Where the hell did the antimatter come from? That's what atmospheric scientist Joseph Dwyer has been trying to figure out for the past six years, after his research plane accidentally flew through a thunderstorm into a cloud of antimatter in 2009.
Dwyer's plane was outfitted to detect atmospheric gamma-rays (or γ-rays), high-energy photons that can be caused by cosmic rays colliding into the atmosphere or by intense lightning storms. Here's what happened on that stormy day in 2009, as recounted by Nature:
It was to study such atmospheric γ-rays that Dwyer, then at the Florida Institute of Technology in Melbourne, fitted a particle detector on a Gulfstream V, a type of jet plane typically used by business executives. On 21 August 2009, the pilots turned towards what looked, from its radar profile, to be the Georgia coast. "Instead, it was a line of thunderstorms — and we were flying right through it," Dwyer says. The plane rolled violently back and forth and plunged suddenly downwards. "I really thought I was going to die."
But Dwyer survived and his particle detector ended up detecting three 511-kiloelectronvolt gamma-rays spikes. Here's another thing you should know about gamma-rays: They can also be the result of an electron colliding with its antiparticle, a positron. Particles of matter and antiparticles of antimatter have the same mass but opposite properties such as charge, and they instantly annihilate when their counterparts collide, turning into things like gamma-rays. As our universe is made of matter, the presence of antimatter is usually fleeting.
And the 511 kiloelectronvolt gamma-ray spikes were a smoking gun for electron-positron annihilation. A few more calculations led Dwyer to the conclusion that the plane was surrounded by a small cloud of positrons.
But where did these positrons, the antimatter, come from? Intense thunderstorms can indeed produce positrons, but other data from this storm led the scientists to rule that explanation out. Same with cosmic rays, which should have caused other types of radiation to show up in the data.
Dwyer ended up publishing his results after failing to come up an explanation. But Nature reports he is now planning to send balloons and even another plane into a thunderstorm to collect more data and get to the bottom of the mysterious antimatter.