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On the 21st of May 2019, we captured a strange pulse coming from the other side of the universe. A gravitational wave the fraction of a diameter of a proton that had traveled more than 17 billion lightyear to reach us. Usually signals of this magnitude are caused by black hole merges. But there was something a little off about this wave. It didn't look like other black hole merges we were used to. It was too short and missing half of the waveform. This signal bamboozled the scientific community until in 2025, a team proposed an explanation so wild it sent theoretical physicists into a frenzy. What if this signal wasn't produced in our universe at all? What if it had traveled through a wormhole from a parallel universe?
I'm Alex Mccoan and you're watching Astramm. Join me today as we break down the physics of wormholes. Untangle the mindbending relationship between quantum entanglement and space-time geometry and examine whether we really eavesdropped on an echo from another universe. When the laser interferometer gravitational wave observatory or LIGO detected the signal of gravitational wave GW190521, researchers realized something exhilarating. If their interpretation of the colliding black hole size and mass was correct, they just made the first detection of an intermediate mass black hole in human history. I've made another video about these types of black holes before that you can watch here. You see, until then,
we had only observed stellar mass black holes. Any black hole under 65 solar masses and super massive black holes or black holes measuring hundreds of thousands to billions of times the mass of our sun. The math says there should be a third category, intermediate mass black holes, measuring about 100 to 100,000 times the mass of our sun. And computer simulations agree, but we'd never seen one directly until this gravitational wave floated across our radars, hinting that one might be out there. This signal seemed to be an echo of two black holes colliding. One measuring 85 solar masses and the other 66. They emerged to form a black hole 142 times the mass of our sun. And if
you're doing the math here, yes, that means nine full sun's worth of mass were instantly converted into pure gravitational energy. As if this weren't exciting enough, in 2025, a research team led by Ki Li at the Hang Cha Institute for Advanced Study, University of Chinese Academy of Sciences, took a closer look at the signal left behind by gravitational wave GW190521. And they noticed something unusual. No matter how they sliced it, this just didn't look like a typical black hole merger signal. They started to wonder what alternative explanation could there be for what they were seeing.
Normally, when two super massive cosmic bodies collide, like neutron stars or black holes, that collision emits tiny ripples in spaceime that travel outward in every direction. Sometimes these gravitational waves eventually reach Earth where we can detect them with our groundbased laser interferometers such as LIGO and Virgo based in the US and Italy respectively. Depending on what the signal we receive looks and sounds like, we can deduce what type of event occurred, how far away it was, and how big the objects involved were likely to be. When two black holes merge, they go through a threepar process which gives its signal key characteristics that are easy to identify. In other words,
scientists know if a gravitational wave was created by a black hole merger thanks to its shape. The whole universe is filled with spectacular patterns, structures, and signals like this. It's one of the things I find most fascinating and not to mention beautiful about the cosmos. It's this mix of beauty and intrigue that I really try to get across in astron videos, but it's also what inspired me to create a book. Incredible universe volume 1 is all about our solar system and is filled with beautiful images of and facts about its planets, moons, and more. This stunning hardback book is back for another limited run. And I'm pleased to report that they're selling
fast. It's a spectacular journey through the solar system filled with not only the very best images, but explanations that bring our cosmic backyard to life. Incredible Universe was a real labor of love, and you don't want to miss it. Click the link below or scan the QR code on screen to make sure you get your hands on one before they're gone. For now, though, let's head back to the gravitational wave signals that black hole merges send out. The first phase is the inspiral phase. As the black holes circle each other, they're constantly radiating energy away in the form of gravitational waves.
Since they're losing energy, their orbit gradually shrinks, which makes them move faster as the gravity they exert on each other increases. The faster they move, the more energy they emit, creating a positive feedback loop. They get closer and move faster and faster. So, what does this mean for the gravitational wave signal? Well, it increases in amplitude and frequency as time goes on, like an upward tick. If you convert that signal into sound, it creates a rising tone, kind of like a bird. That's why we say black hole collisions produce a characteristic chirp. The second phase is the merger, the moment the black holes actually collide. At this moment, the amplitude of the signal reaches its absolute maximum,
marking not only the highest peak, but also the most intense rapid compression of the wave. It's immediately followed by the third and final phase, the ring down. It takes a while for the newly formed black hole to stabilize. Initially, it's wobbly and distorted before finally settling into a spherical shape. And all the while it continues to produce gravitational waves but in a different capacity than before. In the case of GW190521, the ringdown occurred simultaneously in two distinct frequencies. A fundamental tone at 63 Hz and a second at 98 Hz, both of which faded out within 26 to 30 milliseconds.
The black hole is similar to a bell that rings, producing a spectrum of multiple fading tones that encode information about the bell, explains Colin Kapano from the Albert Einstein Institute. Analyzing the ring down of a black hole merger can give us insights into the mass and spin of both the new black hole and its progenitors. So that's exactly what you usually see with a black hole merger. But GW190521 was different somehow. This particular gravitational wave signal completely lacked a clearly identifiable inspiral phase. It just showed the merger and ringdown phases. And this led KI and his team to propose an absolutely outlandish idea. What if this signal was the echo
of a black hole collision not in our universe but in a parallel one? A signal that traveled through a wormhole to reach us. Wormholes might sound like science fiction, but they are a mathematical possibility. In fact, as Einstein worked on his theory of general relativity, the concept of bridges arose naturally from his field equations as hypothetical geometric and topological features of the universe. Later, as scientists in the 1980s speculated about traveling from one side of the cosmos to another, this theoretical bridge evolved into the fan favorite we now call a wormhole. So, what are they?
Essentially, wormholes act as shortcuts through spaceime, a tunnel that connects two very distant parts of the universe, or potentially even parallel universes. But we've never observed a wormhole in reality. But if we did somehow stumble across one, it wouldn't look like the tunnels you might think of. Instead of a flat hole that gets darker and darker, a wormhole would act as a spherical 3D window, showing you a warped view of the final destination on the other side of the hole. Much like a black hole, it would be surrounded by gravitational lensing that distorts the surrounding starfield.
Now, we're moving deep into hypothetical territory, so bear in mind some things we cover will be contested, debatable, and just downright strange. There are different kinds of wormholes, but let's start with the classic one, the Einstein Rosen Bridge. This is a geometric structure where you have a black hole on one side and a white hole on the other that exits into another universe. Let me break that down. As you probably know, matter can only enter but never exit a black hole. Once an object crosses the event horizon, it cannot return. A white hole is the opposite, a hypothetical structure where information
can only exit into the universe but never fall into the white hole. The Einstein field equations that define black holes are symmetric with respect to time. This means that the mathematical solution for a black hole where everything collapses into a singularity at some point in the future can be reversed. In this setup, the singularity becomes the past and the matter is ejected from the white hole. The white hole's event horizon would effectively act as a line beyond which nothing can enter. Because of this, white holes are commonly described as acting like a black hole running backward in time. The Einstein Rosen Bridge is theorized to connect a
black hole with its white hole counterpart via a one-way street of sorts. But the problem is the math says that this structure should be incredibly unstable. It would collapse so instantaneously that even light wouldn't be able to travel through it. So if the GW190521 signal couldn't have passed through an Einstein Rosen Bridge, what other kind of wormhole might it have traveled through? In 1988, astrophysicists Michael Morris and Kip Thorne proposed a way to make wormholes traversible. Thorne went on to consult on the film Interstellar and later won a Nobel Prize in physics for his contributions to the LIGO detector and the first direct observation of gravitational waves. So, let these credentials lend weight to the bizarre
theory I'm about to share. Morris and Thorne suggest the choke point or throat of the wormhole could be held open against gravity by a kind of scaffolding which would make it traversible. However, this would require a theoretical type of material known as exotic matter to act as said scaffolding holding the tunnel open. Exotic matter is not the same thing as antimatter, which does have positive mass and is a real observable material. Instead, it refers to materials that possess unusual properties such as negative mass, negative energy density, or negative pressure. Meaning, it often acts in bizarre and counterintuitive ways. For
example, in the normal world, when you push a glass to the left, it will topple over to the left. But if the glass has negative mass, pushing it to the left would make it fall to the right. it will accelerate in the opposite direction of the force applied. Normal matter attracts other matter through gravity. Drop a shoe and it falls to the ground. But exotic matter with negative energy does the opposite. Instead of being pulled towards other matter, it's pushed away from it. And crucially, it pushes back. That repulsive force is what could theoretically prop a wormhole throat open against the crushing pole of gravity. Even if this breaks your brain
a little, these kinds of properties aren't technically forbidden by the maths, and they don't violate the laws of conservation of momentum or energy. In other words, they can't officially be discarded as impossible, even though we've never seen them. Thus follows the question, if a traversible wormhole like this could exist, could we really hear a signal ring down through it from the universe on the other side? Wouldn't the information get lost or distorted somehow? Well, turns out wormholes might connect more than just black and white holes. They could be the missing link between general relativity and quantum mechanics.
General relativity describes the universe at its largest scales. Gravity, black holes, the fabric of spaceime itself. Quantum mechanics describes it at its smallest. Particles, energy, the subatomic world. But when you try to use both at the same time, say at the center of a black hole, the maths breaks down completely. However, in 2013, theoretical physicists Leonard Suskin and Juan Malda put forth a conjecture that if true could unify these two rival fields. And you guessed it, the answer has to do with wormholes. How exactly? Well, they propose that wormholes and quantum entanglement might actually be the same thing. that when two particles become entangled, they're linked in such
a way that whatever happens to one instantly affects the other, even if they're galaxies apart. For example, if you measure the spin of one, its entangled partner will instantly snap into the opposite spin. At first glance, it might seem like this would violate the law that nothing can travel faster than light. Surely, these particles are somehow communicating. But there isn't actually any information passing from one to the other. The outcome of both particles are random. Suskind and Maldisena suggested these entangled particles might literally be connected by a geometric structure, a tiny wormhole that links them through spaceime. Sound familiar? This is known as the ER equals EPR conjecture. named
after two famous papers from 1935. Einstein Rosenbridge equals Einstein Bodolski Rosen entanglement. If this idea proves true, it blows black hole science wide open. Quantum mechanics states that information cannot be destroyed ever. Yet everything that falls into a black hole eventually seems to evaporate and vanish forever. This is the information paradox. In 2012, a group of physicists tried to resolve it, but ended up creating an even bigger problem. The Amps team from UC Santa Barbara, named after the initials of his authors, showed that if you insist on both quantum mechanics being correct and that information can escape the black hole, then the event horizon would look like a wall of incredibly high energy radiation, not the smooth, unremarkable boundary
predicted by general relativity. Therefore, these two theories seem to directly contradict each other, creating what is known as the firewall paradox. But this is where things for once slot together nicely. The ER equals EPR conjecture offers a way out of this tangle. See, back in 1974, Steven Hawking postulated that black holes have quantum effects near the event horizon that cause them to slowly emit what has become known as Hawking radiation, evaporating over incomprehensibly long time scales. The question is whether that radiation carries any imprint of what originally fell in or whether it's just random noise. If these hawking radiation particles escaping the black hole are entangled with particles inside it via a wormhole, then
information was never truly trapped in the way we always assumed. If the inside and outside of the black hole share a quantum connection, the information is recoverable in principle from the Hawking radiation itself. But the problem with ER equals EPR is that it had only been demonstrated for an extremely idealized scenario. two black holes in perfect thermal equilibrium. Real black holes are certainly not that. They are chaotic and messy. They're constantly being bombarded by infalling matter, radiation, and quantum fluctuations. If ER equals EPR only works for perfectly neat black holes that don't really exist, it's not much
of a solution. So in 2025, a team of researchers set out to test if the conjecture would hold up in more realistic conditions. They created a model of a theoretical pair of deeply entangled black holes connected by an Einstein rose and bridge known as a complex EPR pair. They started with an idealized wormhole, one which is smooth and symmetrical inside, and progressively scrambled the quantum entanglement between the black holes, making them increasingly chaotic. And they found something no one expected. Even when quantum entanglement is messy and random, the wormhole remains a predictable, stable tunnel. It gets longer, bumpier, more deformed, and develops lumpy segments, earning it the title the Einstein rose and caterpillar. And crucially, it remains a
geometrically stable, traversible structure where the classical laws of gravity still hold. And perhaps most intriguingly, nowhere in their typical models, those that started from rest, did they encounter a firewall at the event horizon. So coming back to our gravitational wave, for it to have actually traveled through a wormhole to us, two things need to be true. Firstly, wormholes connecting entangle black holes need to be real and stable enough to transmit a signal, which the Einstein Rosen Caterpillar seems to demonstrate as at the very least a theoretical possibility. Secondly, information needs to be able to travel through it. And in 2022, a Harvard le team managed to do just that in an experiment that sounds
stranger than fiction. They built a holographic wormhole on a quantum computer and successfully sent information through it. While we all pick our jaws up off the floor, let's break down what that insane sentence actually means. The experiment traces back to Daniel Jafferis at Harvard who in 2016 calculated that if you can take two entangled quantum systems and couple them together in the right way, you can perform an operation on one side that according to ER equals EPR should physically hold a wormhole open and push information through it. But the question was, could you actually build that system and test it? 6 years later, a team led by Maria Spyropulu at Caltech did exactly that. They used
Google's Sycamore, a superconducting quantum processor to simulate two entangle quantum systems that by the rules of ER equals EPR should be connected by a wormhole. And here's what happened. A unit of information, a quantum bit or cubit, was injected via a single particle into one side of a two-sided system. That encoded information diffused from just the one particle across all the particles on that side of the system like a drop of ink dissolving into water. Then the team performed a specific rotation across all the cubits, equivalent in the gravitational picture to sending a pulse of negative energy through the wormhole or propping it open with exotic matter.
Eventually, the encoded information reemerged on the other side of the system. Not only that, but it had converged or refocused itself from its diffused state back onto a single particle, the entangled partner of the original particle that carried the cubit into the system in the first place. In other words, researchers had sent information into a quantum tunnel and successfully retrieved it on the other side. Spyro Pulu couldn't believe her eyes, saying the moment felt like seeing the first data from the Higs Bzon discovery. However, the physics community quickly urged caution. Some analyses argued that the quantum model was far too simple to capture the true complex properties of black holes,
meaning the demonstration shouldn't be thought of as a literal holographic wormhole. Yet, even if it wasn't a perfect cosmic replica, her team had just shown that a quantum system governed purely by the rules of quantum mechanics could in principle behave in a way that is mathematically identical to a wormhole in a gravitational theory. The physics of both the quantum and the gravitational scales are similar even if the physical reality looks completely different. So coming back to the strange gravitational wave that started it all in May 2019. If it really did travel through a wormhole to reach us, this experiment is the closest thing we have to a proof of concept that such a journey is both
mathematically and experimentally demonstrable. But can we conclusively say one way or the other whether it did? Well, knowing everything we know about wormholes, quantum entanglement, and information, let's reassess the paper that launched us on this topsyturvy journey. Key lie and his team put forward the idea that gravitational wave signal GW190521 is the echo of a black hole merger in another universe. In that reality, two black holes spiraled and merged together normally. But instead of creating a larger black hole, they created a wormhole with one end in that universe and the other in ours. We didn't hear the inspiral part of the signal because it stayed in the parallel universe. But
as the ringown phase radiated outward, some of those waves traveled down the wormhole and emerged on our side. We know it's theoretically possible for the wormhole to be held open by negative energy and for information to pass through it. So, this isn't as outlandish as it might have initially seemed. The authors go a step further to explain why the signal was so short, just 0.1 seconds long. They postulate we only detected one pulse rather than a series of progressively weaker echoes as you'd expect with a ring down because the wormhole rapidly collapsed into a black hole or the later echoes were simply too weak for our detectors to pick up.
Technically, this can't be ruled out as a theory since there is a nonzero possibility that this could accurately describe what we saw. But the authors admit that even with the missing in spiral phase, a binary black hole merger in our own universe fits the gravitational wave data better than this explanation. Still, this study brings more value than a fun theoretical thought experiment. It's important because it gives astronomers a concrete way to test an exotic idea against real detector data. The Harvard quantum computer experiment showed that wormhole-like dynamics could potentially be mathematically real and testable. The Einstein Rosen Caterpillar shows that wormholes connecting entangled black
holes aren't just science fiction. They can emerge naturally from the maths of quantum chaos. And these two findings together along with the ER equals EPR conjecture build an ever stronger case for a mathematical connection between quantum mechanics and general relativity. By studying real merging black holes like the ones behind GW190521, we get to play with the systems where this frontier pushing physics might apply. In the future, our detection of these events will only get more precise. Since 2023, LIGO and Virgo have been operating with a 30% increased sensitivity, allowing detection of a merger every 2 to 3 days. Given that we've only been able to detect gravitational waves for a decade, this
field is in its infancy. With improvements to our models and technology, who knows, maybe one day we'll not only be able to conclusively find wormholes, but even be able to send stuff through them. I, for one, am hopeful that they won't always remain elusive and confined to equations and sci-fi stories. But for now, we'll have to wait and see. There's a reason these educational mini documentaries are free for everyone. It's not just the ads or sponsors, but it's thanks to our hundreds of Patreon members who make it possible for everyone to get the best possible content. They are the foundation that keeps Astramm steady and focused on quality over clicks. Every video you
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