"Magnetic Trapping Will Help Unlock the Secrets of Anti-Matter"

In this article and others, we find “[CERN] Researchers created 38 atoms of antihydrogen – more than ever has been produced at one time before and were able to keep the atoms stable enough to last one tenth of a second before they annihilated themselves.”

I would be interested to hear Doper scientists comment on the significance of this. (As for Star Trek-style matter-antimatter propulsion engines, a Cern researcher said “Don’t hold your breath.”)

First of all, this is fantastic, but not a major breakthrough. Since the 1990’s thousands of antihydrogen atoms have been produced, but they have generally been high-energy atoms (moving near the speed of light, and/or the electron in a high orbital), and/or have gotten destroyed through annihilation with an imperfect vacuum very quickly. What they’ve done now is useful because these atoms have been slowed, cooled, trapped, are in a low energy state, and last long enough that their properties can begin to be studied with new precision.

Why is this important? We have studied antielectrons and antiprotons in high energy physics for a long time. While necessary in order to probe the highest energy regimes and discover new particles and produce antiparticles in the first place, high energy physics is an inherently imprecise enterprise. The error bars on what we measure are large compared to precision low-energy laboratory experiments. Being able to study anti-hydrogen using low-energy techniques is going to be great, not just because of the extremely precision experiments that are possible, but because the hydrogen atom is a simple enough system to be understood theoretically extremely well, but complex enough that some of its properties are extremely sensitive to tiny changes in the properties of the electron and proton. For example, the slightest difference in the energy-levels between hydrogen and anti-hydrogen can be measured with great precision.

Why do we care if there is a difference between hydrogen and antihydrogen? Because, for example, our best theory of the universe (the standard model) predicts that the energy levels of the two atoms should be exactly the same. If they are not, we have a lot of work to do! On the other hand, for a long time we have been looking for evidence of differences between matter and antimatter, because the universe seems to be mostly made of matter, and yet the standard model predicts that, given a ‘big bang’, the universe should have equal amounts of matter and antimatter.