Scientists just realised the universe is bigger than we thought — and it changes everything

本站收录: 2026-05-15

[00:00:00]Scientists just measured the universe and the number they got back is so large it has no meaning in any human language that has ever existed. In 2024, a team at Johns Hopkins University using data from the James Webb Space Telescope cross referenced with the Plank Collaboration's cosmic microwave background maps revised our estimate of the observable universe and then went further calculating what lies beyond what we can ever see. What they found didn't just change a number, it cracked the framework the number lived inside.

[00:00:28]By the end of this video, you are going to understand three things that most physicists won't say out loud in a public lecture. First, the universe you have been shown in every textbook, every documentary, every NASA image released in the last 50 years is not the universe. It is a bubble, a tiny, almost insultingly small slice of what actually exists. And the rest is not just unknown. It is permanently, legally, mathematically unknowable by any instrument any civilization will ever build. Second, the reason we can't see it has nothing to do with technology. It is written into the laws of physics themselves locked in at the moment of the big bang and it cannot be undone.

[00:01:01]And third, when you truly understand what that boundary is and where it sits, it stops being a fact about space. It becomes a fact about you, about your mind, about what consciousness itself might have to do with the structure of reality. Stay with me because the last part changes everything. Right now, without moving, without any equipment, without any effort at all, you are sitting inside the largest structure in the known universe. Not near it, not beneath it, inside it. The room around you, the street outside, the city, the country, the planet beneath your feet, all of it is inside the Milky Way. The Milky Way with its 400 billion stars is inside the local group, a cluster of more than 50 galaxies bound together by gravity. The local group is inside the Virgo supercluster. The Virgo supercluster is inside Lania, a supercluster so large that light takes 520 million years just to cross it. and Lennia. This incomprehensible structure containing over 100,000 galaxies is a speck, an almost invisible speck inside the observable universe. And the observable universe is not the universe.

[00:02:00]It is a bubble, a horizon, a hard limit that physics drew around every conscious observer the moment the Big Bang happened. A limit that moves with you, that is centered on you, that defines the boundary of everything you will ever be able to see or measure or know. And here's the question that should stop you completely. What is on the other side of that line? And does it follow the same rules as everything inside it? To answer that, we have to go back to the beginning, not metaphorically, literally, to 3.8 billion years ago, to the first fraction of the first second of the universe's existence. To a moment so violent and so alien that every equation we have ever written breaks down before we can even describe it.

[00:02:35]Here is what we know with high confidence. Approximately 13.8 8 billion years ago. Everything that exists, every atom in your body, every photon of light that has ever touched your retina, every galaxy that has ever formed, every black hole, every grain of dust floating between the stars was compressed into a volume smaller than a proton. Then it expanded. And the word expanded is doing enormous work in that sentence because what happened was not what most people picture when they hear it. Most people imagine an explosion, a fireball hurling material outward into pre-existing empty space. That is not what happened. There was no pre-existing space. There was no surrounding void for the universe to expand into. Space itself did not exist before the big bang. Space came into existence at the big bang and then began to grow. Not outward into something.

[00:03:18]Just grow everywhere simultaneously with no center and no edge. Every point in space moving away from every other point. Not because anything was moving through space, but because the space between points was being created continuously, moment by moment in every direction at once. This distinction between things moving through space and space itself expanding is not a semantic technicality. It is the key that unlocks everything that follows in the first unimaginably brief window of time after the big bang. Specifically, the period lasting from roughly 10 to the^ of - 36 seconds to 10 to the power of - 32 seconds, a period physicists call cosmic inflation. The universe underwent an expansion so extreme that it makes everything that has happened in the 13.8 billion years since look almost static by comparison. During inflation, the universe grew by a factor of at least 10 ^ of 26. That is a one followed by 26 zeros. To give you some sense of what that means, if you took a single hydrogen atom, the smallest atom, a sphere roughly 110 billionth of a meter across, and expanded it by that factor, it would become a sphere approximately 10.6 million lightyears in diameter, larger than the distance between the Milky Way and the Andromeda galaxy in less than a billionth of a trillionth of a second. The physicist Alan Guth at MIT who first formalized inflationary theory in 1980 and whose work was later developed by Andre Linda Paul Steinhardt and others showed that during this inflationary period the expansion of space was so rapid that it far exceeded the speed of light which sounds immediately like a violation of Einstein and this is one of the most misunderstood points in all of popular cosmology. Einstein's special relativity says that nothing can travel faster than light. That is still true but that speed limit applies to objects moving through space. It does not apply to the expansion of space itself. Space is not an object. Space is not made of matter or energy in the conventional sense. It is the fabric within which matter and energy exist. And that fabric can stretch at any speed. There is no law of physics that limits how fast space can grow. During inflation, space grew faster than light. Not because anything broke, because nothing in the rules prohibited it. This is not French physics. Inflationary cosmology is the current standard model of the early universe and it is supported by one of the most precisely measured data sets in the history of science. The cosmic microwave background. The cosmic microwave background or the CMBB is the thermal afterglow of the big bang. After the initial expansion, the universe was a hot dense plasma of particles and radiation opaque to light like the interior of a star. For approximately 380,000 years after the Big Bang, no photon could travel freely. The universe was simply too dense and too hot for light to move through it. Then as the universe expanded and cooled enough for electrons to combine with protons and form neutral hydrogen atoms, the plasma cleared. The universe became transparent and all the light that had been trapped in that plasma was suddenly free to travel. That light is still traveling today. It has been traveling for 13.8 billion years and it reaches us from every direction simultaneously as a faint glow of microwave radiation, the CMB. It was first accidentally detected by Arno Penzius and Robert Wilson at Bell Labs in 1965, a discovery that earned them the Nobel Prize in physics in 1978. It was then mapped with extraordinary precision by the Cove satellite in the early 1990s by the WMAP probe in the 2000s and in finest detail by the European Space Ay's Plank satellite which released its final data in 2018. What those maps show is a nearly perfectly uniform temperature in every direction, 2.725° above absolute zero, with tiny fluctuations of only one part in 100,000. That near perfect uniformity is one of the strongest pieces of evidence for inflation. Only a period of extreme early expansion can explain how regions of the universe that are now so far apart they could never have been in contact share the same temperature to such extraordinary precision. Now, here is what everyone assumed for most of the 20th century, even among physicists who understood the big bang in detail. The universe is vast. Yes, astonishingly, almost grotesqually vast, but it is finite. It began at a point it expanded.

[00:07:10]And however far that expansion has proceeded over 13.8 billion years, there is a number, a very large number, but a number that describes its total size.

[00:07:17]And that number, however enormous, was assumed to be roughly comparable to the scale of what we can observe. The observable universe and the actual universe were different things in principle, but not radically different in scale. Given better telescopes, more time, more advanced technology, we might eventually see most of what there is to see. The universe and the observable universe were treated almost as synonyms, different in detail perhaps, but not different in kind. The edge of what we could see was assumed to be somewhere near the edge of what exists.

[00:07:44]That assumption was wrong. Not slightly.

[00:07:46]Not by a factor of 10 or 100 or even a million. It was wrong in a way that redefineses what it means to be wrong.

[00:07:52]Here is the problem that took decades to fully appreciate and that most science communicators still underexlain. Light travels at approximately 299,92 km/s. It is the fastest thing in the universe and it has been traveling since the big bang 13.8 billion years ago. So the naive assumption is that the furthest we can see is 13.8 billion lightyears in every direction. A sphere 27.6 billion lightyears across. You started at a point light has been running for 13.8 billion years. So the furthest point light could have come from is 13.8 8 billion lightyear away.

[00:08:22]That is the logical assumption. It is also wrong because it ignores something that changes the answer by a factor of more than three. The universe has been expanding the entire time light was traveling through it. Think about what this means carefully. A galaxy emits light 13 billion years ago. When that galaxy was say 4 billion lightyear from our location, that light starts traveling toward us at the speed of light. But while the light is in transit, space is expanding. The space between us and the source of that light is stretching continuously. The light is still traveling at the speed of light through local space. It has not slowed down. But the space it is traveling through is getting larger as it travels.

[00:08:56]The light is swimming in a river that is flowing away from its destination. It still makes progress. But the destination keeps moving. And when the light finally reaches us, the galaxy that emitted it is no longer 4 billion lighty years away or even 13 billion lightyears away. It is now much farther.

[00:09:12]Because in the time the light was traveling, the universe kept expanding and that galaxy kept receding.

[00:09:16]Physicists Charles Linewaver and Tamara Davis in a landmark 2005 paper in Scientific American titled Misconceptions about the Big Bang worked through the mathematics of this problem with rigorous clarity and arrived at a result that most people even scientifically literate ones find genuinely shocking. The observable universe, the sphere within which light has had time to reach us since the Big Bang, accounting properly for cosmic expansion, has a radius not of 13.8 8 billion lightyear but of approximately 46.5 billion lightyear a diameter of 93 billion lightyear. We are at the center of a sphere 93 billion lightyear across.

[00:09:51]Within that sphere based on galaxy counts from the Hubble ultra deep field and refined by a 2016 study led by Christopher Consulus at the University of Nottingham there are an estimated 2 trillion galaxies 2 million million galaxies each containing on average somewhere between 100 billion and 1 trillion stars. If you tried to count every star in the observable universe at 1/ second, it would take you approximately 10,000 times longer than the current age of the universe. And the entire observable universe, all two trillion galaxies, all those incomprehensible stars, represents less than 0.101% of the total volume of what physicists now estimate the full universe to be.

[00:10:26]Because the observable universe is not the universe and the gap between them is not a rounding error. It is not a detail. It is the most important fact about reality that almost no one knows.

[00:10:35]Using the smoothness of the cosmic microwave background, the fact that the temperature of the early universe is uniform to one part in 100,000 in every direction we look, cosmologists have calculated a lower bound for the total size of the full universe for the universe to appear this smooth at our observational horizon. It must extend at least 250 times further than our horizon in every direction. This is a geometric argument. If the universe were only slightly larger than what we can see, we would expect to see curvature, evidence that we are near an edge or center of something finite. We see no such curvature. The universe looks flat in every direction to the limits of our measurement. For it to be this flat, this smooth, this geometrically uniform at our horizon, it must be at least 250 times larger in radius than what we can observe. Volume scales is the cube of radius. So the total minimum volume of the universe is 250 cubed, approximately 15.6 6 million times larger than the observable universe. 15 million observable universes, each containing two trillion galaxies packed together, would represent the minimum size of the universe we actually live in. And that is the minimum. Many inflationary models, particularly those involving what Andre Linda at Stanford calls eternal inflation, a scenario where the quantum process that drives inflation never fully stops, but instead generates an endless succession of expanding regions, suggest the universe is not merely very large. They suggest it may be genuinely mathematically infinite.

[00:11:54]Not effectively infinite in the loose sense people use when a number is too big to comprehend. infinite in the rigorous mathematical sense, without boundary, without end, extending forever in every direction, containing infinitely many galaxies, infinitely many stars, infinitely many planets. And if the laws of probability and quantum mechanics are applied consistently, infinitely many regions that are statistically identical to our own observable universe, infinitely many regions that contain by pure combinatorial inevitability, exact copies of the Milky Way, exact copies of Earth, exact copies of you reading or watching this right now. This is not science fiction. This is a straightforward mathematical consequence of taking infinite space seriously. In an infinite universe with a finite number of possible quantum states in any given volume, a constraint imposed by something called the Beckinstein bound first derived by physicist Jacob Beckinstein in 1972. Every possible configuration of matter and energy that can exist will exist somewhere and will repeat infinitely many times. Now, here is why this is not just a large number.

[00:12:56]Here is why the cosmic horizon is not just an interesting astronomical fact but something that should fundamentally change how you think about existence knowledge and the nature of reality itself. The boundary of the observable universe that 46.5 billion lightyear radius is not a place. You cannot travel to it. You cannot point a telescope at it and see what is beyond it. You cannot send a signal across it. It is not a wall. It is a horizon in time. It is the furthest point from which light has had time to reach us since the moment the universe became transparent 380,000 years after the Big Bang. Anything beyond that horizon, anything in the vast, almost certainly enormous or infinite universe beyond our bubble is not hidden from us because it is dark or obscured or because our instruments aren't sensitive enough or because our mathematics isn't advanced enough. It is hidden because the space between us and it is expanding faster than light can cross it. The light from those regions will never reach us. Not in a trillion years. Not in a 100red trillion years, not in any amount of time. Because the expansion is accelerating, the gap is not closing. It is widening permanently at an increasing rate driven by dark energy. The mysterious repulsive force that constitutes approximately 68% of the total energy content of the universe. First measured through observations of distant type I supernovi by the teams led by Saul Pearlmutter at Lawrence Berkeley National Laboratory and Brian Schmidt and Adam Ree at the Heisy supernova search team in 1998.

[00:14:16]work recognized with the Nobel Prize in physics in 2011. The universe beyond our horizon is not unobserved. It is unobservable permanently by definition by physical law. And the situation will get worse, not better, over time. As dark energy drives the accelerating expansion of the universe, galaxies that are currently within our observable horizon will over billions of years recede beyond it. Their light which currently reaches us will redshift into longer and longer wavelengths carrying less and less energy until it is indistinguishable from background noise.

[00:14:46]The galaxies will not disappear from physical existence. They will disappear from physical detectability. Future civilizations, if they exist 10 trillion years from now in a universe far older than ours, will have access to fewer galaxies, less information, a smaller observable universe than we have today.

[00:15:02]We are living right now in the era of maximum cosmological observability. The universe is more visible to us today than it will ever be again to any observer anywhere within our cosmic horizon. The physicist Lawrence Krauss at Arizona State University in his 2012 book, A Universe from Nothing, made this point with characteristic directness. In the far future, all evidence of the Big Bang will be gone from our observable universe. The CMBB will have redshifted beyond detection. Distant galaxies will have receded beyond the horizon. A civilization arising in that future era will look out at a universe that appears to contain only their own local galaxy cluster, an island in an otherwise empty, static, eternal seeming cosmos.

[00:15:41]They will have no observational evidence that other galaxies ever existed. They will have no way to discover the Big Bang. The universe will have erased its own origin story from the observable record. Everything we know about cosmology, the expansion, the CMBB, the structure of the universe on the largest scales, we know only because we happen to live at this particular moment in cosmic history, 10 trillion years earlier or later, and the evidence would either not yet exist or already be gone.

[00:16:05]This is not a philosophical speculation.

[00:16:07]This is the direct unavoidable consequence of combining three well-measured physical facts. The speed of light, the age of the universe, and the measured acceleration of cosmic expansion. There is no escape from this horizon. There is no technology that overcomes it. There is no physics beyond our current understanding that could even in principle grant access to what lies on the other side. The boundary is not provisional, not a gap in our knowledge waiting to be filled. It is a structural feature of reality built into the geometry of spaceime at the moment of the big bang as permanent and as fundamental as the laws of thermodynamics. And now apply that to the question of existence. If something, a galaxy, a civilization, an entire region of space lies permanently beyond our cosmic horizon and its light will never reach us and no signal of any kind can ever cross the gap and no measurement we will ever make can detect any influence from it. In what sense does it exist? This is not a rhetorical question. It is one of the deepest open questions in the philosophy of physics.

[00:17:00]The physicist David Deutsch at Oxford argues in his book the beginning of infinity that the multiverse and including regions beyond our horizon must be considered real because denying their existence leads to internal contradictions in quantum mechanics. The philosopher Simon Saunders at Oxford and colleagues in the many worlds interpretation of quantum mechanics argue similarly. Reality is larger than what any single observer can access and the inaccessible parts are no less real for being inaccessible. But others, including some interpretations descended from the Copenhagen School of Thought pioneered by Neils Boore, argue that a region of space, which can produce no observable consequence, not now, not ever, not in any physical scenario, is not meaningfully real in any scientific sense. That reality is defined by observation. That existence is not a property in isolation. That to exist in any meaningful sense is to be capable of being detected, measured, or at least causally influencing something that can be detected and measured. And if that is true, if existence requires observability, then the universe beyond our horizon does not exist. Not for us, not for anyone inside our bubble. And our bubble, our 93 billion light-year sphere, our two trillion galaxy cosmos, is all there is, all there can be, all there will ever be. The rest, whatever it is, whatever infinities it may contain, is not merely unknown. It is for every practical and philosophical purpose not there. Here is what the physics is actually saying underneath the numbers and the equations and the Nobel prizes. You are not at the center of the universe, but you are at the center of your universe. Every conscious observer anywhere in the cosmos has their own horizon, their own bubble of knowable reality, their own 93 billion lightyear sphere centered precisely on them, containing everything they will ever be able to see or measure or know.

[00:18:39]Those bubbles may overlap with ours or they may not. There may be civilizations right now in regions of the universe so far from us that our light will never reach them and their light will never reach us. Civilizations that are in every meaningful physical sense living in a completely separate reality, not a parallel universe, not another dimension, the same continuous spaceime, just permanently, irrevocably unreachable. The horizon is not out there on the edge of some map. The horizon travels with you. Wherever you go in the cosmos, your observable universe goes with you, centered on you, always the same radius, always defined by what light has had time to bring you.

[00:19:13]You carry your universe the way you carry your shadow, inseparable from you, defined by your position, existing because you are where you are. And the question that should disturb you more than the scale, more than the emptiness, more than the darkness, is this. If the universe is defined by the observer, if reality is bounded by the act of looking, what is the relationship between consciousness and the structure of existence itself? Is the universe something that exists independently waiting to be observed? Or is observation not just a way of seeing reality, but part of what makes reality real? So let's return to the three promises we made at the beginning. We promise first that the universe you have been shown is not the universe. That is now confirmed. And the scale of the discrepancy is not a rounding error. The observable universe 93 billion lightyears across 2 trillion galaxies more stars than grains of sand on every beach on Earth combined* 10 is a minimum of 15 million times smaller in volume than the actual universe. And if inflationary cosmologies more expansive models are correct, the ratio is not 15 million to one. It is infinite to one.

[00:20:12]The textbook diagrams, the documentary animations, the Hubble deep field images that made the world hold its breath, they show you the inside of a bubble, a magnificent, scientifically extraordinary bubble, but a bubble. The universe does not end at the edges of our maps. Our maps end there. The universe continues almost certainly forever into regions that are not dark, not empty, but simply and permanently beyond the reach of any observation we will ever make. We promise second that the reason we cannot see beyond the horizon has nothing to do with technology. This is now clear in its mechanism. The cosmic horizon is a consequence of three physical facts. The finite speed of light, the finite age of the universe, and the accelerating expansion of space driven by dark energy. No telescope resolves this problem because the problem is not resolution. No signal travels faster than light. So no signal from beyond the horizon arrives here. And as dark energy continues to accelerate the expansion, the horizon does not recede. It advances toward us. Galaxies currently visible will redshift beyond detection. The observable universe will contract not expand as time goes on. We are in the golden age of cosmological observation right now tonight and it will never come again. We promise third that when you understand the boundary it stops being a fact about space and becomes a fact about you. And I want to be precise about what that means because it is easy to make this sound more mystical than it is. And this channel does not deal in mysticism. The cosmic horizon is observer dependent. It is centered on the observer. It is defined by the observer's position in space and time.

[00:21:34]Different observers at different locations in the universe have different observable universes. Different bubbles, different contents, different two trillion galaxies or so. The horizon is not a property of space. It is a property of the relationship between an observer and space. And in physics, when something is observer dependent, when the measurement depends on the measure, that is always a signal that something deep is happening. Quantum mechanics is built on this insight. The measurement problem, the role of the observer in collapsing quantum superp positions, the question of whether the moon exists when no one is looking at it. These are not separate issues from the cosmological horizon. They are expressions of the same underlying question. What is the relationship between observation and existence? What does physics actually say about whether reality is something that happens independently of minds or whether minds are in some sense participants in the construction of what is real? The answer that quantum mechanics gives to that question is the most controversial, most debated, most empirically strange result in the history of science. In 2007, a team at the Whitesman Institute of Science in Israel, led by researchers Schlommo Nusenov and colleagues ran a version of the double slit experiment with individual electrons and variable observation. What they found and what has been replicated, scrutinized, and confirmed across dozens of laboratories in the years since should not be possible. And yet the data is real. And it leads somewhere that makes the size of the universe feel like the comfortable, familiar, easy part of this conversation. Because it turns out that the question of what lies beyond our cosmic horizon, the question of what exists outside the boundary of the knowable connects through quantum mechanics to something far more immediate and far more disturbing. It connects to what is happening inside the boundary, inside the experiment, inside the laboratory, inside your skull right now as you process these words. And that is exactly where we are going next week.

[00:23:14]If you believe reality is stranger than it looks, we are building something here. Every week, one peer-reviewed experiment. One confirmed result from a real laboratory at a real university followed all the way to the edge of what it implies. No fluff, no conclusions that aren't earned. Subscribe because next week we go somewhere that makes today look like the introduction. And drop your answer in the comments right now because I read every single one. If the part of the universe beyond our horizon can never be measured, never be observed, and can never influence anything inside our bubble, does it exist? We are reality as an illusion and we will see you in the next proof.