From the mathematics of Einstein’s general
relativity comes an object so peculiar, a
white hole.
The white holes twin, a black hole, was first
thought of in the 18th century by the geologist
John Mitchell.
In those days, black holes were not considered
to be real, Einstein even assumed they didn’t
exist.
Yet Einstein’s theory of general relativity
predicts and allows a concept named a white
hole.
More specifically it’s the mathematics of
general relativity that say that white holes
are possible.
If you take the mathematics of a black hole
and literally reverse it, you get a white
hole.
Or even, a white hole is a time-reversed black
hole.
So, a black hole will not allow any matter
to escape, once the matter is past the event
horizon, an imaginary boundary around a black
hole where no matter can escape, after passing
it.
And so take the opposite of this.
So a white hole has an event horizon, as a
black hole does, but no matter can enter it.
So instead of pulling all material inwards,
once it’s past the event horizon, like a
black hole does, a white hole ejects matter
and matter can never enter it.
Now you may have noticed that I’ve been
saying that black holes only suck in material
when said material is past the event horizon.
It’s very important to make this distinction.
Black holes don’t actually suck, or pull
on things.
They’re just like any other mass when it
comes to gravity.
The only difference is that black holes have
an event horizon.
If you magically replaced the sun with a black
hole with the exact same mass as the sun,
everything orbiting the solar system would
just orbit as they did when the sun was there.
The only difference is that sunlight is no
longer being emitted, because the sun is no
longer there, and so all life on Earth would
die.
But you see the point.
It’s only when material goes just close
enough to the black hole that the speed needed
to escape is faster than the speed of light,
and it’s not possible to go faster than
the speed of light.
It's often said that once you're in a black
hole you are there forever, and while this
is true in the sense that you're never going
to escape and you'll die due to spaghettification,
it's not true that a black hole lives forever,
because they don't.
Like everything else in the universe they
eventually fade away, or more specifically
evaporate.
This is due to Hawking radiation.
All around us, virtual particles are constantly
popping into existence.
It's often said that they come in pairs, a
particle and an antiparticle.
After existing for an extremely short amount
of time, the two particles recombine and annihilate
each other.
Now if you have one of these particle pairs
pop into existence at the event horizon, one
particle will fall into the black hole but
the other particle is able to escape into
space and become an actual particle.
And when particles escape, the black hole
loses a small amount of its energy and therefore
some of its mass, because mass and energy
are related by Einstein’s equation E = mc2.
As I said this is called Hawking radiation.
So, by these virtual particles popping into
existence at the event horizon, the black
hole will eventually evaporate into nothing,
but after an extremely long time.
So it turns out all we need to do to defeat
a black hole is to wait it out.
And as we discussed in the last video, there
aren't any other ways to kill a black hole
apart from waiting eons for Hawking radiation
to do its thing.
I really need to put an emphasis on the fact
that white holes are entirely theoretical.
According to the math of white holes, they
can only theoretically exist as long as there
isn’t a single particle of matter within
the event horizon of the white hole.
Even if a single hydrogen atom drifted into
the region, the entire thing would collapse.
There are several theories about white holes.
One is that a black hole singularity would
compress down into the smallest region possibly
possible, and then it would rebound as a white
hole.
But if you consider the large time dilation
effect going on, this would take billions
of years for even the low-mass black holes
to rebound as a white hole.
Microscopic black holes formed right after
the big bang might explode as white holes
sometime right now.
But if you remember Hawking radiation, the
black holes would’ve already evaporated,
especially the low mass ones, because smaller
black hole evaporate faster than larger ones.
Another theory is that white holes might be
one possible explanation for the Big Bang.
But, as I mentioned, white holes are most
likely just theoretical and don’t exist;
just another concept of our imagination, this
might be the same case for kugelblitz’s
and worm holes, for example.
Comment down below whether you think white
holes exist or not, and give your reasons.
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If you enjoyed this video check out my most
recent video or my playlist on black holes.
Thank you so much for watching, have a nice
day.
