Antimatter. You've probably heard of it, and you probably have no idea what it is
but don't worry, the brightest minds in the world are only beginning to understand what it is
and how it works.
Once they do,
just, whoa.
Antimatter is pretty much what it sounds like:
Matter's Alter-ego
Every particle that makes up matter as we know it like electrons and protons has a twin, with exactly the same mass,
but the opposite electric charge.
These are antiparticles. A positron for example is just like an electron
but it has positive charge and an antiproton is just like a proton
But has a negative charge and when an electron and a positron or a proton and antiproton meet they annihilate.
That doesn't mean that they just disappear nothing in the universe ever disappears. That's the Law of Conservation of Mass
They just turn into something else. In the case of the electron and the positron for example they form two photons,
massless virtual particles that convey the electromagnetic force. So you can see maybe why physicists are so
fascinated with antimatter because the laws of physics are
exactly the same for
antimatter as they are for matter and theories about the origin of the universe you know big bang stuff predict that matter and antimatter should
Have been produced in equal quantities, so those leads to some big questions, like why is everything
we see only made of matter? Wouldn't equal amounts of matter and antimatter
just annihilate each other, and why do we even exist? To get some answers
physicists look at neutrinos, fundamental particles emitted during nuclear reactions.
They are tiny way tinier than electrons with barely any mass and no electromagnetic charge, so they hardly interact with anything,
but they can be observed, even if very briefly, and
observing how they are like and unlike their antiparticles could help us
understand the very nature of the universe. See, there are three different kinds or
flavors of neutrinos: electron neutrinos, tau neutrinos, and muon neutrinos, they're all
electrically neutral and have their own antineutrino alter-egos. Now if you've seen me talk about the four fundamental forces of physics,
and you should, you know that flavors are just a cute way
physicists have of describing the various states that a particle can exist in. In this case flavors are basically different states of
oscillation, but these states are not stable no no,
neutrinos can isolate into different flavors over and over again as they fly through the universe.
So what physicists are trying to learn is how fast neutrinos and their antineutrinos change flavor.
It's just one way of understanding how particles of matter may be similar to and different from their antiparticles.
If it turns out that they're not just mirror images of each other,
but instead differ in some fundamental properties, that could explain why the observable universe seems
so weirdly asymmetrical, why matter is so totally dominant while antimatter is almost non-existent.
So where do we find these neutrinos in their antineutrinos?
Streaming out of a nuclear reactor of course! At the Daya Bay Nuclear Reactor in China's Guangdong Province
physicists are tracking electron flavored neutrinos to see how quickly they change flavors. Since antineutrinos have no charge and only a minuscule mass
they normally pass right through everything like light speed ghosts.
So to have any hope of interacting with one, physicists put enormous tanks of mineral oil spiked with a heavy element called
gadolinium in a cave under a mountain near Daya Bay.
Thousands of antineutrinos of different flavors passed through the cave every day, and every so often an electron antineutrino
passes through and hits a proton in the oil, which starts a chain reaction.
The collision first forms a neutron, and then a positron. The positron then immediately
finds an electron, the two annihilate making a tiny flash of light, a photon. The mineral oil
magnifies the flash, which is picked up by photo detectors. At the same time,
physicists a couple of kilometers away are measuring the amount of electron flavored antineutrinos that are passing through their detectors. What they found is
that fewer of these antineutrinos are being detected farther away, than are found right
beneath the reactor. The difference between these two amounts tells us exactly how fast the antineutrinos are oscillating into different flavors.
So what in the name Paul Dirac's ghost does this have to do with why we exist? Well with a little more data,
physicists will be able to compare how fast all kinds of neutrinos and antineutrinos
oscillate between flavors and if those rates are different, it'll show that neutrinos and antineutrinos
aren't exact mirror images of each other, and understanding how they differ will give us a clue as to why the universe seems to favor
matter over antimatter and
why we exist.
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