Sunday Science: Antimatter

Geordi LaForge inspects the matter-antimatter warp core that powers the Starship Enterprise.

Every particle of matter has an antimatter equivalent*.

An antimatter particle has an opposite charge and spin ​to its "normal" matter equivalent.

But the mass of a "normal" matter particle is the same as its antimatter equivalent.

So, an electron (which is normal matter) has an antimatter partner called a positron. Both have the same mass.

An electron has a negative electrical charge. A positron has a positive electrical charge.

​An electron has an up spin. A positron has a down spin.

What is spin?

In the most basic terms, the spin of a particle describes how that particle is rotating (a property called angular momentum) and the tiny magnetic field of that particle (called a magnetic moment).

When we deal with the science of tiny particles (aka quantum mechanics) then spin has an intrinsic value. It can either be a 1 or a -1. Or a 1/2 or a -1/2, for example.

​Spin is a difficult concept to understand - so I've also included a video explaining spin at the end of this post.

What happens when matter and antimatter meet?

They annihilate each other. Let's look at a quick Lego example with an electron (Superman) and a positron (Superman's doppelganger - Bizarro).

When the pair meets, they annihilate each other. They completely disappear to satisfy a number of conservation laws.

​All that's left behind is some energy in the form of a couple of high-energy light particles called photons.

Why do we live in a universe of matter, not antimatter?

Good question - and one that's baffled scientists for some time. When the universe began equal amounts of matter and antimatter should have been produced - which means that nothing but energy should have been left behind as the matter and antimatter would have annihilated one another.

It turns out that there was one extra matter particle for every one billion matter-antimatter particle pairs. This is known as the matter/antimatter asymmetry. 

* Does every particle have an antimatter partner?

No. Maybe. Not sure.

Higgs bosons (particles that give other particles mass) could be their own antiparticles. And neutrinos (particles that barely interact with the rest of the matter in the universe) can switch between their matter and antimatter states.

It's a hot topic in science at the moment - and if we could find out more about antimatter Higgs bosons and neutrinos then we could solve the matter/antimatter asymmetry problem

Extra reading and watching

Did you know that bananas emit positrons? And that antimatter is a potential candidate for cancer therapy? I love this post from Symmetry covering 10 things you might not know about antimatter. And here's another great piece from New Scientist covering the five greatest mysteries of antimatter.

Dan Brown's book Angels and Demons also introduced the idea of an antimatter bomb. Just let me reassure you this is not at all likely. This would involve making 1 gram of antimatter, and containing it. Which would require approximately 25 million billion kilowatt-hours of energy and cost over a million billion dollars. 

If you're more interested in science fiction than fact, this post discusses how antimatter is used in Star Trek, including the matter-antimatter annihilation propulsion system that allows faster-than-light space travel. And here's a great infographic to explain why harnessing the energy from matter-antimatter annihilation is so difficult: 

Finally, here's a video to help you understand the notion of spin a little more:

What is Sunday Science?

Hello. I’m the freelance writer who gets tech. I have two degrees in Physics and, during my studies, I became increasingly frustrated with the complicated language used to describe some outstanding scientific principles. Language should aid our understanding — in science, it often feels like a barrier.
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So, I want to simplify these science sayings and this blog series “Sunday Science” gives a quick, no-nonsense definition of the complex-sounding scientific terms you often hear, but may not completely understand. 

If there’s a scientific term or topic you’d like me to tackle in my next post, fire an email to [email protected] or leave a comment below. If you want to sign up to our weekly newsletter, click here.

​Image from http://www.treknews.net/2011/04/30/science-fiction-or-science-fact-the-warp-engine-2/