The best known equation in all of science is Einstein's famous E = mc2.
Stated simply, the equation says energy (which is the E) equals mass (which is the m).
The c2 term is just a conversion factor, like when you convert feet to meters.
The understanding that mass and energy were the same was a revolutionary idea, but that's
only part of the story.
In 1928, physicist Paul Dirac realized that not only were energy and matter equivalent,
but there existed another substance called antimatter.
I've talked about antimatter in another video which you can watch for more information.
However, I'll give you the highlights here.
Antimatter is basically the opposite of matter.
If antimatter touches matter, the two substances completely annihilate one another and convert
into energy.
The converse is also true.
Energy can convert into matter and antimatter.
And this is a crucial point.
When energy converts to matter it also converts into antimatter at the same time.
And not some random amount of antimatter.
The amount of matter created and the amount of antimatter created are identical.
This graphic drives this point home.
Energy can turn into matter and antimatter and the amount of matter and antimatter is
equal.
Keep that idea in mind as I redirect your attention to a long, long, time ago, just
fractions of a second after the Big Bang.
The universe was full of a roiling maelstrom of energy, with energy converting into matter
and antimatter and back again.
This was the cauldron of creation, the very foundry in which the universe itself was forged.
As the Big Bang unfolded, the universe expanded and cooled.
And as it cooled, the energy dropped below the point at which it can convert into matter
and antimatter.
Because the universe expanded, the separation between matter and antimatter particles would
grow.
In the simplest scenario, that's it.
The remaining matter and antimatter would wander around the cosmos, occasionally meeting
and annihilating.
As we peered into the sky, we'd expect to see a cooling cosmos, with equal amounts of
matter and antimatter and an occasional flash of energy, signifying a chance meeting of
these two antagonistic substances.
Simple right?
There's only one problem.
That's not what we see.
Everywhere you look, you only see matter.
I'm made of matter.
You're made of matter.
Everything we can see even with our biggest telescopes is matter.
There is simply no antimatter to be found.
The prediction of equal amounts of matter and antimatter is completely falsified.
When a theory is falsified this badly, something has to be changed.
So what gives?
Do we have to reject Einstein's famous equation?
Is the idea of antimatter wrong?
Do we need to discover another explanation?
What do we know?
Well we know that E = mc2 works.
We have tested it countless times.
We know antimatter is made in identical quantities as matter.
We clearly need a new idea.
The mystery of the disappearing antimatter is a big question for modern physics.
So what are some ideas that might explain this conundrum?
One idea is that there is antimatter in the universe, just too far away to see.
Under this thinking, we just happen to live in a piece of the universe that is entirely
matter.
This idea is possible, but is definitely not the most popular one.
The most popular idea is that in the early universe there was some unknown physics that
slightly favored matter over antimatter.
The idea is that for some reason for every billion antimatter particles there were a
billion and one matter particles.
The billions cancelled and the left over matter is what forms our universe.
There is some experimental evidence for this idea.
If we count the number of energy particles in the universe (called photons), and compare
them to the number of heavy matter particles (called protons), the ratio is roughly a billion
to one.
So are there any interesting ideas that support this conjecture?
Yes, there are.
Over the last 50 years or so, we have found little hints in our data that suggest the
universe might have a slight preference for matter.
These hints aren't enough to solve the problem, but it tells us that this might be the right
direction to look.
Several experiments in the recent past and near future have studied and will continue
to study this question.
This is an obvious hole in our understanding of the universe, and, as questions go, it's
a biggy.
I don't know what the answer will be, but what I do know is that scientists are doggedly
following every clue, hoping to solve this difficult mystery.