I was thinking this past week about antimatter. If that seems a strange topic for a humanities person to be thinking about, then consider all of the fictional uses of antimatter in literature and popular entertainment.
Science fiction writers like Robert Heinlein, Isaac Asimov, and Philip K. Dick are a few of the many who have played around with this scientific discovery. The British television series Doctor Who used it for a propulsion system. That sentient android, Data, from Star Trek: The Next Generation has a positronic brain that gives him powerful computational capabilities. In Dan Brown’s Angels and Demons, the Illuminati try to destroy Vatican City using the explosive power of a canister of pure antimatter.
In physics, the idea that there may exist particles and matter that are exact opposites of the matter that surrounds us goes back to the late 19th century. It is difficult to grasp the idea that there are mirror-image anti-atoms for all our known atoms. Take that idea wider and there would be whole anti-solar systems.
And what if in those solar systems the matter and antimatter meet? They would annihilate one another.
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. That is 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. Each type of particle forms a uniquely shaped trail. Anderson noticed a curious trail like that of an electron, with an exactly identical, but opposite curve. An electron and a mirror image. Evidence of an anti-electron.
He took a photograph of the event. A particle is seen approaching the metal plate, and when it hits the plate, it loses energy but continues to curve in the direction appropriate for a positively charged electron. He later called it a positron.
He had discovered antimatter. The discovery earned him a Nobel Prize in Physics in 1936. he was 31, the youngest person to be so honored.
Antiprotons were discovered in 1955, and the antineutron was discovered the following year, and in 1985 scientists created the first anti-atoms. Other antiparticles, such as antiprotons and antineutrons, have been discovered.
These discoveries obviously led to thoughts about its practical use. But writers of fiction also speculated on how it could be used. Back in the 1940s, biochemist and science fiction writer Isaac Asimov used it for his fictional “positronic brain.” Made of platinum and iridium, this brain gave humanlike consciousness to the robots in his collection I, Robot.
Star Trek used it as the basis of high-energy propulsion systems. But the amount of antimatter so far created on Earth is well short of what would be needed to power any type of vehicle or spacecraft. According to an article at symmetrymagazine.org, all the antiprotons created at Fermilab’s Tevatron particle accelerator add up to only 15 nanograms. CERN has even less. Making 1 gram of antimatter requires approximately 25 million billion kilowatt-hours of energy and would cost over a million billion US dollars. No one has a canister full of it – except in fiction.
Matter and antimatter particles are produced as a pair and when they meet, they immediately annihilate each other, leaving nothing but energy behind. Doesn’t that mean that the Big Bang should have created and destroyed equal amounts of these particles? Why do we exist in a Universe made almost entirely of matter?
As far as I can find, physicists seem to think that there was one extra matter particle for every billion matter-antimatter pairs. But those physicists have yet to explain this asymmetry. They are also looking for antimatter left over from the Big Bang using the alpha magnetic spectrometer on top of the International Space Station.