00:00Scientists think there might be a huge onion chilling somewhere out there in space.
00:05Not an actual one, but it's something even crazier.
00:08These are stars stacked inside each other, layer upon layer.
00:13These fascinating objects, called gravastars, could even be cousins of black holes.
00:19But most importantly, they might hold the key to understanding some of the most mysterious puzzles in the universe,
00:26dark energy, and even other dimensions.
00:30Let's start with gravity.
00:32Over a century ago, Albert Einstein helped us understand how gravity works.
00:38Turns out, it's not just something that pulls things on Earth and makes apples fall on Newton's head.
00:45It's much wilder.
00:47It's about warping the very fabric of existence itself.
00:51Let's say you toss a heavy ball, like a bowling ball, onto the middle of your bed.
00:56What happens to the sheets?
00:58They dip, don't they?
01:00They stretch and sag around the ball.
01:03Now, if you roll a smaller ball, like a marble, across the bed, it doesn't move in a straight line anymore.
01:10Instead, it starts circling the heavy ball, rolling closer and closer, as if the heavy ball is pulling it in.
01:17That's gravity!
01:19But instead of bedsheets, we're talking about the fabric of space and time itself, or space-time for short.
01:27Heavy objects like planets and stars make dents in space-time, and moons, planets, or even light move along these dents.
01:36Gravity is the curve that tells them where to go.
01:40In that case, you can guess that black holes are like the ultimate heavy balls.
01:45The heaviest, in fact.
01:47The gravity is so strong, it shrinks them, making them smaller and smaller.
01:52So tiny, they could fit in the palm of your hand, but with the mass of several suns.
01:58Some of them are like holding over 40 billion solar masses in your palm.
02:03It's ridiculous, but they basically create a bottomless pit in space-time with insane gravity.
02:10This area around them, called the event horizon, is the most horrifying thing ever.
02:16It's a point of no return.
02:19Once something gets there, it can never escape being eaten.
02:23When something falls past the event horizon, it can't climb back out, not even light.
02:29Which is why they seem like, well, black holes.
02:33But gravastars, they're something much weirder.
02:36Just like black holes, they're probably very compact.
02:40But instead of being tiny pits of endless gravity, they might have something wild at their core.
02:46Dark energy.
02:48This is one of the universe's biggest mysteries.
02:51Dark energy, this invisible, mysterious something that seems to be pushing the universe apart faster and faster.
02:59It's like a polar opposite of gravity.
03:02While gravity tries to pull things together to slow down the expansion of the universe,
03:07dark energy is trying its hardest to make our world even bigger.
03:12Luckily, dark energy has been winning so far.
03:15Otherwise, we'd all be in some deep pit.
03:18But if we can explain the gravity with balls, then what exactly is dark energy?
03:24A force? An energy field? Something else?
03:28We have no idea.
03:30Scientists have seen its effects.
03:32They know that it's incredibly spread out everywhere.
03:35But they can't tell you what that thing even is.
03:39But if it's trapped inside of gravastars, maybe we'll finally discover the truth.
03:45This name stands for gravitational condensate stars.
03:49Gravastars were dreamed up by two physics professors, Paolo Mazur and Emil Mottola, in 2006.
03:56They tried to think what else, besides black holes, could happen when a massive star collapses on itself.
04:04That's how they created this alternative.
04:07Think of it this way.
04:09Gravity pulls everything inward, making super-heavy objects like stars shrink in size.
04:15The more the star shrinks, the denser it gets, and its gravity grows stronger.
04:20After some point, it can cross a critical threshold and become a black hole.
04:26But what if there was dark energy inside to counteract this?
04:31At the core of a gravastar, there could be a region filled with false vacuum or dark energy.
04:37This energy would push outward, fighting the gravity.
04:41It's like the unstoppable force meets an immovable object.
04:45Thanks to this, the star core doesn't collapse into a black hole.
04:50Sounds wacky.
04:52We don't know what dark energy even is, so how can it fill up anything?
04:57But luckily, even if scientists can't fully explain dark energy,
05:01they still have strong mathematical models to check how it works in our universe.
05:06So, they decided to test this theory.
05:09Here's where things get even weirder.
05:12The new theory says that gravastars might not be simple lone objects.
05:17Instead, they could be stacked one inside another.
05:21Each one is like a layer with its own dark energy bubble inside, surrounded by a thin skin of matter.
05:28The outermost shell would hold a smaller gravastar inside it,
05:32and that one could hold an even smaller one, and so on.
05:36It's like a series of balloons, one inside the other.
05:39The air pressure in each one of them is stable, evenly spread out.
05:43Thanks to that, none of them deflate.
05:46They coexist without one popping or collapsing the others.
05:50In the case of gravastars, the air is dark energy,
05:54and the rubber is the shell of matter surrounding it.
05:57It sounds crazy, but it actually makes this whole idea more realistic.
06:01A single gravastar might have a very thin shell of matter,
06:05but the thicker they are, the more likely it is to exist in a stable way.
06:10And finally, the coolest part about them is that they could explain one of the biggest mysteries of our world,
06:17how universes are born.
06:20When a star collapses into a gravastar,
06:23the matter could theoretically implode through the center and create a new dimension.
06:29This would connect these objects to the Big Bang itself.
06:34Some scientists even speculate that dark energy could be the energy exchanged between our universe
06:40and a child universe that's created from a gravastar.
06:44Of course, these are all just speculations for now.
06:48But where are all those gravastars, and how do we test this?
06:52Well, physicists aren't sure either.
06:55They're more of a what-if thing than an actual object that they discovered.
07:00Those two professors just tried to imagine what would happen if gravity and dark energy worked together like this.
07:07For now, the LIGO, a big observatory which detects ripples in spacetime,
07:12hasn't found clear evidence of gravastars.
07:15Another problem is that gravastars would only be stable in specific cases.
07:20For example, if they spin too fast or their shell will be too thick,
07:24they might start to wobble or break apart eventually.
07:28Though it could actually take billions of years.
07:31Plus, even if we don't see them right now,
07:34remember that this is exactly what happened to the black holes themselves.
07:38When Einstein published his groundbreaking theory of general relativity,
07:43another scientist, Carl Schwarzschild, took his equations and found a solution to them.
07:49And that's when he realized, if gravity becomes incredibly strong,
07:54the light wouldn't be able to escape, and this could create a sort of hole in space.
08:00Einstein even thought that this sounds too weird to be true.
08:05It took many years for us to confirm black hole's existence,
08:09and we finally took a photo of one just a couple of years ago.
08:13You might remember that blurry picture that blew up online?
08:17It was Sagittarius A star, an incredible supermassive black hole in the center of our galaxy, Milky Way.
08:25So, that's why scientists approach gravastars so seriously.
08:30And since all the math checked out, which means that these objects are actually possible in real life.
08:36Now, we just need to see if they're somewhere out there.
08:40What's interesting is that they'd probably look like regular black holes.
08:44They could emit high energy radiation as they consume matter.
08:48They might even produce something called Hawking radiation,
08:52a type of energy that escapes from black holes.
08:55In other words, it would be nearly impossible to tell the difference.
08:59But gravastars have a small trick up their sleeve.
09:02If their shell is transparent to light, they might bend light in a slightly different way than black holes do.
09:09So maybe if they check the way light is bent around the mysterious object, they could spot the difference.
09:16And even if it turns out that gravastars don't exist in our reality, they're still valuable to science.
09:23They still taught us more about gravity, black holes, and the limits of relativity.
09:33That's it for today!
09:34So, hey, if you pacified your curiosity, then give the video a like and share it with your friends.
09:39Or if you want more, just click on these videos and stay on the Bright Side!
Comments