MICHIO KAKU: First we think that out of the
Big Bang came dark matter, invisible matter.
If I held dark matter in my hand it would
literally ooze its way right though my fingers,
go right to the center of the Earth, go to
China and then go back and forth between China
and my hand.
That's dark matter.
We think that dark matter began to clump first
because of gravity.
Then matter was attracted to the clumpiness
creating the super massive black hole and
then later the galaxy itself began to form.
We have computer simulations about this, but
still the relationship is not yet clear.
Now remember, stars.
We know almost everything about stellar evolution.
That's because the pentagon has given us physicists
billions of dollars to model hydrogen bombs,
and a star is nothing but a hydrogen bomb.
However, a galaxy consists of over a hundred
billion stars so it's much more difficult
to tell which came first, the black hole or
the galaxy itself.
BILL NYE: The way I like to describe a black
hole.
It's a star.
A black hole is a star.
Now when you and I think of stars we think
about the sun which is giving off all this
light.
But the other thing about the sun to keep
in mind is it has a lot of gravity because
it's huge.
One of Einstein's discoveries, Albert Einstein's
discoveries was that gravity changes the path
of light.
It can bend light.
It's just not in our everyday experience.
To measure it we usually find objects way
out in space and we have known brightness
and we see where we think they're going to
be and then where they really appear to be
and then we infer or figure out that they're
not where we thought they were going to be
because gravity bent the beam of light.
It's amazing.
Anyway, so a black hole is a star so massive
that not even light can escape from it.
MICHELLE THALLER: What you're looking at is
something called the shadow of a black hole.
Now, black holes tend to have material orbiting
around them.
Black holes have a lot of gravity and gas
begins to fall in towards the black hole and
it begins to spin up into a disk around the
black hole.
And as that gas gets closer and closer to
the black hole its accelerated faster and
faster.
And so in this disc of gas some of it is traveling
very close to the speed of light.
You have a lot of friction.
You have lots of things rubbing up against
each other at very high speeds and incredible
amounts of heat and light are generated in
this disk.
So black holes usually are surrounded by disks
of very, very bright, very hot material and
that's how we find them.
Black holes themselves give off no radiation
at all.
Any light gets absorbed into the black hole
and when I say light I mean every possible
form of light from gamma rays, x-rays, infrared
light that we think of as heat, radio waves.
Nothing comes out of a black hole at all.
So what you're looking at in this image is
the black hole is sort of framed by this bright
ring.
And that bright ring is this hot material
that's orbiting around the black hole.
One of the first things you'd say well okay,
it's really kind of a wonderful stroke of
luck that the particular black hole we're
looking at the ring was right face onto us.
You see this bright ring exactly around the
black hole.
And, in fact, that's probably not the case.
The disc of material could be at many different
orientations around the black hole.
Light itself has no mass.
Light should not be attracted by gravity,
right.
I mean gravity is the force between two things
that have mass.
Light has no mass.
It just flies straight through space.
So why should light be affected by a black
hole?
And amazingly this is what happens.
A black hole's gravity is so strong it actually
bends the space itself.
So light thinks it's traveling through straight
space, just traveling in a straight line.
The disk can be pretty much any orientation
you like.
What will happen is light from any part of
that disk will get bent around the black hole.
So you'll be able in a very real way to see
the underside of the disk at the front of
the black hole.
The backside all the way over the front because
light itself is being bent around.
So if there's any hot, glowing material at
all you're going to see it sort of surrounding
the entire black hole because the light's
been bent around it.
KAKU: We're not swallowed up by a black hole
because we orbit around them.
However, are there wandering black holes?
And the answer is yes.
In fact, we've been able to track wandering
black holes as they wander through the galaxy.
One day one of them may catch up with us and
eat us for breakfast and it wouldn't even
burp in the process.
Now, a black hole is black.
It's invisible so how the hell do we know
that there's a wandering black hole in our
vicinity?
The answer is quite easy.
It was found by accident.
By taking a picture of the night sky and taking
the same picture at a different time you see
a distortion.
A distortion of light and then like time lapse
if you put these photographs together you
see that the distortion goes in a straight
line.
And then you say aha, that's the black hole.
Even though it's invisible it distorts light.
For example, many people wear glasses.
There's glass inside your glasses, but how
do you know that?
How do you know that there's glass inside
your glasses when glass is invisible.
Well, it's obvious.
Glass distorts light.
That's how you know that something that is
invisible is actually there.
And the same thing with black holes.
They are invisible but they distort starlight
as they move.
So one day if a wandering black hole snuck
up behind is how would we know?
First of all Pluto and Neptune would begin
to perturb.
Some of them would be, in fact, flung into
outer space.
As the black hole got closer and closer to
planet Earth we would see more and more disruptions
in the solar system as more planets got flung
into outer space.
And, in fact, as it whizzed by the Earth it
could even gobble up the Earth, in fact, eat
up the sun and hardly even notice.
And so the appetite of a black hole would
be enormous and it's something that at some
point in the future we may encounter.
THALLER: If you were around a black hole which
is a dead star and say the mass of the black
hole was about 20 times the mass of the sun.
A black hole like that is actually not very
physically large.
You have all that mass, but the black hole
itself may only be say on the order of about
30 miles across.
That means you have all that mass packed into
a tiny little area.
If you were nearby a black hole that means
there really would be a detectable gravity
stretching across something as small as your
body.
And not just the water in your body would
feel that.
As you got closer and closer to a black hole
you would actually feel your head stretched
away from your feet.
There would be tidal forces just like the
Earth goes through with the sun and the moon,
but next to a black hole the gravity is so
extreme there would be tides over something
as small as a human body.
Get closer and closer to a black hole and
your head keeps getting stretched more and
your feet keep getting stretched that way
and you would actually turn you into a stream
of particles.
Scientists have a really cool name for this.
It's called spaghettification from the word
spaghetti.
If you got close to a black hole there would
be tides over your body that small that would
rip you apart into basically a strand of spaghetti
that would fall down the black hole.
CHRISTOPHE GALFARD: Picture yourself in outer
space.
There is a black hole right in front of you.
You don't see anything.
No light can come out of it so it's like a
dark patch that distorts the stars that are
around.
The matter that surrounds you, the light that
surrounds you obeys a different kind of law.
They obey quantum physics.
They obey the law of the quantum world.
And everything we had known about black holes
until the mid-1970s was only related to gravity.
Now what Hawking did at the mid-1970s is to
add some quantum aspects to all this.
He took a quantum particle and threw it in
his mind towards the black hole to see what
would happen to it and he found out that some
part of that particle was getting out of the
black hole.
That the black hole was evaporating.
It was not the exact same particle he had
sent inside and that's what's tricky about
this problem and that's what's interesting
about this problem.
In a way that means that the information gets
bleached by a black hole.
Why is that?
You could imagine that it's the same with
an encyclopedia that you would throw in the
fire.
You take an encyclopedia and you threw it
in the fire it's gone.
Well, not quite.
If you could get back the ashes, if you could
collect all the lights that was shown during
the fire, if you could get the heat and everything
you could build back the encyclopedia.
It's not gone.
It's just difficult to retrieve.
For a black hole it's worse.
If you throw an encyclopedia inside what the
black hole will evaporate has nothing to do
with the encyclopedia whatsoever.
You could have thrown in something else.
So why is that a problem?
It is a problem because it means that our
universe has memory losses.
It means that whatever a black hole has swallowed
would get inside, never again back out and
we would never be able to understand the past
of our universe.
There are some things that are not retrievable
at all, not just in practice but also in theory.
And as it evaporates the black hole eventually
disappears completely maybe.
And if it's gone where did the information
go about the encyclopedia.
Where did it go?
We don't know.
THALLER: Information can be almost anything.
All of the different atoms in my body have
angular momentum.
They have charge.
They have mass.
There's all sorts of little bits of information
that make me me.
At the quantum mechanic level, at the tiniest
of levels there are different amounts of energy.
There are different probabilities that are
contained in the structure of my matter.
And information in some ways is a form of
energy.
Energy and mass are the same thing.
They're equivalent.
You can actually make mass into energy and
you can make energy into mass.
Around a black hole where there's very hot
gas, very high temperatures, very strong magnetic
fields perhaps.
There's a lot of energy.
And that energy can actually manifest itself
as particles, mass.
And the energy always creates particle anti-particle
pairs.
They're called virtual particles.
And matter and antimatter, the thing you know
about it is that it annihilates immediately.
So these tiny little particles come into existence
then annihilate and you're back to energy.
And this happens all around us all the time.
So if this happens near a black hole it's
possible one of these little particles can
go into the black hole and the other one escapes.
And all of a sudden there's a particle that
shouldn't be there.
The universe basically has a new particle,
energy from nowhere and how can that work?
And the information theory people say that
what happens is that energy has to come out
of the black hole.
The black hole's mass begins to decrease if
there is this poor little orphan particle
that shouldn't have been there in the first
place.
So over time tiny particle by tiny particle
these black holes can evaporate away.
And maybe there's something about those virtual
particles that contain some information about
the black hole and what fell into it.
Black holes may be the key to where the next
physics has to go.
We all know that we need a next Einstein,
a next quantum theory, something that actually
describes how gravity works in very intense
situations like a black hole.
Now we're actually observing black holes well
enough that we really have to get on this.
We really have to figure out how the universe
works around one of these things.
And we may end up learning what the universe
itself really is.
