Does Antimatter Fall Up or Down?

By Matthew Francis

There are two kinds of matter in the universe: ordinary matter, which makes up all the stuff of everyday life, and antimatter, a sort of mirror image of matter. When the two meet, they annihilate in a flash of energy. It’s our good fortune that, in the early Universe, there was just a tiny bit more matter than antimatter, leaving us with a cosmos almost empty of stuff that could destroy us. Otherwise, we wouldn’t be here to ask what, exactly, antimatter is. 

Here’s what we know: Anti-electrons, known as positrons, are nearly identical to electrons, but instead of being negatively charged they are positively charged. The same goes for other antimatter counterparts: antiprotons are negatively charged and made of the antiquarks corresponding to the quarks in normal protons.

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The November Revolution

A feature article in Symmetry Magazine discusses the contribution of Cornell’s Department of Physics to a breakthrough in particle physics concerning the possible existence of a fourth quark.

On November 11, 1974, the members of Cornell’s high-energy physics group came together in a lunch meeting to chat about the discovery of a new particle, now known as J/psi, by researchers from two different labs on opposite sides of the country. It would be Ken Wilson, a physics professor, who would make the connection between the discovery of J/psi, and a seminar by Tom Appelquist, a physicist at Harvard University, on “charmonium,” a bound state of a quark and an antiquark.

“Only a few of us were thinking about the idea of a fourth quark,” Appelquist said. “Ken called me right after the discovery and urged me to get our paper out ASAP.”

The possibility of a fourth quark pointed to cracks in the three-quark model and would contribute to the Standard Model of particle physics as we know it today.