Scientists Believe Our Universe May Have an Evil Twin

Added: 2026-06-01

[00:00:00]Scientists have a serious problem with the universe.

[00:00:03]According to the laws of physics, the Big Bang [music] should have created equal amounts of matter and antimatter, and that's bad news for us.

[00:00:12]Whenever matter and antimatter meet, they destroy [music] each other in a burst of high-energy radiation. If the universe started perfectly [music] balanced, then everything should have canceled out almost instantly.

[00:00:24]That means there would be no stars, no planets, no galaxies, and obviously no human beings, either. There would just be radiation floating through empty space.

[00:00:35]But clearly, that didn't happen.

[00:00:37]Somehow, in the earliest moments of the universe, matter gained a tiny advantage. For roughly every billion antimatter particles, there was one extra particle of matter left over. That tiny imbalance became everything we see around us today.

[00:00:54]For decades, scientists have struggled to explain why. Now, a new theory suggests the answer could be far stranger than anyone expected. Our universe may have been born alongside a mirror universe.

[00:01:09]Imagine a second cosmos connected to ours from the moment of the Big Bang. In this mirror universe, space would be flipped in the opposite direction, and time itself would move backward compared to our perspective.

[00:01:24]To anyone living there, their universe would feel completely normal, but from our point of view, it would look like reality running in reverse.

[00:01:32]This idea matters because of something called CPT symmetry.

[00:01:37]These are three fundamental rules that physics is supposed to obey everywhere and at all times.

[00:01:44]Together, they describe how particles behave if charge, [music] spatial direction, and time are reversed.

[00:01:51]Normally, scientists believe these [music] rules can never be broken, but the new study argues something different. Instead of one universe preserving those rules alone, maybe two universes preserve them together.

[00:02:05]In other words, the pair remains perfectly balanced overall, while each individual universe temporarily breaks the rules during its earliest moments.

[00:02:14]And that brief imbalance may have changed everything.

[00:02:18]Researchers think these local rule-breaking effects could have [music] slightly altered a field known as the inflation field.

[00:02:25]The mysterious energy field believed to have driven the universe's incredibly fast expansion right after the Big Bang.

[00:02:34]That disturbance may have caused matter and antimatter to form at slightly different rates. Not by much, just enough to leave behind one extra matter particle out of every billion particle pairs.

[00:02:48]It sounds insignificant, but that tiny leftover became all the matter in the universe. Every galaxy, every star, every planet, every living thing.

[00:02:59]The idea is still just a theory, but scientists think it could eventually be tested. One key test for this theory would be the absence of primordial gravitational waves in the cosmic microwave background.

[00:03:13]A signature that future experiments could look for.

[00:03:16]Tiny particles called neutrinos could also reveal clues if they behave in unexpected ways.

[00:03:24]If the theory is correct, it might even help explain mysteries like dark matter and dark energy.

[00:03:31]So the reason anything exists at all may come down [music] to a tiny cosmic imbalance caused by a universe we can never directly see, where time runs backward and reality itself is reversed.

[00:03:48]>> Incredible news has recently spread across the internet. NASA has discovered evidence of a parallel universe. But, is this [music] actually the truth? Well, there is a grain of truth in this story, but it's not that simple. Let's consider it. Perhaps you've seen the [music] articles that said, "NASA has finally found a parallel universe." The story was widely publicized, and people got divided [music] into two camps. Those who took this news at face value, and those who considered it all complete nonsense. But, both sides aren't [music] exactly right.

[00:04:22]Let's start from the beginning.

[00:04:24]The discovery [music] was made by NASA's ANITA. This name stands for the Antarctic Impulsive Transient Antenna.

[00:04:31]Yeah. It was designed to study neutrinos. Neutrinos [music] are high-energy cosmic particles.

[00:04:37]They're incredibly small, lack any charge, and have almost no mass.

[00:04:42]Trillions of such particles pass through our [music] bodies every second, and we don't even notice them. All because they almost don't affect ordinary matter.

[00:04:51]That's how insignificant they are. On average, in our entire life, each of us [music] gets affected by a maximum of one neutrino. So, basically, hunting [music] neutrinos is like hunting ghosts. To catch them, you would have to send a whole stream of these particles through a giant piece of lead, and it has to be trillions [music] of miles thick. At the same time, you have a 50/50 chance that you'll stop [music] one of them.

[00:05:16]Therefore, in order to detect them, scientists had to come up with some clever tricks.

[00:05:22]We know that neutrinos, like other similar particles, come to [music] us from outer space. Ooh. They travel to Earth from the Sun, stars, and even from the Big Bang itself. Some of them come to us from particularly big sources, such as black holes, supernova, pulsars, and even from various unidentified objects. Some of these particles have particularly high energy. [music] And for scientists, these neutrinos are the most interesting ones. But, oddly enough, most high-energy neutrinos don't actually come to us from afar. They form right here, next to Earth. This process has a cute name, particle shower.

[00:06:00][music] Well, this is how [music] you can explain it in simple words. A granny particle gets into Earth's atmosphere.

[00:06:10][music] Usually, it's a particle with very high energy. Then, it generates several children that have less energy. Each of them then makes more grandchildren whose energy is even less than theirs, [music] and so on, until we have a giant family tree of low-energy particles. In the end, there may be billions of them.

[00:06:30]During this process, piles of neutrinos are created. Then, they begin to sink deep into our Earth. [music] During their journey through the planet, they touch the upper layers of its crust or ice, for example, Antarctica's ice.

[00:06:44]When faced with all these obstacles, they [music] create radio pulses. And as you might have guessed, these are the exact radio pulses that scientists are trying to find. It may be a surprise to you, but Antarctica is pretty deserted.

[00:06:57][music] You think? And that's why it's the best place to study microscopic particles, [music] which usually can barely be traced. There won't be any interference or anything like that.

[00:07:09]We can catch these pulses with the help of powerful antennas. [music] NASA places these antennas on balloons that can rise as much as 20 mi above Earth's surface. That's how they've been tracking these neutrinos for the past years.

[00:07:23]All right, [music] now we know what ANITA is doing. But what about that parallel universe stuff? Nah, don't worry, we're getting there. In 2018, ANITA began receiving abnormal radio signals >> [music] >> that caused quite a stir in the scientific community.

[00:07:38]Remember how neutrinos come to us from outer space and then gradually sink deep into our planet. So, recently, Anita has discovered neutrinos that didn't [music] descend from space as usual, but rather rose up from Earth. In other words, these particles called tau neutrinos basically travel back in time. But, how is this possible?

[00:08:00]Scientists began to research them. At first, they thought that maybe it was a detector error or an error in interpreting the data. But, no, everything was correct. [music] Something very exotic was happening.

[00:08:14]If so, then first we must try to find a simple explanation. What if these tau neutrinos just came to Antarctica [music] from some other source? Maybe they came to Earth from the other side and somehow passed [music] through the boundary.

[00:08:28]To test this theory, scientists decided to seek help from another cool neutrino observatory called IceCube. Yes, very cool. This observatory is located near the South Pole. It consists of 5,160 optical detectors buried in ice. And all these powerful detectors are designed to detect neutrinos.

[00:08:49]Anita researchers were like, "Hey guys, we found some strange radio signals.

[00:08:53]Could you please check where they come from?" "No problem," IceCube replied and started the research. And as a result, they found nothing.

[00:09:02]Yep, IceCube [music] didn't detect any signal sources at all. It turned out that these strange particles [music] had basically appeared out of nowhere.

[00:09:11]How could this be?

[00:09:13]Scientists tested many different theories, >> [music] >> but none of them could explain the situation accurately. Later, IceCube published an article which basically said, "Nope, we have no idea where these signals came from and [music] how to explain them in terms of the standard model of the universe."

[00:09:30]Oh, now it's getting interesting. So, what on Earth are these signals? Having exhausted normal explanations, scientists began to consider ideas that go beyond our understanding. One of them said that perhaps these particles had come to us from a parallel universe where time flows in the opposite direction. This crazy-sounding theory [music] is the result of the famous multiverse theory. According to it, about 14 billion years ago, when the Big Bang [music] happened, two twin universes were born. One of them was ours, and the other was a parallel [music] one. And they're almost identical in everything except for some things. For [music] example, time in this parallel universe doesn't move in the same way as it does in ours. It moves [music] backward. Besides, everything there would look upside down to us, as if we're looking in a mirror.

[00:10:23]Therefore, [music] scientists call it the antiverse and believe it could be filled with antimatter. And even though all this may seem [music] strange and crazy to us, for those who live in that antiverse, their way [music] of life would be quite normal. In fact, they would rather find us the strange ones.

[00:10:40]So, these mysterious neutrinos could be born in this antiverse. Let's say they somehow existed there >> [music] >> and then accidentally got into our world, where we were able to detect them.

[00:10:52]The idea of the multiverse itself [music] is really incredible. If it's true, then it may mean that there is an infinite number [music] of realities, many of which are much better than ours.

[00:11:02]Quantum mechanics [music] even says that it's quite possible that every second of every day any of your decisions divides the universe [music] into two. And so, there are quintillions of parallel universes where our lives have gone very differently. [music] Something like this is hard to even imagine. Of course, it would be great if we could find a way to get into another universe.

[00:11:25]>> [music] >> And if these mysterious tau neutrino particles were able to cross the boundaries of two worlds, well, maybe we can do that too.

[00:11:33]But, unfortunately, this phenomenon alone isn't enough [music] to say whether the multiverse theory is true or not. This is just one of several possible options. At this stage [music] of human development, we cannot prove or disprove this theory.

[00:11:48]Maybe someday in the future we'll find out the truth, but definitely not now.

[00:11:54]The only thing [music] we can say now, after this discovery, is that we found strange radio signals which standard physics [music] can't explain. So, we need to move in this direction and study them to learn more about this incredible phenomenon.

[00:12:07]>> [music] >> But, people like to dream about space.

[00:12:10]So, no wonder we've gotten so excited about this.

[00:12:13]>> [music] >> And it would be great if one day it turned out that this theory was actually true. The theory of parallel universes has been popular in various movies and books for a very long time. Where would you [music] go if you found out that you could travel between realities? Me, I'd look for a different reality of ice cream.

[00:12:41]Our universe is starting to glitch, and it looks like we're going through the biggest tension in astronomy since Einstein redefined gravity. But, scientists aren't having a cow yet because this kind of chaos usually means we're about to discover something huge.

[00:12:57]So, let's run through the biggest issues driving the crisis.

[00:13:01]For decades, cosmetology, whoops, I mean, cosmology ran on the idea that the universe should look uniform in all directions for anyone anywhere within it. They call this idea the basic [music] cosmological principle, not to be confused with a cosmetological principle, which states all women should wear [music] a color of lipstick right for them. But, I digress. Cosmologically speaking, it means you might see clumps up close, but on [music] massive scales, everything should smooth out. Because of that, scientists [music] figure no structure should be bigger than about 1.2 billion light-years. Yeah, that's big. So, they were more surprised to find a structure called the Big Ring.

[00:13:44]This thing is nearly a perfect circle made of galaxies and galaxy clusters, and it's about [music] 1.3 billion light-years wide.

[00:13:52]Now, a light-year is the distance light travels in a year, and since light is the fastest thing in the universe, that already tells you how enormous this distance [music] is.

[00:14:02]If your eyes could see it, it would stretch across the sky like 15 full moons lined up side by side. See?

[00:14:10]And the Big Ring isn't alone. A couple of years earlier, the same astronomer spotted something called the Giant Arc, a curved structure stretching 3.3 billion light-years.

[00:14:22]Then, there's the Giant GRB Ring found in 2015 with a mind-melting diameter of 5.6 billion light-years. The Big Ring and the Giant Arc show up in the same part of the sky at about the same distance from Earth. So, there's a real chance they're actually parts of an even bigger structure hiding in plain sight.

[00:14:44]Now, another scientific [music] drama has to do with something called the Hubble constant. That is, how fast the universe expands, the connection between [music] how far away an object is, and how fast it's moving away from us.

[00:14:57]That number helps scientists figure out the age, size, and future of the universe.

[00:15:03]The Hubble Space Telescope determined that number with an accuracy of almost 1%. The universe is about 13.8 billion years old.

[00:15:13]So, there was Hubble, and later the James Webb Space Telescope that measured distances to faraway galaxies, and figured out how fast they're moving away from us.

[00:15:22]In everyday terms, they showed that for every million light-years you go out into space, galaxies move away about 45 to 47 miles per second. That expansion speed lines up nicely with a universe that's 13.8 billion years old. But, there's another totally different way to measure the universe's expansion, and it looks way further back in time.

[00:15:47]Scientists study the cosmic microwave background, or CMB, which is the leftover heat from the Big Bang.

[00:15:54]It's the oldest light in the universe, released when the universe cooled enough for light to travel freely.

[00:16:01]When scientists use the CMB to calculate how fast the universe should be expanding, they get a slower number, about 42 miles per second [music] per million light-years, instead of 45 to 47. Now, that might not sound like much, but in cosmology, that gap is enormous.

[00:16:20]Both methods are extremely precise, and yet they stubbornly refuse to agree.

[00:16:25]This disagreement has a name, the Hubble tension. Right now, nobody knows why this is happening. Something might be missing from our understanding of the early universe.

[00:16:37]Now, just when astronomers thought it couldn't get stranger, the James Webb Space Telescope kicked the door down. It spotted some impossible early galaxies.

[00:16:46]These galaxies show up just 500 to 800 million years after the Big Bang.

[00:16:52]According to everything we thought we knew, galaxies at that age should look messy, small, and half-finished. But instead, Webb keeps spotting galaxies that look like they've had billions of years to grow up. They already show organized shapes like discs and bulges, basically the same structures you see in modern galaxies like the Milky Way.

[00:17:14]Features like that should take several billion years to form, not a few hundred million.

[00:17:19]It's like meeting a teenager who somehow has the wisdom of an 80-year-old.

[00:17:24]Now, in some cases, smaller galaxies seem to pack more mass than bigger ones, which also completely flips our expectations.

[00:17:32]Even cooler, some of those early galaxies contain heavy elements like oxygen and carbon. Stars make those elements, but stars need time to cook them up through nuclear fusion.

[00:17:45]Seeing heavy elements like that early is like finding baked bread before anyone invented ovens.

[00:17:51]Either the universe evolved way faster than we thought, or our timeline is missing entire chapters.

[00:17:58]Another weird headache in cosmology is all about lithium. Yeah, the same element in phone batteries.

[00:18:05]According to the Big Bang [music] idea, the early universe was insanely hot and dense. Hot enough to smash particles together and create a tiny amount of lithium. Not much, but enough that we should still see about five lithium atoms for every 10 billion hydrogen atoms floating around today.

[00:18:24]Astronomers can actually check this >> [music] >> by looking at stars.

[00:18:28]They use a trick called spectroscopy, which means splitting starlight into colors >> [music] >> to see what elements are inside.

[00:18:35]Now, to estimate a star's age, they look at iron. Iron only forms [music] in supernova explosions, so stars with very little iron are super old, born when the universe was still young.

[00:18:47]But, here's the [music] problem. Those ancient low-iron stars barely have any lithium. [music] Not just a little less, sometimes less than 1/20 of what the Big Bang predicts. And the older the star, the worse the mismatch gets. [music] Scientists call this mess the lithium problem, and it's been haunting cosmology for decades. Some researchers tried to explain it by saying stars somehow destroy lithium internally. But every version of that idea crashes into other observations.

[00:19:19]Instead of getting better, the problem keeps getting worse. And when a simple element refuses to behave, it usually means our picture of the early universe still misses something big.

[00:19:31]Well, dark matter [music] adds another dark spot to the picture.

[00:19:35]Scientists invented it to explain why galaxies don't fly apart. It acts like invisible glue.

[00:19:42]Models predict dark matter should pile up densely in galaxy centers and form sharp spikes. But observations keep showing smooth, soft cores instead. It's like expecting a mountain peak and finding a gently rolling hill.

[00:19:57]That mismatch shows that dark matter isn't behaving the way scientists assumed at all.

[00:20:02]Some of them even suggest dark matter might feel a fifth force, >> [music] >> something beyond gravity, electromagnetism, and other known forces. That idea sounds wild, but it neatly explains why dark matter spreads differently than predicted. If it turns out to be true, it would change how we perceive the way galaxies form, how they evolve, and how the universe structures itself on [music] every scale.

[00:20:29]And finally, there's dark energy that has confused scientists ever since they stumbled on it about 25 years ago. It makes up most of the universe, and we still don't know what it is.

[00:20:41]The default idea said dark energy stays constant, like a built-in pressure of empty space itself.

[00:20:48]Some theories linked it to quantum fluctuations, which are tiny particles popping in and out of existence in empty space. [music] But when scientists calculated how strong that effect should be, they got a value trillions upon trillions of times too big.

[00:21:04]So clearly, something didn't add up.

[00:21:07]Now, a massive project [music] shows that dark energy might not be constant after all. Instead, it might have peaked about 4.5 [music] billion years ago and slowly weakened since then.

[00:21:19]If that's true, dark energy [music] changes over time.

[00:21:23]Why does this matter?

[00:21:25]Because dark energy controls the universe's future. If it stays strong, the universe keeps expanding faster and faster [music] until galaxies drift so far away we can't see them anymore. The scenario called the Big Freeze.

[00:21:39]If dark energy weakens enough, gravity might slowly fight back. Expansion would slow and galaxies that are currently disappearing could drift back into view.

[00:21:50]All these problems share something unsettling. They're systematic. They repeat across instruments, methods, and research teams. Random errors don't behave this consistently.

[00:22:02]The universe keeps giving conflicting answers, no matter how carefully scientists ask the questions.

[00:22:08]That's why researchers call this a crisis. Not because science failed, but because it's working exactly as it should by revealing where our ideas fall short.

[00:22:20]Our universe is like a giant highway and galaxies are constantly moving along this highway. And just like cars driven by careless drivers, they can collide and crash. So, astronomers have recently witnessed such an incredible cosmic collision. It involved galaxies traveling at incredible speeds. Using advanced instruments, [music] researchers clocked one galaxy traveling at a speed of around 2 million miles per hour as it crashed [music] into a group of other galaxies. This collision has created shockwaves that are so powerful they can completely reshape the entire region leaving long-lasting effects on its structure and dynamics. Will it somehow influence our solar system?

[00:23:02]Before we find out, let's learn more about the region where [music] this collision occurred.

[00:23:07]Actually, this collision is still happening in Stephan's Quintet. That's a fascinating cluster of galaxies that has been the subject of study for scientists for over a century.

[00:23:18]It's a group of five galaxies located in the constellation Pegasus.

[00:23:23]This group of galaxies was first discovered in 1877 by the French astronomer Edouard Stephan, who used a telescope at the Marseille Observatory.

[00:23:32]Despite its tranquil name, Stephan's [music] Quintet is anything but peaceful. It's a chaotic spot filled with galactic collisions and turbulence.

[00:23:42]Four out of the five galaxies are gravitationally bound. It means they're physically interacting with one another.

[00:23:49]Such interactions are ejecting material from the galaxies, and over time, it forms vast debris fields in the space surrounding the galaxies.

[00:23:58]Astronomers believe that in the end, these galaxies will merge into one giant galaxy, but it will only happen in millions of years.

[00:24:07]The curious thing though, is that the fifth galaxy in the Quintet, located in the upper left corner of images, is not part of the collision. This galaxy is much closer to Earth, more than 200 million light-years closer [music] to be precise. So, its alignment with the other galaxies is just a chance perspective from our vantage point, making it appear as part of the group.

[00:24:29]Stephan couldn't know this in the 19th century, so the name Quintet has remained, even though only four galaxies are physically involved in the collision.

[00:24:39]Now, how about we look at this collision in detail?

[00:24:42]At the center of this event is one of the galaxies in the group, which is currently crashing into the others at a breathtaking speed.

[00:24:50]From our perspective on Earth, this galaxy appears to be approaching the Quintet from behind, heading directly toward the viewer. The collision is creating a massive shockwave that ripples through the surrounding galaxies.

[00:25:03]>> [music] >> As the shockwave is moving through packets of cold gas, it's traveling at hypersonic speeds, several times the speed of sound [music] in the intergalactic medium.

[00:25:13]This process strips electrons from atoms, leaving behind long trails of glowing ionized gas.

[00:25:20]>> [music] >> But when the shockwave comes across regions of hot gas, it compresses the material rather than disrupting it. This compression produces radio waves, which can be detected by radio telescopes.

[00:25:32]While reshaping the structure of the intergalactic medium in Stephan's Quintet, [music] this shockwave also influences the future evolution of the galaxies involved.

[00:25:42]Now, how did scientists even manage to spot such a dramatic [music] space event? All thanks to innovative technologies. The most important participant [music] was WEAVE, a cutting-edge spectrograph that's installed on the William [music] Herschel Telescope in La Palma, Spain.

[00:25:59]This tool specializes in gathering [music] spectroscopic data, which is the information about how matter absorbs or sends out light and radiation.

[00:26:07]>> [music] >> It allows astronomers to examine the movement and composition of space objects with great precision.

[00:26:14]Besides WEAVE, >> [music] >> researchers have used data received from a few other large observatories. One of those was LOFAR, Low Frequency Array.

[00:26:23]It's a radio telescope with an antenna network observing the radio waves the weaker shockwave produced while compressing hot gas.

[00:26:31]Astronomers combined the data received from all these instruments and managed to study the shockwaves and their effects in amazing detail.

[00:26:40]This collision in Stephan's Quintet gives us a fantastic opportunity to find out more about the interactions between galaxies, which can influence [music] the evolution of the the You see, when galaxies crash into each other, their gas and dust gets redistributed, and it can trigger [music] the formation of new stars and even cause central supermassive black holes to grow. And if we talk about Stephan's Quintet, the ongoing collision in this area helps us get additional information about the behavior [music] of gas under extreme conditions.

[00:27:13]Now, at the same time, galactic collisions aren't as rare as you might think. They're common on [music] a cosmic scale, and in the early universe, collisions occurred even more frequently because galaxies were located much closer together. With time, such interactions have played a key role in shaping the universe.

[00:27:32]Even our own galaxy, the Milky [music] Way, has experienced tons of past collisions.

[00:27:37]We can see the evidence of such [music] destructive interactions in the form of debris streams and disrupted star clusters within the galaxy. In fact, astronomers predict that the Milky Way will collide with the neighboring Andromeda galaxy in about 4.5 billion years, eventually forming a new, larger galaxy.

[00:27:57]Even though they're moving at incredible speeds, galactic collisions are super slow processes from our human point of view.

[00:28:04]While galaxies may travel at millions of miles per hour, the distances they cover are so vast that mergers take millions to billions of years to complete.

[00:28:14]Now, galactic collisions don't look like explosive crashes you might be imagining. Instead, they resemble when fluid merges.

[00:28:22]When two galaxies collide, their gravitational forces distort their shapes. They stretch and warp and exchange their material, stars, gas, and dust. As a result, tidal tails, rings, and even bridges between galaxies form.

[00:28:38]One of the most famous collisions between galaxies is ARP 148. During this cosmic crash, one galaxy became shaped like a ring, while the other stretched in a long tail-like form. That's how powerful gravitational interactions between galaxies during collisions are.

[00:28:56]But, however impressive intergalactic collisions are, collisions between neutron stars, those ultra-dense remnants of massive stars, are among the most energetic phenomena in the universe. Neutron stars are incredibly small and dense. Just one contains the mass of our sun packed into an area the size of a city.

[00:29:17]When two neutron stars collide, they often merge to form a black hole, releasing immense amounts of energy in the process.

[00:29:25]These events produce gravitational waves, ripples in space-time that can be detected by instruments like LIGO and Virgo, as well as bursts of light that outshine billions of stars.

[00:29:37]On Earth, the possibility of a galactic collision directly affecting us is extremely low.

[00:29:43]Luckily, the time scales and distances involved make such events harmless to life on our planet. However, smaller-scale collisions, such as an asteroid impact, are more plausible.

[00:29:55]Asteroid impacts have occurred in Earth's history, and the most infamous of them caused the extinction of the dinosaurs 66 million years ago. And while large impacts are rare, astronomers closely monitor near-Earth objects to protect our planet from potential threats.

[00:30:13]Now, while we're talking about space collisions, a question may arise. Can life travel between planets? This is the idea of lithopanspermia, the transfer of life between planets via debris from collisions. If an asteroid or comet hits a planet, fragments of rock could be ejected into space. If those fragments carry microbial life, they might land on another planet and seed life there.

[00:30:39]And guess what? According to experiments, certain super tough microorganisms like cyanobacteria could survive the harsh conditions of space travel, including radiation and re-entry into the atmosphere of another planet.

[00:30:54]In any case, lithopanspermia is still only a theory and a controversial one among scientists, but it doesn't make it less fascinating. It might eventually help us understand how life could have spread across the universe.

[00:31:07]But let's return to the ongoing collision in Stephan's [music] Quintet.

[00:31:11]By studying such events, astronomers learn more about how galaxies interact, evolve, and influence their surroundings. Hopefully soon, we'll find even more interesting facts about this process. [music] Stay tuned. Now, scientists have a wild theory. What if our entire universe is actually inside a black hole?

[00:31:32]This is called the black hole cosmology.

[00:31:34]Some scientists have the idea that our observable universe and everything we see around us might be tucked inside a black hole, which exists inside another parent universe or even multiverse. And then this multiverse could be part of a bigger one and so on. Kind of like a stacking doll. Sounds like pure science fiction, but this is based on some curious facts.

[00:31:57]When scientists create the timeline of our world, they [music] say that everything started from a singularity.

[00:32:03]If you kept squeezing a giant ball smaller and smaller, at some point it would get super dense before it crushed.

[00:32:10]Well, it's hard to imagine, but in space, it's possible to squeeze a crazy amount of mass into a teeny-tiny point.

[00:32:18]This point is called a singularity. The matter gets crushed into an infinitely small space less than an atom [music] and it holds all the same mass of everything well taking basically no volume.

[00:32:31]Inside this singularity point, things [music] get so intense that the normal rules of physics just stop working.

[00:32:37]>> [music] >> Everything we know, time, space, matter, breaks down and can't be applied anymore. Basically, what happens from now on is beyond our understanding.

[00:32:48]So, [music] scientists say that this was the starting point of our world when the Big Bang happened. It's like this tiny dot with everything inside it [music] expanded to everywhere. This started forming the universe as we know it. And here's the thing. Scientists assume that singularity also exists deep within black holes.

[00:33:10]General relativity says that a black hole is born when something really big, like a huge star, collapses under its own weight. Gravity gets stronger the bigger the mass is.

[00:33:21]>> [music] >> With a mass of a huge star tens of times bigger than our sun, this tiny point would have an unbelievable gravity. It's why it starts sucking in all the stuff around it and curves the fabric of [music] space-time so much it looks like a hole in space.

[00:33:37]And this would be the center of a black hole. It's a dot where all these things fall into and get crushed into an infinitely dense point.

[00:33:46]So, could our universe itself be just a little singularity dot inside a huge black hole inside of another universe?

[00:33:54]Well, that would be wild.

[00:33:56]So, it's not that easy to compress something so much that it literally warp space-time. You need to squeeze it like crazy. If you wanted to make a small black hole, like a human size, you'd need to shrink them down to the size of an atomic nucleus.

[00:34:12]If you want a black hole the size of a chickpea, you'd have to compress our entire planet to that.

[00:34:18]But our universe is 99% empty space.

[00:34:21]There are trillions of miles of just nothingness between the stars.

[00:34:26]If you were to pack all the matter in the universe together, the result would be surprisingly small. Everything around us, including galaxies, stars, planets, [music] and dust, would only fill about 1 billion cubic light years. It would be a cube about 1,000 light years on each side. For comparison, our Milky Way alone is 100,000 light years in size.

[00:34:48]That's how sparse the universe is.

[00:34:50]>> [music] >> But at this density, it would also be very, very massive. The resulting mass would likely collapse into a black hole.

[00:34:59]And here's the wildest part. The resulting black hole would be roughly the same size as the universe itself. It would also have the same mass and energy, as well as the same average density.

[00:35:11]The size or radius of the black hole grows together with its mass. The more stuff it eats, the bigger it is. But the density works the other way around. The black hole gets less dense as it [music] grows. For a size that big of our entire world, it would be pretty sparse as well.

[00:35:29]And it's not the coincidence.

[00:35:32]We have this thing called the Hubble radius, also known as the cosmological event horizon. If we imagine our observable universe as a giant bubble, then think of its edge like the farthest part of the universe we can see.

[00:35:46]When you stand in a field and look around, trying to see as far as you can, your eyes will draw a circle. This is like that.

[00:35:54]There might be more beyond that point, but we'll never know. Beyond this horizon, the light from distant parts of the universe will never reach us. That's because light travels at a certain speed, and the space between us and those regions is expanding too quickly.

[00:36:10]It's like running towards something while super strong winds try to blow you away.

[00:36:15]Until we stay on Earth, we're cut off from those far-off corners forever.

[00:36:20]The black holes have something eerily similar called an event horizon, or the Schwarzschild radius. This is the point of no return. This is the imaginary line that's often depicted as a light contour around the black holes.

[00:36:33]Anything crossing an event horizon, falling inside, is lost forever. No light, no matter, no information can escape from there.

[00:36:42]Black hole's gravity is way too strong, so they're perfect space vacuum cleaners.

[00:36:48]And as we mentioned before, if we create a black hole the size of the universe, they would have the same mass and the same event horizon radius.

[00:36:58]Now, while some scientists think [music] this could just be random coincidences, others believe it's a clue that our universe might actually be inside a black hole.

[00:37:08]The theory also suggests that our universe might not be the only one. It could exist in one of many black holes scattered throughout a large multiverse.

[00:37:18]In this crazy model, each one of them, both in our world and our parent world, could lead to its own universe with its own set of physical laws and structures.

[00:37:28]Now, that would be some weird chain.

[00:37:30]There's this theory that says that universes could be born inside of black holes, sort of. It's called the Einstein-Cartan theory.

[00:37:39]This idea talks about singularity as well, but in a different way. It says that instead of collapsing into an infinitely dense dot, the matter might create a wormhole. This is like a tunnel through space and time.

[00:37:53]This wormhole, also known as an Einstein-Rosen bridge, could connect two different places of our universe. In that case, one side of the tunnel is the black hole, and on the other side, there would be a whole new universe forming.

[00:38:07]So, it could work like a teleport. As soon as you pass the event horizon, you travel to the new world. But in that case, there should be an exit. Some scientists made it up and called it a white hole. It doesn't literally exist, not as far as [music] we know, but it could be possible somewhere on the other side.

[00:38:28]It would serve as an exit of a wormhole, [music] an area where matter is always ejected instead of pulled in. So, it's like you can't throw anything in there. It would get expelled immediately. It's all purely hypothetical, of course.

[00:38:42]All this stuff fits well into the concept of the Big Bounce.

[00:38:46]This idea says that instead of our universe beginning with a singular Big Bang, it bounced from a previous state of collapse.

[00:38:54]Remember the squeezed ball analogy?

[00:38:56]Well, maybe there used to be another universe ball that got super compressed to a minimum size before rebounding and expanding again. So, instead of a universe born from nothing, we might live in one that's a cosmic [music] recycling of another.

[00:39:12]There's also another version of this theory, sometimes called shockwave cosmology.

[00:39:18]The idea says that the Big [music] Bang could have been caused by a boom inside a black hole, and this could create the expanding universe we see today.

[00:39:27]As the universe expands and the matter density decreases, the black hole would eventually transform into a white hole, the reverse of a black hole, >> [music] >> where matter is expelled instead of pulled in.

[00:39:39]But even though we have all these interesting [music] connections, they're not evidence. There are no experiments or observations that could prove or disprove these wild theories. So, they all remain speculation [music] for now, but at least it's fun to speculate.

[00:40:01]>> [music]