What is antimatter?
It’s the favoured fodder of sci-fi writers, but antimatter is no fiction; it’s real and our very existence depends upon its properties.
It’s the favoured fodder of sci-fi writers, from fuel to power interstellar spaceships to the volatile ingredient in Vatican-annihilating bombs. But antimatter is no fiction; it’s real and what’s more, our very existence depends upon its properties.
Carl Anderson’s cloud chamber photograph confirming the existence of the positron. © Science Museum
Why are we here?
Because of this symmetry, when everything came into existence at the Big Bang, matter and antimatter should have been created in equal amounts. As the firestorm of creation cooled, the matter and antimatter would have totally annihilated each other, leaving a cold, dark and lifeless universe. No matter, no stars, no planets or museums. Just a few lonely photons whizzing through the endless blackness.
So the fact that we exist is one of the biggest unsolved problems in physics.
To unpick this conundrum a number of experiments are underway to test the matter-antimatter symmetry. One of the largest is the LHCb detector at the Large Hadron Collider, CERN.
A question for quarks
The 'b' in LHCb stands for the beauty or bottom quark (depending on taste) which is a member of a family of particles called quarks.
LHCb physicists are interested in them because some composite particles containing b quarks constantly flip backwards and forwards between their matter and antimatter versions, in a sort of quantum split-personality disorder. This gives us a unique opportunity to study matter-antimatter symmetry by seeing if they spend more time as particles than anti-particles.
The interesting thing about all this is that the size of this asymmetry must be absolutely tiny. We know from astronomy that for every particle in the Universe, there were roughly a billion produced at the Big Bang. So 999,999,999 in a billion were annihilated by 999,999,999 anti-particles, leaving just one survivor.
In other words, everything that exists is a tiny one in a billion leftover from a cataclysmic battle between matter and antimatter at the beginning of time. Matter only won by a whisker. If things had been even a tiny bit different we wouldn’t be here to wonder about it at all.
Written for the Science Museum's Collider exhibition, 2013. © Creative Commons - CC BY