This note accompanies the follow episode(s):
The Writer’s Almanac for August 2, 2017: The House Was Quiet and the World Was Calm

August 2, 2017: on this day: Carl Anderson discovers the first physical evidence of antimatter

Physicists began speculating in the late 19th century that there may exist particles and matter that are exact opposites of the matter that surrounds us, mirror-image anti-atoms and perhaps even whole anti-solar systems where matter and antimatter might meet and annihilate one another. But on this day in 1932, American physicist Carl Anderson discovered the first physical evidence that antimatter was more than just an idea.

Anderson was photographing and tracking the passage of cosmic rays through a cloud chamber, a cylindrical container filled with dense water vapor, lit from the outside, and built with a viewing window for observers. When individual particles passed through the sides of the container and into the saturated air, they would leave spiderweb tracks of condensation, like the vapor trails of miniscule airplanes, each type of particle forming a uniquely shaped trail. Anderson noticed a curious pattern — a trail like that of an electron, with an exactly identical, but opposite curve — an electron’s mirror image and evidence of an anti-electron. Anderson named the antimatter particle the positron and won a Nobel Prize for his discovery four years later.

Around 1940, biochemist and science fiction writer Isaac Asimov took up the newly discovered particle, using it as the basis for his fictional “positronic brain,” a structure made of platinum and iridium and his means for imparting humanlike consciousness to the robots in his story collection I, Robot.

The fictional uses of antimatter and the positronic brain have since spread throughout literature and popular entertainment, from the writing of Robert Heinlein to the classic British television series Doctor Who to propulsion systems and the sentient android, Data, in the American science fiction series Star Trek — even to Dan Brown’s Angels and Demons, the sequel to his wildly popular DaVinci Code, in which the Illuminati intend to destroy Vatican City using the explosive power of a canister of pure antimatter.