(music)
(music)
- Scientists seem to have
a pretty good description
of nature, right?
After all, we can identify every type
of matter we've ever encountered.
What could possibly be missing?
You may be shocked to discover
that scientists only understand, at most,
five percent of the universe.
But, let's start with what we do know.
Physicists used to divide
all energy in the universe
into just two types,
matter, which is just atoms,
like what you and I are made of,
and radiation, which is just light,
like what is coming from
the screen in front of you.
Until the 1960s,
it was believed that these two categories
could describe everything
in the observable universe.
But then a young
physicist named Vera Ruben
discovered something strange.
There was a very close relationship
between the speed the galaxies rotate at,
and the mass contained in the galaxy.
She noticed that for many galaxies,
the rotation speed
suggested much more mass
than we actually saw.
A variety of explanations were suggested.
Maybe the measurements were wrong.
Maybe Einstein's gravity was wrong.
The issue has been intensely
debated by physicists,
but the conclusion seems to be
that there is a new type of matter,
one which is not visible to us.
This dark matter is stuff
which you could probably
hold in your hand,
but is completely invisible.
Hold on.
If scientists can't see dark matter,
how do they know it exists?
Physicists don't like to
invent new types of matter
for no reason,
but this dark matter actually
shows up all over the place
in our equation.
The universe appears to
be 25 percent composed
of this dark matter.
We also have some good
guesses for how to produce it.
It's possible that in the next few years,
we could be producing dark
matter particles in a laboratory,
and its exotic properties
harnessed for engineering.
As for what the other 70
percent of the universe is,
that's another matter.
(electronic whoosh)
