly can't get inside Einstein's head, but Muller speaks very directly on this subject, and, I must say, very boldly.
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The laws of physics, as we understand them, do not prohibit the creation of a teleporter. And a teleporter would likely become the most terrifying device ever created. The most terrifying, because it would be impossible to prove its danger.
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Renowned physicist Michio Kaku believes that human teleportation will supposedly become possible within the next 100 years. So, imagine that you step under a beam that scans the quantum state of every atom, every electron, every particle of your body.
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In the process, the beam will completely deconstruct you into elementary particles, and the collected information will be sent at the speed of light to any point in the universe, where a second beam, using this data, will simply reassemble you from local
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atoms. Just like in the movie Star Trek . Wait a minute, but the atoms on the other end will be different. There are no "other" atoms. The standard understanding of quantum mechanics says that all atoms of the same isotope are
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absolutely and fundamentally indistinguishable from one another. I emphasize, they are not just nearly identical, they are fundamentally indistinguishable. All the atoms in your body are constantly being replaced anyway, and the atoms you have today did not belong to you 10 years ago.
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Therefore, after teleportation, every atom will end up in its rightful place. Every molecule, every neuron, memories, every thought—from the point of view of physics, the beam at the other end will assemble not just someone who looks like you, not just a very, very
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similar copy, but an object that cannot be distinguished from the original by any experiment in the Universe. From the point of view of physics, that will be you. And yet, would you step into that beam? Or does your intuition
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scream that the person who opens their eyes at the other end will not be you; that someone will appear there who thinks they are you, and that the teleportation was successful, while you personally will be dead, because something important is lost during
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teleportation—something that cannot be described in terms of physics? Are you prepared to stake your own life by trusting entirely and only in a physical description of reality? Would you allow yourself to be transmitted like that? I would not. Why? I fear
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that the new person who appears at the end of the beam might not be quite me, even accepting the claim that the created human being will possess all my memories, qualities, weaknesses, and habits, and will be indistinguishable from me by all physical parameters. But
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will it be me? Richard Muller. At one time, I liked how this question was explored in the computer game SOMA. I recommend it if you haven't played it.
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For Muller, it is that elusive essence which cannot be contained within the framework of modern physics and which, perhaps, would be lost during teleportation. It is your consciousness that is responsible for the sensation of the present moment. Without
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consciousness, there would be no one for whom the experience of "now" exists . Regarding the understanding of reality, it is time to admit that physics is incomplete. It is time for other disciplines to stop bowing before physics and acknowledge that not all
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truths are based on mathematical models , Richard Muller. It is, of course, generally surprising to read such things not from some philosopher or theologian, but from a world-renowned experimental physicist who has spent decades conducting the most physical measurements imaginable.
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But does all this mean that our consciousness plays no role in the physical picture of the world?
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Absolutely not. Moreover, you see, Richard Muller literally titled his book "Now" and, I repeat, not without reason. He believes that our sensation of the present moment holds the key to solving the mystery of time. What key are we talking about? I will explain
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with a simple example. Do you know what magnets are? Do you know that magnets have a special, invisible field? And that the whole Earth has such a field?
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We know how to measure it with incredible precision. We know how this field arises, how it protects us from solar wind, and how it changes over time.
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There are people who have dedicated their entire lives to researching the magnetic field. But even if you study absolutely all the physics of magnetic fields, there is something that even the most gifted physicist will never know about them. Something that a
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Florida sea turtle knows, capable of swimming 12,000 km across the Atlantic and returning to the very same beach, to the exact spot where it hatched, with precision to within a couple of meters. The turtle does this by navigating according to the Earth's
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magnetic field. It doesn't know what a magnetic field is, doesn't know how it arises, can't measure it, and can't describe it with equations.
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No, it simply feels it. From a physics standpoint, you can learn everything about a magnetic field, but what it's like to feel one you will never be able to know. So, imagine that there are people out there who, like turtles, can
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sense the Earth's magnetic field. How would these people explain to us what they are experiencing? They couldn't.
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In the same way, you wouldn't be able to explain to someone born blind what you experience when looking at the color red. Our most fundamental science , physics, can describe light wavelengths, magnetic field strength, or time dilation at near-light speeds.
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But it doesn't tell us what it's like to see the color red, to feel a magnetic field, or to be in the present moment. Does this make such knowledge any less real? After all, sea turtles were successfully relying on their
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sense of the Earth's magnetic field tens of millions of years ago, while physics only discovered this field in the 15th century. Perhaps we should also rely on our own sense of the present moment? It clearly doesn't exist for no reason. So just focus and
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feel the passage of time. Sense the present moment. Feel how strange this experience becomes if you accept the block universe model. But is this the strangest thing you are experiencing right now, or is there something else?
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Think about it, in every instant you are experiencing a far more paradoxical sensation than just the flow of time.
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Why, when I used the game Portal to describe a situation where you exit the lower wormhole mouth before you enter the upper one, did it seem to you that something was fundamentally wrong with that situation? Why on earth did that
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example leave you so perplexed? If all moments of the past and future are rigidly fixed and immutable, and if fundamental physics equations are time-symmetric, then why don't you feel the future in the same way as the past, as something already accomplished and
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unchangeable? Why don't you feel that you are obligated to step in a puddle, as it was in the movie Tenet? If all points in time already exist, why do you think that, seeing yourself emerging from the bottom mouth...why
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are you so sincerely convinced that no law of the Universe, no principle of self-consistency, will stop you from changing your mind after seeing your future self and refusing to enter the top mouth, thereby sending the principle of causality—the very
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foundation not just of science, but of any common sense—to hell? Where do you get such a powerful sense of agency ? Where does your "self" get this ineradicable feeling that it is not just observing the present moment, which is strange in itself, but that it
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can also choose the future? If your watching of this video was predetermined at the moment of the Big Bang, then why on earth would nature create such a realistic sensation of choice in an absolutely predetermined world? And to be perfectly honest, this
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is a far more contradictory and strange paradox than the paradox of black holes , Wigner's friend, or the incompatibility of quantum mechanics and relativity. If you look into the very essence of things, it becomes obvious that, in reality, we aren't
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worried about the laws of physics at all. The main problem is free will. We live with the certainty that we cannot be burdened by any predetermination that forces us to do something we don't want to do, one way or another. Sean
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Carroll. How can one choose the future in a static block universe? In Cixin Liu's novel, The Three-Body Problem, a wave of suicides by prominent scientists sweeps across the globe. In their suicide notes, many of them write roughly the same thing: that physics
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never existed and never will. Without giving away any spoilers, this is because experiments aimed at studying the very foundations of reality started yielding unpredictable results. At the most fundamental level, nature suddenly stopped behaving in a regular, lawful way. The idea that fundamental
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unpredictability could lie at the base of the world called into question the very possibility of understanding the Universe.
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This led scientists into a state of profound existential horror. And you know, something similar actually happened in reality at the dawn of quantum mechanics, albeit in a less dramatic fashion.
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I will explain what I mean with a simple example. You have surely heard that after the Chernobyl disaster, the area will remain radioactive for many centuries because the half-life of Cesium is about 30 years. But how do such elementary things as atoms know
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when they are supposed to decay? Do they have some kind of built-in clock? What I am about to say next seems almost absurd. Atoms have no equivalent of a built-in clock. Atoms have no age, and they have no memory. An atom that
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has existed for a minute and an atom that has existed for 100 years have the exact same probability of decaying within the next second. The phrase " half-life of 30 years" means only one thing. If you take a huge number of
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Cesium-137 atoms, about half will decay in 30 years, half of the remainder in another 30 years, and so on. This is just statistics, not the fate of any individual atom. Okay. It’s suspicious, but nothing particularly strange so far.
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The madness begins when you ask: "Why do atoms decay at different times?" What distinguishes a cesium atom that will decay right now from one that will only decay in 1,000 years?
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The answer is: nothing. They are completely identical. Think back to the teleporter. So for what reason do completely identical atoms decay at different times? You are listening closely. There is no reason. There is no reason. This is not a case of scientists just not
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having found it yet. In the standard understanding of quantum mechanics, a reason simply does not exist. Many of the greatest scientists desperately refused to accept this state of affairs . Schrödinger, de Broglie, Bohm.
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Einstein simply could not believe it. He believed that atoms had some kind of hidden variables, which we just don't know about, and he famously exclaimed that God does not play dice. Why God?
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Not because Einstein was a believer, although that's another topic, but because it concerns the very foundation of being. He could not believe that at the deepest level of nature, the future could emerge independently of the past.
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He refused to believe that events could occur without a definite cause and that the universe ceases to be ultimately predictable. Einstein never accepted this worldview until the day he died.
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It’s no coincidence that in Cixin Liu's novel, he appears as a broken old man who has lost faith that the universe can be fully explained. Today, the standard understanding of quantum mechanics says that even if there were an absolute super-intelligence that
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knew all physical laws, knew every moment of the universal past, and had infinite computing resources, even it still could not say when exactly this single atom would decay. So, you see, quantum mechanics strongly hints that the point isn't that we don't know the
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future, or that we are unable to calculate it. But that, perhaps, the future literally does not exist yet.
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But then how can the future be part of the already existing four-dimensional block universe? Someone might stop me and ask, but haven't I spent the entire first half of the video listing methods for time travel to the past? So
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couldn't we just find out the atom's decay time, go back, and tell everyone? Certainly, in theory, we can allow for such a possibility, but currently, most physicists agree that all known scenarios with closed timelike curves require extremely exotic conditions,
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fine-tuning, and, in all likelihood, exist only in idealized mathematical models. Even when talking about the most theoretically developed time machine concept, wormholes, things aren't exactly smooth. If wormholes do exist, they are most likely extremely unstable. And they simply won't let you
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travel through them into the past. As for white holes, we haven't found them yet, and they might just be a mathematical artifact of relativity theory. Some physicists allow that, theoretically, travel into the past is possible on a microscopic level. But
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even if the positrons you see in a Wilson cloud chamber are actually electrons moving backward in time, it would still be impossible to send any information through such travel. At least, that is what most scientists believe.
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Nature goes to great lengths to prevent us from building a time machine. Accumulated circumstantial evidence led Stephen Hawking to propose what is now called the chronology protection conjecture. The laws of physics, whatever they may be, forbid the creation of closed timelike curves. We
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have a lot of evidence that these assertions are at least partially true, even if we don't have reliable proof in our arsenal yet. Sean Carroll. In short , there is something wrong with all this time travel into the past. And if
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the universe is a four-dimensional static block where all moments exist simultaneously, it is not quite clear why there are so many difficulties in switching between those moments.
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Enough. Let’s just count up the contradictions that have piled up. Our physical models say that fundamental equations are time-symmetric, but in practice, we cannot freely travel along the timeline. Models say that "now" doesn't exist, while our consciousness screams that "now" is the most obvious
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thing in the universe; we feel that we can choose our destiny in every instant . Theories say that the future is already set in the geometry of spacetime, just as the past is. And on the other hand, the future of even a
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single atom is fundamentally not predetermined. Is reality itself just stuffed to the brim with contradictions ? Perhaps no one promised us an elegant universe.
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However, Richard Muller believes that it is we who are simply missing something. And he has a very radical way to stitch this patchwork quilt together. So, look around you. In the universe, everywhere, including even your room, new space is being born
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endlessly. You don't see it only because the physical forces acting in your room, such as the forces binding atoms together, completely mask any noticeable effects from the emergence of new space. Yes, even weak gravity overrides these effects, which is why
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the creation of new space remains unnoticed even within our galaxy across vast interstellar distances. What more can be said about your apartment?
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However, if you look at intergalactic voids, at distances where objects are so far apart that they are practically disconnected by any physical interactions, that is where you will witness the colossal effects of new space being born. For instance, between
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us and the most distant galaxy ever discovered, so much new space is generated that it seems to us as if that galaxy is moving away at roughly 2.5 times the speed of light. In modern cosmology, this recession of galaxies
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is called Hubble's Law. Hubble expansion does not represent the movement of galaxies, but the creation of new space. Richard Muller. The creation of new space was triggered 13.8 billion years ago. Physicists call this event the Big Bang. And here we
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arrive at the most important part. The theory of relativity tells us that we do not live in space alone. It tells us that we live in spacetime. And if new space is being born infinitely all around, why shouldn't the same be
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happening to time? In fact, that is exactly what is happening. Every second , we are adding a new second to time.
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Perhaps it is more accurate to think of the flow of time as the creation of new time. Richard Muller. From this comes a consequence that turns your brain inside out. If Muller is right, then yes, you cannot see the creation of new
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spacetime in your room, but you can feel it. What you are experiencing right now, in the present moment, is not a conscious illusion. Oh, no. I hope you are listening carefully. The present moment has a special status because it does not happen inside the
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universe. "Now" is the very emergence of the universe right before your eyes. "Now" is the physical frontier of a reality that is still being built. Just imagine it on a plane. To the left is everything that already exists; to the
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right is absolute nothingness. And you are right on that border. That border is "now." The moment when total ontological void turns into the solid ground beneath your feet. So, you see, we are all used to thinking that the
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Big Bang happened from nothing some unfathomable billions of years ago. But Muller says: "No, the Big Bang did not stay in the past. It continues right here and now, and you are literally on the very edge of this universal
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shockwave, which is what you feel as the flow of time, and nothing is closer to you than the nearest molecules of the air around you." According to Muller's position, the universe does not just exist statically; it is being
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built right now. It is an infinitely growing four-dimensional block of spacetime. The continuous and infinite generation of new time determines both the direction of the arrow of time and its speed. Every moment, the universe becomes slightly larger, and there is
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slightly more time in it. It is precisely this leading edge of time that we call "now." The flow of time is driven not by entropy or the universe, but directly by the Big Bang. Richard Muller. But can we leave the present
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moment? In a sense, you can travel into the future by moving at great speed, but not because you are moving into an already existing future, simply because your own time slows down. You and the outside world continue to exist in the
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present moment. You just experience it at different rates, but you cannot travel into the past. And the reason is quite unexpected. If "now" is the leading edge of reality, then the past is already formed. And to turn time
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backward, it is not enough to just invert entropy, like in the movie Tenet .
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No, to return to the past, you would have to start destroying space, at least locally. Suppose we could destroy space, get rid of it. Then time would run backward, wouldn't it? The only way to destroy space very quickly is a
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phenomenon called black hole evaporation. However, black hole evaporation has a lot of buts, and that is why Muller concludes that, in practice, time travel is impossible. In Muller's picture, everything falls into place. We remember the past, not the
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future, because the past exists and is part of the already formed four-dimensional geometry of the universe. But the future does not exist in this geometry. Reality actually ends completely at the present moment. We are, as it were, at the cutting edge of
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creation. And this whole Muller picture is, of course, very fascinating. But does it have any physical manifestations? How can his hypothesis be tested experimentally? First, data indicates that the universe is expanding with acceleration, which means your clock today is literally
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running slightly faster than yesterday, and we could measure that. And secondly , we can literally catch the moment of the birth of space-time. In 2015, humanity first detected gravitational waves from the merger of two black holes. Their masses were approximately
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29 and 36 solar masses. Accordingly, Muller calculated that this collision created millions of cubic kilometers of new space, which means new time also appeared. Do you know how much? About one real millisecond of new time. And we could have registered this if we had
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been just three times closer to the collision site. There are other ways to verify it. So, Muller's idea is not just a sophisticated phrase, but a truly scientific, testable hypothesis.
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So just focus and feel the flow of time . Sense the present moment. Perhaps what you are experiencing right now is the Big Bang that gave birth to the entire universe passing through your body. This is Richard Muller's view of
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time from the perspective of physics. But as you remember, he believes that physics does not describe all of reality. Therefore, Muller suggests taking one more step. A metaphysical one. Richard Muller asks the question: "Why do we even feel that we are living
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in the present moment?" If in the growing block universe we exist as a four-dimensional figure stretched into the past all the way to birth, why don't we feel ourselves in all the moments of the past as well? Let's
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think about it. Everything that happened even a moment ago is already dead in the sense that it is forever frozen in the four-dimensional structure of spacetime. Like cooled, fossilized lava. As for the future, we have realized it does not exist. And
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only the present moment is always alive in the sense that "now" is the only place in the universe where reality is not yet finally determined. So, think about what that means. We have always trusted the feeling that the present
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really exists. And if this feeling turned out to be true, then why should we consider another equally fundamental feeling to be an illusion in advance?
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The feeling that we are capable of choosing our own destiny independently of the physical factors influencing us.
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And if free will exists at all, it can only act in the present moment. The most powerful historical argument against the existence of free will sounds something like this: "If we knew everything about every particle in a person's body, we could fully calculate
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their behavior in advance." But, as we have seen, quantum physics says we could not. Two absolutely identical atoms, placed in absolutely identical conditions, for some reason can have absolutely different futures. And this applies not only to the decay of atoms.
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Nature at its most basic level has fundamental uncertainty. The future of any quantum system cannot be definitively predicted based on its past. A human being is also a quantum system. The key assumption of philosophers that the past completely
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determines the future is not supported by modern physics. Their arguments that free will does not exist are based on false premises. We cannot conclude that free will exists, but we can firmly say that nothing in science excludes its
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existence, according to Richard Muller. Yes, quantum uncertainty does not automatically prove the presence of free will, but Muller is convinced that we do have free will. And this conviction, as we can see, does not contradict science. Beyond that, Muller
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makes an even bolder assertion. He says that it is precisely thanks to free will that our non-physical consciousness is able to choose or even impose on the physical universe a single outcome from an infinite set of possibilities.
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For example, time and again turning a chaotic deck of cards into a perfectly ordered one. And Muller believes that perhaps this is exactly why we are only conscious of ourselves in the "now," because what function would consciousness have without free will?
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Why would nature preserve consciousness in the past, where that consciousness is incapable of influencing anything?
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According to physics as we now understand it, the past does not completely determine the future.
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Quantum physics introduces at least some element of randomness into the unfolding of events. Its presence implies that physics is incomplete. The future is not uniquely determined by the past, and non-physical factors may play a role in defining what is to come
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. And the fact that physics is incomplete leaves the door open to influence the future through free will.
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Richard Muller. In my opinion, this gives us something to think about. On one hand, free will is a plus. On the other, in a growing block universe, any choice you make instantly becomes part of the four-dimensional structure of
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the cosmos, making you the sculptor of your own worldline without the right to a mistake. Because the past can no longer be rewritten; it will exist forever. Every act of kindness, every cruelty, every instance of inaction— all of this permanently becomes a
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detail in the geometry of the created spacetime. Regret may change you, but it is incapable of carving an already created fragment out of the architecture of four-dimensional reality. This lends an almost unbearable moral weight to every moment of your existence. Such is Richard
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Muller's concept in its physical and non-physical aspects. As usual, there are things I agree with and things I could argue about. But all these months , while I endlessly wrote and rewrote scripts, it was deeply, chillingly interesting to look at the world
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through the prism of a growing block universe. Because if Muller is right, then the "now" is not some empty illusion of the human mind. The "now" is the only place in the entire universe where reality itself is forged
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, including by the blows of your own hammer. Thanks for watching, and as always, infinite gratitude to those who support my work on Boosty and Patreon.
Topics:time symmetryphysics of timeblock universetime reversalpositronRichard FeynmanStephen HawkingCarlo Rovelliquantum mechanicsDNA and time
