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  • If you saw a wormhole in reality, it would appear round, spherical, a bit like a black hole.

  • Light from the other side passes through and gives you a window to a faraway place.

  • Once crossed, the other side comes fully into view with your old home now receding into that shimmering spherical window.

  • But are wormholes real,

  • or are they just magic disguised as physics and maths?

  • If they are real, how do they work and where can we find them?

  • [Kurzgesagt Intro]

  • For most of human history,

  • we thought space was pretty simple; a big flat stage where the events of the universe unfold.

  • Even if you take down the set of planets and stars, there's still something left.

  • That empty stage is space and it exists,

  • unchanging and eternal.

  • Einstein's theory of relativity changed that.

  • It says that space and time make up that stage together, and they aren't the same everywhere.

  • The things on the stage can affect the stage itself, stretching and warping it.

  • If the old stage was like unmoving hardwood, Einstein's stage is more like a waterbed.

  • This kind of elastic space can be bent and maybe even torn and patched together, which could make wormholes possible.

  • Let's see what that would look like in 2D.

  • Our universe is like a big flat sheet, bent in just the right way,

  • wormholes could connect two very, very distant spots with a short bridge

  • that you could cross almost instantaneously.

  • Enabling you to travel the universe even faster than the speed of light.

  • So, where can we find a wormhole?

  • Presently, only on paper.

  • General relativity says they might be possible, but that doesn't mean they have to exist.

  • General relativity is a mathematical theory.

  • It's a set of equations that have many possible answers, but not all maths describes reality.

  • But they are theoretically possible and there are different kinds.

  • EINSTEIN ROSEN BRIDGES

  • The first kind of wormholes to be theorized were Einstein Rosen Bridges.

  • They describe every black hole as a sort of portal to an infinite parallel universe.

  • Let's try to picture them in 2D again.

  • Empty space time is flat,

  • but curved by objects on it.

  • If we compress that object, space-time gets more curved around it.

  • Eventually, space-time becomes so warped that it has no choice but to collapse into a black hole.

  • A one-way barrier forms: the event horizon, which anything can enter but nothing can escape;

  • trapped forever at the singularity at its core.

  • But maybe there is no singularity here.

  • One possibility is that the other side of the event horizon looks a bit like our universe again

  • but mirrored upside down, where time runs backwards.

  • In our universe things fall into the black hole.

  • In the parallel universe, with backwards time,

  • the mirror black hole is spewing things out a bit like a big bang.

  • This is called a white hole.

  • Unfortunately, Einstein-rosen bridges can't actually be crossed.

  • It takes an infinite amount of time to cross over to the opposite universe and they crimp shut in the middle.

  • If you go into a black hole, you won't become the stuff coming out of the white hole.

  • You'll only become dead.

  • So, to travel the cosmos in the blink of an eye, humans need a different kind of wormhole;

  • a Traversable Wormhole.

  • VERY OLD STRING THEORY WORMHOLES

  • If string theory or one of its variations is the correct description of our universe,

  • then we could be lucky and our universe might even have a tangled web of countless wormholes already.

  • Shortly after the Big Bang,

  • Quantum fluctuations in the universe at the smallest scales

  • far far smaller than an atom may have created many, many

  • traversable wormholes.

  • Threaded through them are strings, called cosmic strings.

  • In the first billionth of a trillionth of a second after the Big Bang, the ends of these tiny, tiny wormholes were pulled light-years apart;

  • scattering them through the universe.

  • If wormholes were made in the early universe,

  • whether with cosmic strings or some other way, they could be all over; just waiting to be discovered.

  • One might even be closer than we realize.

  • From the outside, black holes and wormholes can look very similar;

  • leading some physicists to suggest the supermassive black holes in the center of galaxies are actually wormholes.

  • It will be very hard to go all the way to the center of the Milky Way to find out though, but that's okay.

  • There might be an equally extremely hard way to get our hands on a wormhole, we could try to make one.

  • MANMADE WORMHOLES

  • To be traversable and useful, there are a few properties

  • we want a wormhole to have.

  • First, it must obviously connect to distant parts of space-time.

  • Like your bedroom and the bathroom,

  • or Earth and Jupiter.

  • Second, it should not contain any event horizons, which would block two-way travel.

  • Third, it should be sufficiently sized so that the gravitational forces don't kill human travelers.

  • The biggest problem we have to solve, is keeping our wormholes open.

  • No matter how we make wormholes, gravity tries to close them.

  • Gravity wants to pinch it closed and cut the bridge; leaving only black holes at the ends.

  • Whether it's a traversable wormhole with both ends in ours, or a wormhole to another universe,

  • it will try to close unless we have something propping it open.

  • For very old string theory wormholes, that's the cosmic strings job.

  • For man-made wormholes, We need a new ingredient.

  • Exotic matter.

  • This isn't anything like we find on earth, or even antimatter.

  • It's something totally new and different and exciting, with crazy properties like nothing that's ever been seen before.

  • Exotic matter is stuff that has a negative mass.

  • Positive mass like people and planets and everything else in the universe, is attractive because of gravity.

  • But negative mass would be repulsive; it would push you away.

  • This makes a kind of anti-gravity the props open our wormholes.

  • And exotic matter must exert enormous pressure to push space-time open, greater even than the pressure of the centers of neutron stars.

  • With exotic matter, we could weave space-time however we see fit.

  • We may even have a candidate for this exotic matter, the vacuum of space itself.

  • Quantum fluctuations in empty space are constantly creating pairs of particles and antiparticles,

  • only for them to be annihilated an instant later.

  • The vacuum of space is boiling with them, and we can already manipulate them to produce an effect similar to the negative mass we're looking for.

  • We could use this to stabilize our wormholes.

  • Once we're keeping it open, the ends would start together. So, we'd have to move them around to interesting places.

  • We could start by wiring the solar system; leaving one end of each wormhole in orbit around the earth.

  • We could flick others into deep space.

  • The earth could be a wormhole hub for a vast interstellar human civilization spread over light-years,

  • but only a wormhole away.

  • However, wormholes have a dark side.

  • Even opening a single wormhole, kind-of breaks the universe in fundamental ways, potentially creating time travel paradoxes,

  • and violating the causal structure of the universe.

  • Many scientists think that this not only means they should be impossible to make, but that it's impossible for them to exist at all.

  • So, for now, we only know that wormholes exist in our hearts, and on paper in the form of equations.

  • We know you want to know more about universe stuff, so, we're trying something new.

  • Kurzgesagt and Brilliant are collaborating on a six-part video series about our favorite science and space things.

  • Thanks to their help, there will be more videos on this channel in the next six months.

  • Kurzgesagt has worked with Brilliant for a while now, and we love what they're doing.

  • In a nutshell, Brilliant helps you to get ahead by mastering maths and science skills

  • through actively solving challenging and fascinating problems.

  • To support our collaboration with them, visit brilliant.org/nutshell and sign up for free today.

  • The first 688 people that use the link

  • will get 20% off their annual premium subscription.

  • --FINAL SUBTITLE EDIT/READ BY: WinterPyro

If you saw a wormhole in reality, it would appear round, spherical, a bit like a black hole.

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