Welcome to the universe... Where you need to
keep in mind these 2 eternal truths for the
rest of your life:
First...The closer you get to the center of
a round thing the more is the gravitational
force you'll experience by that thing.
Center!
NOT the surface.
Second...
The less mass the round thing has, the less
is the gravitational force.
What's so special about black holes?
Nothing except the fact that they allow you
to get closer to them.
Imagine you are standing on earth and the
earth gets compressed to half but you are
kept at same distance from center using a
platform.
There'll be no change in gravity you experience.
Coz none of the two factors mentioned in eternal
truths changed.
But when you go to the surface, you'll find
out that gravity has increased 4 times.
As the earth got compressed you can go closer
to its center.
BUT! Wait!
You can also get closer to the center
by digging a hole through the earth.
But then the mass below you that is exerting
gravitational pull on you also decreases resulting
in an overall decrease in gravitational force.
When you compress that earth even further
to the size of peanut it becomes a black hole
as now it allows you to get so close to its
center that you can't get out.
But at distance the gravity of black hole
seems normal just like any other body of same
mass.
So, if we suddenly replace our sun with a
black hole of same mass, everything else in
the solar system will continue to be normal.
Only it'll get very cold!
There is also this thing called escape velocity
which depends on the gravitational force at
the surface of planets.
Escape velocity for earth is 11.2 km/sec.
If you throw something faster than that, earth's
gravity will not be able to pull it back and
it'll leave earth's atmosphere.
The more the gravity on surface the more is the
Escape Velocity.
The gravity at the surface is so high at black
hole that the escape velocity is equal to
the speed of light.
That region where escape velocity becomes faster than the speed of light
is called Event horizon.
So, in summary everything that comes to earth
stays on earth until it has a speed faster
than 11.2 km/s, everything that goes to the
moon stays on moon until it has got a speed
faster than 2.38 km/s.
Everything that goes inside black hole stays
inside black hole until it is going faster than
the speed of light....
But! Wait.
Nothing can go faster than the speed of light.
So, anything that goes inside black hole stays
inside black hole forever!
Also, not anything can become a black hole.
Only stars with very large mass can become
black holes.
Mass high enough to allow collapse within
themselves up to the point when escape velocity becomes
the speed of light.
Our sun is not a worthy star to become a black
hole.
Now let me tell you one more thing that makes
black hole special.
Let me tell you what's inside black holes?
NOBODY KNOWS.
NOBODY knows whats inside them.
There can be anything: wormholes, higher dimensional
space, an entire freaking universe, a duck,
a potato...
Nobody knows exactly what there is.
What do you think there might be inside a
black hole?
Leave your answers in the comments below...
