Matter and Antimatter

In the sky this week…

  • The Summer Solstice, the northernmost point in the Sun’s yearly travels, will be at 10:16 PDT on June 21.
  • Saturn is high in the southern sky.
  • Jupiter, Mars and Venus form a procession out of the sunrise glow.
  • The Moon will be Full on June 15.

Ken Tapping, June 15, 2011

The science headlines around the world are currently reporting how a Canadian-led group of researchers have managed to trap antimatter for more than a quarter of an hour. They used instruments at CERN, near Geneva, Switzerland, to make this elusive material and a novel idea to trap it. This is amazing news! In the past we could only look at our data and see that, for a minute fraction of a second, we had only a particle or two of antimatter. In movies, “losing antimatter containment,” is usually the last phrase uttered before the explosion occurs.

Antimatter has been described as the mirror image of what we call “ordinary matter”. We are made of “ordinary matter”, made of atoms, which in turn are collections of protons, neutrons and electrons. Antimatter is made of antiprotons, antineutrons and antielectrons (which we call positrons). If we bring a particle and its corresponding antiparticle together, they annihilate each other, releasing energy.

The Antiproton Decelerator is a storage ring at the CERN laboratory in Geneva. Photo: CERN

The Antiproton Decelerator is a storage ring at the CERN laboratory in Geneva. Photo: CERN.

Even though the processes involved were somewhat different, the effect was very similar to what we see in a thick fog. The rays of light coming from objects we would like to see are deflected multiple times by water droplets, until all detail blurs out. This foggy period lasted until about 400,000 years after the beginning, at which point the universe had cooled significantly. The particles that had been freely moving around and contributing to the fog condensed into atoms, and the fog cleared.

Imagine you have no money, so you find a kindly and wealthier friend and ask him to loan you a dollar. Now you have a dollar, but you are also in debt for the dollar you borrowed; essentially you still have no money. You could say that you have a dollar and an antidollar. If you bring the dollar and antidollar together, they annihilate one another. The banking industry makes a huge amount of profit in trading real and antidollars. To a large degree, the recent financial explosion happened because some major banks lost containment of their antidollars.

Our universe started as a colossal burst of energy. When the temperature had fallen enough, the energy started to turn into matter. We would expect that this process would be exactly the reverse of what happens when a particle and its corresponding antiparticle meet. In this case, a chunk of energy would convert into a particle and antiparticle. Some would likely annihilate each other, releasing energy again, but many of them must have avoided this fate because there is a lot of matter around today. We would therefore expect that for every proton, neutron and electron making us (the Earth, the Solar System, etc.), there are corresponding antiprotons, antineutrons and positrons out there somewhere, just as for every dollar you borrowed to buy your home or new car, there is an antidollar circulating in the banking system.

If our universe was once filled with equal amounts of matter and antimatter, we could imagine that, where they were mixed equally, they would eventually wipe each other out. In other places, where there was an excess of one form over the other, we would be left with a remnant of whatever form of matter was in excess. We would get neighbourhoods composed of 100% of one form of matter, quarantined from other neighbourhoods by large chunks of empty space. If we were to bring all those clouds together, all the matter would cancel out. However, so far our observations suggest our universe is dominated by ordinary matter. Hopefully, having some real antimatter to study, rather than having to work with theoretical concepts, will help us find out what is really going on.

Ken Tapping is an astronomer with the National Research Council's Dominion Radio Astrophysical Observatory, Penticton, BC, V2A 6J9.

Telephone: 250-497-2300
Fax: 250-497-2355
E-mail: ken.tapping@nrc-cnrc.gc.ca

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