Matter versus antimatter
Matter is built from a handful of subatomic particles
When we look at the world around us, we see what appears to be almost limitless variation. At a fundamental level, however, we know that everything is made up of just one thing: atoms.
Although tiny - a human hair, for example, is about a million atoms wide - atoms are themselves made up of a compact nucleus of protons and neutrons, around which electrons whirl. Like a sub-atomic set of Russian dolls, protons and neutrons are, in turn, built out of yet smaller pieces called ‘quarks’.
From here on it’s impossible to get any smaller. As far as scientists can tell, both quarks and electrons seem to be truly fundamental particles – indivisible, basic pieces of matter from which everything is built.
Antimatter: a mirror image of matter
Matter might dominate the Universe today, but this hasn’t always been the case. When particles of matter were forged in the intense heat of the Big Bang, they were accompanied by equal quantities of ‘anti-particles’, identical in mass but with an opposite electric charge.
Although antimatter doesn’t seem to be very common in the Universe today, it is frequently created at laboratories like CERN, where particle accelerators simulate the high-energy conditions that existed at the beginning of the Universe.
From these experiments, we're sure that every time energy is transformed into a quark or an electron, an anti-quark or anti-electron (called a positron) is also produced, and many hundreds of different antiparticles are now known. At CERN, things have even gone a step further with the creation of the first ever anti-atom - anti-hydrogen - in 1995.
In theory, there is no reason why antiparticles couldn’t combine to build larger and larger objects - anti-molecules, anti-life, even whole anti-galaxies.