Einstein hated the idea of black holes,
but now they're a fundamental part of our understanding of the universe.
So what other holes could exist in space?
Black holes are the remains of huge stars—at least eight times bigger than our sun—
but in mass is concentrated into a tiny area called a singularity.
This singularity is so dense they warp space creating a hill that's so steep
no matter can escape from it. Not even light can escape.
It can't travel fast enough. Hence, you get a black hole.
Now amazing as it sounds, it is actually possible to see a black hole.
As material is sucked into the black hole it starts to warm up,
much like rubbing your hands, and it can give off really high energetic photons,
gamma rays, and x-rays, but occasionally visible light as well.
Now even more amazing is that occasionally two black holes can start to orbit each other,
and when they come into contact some of their mass can be annihilated.
In this region, space where it's been deformed can pop back up
sending ripples out in all directions, much like when you throw a pebble into a pond.
These ripples spread out all through space,
and they can reach us here on Earth. But they're tiny,
less than the width of an atom. But recently scientists here on Earth
were able to discover them.
And for the first time they were able to prove that these gravity waves existed.
White holes are theoretical objects and can be thought of as the opposite of black holes.
White holes can be thought of as massless regions of space.
Now, one theory of their existence is that once a black hole has sucked in
as much material as it can, it almost rebounds back out
pushing all of its material back out into space.
A white hole can be though of almost like a giant peak in space,
and you never have enough energy to climb up that peak.
Everything gets reflected back out including light. Hence, you have a white hole.
White holes are actually a quirk of the mathematics of black holes,
and a lot of scientists dispute their existence.
However as we've seen in the past, lots of strange theories can sometimes turn out to be real.
A worm hole,  called an Einstein-Rosen bridge, can be thought of as a tear
in the fabric of space. It's a tunnel that connects two very distant points in space together.
Now, I've got my two points of space here, A and B.
As you can see, they're very far away.
However, if I kind of bend space,
connect them together, and now create a worm hole between them
I can go from point A to point B instantly.
So I can travel huge distances in space in a fraction of a second.
Like white holes, worm holes are a quirk of mathematics of black holes,
but they are generally accepted by scientists.
However, it might be almost impossible to develop one
that would be traversable by human beings.
To build a stable worm hole, you need something called exotic matter,
and it is matter that's got negative mass and negative energy,
and this sounds fantastical. At the quantum level it is possible
to have negative energy states, and worm holes are a widely accepted part of quantum mechanics.
So they do exist, but it might not be possible to use them to explore the galaxy any time soon.
