Narrator: The first clue came from a Swiss
astronomer named Fritz Zwicky.
Just a few years after the discoveries that
had suggested the Big Bang, Zwicky noticed
that these newly discovered galaxies…were
behaving oddly.
Alex Filippenko: Fritz Zwicky looked at clusters
of galaxies and found that the individual
galaxies within those clusters are moving
so fast, that the clusters should fly apart.
Priya Natarajan: Moving around so rapidly,
that it was impossible to understand why they
didn't just wander away.
Something clearly held them in these orbits.
Narrator: Zwicky could see nothing in his
telescope to explain it, so he called the phenomenon…
“Dunkle mature" translated as “dark matter."
And then the idea promptly faded away.
Zwicky’s observation might have ended up
forgotten.
And for nearly forty years, it was.
Until an astronomer named Vera Rubin entered
the field.
Flip Tanedo: Vera Rubin was one of these astronomers
who was not appreciated until much later.
She was a woman in astronomy at a time when
the field was not particularly friendly to women.
Vera Rubin: Here’s what we get.
Narrator: She too noticed something bizarre
was happening:
Rubin: The stars way out here are going very
fast.
Narrator: The stars at the edge of the galaxies
were moving so fast—that they should have
been flung off into space.
André Fenton: Think about a spinning wheel,
covered in water.
If the wheel is moving slowly, the water clings
to the wheel.
But spin it fast enough, the water flies off.
The same thing should happen out in the universe.
Stars swirling around in a galaxy.
If they orbit too fast, they’ll get flung
off out into space.
Except that’s not what Vera Rubin sees.
Narrator: The galaxies are spinning fast—but
the stars stay in their orbits.
What is holding them there?
It has to be gravity.
Rubin: A gravitational pull from something
that’s not bright.
And we don’t know what that is.
