Out of everything that lies out there in the
cosmos, one type of body that usually get
more than their fair share of attention are
black holes.
Just because we’re not likely to get close
to one anytime soon, that doesn’t take away
our right to wonder what would happen if we
ever did, right?
Let’s take a look.
Well first off, if you wanted to travel anywhere
close to a black hole, you would have to find
a supermassive one.
Now this may seem counterintuitive at first,
but stay with me.
This is because of something called tidal
force.
We know that the strength of the gravitational
pull of an object decreases the farther away
from it you go.
But usually this effect is too weak for us
to notice, so standing here on earth your
feet won’t notice gravity being any stronger
than your head feels it.
Replace the earth with a small black hole,
however, and the tidal forces there would
have such a drastic gradient that just the
difference along the length of your own body
would be large enough to tear you apart, way
before you even reach the event horizon.
Fun fact: this process is called spaghettification.
Luckily, the more massive the black hole gets,
the slighter the tidal forces.
So, all we have to do is find ourselves a
supermassive black hole that is millions of
times heavier than the sun.
Tada!
Of course, as you get closer to the singularity
at the centre, the tidal forces here will
become stronger too, and eventually even this
gentle giant will no longer be as gentle,
but at least your experience here will last
a little longer.
Now this may be slightly disappointing, but
if you’re falling towards a black hole,
you likely won’t notice anything different
when you cross the event horizon.
The only way you could make sure if you’ve
crossed it, in fact, is if you tried to get
back out.
The event horizon marks the boundary where
the escape velocity, that is the launch speed
required to escape the gravitational field
of an object, is equal to the speed of light.
Since it is impossible for you to travel at
that speed, you’re gonna find yourself stuck.
On the brighter side, light from the outside
universe would still be able to get in, so
you’ll have a nice little bright patch to
keep you company on your way down.
Now let’s say you took a friend with you
on this mission, but she came to her senses
at the last minute and decided to stay behind
and watch as you fell in to the black hole.
While you believe you are falling in faster
and faster, she would see you slow down as
you got closer to the event horizon, and eventually
freeze when you reached it, only to disappear
soon after.
Now, there are a lot of things going on here.
Firstly, the relativistic effects of time
dilation would come into play, which means
that your friend would see time slowing down
for you, and stopping entirely at the event
horizon.
Because of this apparent time dilation, the
light from you that reached her will also
shift to a lower frequency, and hence a longer
wavelength.
This wavelength will soon shift out of the
visible region of the spectrum.
Since light is too slow escape from inside
the event horizon, that is the last time your
friend will see you while you proceed to eventually
become spaghettified and become one with the
singularity at the centre.
Well, maybe now you’re thinking you’d
rather avoid such an experience, and I’d
be with you on that.
So, if they ever really do send a space mission
of suicidal astronauts out to a black hole
and you’re considering whether or not to
go, remember, it’s a one-way ticket only!
