Will a black hole destroy the Earth?
It’s a question everyone asks when they
find out about black holes.
The short and simple answer is probably not,
because the closest black hole, that we know
of, is located about 3000 light years away.
This black hole is called V616 Monocerotis,
or V616 Mon. for short.
As I mentioned, V616 Mon. is located about
3000 light years away and has between 9 to
13 times the mass of the sun.
The only reason we know a black hole is there
is because it's located in a binary system
with a star with about half the mass of the
sun.
The only thing small and heavy enough to make
this star move like it does is a black hole.
And without this star we wouldn't know about
V616 Mon. because we can't actually see black
holes, they’re black, we can only see their
gravitational effects on other objects, such
as this star.
One of the most famous black holes, Sagittarius
A*, was discovered the same way.
Since the start of this century, for over
16 years now, some astronomers have been observing
certain stars, near the centre of the Milky
Way, using infrared telescopes, in order to
see past the dust.
They watched the movement of these stars and
found that they seemed to have slingshot orbits
around something that wasn’t there.
The astronomers concluded that these stars
were orbiting a black hole because that’s
the only thing small and heavy enough to cause
these stars to act like they do.
This black hole was of course named Sagittarius
A*, or Sgr A* for short and is the supermassive
black hole in the centre of the Milky Way.
The second closest black hole to Earth is
Cygnus X-1, which is located 6000 light years
away and has 15 times the mass of the sun.
Unsurprisingly, it’s located in a binary
system, like V616 Mon.
The third closest black hole is also in a
binary system.
Someone with no knowledge about this topic
might say that “It must be that black holes
are just usually in a binary system” but
this is absolutely not the case.
In reality, all these black holes we have
discovered have something nearby them because
that’s the only way we can detect them.
Or it’s one of the only ways.
One of the coolest ways to discover black
holes is by detecting gravitational waves.
Einstein predicted the existence of gravitational
waves in 1916, based on his theory of general
relativity.
And then on the 14th of September 2015 LIGO,
or Laser Interferometer Gravitational-Wave
Observatory, detected gravitational waves
for the first time.
Later on, on the 4th of January 2017 (this
year) LIGO have detected gravitational waves
for the third official time.
If you want to know more about this, check
out my video on the third gravitational wave
after watching this one.
There are two different types of black holes,
and I’ve mentioned examples of each type.
V616 Mon. and Cygnus X-1 are examples of stellar
black holes, black holes created when a massive
star collapses.
The other type of black hole is a supermassive
black hole.
These black holes are located in the centre
of most galaxies, including our galaxy, Sagittarius
A* is the Milky Way’s supermassive black
hole.
We don’t know exactly how supermassive black
holes form but we do have theories.
On my other video of how we may have a picture
of a black hole soon Robert Lorrison commentated
and proposed a theory of how supermassive
black holes form.
He basically said that the very first massive
stars exploded in a hypernova, leaving a stellar
black hole behind, which (as he said) “served
as the starting point for a galaxy to eventually
form around it”.
It’s very possible but we just need more
evidence for it, so we can confidently say
“Yes, this happened”.
There is another type.
Miniature black holes are black holes that
would have a mass much smaller than the sun’s
mass, but we’ve never seen this type of
black hole.
V616 Mon. is the closest black hole, that
we know of, but honestly there are most likely
black holes closer than V616 Mon, because
we can’t actually see black holes.
And it’s important to make that clear.
Black holes don't emit any radiation because
they’re so gravitationally strong.
Light, the fastest thing in the universe,
can’t even escape it.
Sometimes, we can see the shadow the black
hole causes onto the bright matter zipping
around it.
When matter falls over the event horizon it
lets out radiation, which is why rims of black
holes tend to be extremely bright.
But why are they so bright?
Not just black holes, quasars as well.
How can they be so bright when black holes
don’t let anything escape, or more specifically
don’t let any radiation escape.
Well it all comes down to the matter orbiting
and falling into the black hole.
Imagine placing each end of a rubber band
to two different cars, and then driving these
two cars in the same direction.
If the cars are going at the same speed, there’s
not a problem.
But if the front car suddenly starts going
faster, let’s say 20 miles per hour, while
the car behind is going 10 miles per hour,
the rubber band is inevitably going to reach
it’s stretching point and snap.
This is what happens to objects when they
approach a black hole and is called “spaghettification”.
The side closest to the black hole is being
pulled faster than the far side of the object.
And this is also true for material orbiting
the black hole, not just heading straight
into the black hole, because the near side
of the object will be orbiting faster than
the outside, forcing it into a spiral.
Both scenarios, when material is spaghettified,
creates so much friction that it can heat
the particles hotter than most stars.
And since there’s usually a lot of material
orbiting a black hole or an accretion disk,
there’s a lot of fuel to keep it shining.
For all we know there could be a black hole
heading straight for our solar system or worse,
Earth, but even if a black hole did get close
to our solar system it would be pretty obvious
because we would start to see the effects.
But let’s say a black hole was heading straight
for our solar system, if we could we would
want to kill it right?
But how do you kill a black hole?
Well, according to Stephen Hawking, black
holes can actually evaporate… but over a
very, very long period of time.
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.
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.
But aside from Hawking radiation, is it possible
to destroy a black hole?
For instance, what if we detonate a nuclear
bomb near the black hole or inside the event
horizon?
Or instead, how about we shoot bullets at
the black hole?
Or even lasers?
What if we sent a star into the black hole?
How about we construct a black hole out of
antimatter somehow, would that destroy the
black hole?
No.
Sending any matter into a black hole just
adds to its mass and makes the black hole
larger, whether it’s a nuclear bomb, bullets,
lasers, a star or even another black hole.
At the moment, it seems that waiting eons
is the only way to destroy a black hole.
Comment any ideas in the comment section on
how to kill a black hole.
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If you enjoyed this video check out my most
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Thank you so much for watching, have a nice
day.
