If matter falls down, does antimatter fall up? - Chloé Malbrunot
"Hey, another atom.
I'm hydrogen, nice to meet you.
How are you feeling about the jump?"
"Hi there, I'm antihydrogen,
your antiatom,
and to be honest, I'm feeling
kind of neutral.
My positron and antiproton balance out,
just like your electron and proton, right?"
"Hey, yeah! You look just like me,
but different somehow."
"Whoa, be careful! If we get too close,
we'll disappear in a spark of energy.
I'd like to stay in one piece."
"Oh wow, sorry."
"It's okay. I was just thinking,
it's kind of weird for us to be
chatting like this before our
jump above CERN."
"Why's that?"
"Well, for starters, how do we know
we'll both fall?"
"Of course we'll fall. It's gravity,
you know, the force of attraction
between masses.
I even know how fast we should fall.
Galileo showed in that tower experiment
that all falling objects accelerate
at the same rate, regardless of mass."
"That's for bigger objects.
It's a different story
for small particles like us.
Our mass is so tiny that the gravitational
force we experience is miniscule,
and if the particles are charged,
like my antiproton or your proton,
then it becomes impossible to detect
compared to the much greater
electromagnetic force acting on them."
"But that's only for charged particles.
You and I are both neutral.
Our charges balance out,
so the electromagnetic force is small
and the gravitational force
should be detectable.
I know mine's been measured."
"Because you're everywhere,
but I'm kind of hard to find."
"Why is that, anyway?
Shouldn't there have been an equal amount
of matter and antimatter created
in the Big Bang?"
"You'd think so, but then all of
those particles
would have annihilated
each other into energy, remember?
And the Universe is obviously
full of matter.
No one knows why there is more matter
than antimatter,
which is why scientists
are so interested in studying me."
"So where do they find you anyway?"
"Actually, I was made in that
lab down there.
They needed an accelerator to make
my antiproton because it's so heavy,
just as heavy as your proton.
Getting my positron was easier.
It's much lighter, like your electron,
and there are materials
that naturally decay by emitting one.
Then they just had to put the two together
and they got me.
But it's only recently
that they've been able to keep me
around long enough
to study my properties."
"And now they've sent you on this
jump with me. Hey, wait a minute."
"That's right. We're reenacting
Galileo's experiment,
but with matter and antimatter
instead of two objects made of matter."
"So what's going to happen?
Are you going to fall
upwards or something?"
"Only one way to find out!"
