As mysterious as they appear, our knowledge
about blackholes seem to be as dark as how
they are pictured to be.
That’s why we’re taking on the six most
frequently asked questions about blackholes,
in today’s episode!
I think none of us here haven’t heard about
blackholes, right?
It’s basically a great conversation starter,
and a plot device for a lot of science fiction.
It’s like one of the great things that gets
you interested in exploring the field of astronomy.
And I wouldn’t blame you at all!
I mean, it’s pretty easy to get amazed by
how extreme, how bizarre, and how mysterious
black holes are.
If that doesn’t get you to be attracted
to, let’s say science at the very least,
I don’t know what will.
Maybe some dinosaurs?
But as majestic as they come, there’s really
a lot that we don’t know about it.
Even the scientists who study these kinds
of objects still have a lot of questions,
and each time they try to answer them, they
end up with more questions.
It’s a crazy Russian doll!
That’s why today, why don’t we both get
down to the bottom of it all.
Let’s talk about the six most asked questions
when people talk about black holes
Number 6: How do we make blackholes?
Okay, to set the pace, let’s get this going
with something very basic and simple: the
origin of a blackhole.
If we’re going to talk about something,
it’s one of the best places to start, right?
In theory, anything can be turned into a blackhole.
All you have to do is to compress the volume
of the object into what’s called its Schwarzchild
radius.
Easy!
But okay, let’s get real.
We know that we don’t have that amount of
force.
Some of us here can barely open a can of pickles,
let alone have the capacity to crush an object
to an infinitesimally small size.
So instead, let’s look at where there is
an abundance of it: where else but space.
Like it’s equally extreme cousin, the neutron
star, blackholes can be thought to be some
sort of stellar phoenixes: they arise from
the ashes of another dead star.
Well, technically speaking, they didn’t
arise out of nowhere.
They’re the former nucleus of that other
star.
It’s like if a heart of some human comes
out of its body and decided it wanted his
own life.
If you know Ricardio of Adventure Time, you’ll
know what I’m talking about.
Okay, that’s too much tangent.
So let’s discuss how exactly an old star
gives birth to a black hole.
Stars undergo their own respective life cycles.
It starts as a cloud of dust particles, to
a young star, to a giant, then it goes to
its inevitable death.
So basically, a star fuses hydrogen most of
its life, but once it runs out of hydrogen,
it goes off script and begins fusing helium,
and running out of that, it starts to fuse
heavier elements instead.
Now, you may think that’s nothing to be
afraid of, but when you fuse heavier elements,
you expect to generate more energy.
This energy generated by fusion battles the
gravity that’s been trying to crush the
star, until the balance tips and gravity wins
resulting in a massive, bright supernova.
Whether or not it ends up as a blackhole normally
depends on how massive the star was.
On one hand, the core could collapse to a
neutron star.
On the other hand, if it's too massive, it
becomes a blackhole.
According to studies, the bare minimum mass
range to determine whether a star will collapse
to a blackhole or not is around 3 to 5 times
Solar masses.
Actually, it is guaranteed that if a star’s
mass falls in that range, expect a black hole
at the end of its life.
Number 5: How can a black hole pull light?
If you have studied quantum mechanics, one
of the characteristics of light that you might
have heard is how the particles of light,
photons, are actually massless, by the common
convention.
And, the kind of force that black holes use
is exactly gravity.
From the basic definition of gravity, we know
that for something to have this kind of force,
it’s got to have mass.
An object with extreme mass sucks in a massless
object?
How exactly do black holes accomplish this?
First, let’s explore a theory first brought
by Einstein: general relativity.
Specifically, the most important part of it
which can help us understand how black holes
work.
Newton established gravity as some sort of
non-contact force.
It acts from one object to another event without
contact.
However, our hero Albert remediated this by
explaining how gravity isn’t really an eerie
force transmitted without contact, but is
actually a distortion of spacetime by massive
objects.
Think of it this way, let’s say we have
a trampoline, and that nobody is jumping up
and down on it.
You expect the trampoline to be flat, right?
But for instance, we place a gigantic rock
anywhere on it, that area gets pushed down,
effectively making some kind of bowl around
the rock.
If you place a marble anywhere on the surface
of it, you expect it to roll towards the rock,
right?
That’s how gravity actually works, according
to Einstein.
Now, let’s go back to the black hole.
Since gravity is a distortion of spacetime,
and black holes exerts possibly the strongest
gravity we can expect in the universe, then
it just makes sense that light will have no
choice but to bend as well in the presence
of a black hole, right?
Think of it this way.
If you’re on a bathtub, and you apply force
to one of your rubber duckies such that it
moves to a specific direction, then you open
the drain, the duck will technically still
be moving at the pace you set it to.
It’s just that it experiences a stronger
force distorting its motion.
Who thought something as extreme as black
holes can be explained using rubber duckies?
Number 4: What’s the biggest and smallest
a black hole can get?
Well, I think the first thing and the easier
thing we can answer here is how large can
black holes get.
According to astrophysicists, theoretically
speaking, there isn’t a limit to how big
black holes can get.
But let’s talk about what currently holds
the record in terms of being the largest we
currently know.
In the center of every galaxy, it is expected
that we will find something that we call a
supermassive black hole.
It is estimated that one of these can have
a mass of a billion suns.
I know what you’re thinking.
If this is what holds the record as the largest
kinds of black holes, what’s the largest
supermassive black hole that we know to date?
We’re gonna answer that, but I want to know
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So okay, back to the question.
What’s the largest supermassive blackhole
in record?
The current title holder is M87: a supermassive
blackhole with a mass of about 40 billion
suns, with an apparent size of about 9.5 trillion
kilometers!
Even if you travel at the speed of light could
take you more than a year to travel that diameter!
Assuming you won’t get torn to pieces by
the gravity first, that is.
How about now, we explore the other end of
the spectrum.
What’s the smallest size a black hole can
get?
Of course, this one is a bit more harder to
find, since far away objects have to be of
a certain size for us to be able to observe
it from Earth, but as per recent studies,
it is hypothesized that a blackhole can reach
no smaller than 10 to the negative 33 centimeters.
That’s way, way smaller than a proton!
Number 3: How does time work in a black hole?
If you have watched the movie Interstellar,
it’s most probable that you have stumbled
upon the crazy scene when the crew was near
a black hole.
For those of you who haven’t seen it, there
were a few scenes where time was severely
depleted for the characters as they were near
a black hole.
Going down to a planet close to it cost them
more than 20 years, even though in their experience
on the planet, they only stayed for about
an hour.
Pretty crazy, right?
It’s like you went to Taco Bell for a quick
bite, and then you come back and your kid
is already finishing a postgraduate degree
in economics.
So, obviously black holes have a way of messing
with time, but how exactly does this work?
Well, the answer can again be derived from
arguably Einstein’s best work, general relativity.
Remember earlier, how we established that
gravity is more than just a non-contact force,
and that what it essentially is is a dent-forming
entity in spacetime?
Let’s work from that analogy.
If you pay close attention to the word spacetime,
then the answer is already there!
Special relativity tells us that as you move
closer to the speed of light, time goes by
faster for everybody else outside.
Let’s extend that to gravity.
Gravity effectively stretches spacetime.
This is why one step near a massive object
on the fabric of spacetime, definitely is
longer than a step far from it.
In simpler words, as you get nearer to a black
hole, time slows down.
And in the spirit of that question, we move
on to the next!
Number 2: What happens when you fall inside
a black hole?
Let’s play a bit of a god here, where we
have the entire universe as our sandbox.
Let’s create two persons, which we will
call Popper, and the other, Copper.
Let’s protect these two guys with the perfect
material, in such a way that they won’t
be harmed in space.
And also, let’s make their visions perfect,
such that whatever they see will be extra
clear.
Now, let’s create a black hole.
Copper and Popper tossed a coin, and Popper
won so he got to pick where he wanted to be,
in this thought experiment.
He chooses to travel inside the black hole.
Copper, on the other hand, we place on a safe
point, where he could see Popper falling into
the event horizon.
Let’s take Copper’s perspective first.
How does he see Popper as he falls straight
into the black hole and crosses the event
horizon?
Since the force from the black hole will be
so powerful, you expect Popper to fall really
quick, right?
That’s not what happens, however.
The photons coming from Copper will be relatively
slower as compared to his descent to the black
hole.
So what happens is, as he falls in, Copper
sees Popper falling extremely slowly, as his
time is also slowing down, and he’s falling
faster than the photons could reach the other
guy’s eyes.
Later on, Popper would turn red, as a result
of Doppler effect, and then, his image would
simply freeze.
Copper would witness Popper’s image suspended,
as it becomes dimmer and dimmer, until it
completely disappears.
Freaky!
Now, let’s take Popper’s perspective.
What does he see as he falls into the black
hole?
He still sees Copper at a distance, but since
he is falling at a crazy fast rate, his eyes
only receive a finite amount of photons.
The stars and everything begin to look as
blue, due again to the doppler effect.
You begin to have trouble discerning what’s
happening outside, until the usual universe
collects into a globe-like figure, and compresses
to a single dot.
This is counter intuitive to the suggestion
that since time happens faster outside the
black hole, there is a chance that you will
observe the universe until its end, but that’s
just not the case, as was demonstrated by
our boys, Copper and Popper.
Number 1: Will there be a time when black
holes consume all of the universe?
It’s definitely alarming how this grim question
is the most asked question about black holes,
but let’s tackle it anyway.
However, let’s ease out that fear and answer
it very shortly: the chances of that happening
is very small.
Why?
Because as black holes are effectively powerful
vacuum cleaners of the universe, paradoxically
speaking, they also leak out mass through
something that we call Hawking radiation.
So apparently, empty space isn’t actually
empty.
It’s simply a constant annihilation of virtual
particle-antiparticle pairs, which is why
conservation laws remain intact.
However, at the event horizon of a black hole,
this process becomes disrupted.
Due to the gravity of a black hole, there’s
a chance where a particle loses its partner
and falls into it.
Now, our lonely particle won’t be annihilated,
and becomes real, and now has mass that is
somehow “supplied” by the energy from
the black hole.
In theory, it is possible that if the process
continues long enough, a black hole might
eventually disappear.
That’s of course if we follow conservation
laws very strictly.
Black holes are definitely an interesting
bunch, and the more we know about them, the
more we discover about our very own universe.
But hey, at this point, I want to know more
about you guys.
What about you?
What’s the one thing on your mind that bugs
you most about black holes?
Let us know by leaving your ideas in the comments
section down below!
Who knows, maybe we can make a part two of
this video using those questions?
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Till next time, black hole fans!
Stay insanely curious!
