Hello, I am Daryl Haggard. And I am here
to tell you about black holes.
I really enjoy some call and response,
especially since now we're coming
toward the second to last talk, so I'm
gonna ask you questions, a few questions,
over the course of my talk and I would
like you to respond if at all possible.
So my first question to you is: what
planet are we on? (Earth!) Awesome.
Ok, so we're off to a very good start. At
the end of this presentation, what I
would like you all to say to me is, if I
tell you that black holes are truly
awesome and that they really don't suck,
I would like you to be able to respond
to me that black holes don't suck and
really believe what you are saying.
So that's my objective here today. I want
you to know that black holes
are not cosmic vacuum cleaners, they
don't go rogue around the galaxy and
gobble things up. That's not what they're
about and that's not what they're up to.
I would like you to think of them as
very massive objects with very excellent manners.
So black holes are truly and
very, very well governed by our theory of
general relativity. So far, despite many
tests that we have put these to, we have
never seen deviations away from general
relativity. And they seem to really be
guided by this kind of amazing theory
that governs a lot of what we think is
going on with gravity. So you've heard a
little bit about gravity from other
speakers today and I would like you to
think now about the mass involved in
black holes, to remember that they are
indeed truly very, very small, but they
are still spectacular. I'd like
you to start thinking a little bit about
the awesomeness of black holes in the
context of this really amazing image
that I think might appear.
(Oh that's up to me, I guide the image, yes)
Ok here's the black hole. Have
you all seen this picture before?
It's kind of an awesome thing to be an
astronomer and have a lot of people say
yes when you show them a picture of a
black hole. That's a new thing that we
can actually show you an image
and be able to tell you a little bit
about what's going on with this
incredible image of the black hole.
They are really awesome creatures. This
is the very first picture we've ever
been able to take of the photons
swirling around very close to the event
horizon of a supermassive black hole. So
I'm gonna use this image as my prop for
a minute to help you understand a little
bit my favorite definition of what a
black hole is. I like this very toy
model, there's a lot more complications
to it than this, but think of a baseball
and what happens when I, Daryl Haggard,
throw a baseball? Be honest with me. I see
some people doing this. That's literally
what would happen. It would just fall
down, right? So the baseball, it falls back
down to the surface of the Earth, I'm not
that strong. I've actually got a
pretty terrible throwing arm. So this
baseball falls back down because of the
gravity of our planet. And so it's
experiencing our gravitational pull,
the planet's gravitational pull, but it turns
out that if I could accelerate, just put
a little rocket on the back of that
baseball and accelerate it up to 11 km/s
or just a little bit more, I can actually
get that baseball out into orbit or even
completely out into outer space, off the
surface of our planet.
So 11 kilometers per second, if that's
not your ball of wax, maybe you
prefer Queen's Units that's something
like 25,000 miles per hour, right.
Our cars don't go that fast but sometimes
our rocket ships do. So the thing about a
black hole is that that velocity, that
escape velocity, the velocity would need
to give a particle for it to escape off
the surface of that body, is faster than
the speed of light. So light is trapped
inside the black hole and light is the
fastest velocity those photons are
traveling at the fastest velocity we
know of it's a fundamental constant. So
light is stuck in there. And that's why we
call them black holes. But this image is
a picture of all of this stuff just
outside the black hole. Just outside the
event horizon of the black hole. These are
the photons and the hot gas and the hot
material swirling just outside the
horizon of this black hole. So let me
tell you just a
little bit more about this particular
black hole. This one, we like to use
relative units in astronomy, so we often
measure things in terms of other things,
because otherwise the numbers are just a
little bit hard to hold in your mind. So
this black hole is 6.5
billion times the mass of our own Sun.
So that's a lot of mass. But that mass is
packed into a really small space.
I'm borrowing this cartoon from xkcd which
some of you might recognize, that's a
little picture of our Sun and Pluto's
orbit and the Voyager satellite which is
the farthest thing we've ever managed to
throw out into space. And that scale is
superimposed on this supermassive black
hole. So 6.5 billion times the mass of
our Sun crammed into a space roughly the
size of our solar system. That's what
makes it a black hole. If that still
doesn't quite match your
intuition, let me give you another
example. Here's a really small number,
relatively speaking, this is three
millionths of the mass of our Sun.
Anybody know what that might be? I made you say
it before. Earth! Okay, that's exactly
right. So our earth has about three
millionths the mass of our Sun, but the
Earth could be a black hole too. If you
could just smash everything: your mom,
your dad, some of the moms and dads in
the audience tonight, all the trees,
all the oceans, all the buildings, all the
continents, into something the size of a
sugar cube, that would also be a black
hole. It's not that our earth all of a
sudden sucked everything in it's just
that you compacted all of the mass down
into a very small volume and that's what
gives you a very high escape velocity.
I'm just gonna let us now take a little
journey to wrap up my time, since I'm
running out. This is a beautiful image
made to help you walk you into the
universe where this amazing supermassive
black hole resides, at the heart of the so
called "Virgo cluster" of galaxies. We're zooming toward the constellation
Virgo in the night sky and there's a
massive cluster of galaxies, it's the
nearest structure of galaxies to our own
Milky Way galaxy and in the inside of
this incredible cluster of galaxies
there's a particularly massive galaxy
right in the center called m87, and you
can already see here that, through other
pictures we can see a jet zooming out of
the black hole. And as we zoom in a
little bit further we can actually see
that jet structure continued
all the way down toward the very very
heart of this galaxy this jet is kind of
pointed toward our line of sight which
is a little hard to make out in these
images, but this is all real data. Zooming
in closer and closer and closer until we
reach the event horizon. So not only does
this black hole not suck, it is throwing
material and energy out into the
universe at scales that are enormous
compared to the size of the galaxy that
hosts the black hole. Let me just show
you one last little video here, which is
actually going to show you the photons
in orbit around the black hole just to
further make the point that not only
does it not suck in mass and dust and
people and astronauts, the black hole
doesn't even suck in the photons. These
are simulated paths now of photons in
orbit around a supermassive black hole
like the one that we saw in m87.
And you'll see that they're bending just
like the light and through your glasses
gets bent to focus on your retina, the
black hole does bend the photons just a
little bit due to gravitational lensing
and make this beautiful ring image that
we see. It's not sucking the photons
in but it does redirect them a little
bit to give us this really amazing kind
of structure that we've now viewed.
All right, so that's all she wrote. So when I
tell you that I think black holes are awesome,
you are now going to tell me...("Black holes don't suck!")
Thank you.
