What James Webb Saw At the Edge of... Everything

[00:00:01][music] >> Something is wrong at the edge of the universe. NASA has been staring at it for 30 years, and the longer they look, the worse it gets.

[00:00:12]This isn't a small problem. It isn't a rounding error.

[00:00:16]The instruments we built, the telescopes we launched, the satellites parked a million miles from Earth to listen for the oldest light in existence, keep coming back with the same uncomfortable answer. The universe we mapped, the universe in the textbooks, the universe scientists have spent a century building with equations and supercomputers, doesn't quite match the universe NASA is actually looking at. So, how big is the difference? Big enough that some of the people who built the model are starting to wonder if the model is broken. We'll get to the strangest piece of evidence later in this video. A single discovery [music] from 2008 that, if it's real, means there's something on the other side of the observable universe pulling on us. Something we shouldn't be able to feel.

[00:01:04]>> [music] >> Let's start at the wall.

[00:01:13]If you point a sensitive enough radio telescope at any patch of empty sky, anywhere, day or night, summer or winter, you'll find a faint hum. It's not noise from the equipment. It's not interference from Earth. It's a signal that arrives from every direction at once with almost the same temperature in every spot, about 2.7° above absolute zero, which is the coldest temperature physically possible. That hum is the cosmic microwave background, and it is, in a very literal sense, the edge of everything you can see. That light has been traveling toward us for about 13.8 billion years. It was emitted when the universe was around 380,000 years old. When the first atoms had finally cooled enough to let photons escape. Before that moment, the universe was a fog of charged particles, opaque to light, hotter than the inside of any star.

[00:02:13]After that moment, the universe became transparent. The flash of light from that transition is still arriving right now at every telescope and every square inch of sky on Earth.

[00:02:25]That flash is the oldest thing you'll ever see.

[00:02:28]It is the back wall of the visible universe.

[00:02:32]Everything in [music] existence, every galaxy, every star, every black hole, every atom in your body, sits inside the bubble that wall surrounds. There is no looking past it with light. The wall is the limit. In 2004, a NASA satellite called WMAP found something on that wall [music] that nobody could explain. The cold spot.

[00:02:55]Picture the entire wall of the universe as a giant, [music] almost perfectly even glow. The temperature variations across the whole sky are about one part in 100,000.

[00:03:07]Microscopic ripples on a nearly flat ocean. The math of the early universe predicts those ripples almost exactly.

[00:03:15]They're the seeds that grew into every galaxy you can see. Then, there's the cold spot. Sitting in the southern sky in a region near the constellation Eridanus, is a patch of the [music] background that's colder than the rest by about 70 millionths of a degree. That sounds small. It isn't. Statistically, that patch shouldn't exist. The odds of finding a region that cold, that big, on a wall that should be that uniform, are roughly [music] one in 50.

[00:03:45]Not impossible, just deeply uncomfortable. How big? The cold spot stretches across roughly 1.8 [music] billion light-years of sky. If you wanted to fly through it at the speed of light, with no stops, no detours, it would take you nearly 2 billion years to come out the other side. That's longer than complex life has existed on Earth.

[00:04:08]That isn't a glitch. That's a feature carved into the back of the universe.

[00:04:14]The leading explanation might be worse than the anomaly. The current best guess is that the cold spot lines up with something called the Eridanus Supervoid.

[00:04:23]A region of space almost a billion light-years across, containing far fewer galaxies than it should. An empty pocket in the structure of the universe. When light from the microwave background passes through that void on its way to Earth, it loses a tiny amount of energy.

[00:04:41]That energy loss shows up here as a colder spot. That sounds tidy. Except the void, if it exists at the size we'd need it to be, is also a problem. A void that big, that empty, shouldn't be possible inside the timeline of the universe. The standard model of cosmology doesn't predict structures of that scale. So, either the void isn't there, or it is there, and our model of how matter clumps together is missing something fundamental.

[00:05:11]Pick your discomfort. There's a third possibility, and it's the one a small group of physicists have whispered about for years.

[00:05:19]The cold spot might be a bruise. A mark left over from when our universe collided, or brushed past, another universe in the first moments after the Big Bang. The math allows for it. The data doesn't prove it. The idea hasn't gone away because no other explanation has fully closed the case.

[00:05:39]While we're already on the subject of holes in the universe, there's another one you should know about.

[00:05:45]It sits much closer to in the constellation Boötes, about 700 million light-years away.

[00:05:52]Astronomer Robert Kirshner found it in 1981.

[00:05:56]He called it a [music] void, but the word doesn't really land.

[00:06:01]The Boötes void is a region of space roughly 330 million light-years across, which in a typical part of the universe would contain about 2,000 galaxies.

[00:06:14]The Boötes void contains about 60.

[00:06:17]Stand inside that void on some hypothetical planet drifting through it and look up.

[00:06:24]You wouldn't see the sky full of stars and faint galaxies that we see from Earth.

[00:06:29]You wouldn't have a Milky Way arcing overhead.

[00:06:32]If a typical patch of the universe is like a busy American city at night, every direction lit up with porch lights [music] and headlights, the Boötes void is the middle of Wyoming at 3:00 in the morning with the nearest town a thousand miles away.

[00:06:50]Until astronomers invented telescopes capable of detecting distant light, you wouldn't even know there was a universe beyond your own solar system.

[00:06:59]The neighbors are too far away.

[00:07:02]Whatever made the Boötes void took almost everything with it.

[00:07:06]The universe was not supposed to have holes that big, and yet the holes are there.

[00:07:13]Now, point your eyes farther south toward the constellation Centaurus, low in the southern sky if you're in the northern hemisphere, high if you're south of the equator.

[00:07:24]You can't quite see what's there from your backyard.

[00:07:27]Even the best telescopes have trouble.

[00:07:30]The plane of our own galaxy gets in the way, a strip of dust and stars astronomers call the zone of avoidance.

[00:07:39]It's a curtain we can't fully pull back, but something behind that curtain is pulling us.

[00:07:46]In the late 1970s, astronomers started noticing that the Milky Way wasn't drifting through space the way it should.

[00:07:54]We were moving fast.

[00:07:57]About 1.4 million miles per hour in a specific direction.

[00:08:02]That's more than three times faster than the fastest spacecraft NASA has ever built.

[00:08:08]Not just us, the entire local group, the cluster of galaxies that includes the Milky Way, Andromeda, and a few dozen smaller ones, was being yanked toward a single point in the sky.

[00:08:22]They called it the Great Attractor.

[00:08:25]For decades, nobody could see what it was.

[00:08:28]The dust of the Milky Way's disk blocked the view.

[00:08:33]X-ray telescopes started peaking through in the 1990s, and the picture began to clear.

[00:08:40]The Great Attractor turned out to be a massive concentration of galaxies centered on something called the Norma Cluster, about 200 million light-years away.

[00:08:51]Enough mass packed into one region to drag everything in our corner of the universe toward it.

[00:08:57]That should have been the end of the mystery.

[00:09:00]It wasn't.

[00:09:01]When astronomers measured the pull more carefully, the Great Attractor wasn't enough.

[00:09:07]It explained part of the motion, but not all of it.

[00:09:11]There was something farther out, something even bigger, pulling on both us and the Great Attractor.

[00:09:18]They found it, eventually.

[00:09:20]The Shapley Supercluster.

[00:09:23]About 650 million light-years away. Four times as massive as the Great Attractor.

[00:09:29]The densest concentration of galaxies anywhere in the nearby universe.

[00:09:35]So, we are being pulled toward Norma, which is being pulled toward Shapley.

[00:09:40]A chain of gravitational tugs across hundreds of millions of light years.

[00:09:45]Every piece of that chain is real, mapped, cataloged.

[00:09:50]For a brief window, this looked like the whole story.

[00:09:55]Then in 2008, a NASA astrophysicist named Sasha Kashlinsky published a paper that broke something nobody knew how to fix.

[00:10:05]Kashlinsky was studying galaxy clusters.

[00:10:08]Specifically, the way light from the microwave background changes when it passes through the hot gas inside those clusters.

[00:10:17]The effect has a complicated name. The kinematic Sunyaev-Zeldovich effect. But the idea is simple.

[00:10:25]It's one of the few ways to measure how galaxy clusters are actually moving through space.

[00:10:31]Not just expanding apart from each other, which all distant galaxies do.

[00:10:36]But moving in a specific direction relative to the universe itself.

[00:10:42]When Kashlinsky and his team ran the numbers on about 700 galaxy clusters, they found something they weren't supposed to find.

[00:10:51]The clusters weren't moving randomly.

[00:10:54]They were drifting, all of them, in roughly the same direction.

[00:10:58]About 2 million miles per hour. Toward a point in the sky between the constellations Centaurus and Vela.

[00:11:06]He called it dark flow.

[00:11:09]This is what made dark flow frightening.

[00:11:12]The Great Attractor and the Shapley Supercluster are inside our observable universe.

[00:11:19]We can point a telescope at them. We can see the galaxies they contain.

[00:11:24]They pull on us, but they're things we can measure.

[00:11:28]Dark flow, if it exists, isn't. The direction the clusters appear to be moving in, points to something outside the visible universe.

[00:11:38]Past the wall.

[00:11:40]On the other side of the microwave background itself, whatever is over there, according to Kashlinsky's data, is big enough and dense enough to grab a thousand galaxy clusters and tow them through space.

[00:11:55]Other teams have looked. Some have found evidence supporting dark flow.

[00:12:00]Others have found nothing or weaker signals than Kashlinsky's original paper.

[00:12:05]The European Space Agency's Planck satellite, when it analyzed the same background in higher resolution, came back with results that, depending on who you ask, either confirmed dark flow at a smaller scale or ruled it out.

[00:12:20]Nobody has settled the argument.

[00:12:23]Not in 2008. Not now.

[00:12:27]If dark flow is real, the universe is bigger than we thought and shaped in a way we never expected.

[00:12:34]There would have to be enormous structures beyond the edge of what we can see.

[00:12:38]Structures pulling on us right now.

[00:12:41]Reaching through the wall.

[00:12:44]If dark flow isn't real, then a respected NASA scientist published a result that's been cited thousands of times and we still don't fully understand why his data looked the way it did.

[00:12:57]Either answer leaves the model with a hole in it.

[00:13:00]To grasp the scale, picture the distances stacking up.

[00:13:04]Voyager 1 has been flying for almost 50 years and sits about 15 billion miles from Earth.

[00:13:12]The light from the Great Attractor takes 200 million years to reach us.

[00:13:17]The light from Shapley takes more than three times as long.

[00:13:22]Dark flow, if it's real, points to something well past the edge of the entire observable universe.

[00:13:29]We are talking about gravitational influence reaching across distances that light itself cannot cross in the age of the universe.

[00:13:38]The math says it shouldn't be possible.

[00:13:41]The data [music] in Kashlinsky's reading says it might be happening anyway.

[00:13:47]There's a related strangeness in the data and it deserves its own name.

[00:13:52]Some astronomers have started calling it the axis of evil.

[00:13:56]It refers to a pattern in the same background radiation that, according to the standard model, has no business being there.

[00:14:04]Certain large-scale ripples in the wall appear to be aligned with each other and aligned with the plane of our own solar system.

[00:14:12]They shouldn't be.

[00:14:14]A pattern carved into the universe at the dawn of time has no reason to line up with the orbit of Earth around the Sun.

[00:14:22]And yet, in the WMAP data and again in the Planck data, the alignment is there.

[00:14:29]Most physicists think it's a coincidence, statistical noise, a trick of the way we measure the data.

[00:14:36]Some of them don't.

[00:14:38]The argument has been going on for over 15 years and shows no sign of stopping.

[00:14:44]Push past Voyager 1, past Pluto, past the Oort Cloud, past every star you've ever heard of, and the cracks only widen.

[00:14:55]In 2022, a brand new telescope joined the team.

[00:15:00]The James Webb Space Telescope, launched on Christmas Day 2021.

[00:15:06]It sits about a million miles from Earth, four times farther than the moon, parked at a gravitationally stable point called L2.

[00:15:16]It is the largest and most sensitive [music] infrared telescope ever built.

[00:15:21]It was designed to look back deep into time at galaxies so far away that their light has been traveling towards us for the entire history of the universe.

[00:15:32]In other words, Webb was built to look at the wall.

[00:15:36]To see what was happening just inside it in the first few hundred million years after the Big Bang.

[00:15:43]What Webb saw broke the model.

[00:15:46]According to the standard story, the first galaxies should have been small, dim, and chaotic.

[00:15:53]Loose clouds of gas slowly assembling into shapes.

[00:15:58]Big, well-organized galaxies aren't supposed to exist until the universe is at least a billion years old.

[00:16:06]There simply wasn't time for them to form earlier than that.

[00:16:10]Webb found them anyway.

[00:16:12]In its first year of operation, the telescope began returning images of galaxies that, according to the redshift of their light, existed when the universe was less than 500 million years old.

[00:16:26]Some appear to be fully formed with stars older than the galaxies themselves should be.

[00:16:32]Others were too massive, too bright, too organized.

[00:16:37]One specific galaxy called JADES-GS-z14-0 has been confirmed by spectroscopy at a distance corresponding to just 290 million years after the Big Bang.

[00:16:55]It's brighter and bigger than anything that should be possible at that age.

[00:17:00]It's not one galaxy. It's a pattern.

[00:17:03]Across multiple deep field surveys, Webb keeps finding objects that contradict the timeline.

[00:17:10]The early universe, according to Webb, was already grown up.

[00:17:15]Some of these galaxies are also chemical signatures that don't fit.

[00:17:20]Heavy elements like carbon and oxygen, which are supposed to be forged inside stars and then scattered when those stars die, are appearing in galaxies that haven't had time to host more than one or two generations of stars.

[00:17:35]The enrichment is happening too fast.

[00:17:38]The universe, in those first hundreds of millions of years, was running ahead of schedule.

[00:17:44]>> There are explanations being proposed.

[00:17:47]Maybe the first generation of stars was much larger than we thought, allowing galaxies to assemble faster.

[00:17:55]Maybe early black holes accelerated the formation of structure.

[00:17:59]Maybe dark matter behaved differently in the early universe than it does now.

[00:18:05]Each of these explanations has supporters. None of them is settled.

[00:18:10]And every explanation comes with the same trade-off, which is that fixing the problem at the edge of time tends to break something else in the [music] middle.

[00:18:20]Now the puzzle has a bigger version, and this is where it gets dangerous [music] for the whole model.

[00:18:27]For about a hundred years, every measurement of how fast the universe is expanding has fed into a single number called the Hubble constant.

[00:18:36]It's one of the most important numbers in physics. It tells you the age of the universe, the size of the universe, and ultimately how the whole thing will end.

[00:18:46][music] There are two main ways to measure that number. One is to look at the microwave background, the wall, and use the ripples in it to calculate how the universe has expanded over time.

[00:19:00]The other is to look at nearby exploding stars and pulsating stars, and measure the expansion directly.

[00:19:08]These two methods, in theory, should give you the same answer.

[00:19:13]They don't.

[00:19:14]The microwave background says the universe is expanding at one rate. The nearby measurements say a rate about 9% faster.

[00:19:24]That difference doesn't sound like much.

[00:19:26]The gap between those two numbers has held up across decades of better and better instruments, including measurements from the Hubble Space Telescope, the Planck satellite, and [music] now the James Webb.

[00:19:39]The discrepancy isn't shrinking. It's growing.

[00:19:44]Astronomers call it the Hubble tension.

[00:19:47]If the two methods gave the same number, we'd have one universe.

[00:19:51]Because they don't, we either have a measurement problem so persistent that nobody can find it, or we have a missing piece of physics.

[00:20:01]Something is happening between the early universe and now that nobody has accounted for.

[00:20:06]Something that changes how the universe expands at different points in its history.

[00:20:12]Some theories point to a new form of dark energy.

[00:20:16]Others suggest dark matter has properties we haven't yet detected.

[00:20:20]A few suggest that gravity itself behaves slightly differently on the larger scales.

[00:20:27]Every proposed solution requires adding a new ingredient to the standard model of cosmology.

[00:20:33]And so far, none of those ingredients has been confirmed.

[00:20:38]There's another tension creeping in. One that hardly anyone outside cosmology has heard of yet.

[00:20:45]When astronomers count distant quasars, the brightest objects in the universe, they find a strange asymmetry.

[00:20:53]There are more of them in one direction of the sky than the other.

[00:20:58]The difference is small, but it's bigger than it should be. Bigger than our motion through space can explain.

[00:21:05]If the data holds up, it means the universe isn't quite as uniform on the largest scales as we always assumed.

[00:21:13]The bedrock assumption of cosmology, the idea that the universe looks roughly the same in every direction, is starting to creak.

[00:21:23]So, let's add it all up.

[00:21:25]A cold spot on the back wall of the universe that shouldn't be that cold.

[00:21:30]Sitting in front of a void that might be too big to exist.

[00:21:34]A separate void in Boötes that has no business being that empty.

[00:21:40]A chain of superclusters pulling our galaxy through space with hints of something beyond the wall pulling on the chain.

[00:21:48]A pattern in the background radiation mysteriously aligned with our own solar system.

[00:21:54]A telescope showing us galaxies in the early universe that grew up too fast.

[00:22:00]An asymmetry in the count of distant quasars.

[00:22:04]And two different ways of measuring the size of everything that give two stubbornly different answers.

[00:22:12]None of these problems on its own is fatal.

[00:22:15]Cosmologists have lived with anomalies before.

[00:22:18]The history of physics is full of small disagreements that turned out to be measurement errors.

[00:22:24]Quite often, they were.

[00:22:26]These are not separate problems.

[00:22:29]They might all be the same problem.

[00:22:32]When a model of the universe is broken in one place, you fix that one place.

[00:22:38]When a model is breaking in five or six places at once, all of them pointing toward issues at the largest scales of space and time, the model itself starts to look fragile.

[00:22:50]The standard cosmological model, often called lambda-CDM, is still the best framework we have.

[00:22:58]It explains an extraordinary amount of what we see.

[00:23:02]The edges are fraying.

[00:23:04]Edges are where new physics has always lived.

[00:23:08]Coming next is straightforward. NASA's Roman Space Telescope, scheduled to launch later this decade, will survey hundreds of millions of galaxies to map the expansion history of the universe with precision nobody has had before.

[00:23:23]The Vera C. Rubin Observatory, now beginning operations in Chile, will detect billions of objects and watch the sky every few nights for changes.

[00:23:33]The European Space Agency's Euclid mission is already flying, already returning data, already mapping the geometry of dark matter and dark energy across the breadth of time.

[00:23:45]Within the next 10 years, we will either confirm the anomalies and rewrite the textbooks, or we will explain them away with better measurements and refine the existing model.

[00:23:56]Either outcome is enormous.

[00:23:59]One means we discover new physics. The other means we finally close the most stubborn questions in modern cosmology.

[00:24:08]Either way, the edge of the universe will not be quiet for much longer.

[00:24:13]Stand outside on a clear night, somewhere far from city lights, and look up.

[00:24:18]The sky you see is a thin layer of nearby stars in our own galaxy.

[00:24:24]Past them, invisible to the naked eye but real, are billions more galaxies.

[00:24:30]Past those, the cosmic web of filaments and voids. Past that, the wall.

[00:24:36]Past that, possibly, structures we cannot see and cannot measure and may never reach.

[00:24:42]For most of human history, the night sky was a decoration, a pattern, a backdrop for stories.

[00:24:50]It took thousands of years to figure out that it was a place.

[00:24:53]Once we did, we built telescopes and we sent probes and we started measuring.

[00:24:59]What we found, again and again, is that the universe is bigger and stranger than the previous generation believed.

[00:25:07]We are now the previous generation.

[00:25:10]The people studying these anomalies right now, looking at the cold spot and the dark flow, and the impossible galaxies, and the Hubble tension, are the ones who will hand the next picture of reality to whoever comes after them.

[00:25:24]Maybe that picture will be cleaner than ours. Maybe it will be wilder.

[00:25:29]Almost certainly, it won't match the one in the textbooks today.

[00:25:33]And that's it for this video. Thanks for watching, and I'll see you in the next one.