Black holes are so mysterious that all the known physics break down inside them.
Because they are so massive, they can drag and completely twist spacetime around themselves.
But then, much weirder than a black hole is space itself.
Space is a vacuum.
It's not perfect though, it's an imperfect vacuum because it's not completely empty.
Intergalactic space contains a few hydrogen atoms per cubic meter.
After all, no vacuum is truly perfect.
Everything occupies an area of space and relative to everything is a measure of time which can
be described as the rate of any movement through that space.
Einstein explained how what we perceive as gravity comes from the curvature of space
and time.
And as a way to reformulate Einstein's special theory of relativity, mathematician Hermann
Minkowski combined space and time into a single entity called spacetime.
For everything in the universe to happen, it takes time.
That's why if you want to describe the behavior of the universe you have to think in terms
of spacetime.
Think of space and time as the two sides of the same coin called spacetime, and that will
conclude space and time are the same thing.
Space is woven together, along with time, into a single fabric, spacetime, which is
continuous and can get distorted and bent by mass and energy.
Why?
Because mass sits on the fabric of spacetime like this, and curves spacetime around it.
But this is just a 2D representation of spacetime fabric.
A better way to visualize it is this 3D representation.
Any massive body, including us, the Earth, and everything else, bends spacetime.
However, the amount of spacetime bent depends upon how massive the body is.
Black holes are the most massive bodies in the universe.
The most obvious and intense bending happens around black holes.
Hence, the question "how do black holes bend time?".
So the bending of time is the curvature of spacetime fabric.
Black holes bend spacetime in a way that can force light to start traveling around it if
it gets too close.
Because a black hole completely twists and bends space around it, any passing light will
eventually be dragged in.
This is the power of gravity.
What we perceive as gravity is actually the curvature of spacetime.
What's interesting is that any object, even an apple, can be turned into a black hole
if only you could squeeze it into a tiny enough volume.
In this case, the object continues to collapse under its own weight, crushing itself down
to zero size.
However, according to Einstein's theory, the object's mass and gravity remain, in the form
of an extreme bending of space and time around it.
This bending of space and time is the black hole.
What's even stranger is that as you get closer to a black hole, time's flow slows down compared
to regions far away from the black hole.
As we said before, any massive body can do this.
Even Earth.
Time runs slower by a billionth of a second every day on Earth as compared to outer space.
This is trivial because Earth's gravity is so weak but enough to make GPS satellites
become inaccurate.
Even though the flowing of time is not noticeable on Earth, near a black hole, the flowing of
time is extreme.
So extreme, in fact, that to an observer outside the black hole, time completely stops.
If you were to watch an object falling into a black hole, it would appear frozen in time
at the edge of the black hole.
But inside the black hole, something completely strange happens.
The flow of time draws falling objects into the center of the black hole, and no force
in the universe can stop this fall, any more than we can stop the flow of time.
At the center of the black hole, our understanding breaks down.
Einstein's theory of gravity, however, predicts that time itself is destroyed at the center
of the black hole, meaning time comes to an abrupt end there.
And that's it, ladies and gentlemen.
No one knows why time would end there in the same way no one knows how time began in the
first place.