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Language: en
you're watching a Nova science Now video
podcast my Galaxy's a purple what color
are yours M are sky blue SK here at Nova
we do a lot of things in the name of
science are you ready
ready 1 2 just ask Nova science now host
Neil degrass
Tyson and not all of it is done purely
for
fun like astronomer Doug CLA sometimes
we're trying to explore the deepest
Mysteries of the universe and dark
matter is definitely one of those
Mysteries when astronomers refer to dark
matter right we we mean something that
doesn't interact with light in any way
it doesn't give off light it doesn't
absorb light scientists like CLA think
Dark Matter makes up 20 some per of our
universe but there's something else they
aren't so sure about we don't know what
dark matter
is we think it's probably some sort of
particle that we haven't discovered yet
but it might turn out to be something
different we're not entirely sure so why
is clout convinced that it actually
exists say hello to the bullet cluster
two immens groups of galaxies billions
of light years away that offer some
clues in the dark matter mystery
so the Bullet cluster is actually made
up of two separate clusters of galaxies
about 100 million years ago gravity has
pulled them together and smash them into
each other so in this in this Collision
we have these these two types of matter
we we have the galaxies and and we have
the 100 million degree gas which sits
between all the galaxies 100 million
degree gas yeah so what you might be
asking do the galaxies and gas of the
bullet cluster have to do with dark
matter let's create a mini bullet
cluster Collision to demonst straight
and here to help is NE to Grass
[Music]
Tyson so when we take these two separate
clusters of galaxies in the in the
bullet cluster and smash them together
the galaxies continued straight on
without without really any effect the
gas clouds however are going to behave
just like any other sort of gas and so
they actually do Collide so it's going
to slow them down and so now when we
look at this cluster about 100 million
years later the galaxies are moving
faster than the gas clouds and so
they're going to be further away from
from the center of this Collision in the
center of this Collision are the
intergalactic gas clouds lagging behind
the faster moving galaxies the the the
galaxies are now in in a physically
separate part of the sky from what the
gas is and so we've separated out the
two types of matter which we can see now
here's the important part matter creates
gravity more matter more gravity 90% of
this matter is in the gas cloud and so
that is where the gravity should be but
when all the data was put together that
wasn't the case instead we see that most
of the gravity is actually around the
galaxies and that tells us that
something else has to be there causing
this gravity it can't just be the stars
in galaxies themselves so is this
evidence for Dark Matter let's ask three
top experts in the field there is
clearly some stuff there that that is
not normal matter and that's making a
lot of
gravity I I really believe that there
really there is some D matter there so I
think the bullet cluster really is the
Silver Bullet that kills off a lot of
theories trying to explain away Dark
Matter although the Dark Matter mystery
isn't completely resolved we may have
good reason to be Greatful for this
mysterious stuff dark matter is
basically the glue that holds all the
large structures in in the universe
together so without dark matter we would
not currently be here so three cheers
for dark matter whatever it may
be for more on Dark Matter watch Nova
science now airing Wednesday June 25th
on PBS or join us online at
pbs.org NOA sciencenow