Where Are the Anti-People? [Excerpt]

Physicist Dave Goldberg breaks down the mysteries of the cosmos in his new book The Universe in the Rearview Mirror. In an excerpt, Goldberg explores the matter-antimatter divide

By Dave Goldberg

Image: Courtesy Dutton Books

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The article below is excerpted from?The Universe in the Rearview Mirror: How Hidden Symmetries Shape Reality, by Dave Goldberg. Dutton, 2013.

It is generally a bad idea to watch science fiction in the hopes of bolstering your understanding of science. Doing so would give you a very distorted impression of, among other things, how explosions sound in deep space (they don?t), how easy it is to blast past the speed of light (you can?t), and the prevalence of English-speaking, vaguely humanoid, but still sexy, aliens (they?re all married). But if we?ve learned one good lesson from Star Warses and Treks, it?s that no one should ever mess with antimatter.

Antimatter is not only no more exotic than ordinary matter but in almost every way that matters, it looks and acts the same. Were every particle in the universe to suddenly be replaced by its antimatter ver?sion, you wouldn?t even be able to tell the difference. To put it bluntly, there is a symmetry between how the laws of physics treat matter and antimatter, and yet they must be at least a little bit different; you and everyone you know are made of matter and not antimatter.

We like to think accidents don?t happen, that there is some ulti?mate cause to explain why, for instance, you?re not standing around in a room full of anti-people. To understand why that is, we?re going to delve into the past.

Origin stories are tough. Not everything can be explained as neatly as being bitten by a radioactive spider, having your home planet explode, or even by the reanimation of dead tissue (you know, for science). Our own origin story is complicated, but you?ll be pleased to know that, much like The Incredible Hulk we?re also ultimately the result of expo?sure to gamma radiation. It?s a long story.

Based on everything that we?ve ever seen in a lab, you should not exist. It?s nothing personal. I shouldn?t exist, either, nor should the sun, the Milky Way Galaxy, or (for many, many reasons) the Twilight movies. Let me try to put that another way.

First a summary: You are made of fundamental particles, which are almost entirely empty space, and the tiny bits that aren?t empty space aren?t all that massive. Ephemeral energy just makes them ap?pear that way. Particles can be created from whole cloth and energy and destroyed just as quickly. You are not just much more than the sum of your parts; strictly speaking, your parts add up to a small pile of matchsticks in a tornado of pulsing, screaming energetic interactions. Yippee?ki?yay!

Energy can be used to make matter from whole cloth, but as a side ef?fect, antimatter gets made as well. I?ve referred to antimatter by its effect, but haven?t really said what it is. Prepare to be underwhelmed!

Every type of particle has an antimatter version that behaves al?most exactly the same?the same mass, for instance?but has the op?posite charge. A positron behaves just like an electron, but has a positive charge rather than a negative one. An anti-proton has a negative charge, contrary to a proton?s positive one, and so on.

One of the craziest things about antimatter is that if you are smart enough?and apparently only the English physicist P.A.M. Dirac was?you could have actually predicted antimatter before it was ever discovered. In 1928, Dirac derived the equations of relativistic quan?tum mechanics. Yes, that?s exactly as difficult as it sounds. Plugging through the equations, he noticed that there were missing solutions. He found, for example, that electrons should pop out of the theory naturally, but other particles with the same mass and opposite charge should also be allowed.

Source: http://rss.sciam.com/~r/sciam/basic-science/~3/Oo71lWqRx2M/article.cfm

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