Everything that we can see, like people, trees, stars and galaxies, are made up of matter. But, it has a mysterious twin that is like its photo negative.
It’s called antimatter.
You can have an anti-person, an anti-tree or an anti-galaxy.
This is the basic outline on how works. Ordinary matter is made up of atoms, which are made up of certain kinds of quarks. But every quark has an opposite, and they can be arranged in the same way as atoms, to create a stable anti-atom. These anti-atoms can combine to form molecules, stars, and galaxies in just the same way that ordinary matter can.
When I was researching this topic, I thought that maybe their colours would be inverted, or they’d be see-through or something like that.
But it turns out each one would be indistinguishable from their ordinary version except for one thing. If the two ever come into contact, they’ll explode with a force greater than an atomic bomb.
If an antimatter Earth fell into the Sun, the blast would outshine the light of over 2,000 galaxies.
This happens because matter and antimatter, including people, trees, and stars, are actually made up of huge amounts of energy, which comes from their mass. When they encounter each other, their atoms cancel each other out and convert their mass to radiation and heat.
The reason why we are made of matter and not antimatter is one of the largest unsolved problems in physics.
We know that in the seconds following the big bang, huge quantities of matter and antimatter were created, and collided. They annihilated each other in a series of cosmic sized explosions.
As a result, the universe was almost over before it started. If all the matter and antimatter annihilated each other, the universe would be entirely empty, without stars, planets, or life.
But for unknown reasons, a tiny proportion more matter than antimatter was created. It outlasted the explosions, and went on to become all the matter in the universe, from galaxies to coffee cups. Everything that we see consists of that tiny proportion of remnant matter.
It’s kind of amazing to think just how much matter was created in the first place.
This is called the ‘baryon asymmetry’, and why it happened is unknown.
Antimatter still occurs naturally in some extreme circumstances like cosmic rays, but it only lasts until it encounters a regular atom. But in the last few decades, there’s been a new source of antimatter in the universe; human beings.
We have (pretty incredibly) learned how to manufacture anti-hydrogen and anti-helium, by smashing together their component quarks in just the right way.
It is the most expensive substance in the world, at $25 billion per gram. For reference, gold costs about $40.
Part of the reason of its expense is that, apart from needing a particle accelerator to make it, antimatter is incredibly difficult to store. If you put it in any container made of atoms, it will annihilate them and explode. Instead, we levitate it in a high-tech vacuum sealed chamber using electromagnetic fields.