One of the more interesting things about paying attention to new science releases is watching our knowledge grow. Bearing in mind that many of the books that I read growing up were not published that year, I’ve watched our knowledge about the age of the universe, the origins of the planets, and even theories of where our moon came from get changed and solidified as new info poured in from space exploration. I got to see man walking on the moon, Skylab, Viking, Mir, watched the shuttle develop… it’s a trip.
And so is this. A couple of decades ago, astronauts reported seeing flashes extending upwards from the tops of thunderheads, confirming a few reports from airline pilots of the same thing, which had been roundly dismissed by meteorologists at the time – there was no mechanism nor reason for lightning discharges to travel upwards into the rarefied atmosphere.. Eventually, both photos and video were obtained, from shuttle flights and residents on the various space stations, and the phenomenon gained more attention.
Just days ago, it got a lot more interesting. The Fermi Gamma-ray Space Telescope has been monitoring gamma ray bursts from all directions since its launch, and one of the directions it was receiving rays from was the tops of thunderstorms (it was intended to be monitoring space, but hey, you pay attention to whatever you get.) Now, they got something even more: direct evidence that the gamma rays produced by thunderstorms are giving birth to antimatter.
Definitely check out that link for some great video and explanations. Basically, lightning is sometimes powerful enough to produce not just an electrical charge and ionized particles, but gamma rays as well. And the gamma rays occasionally interact with atoms in the atmosphere and produce a pair of particles: an electron (negative charge) and its antimatter evil twin, a positron (positive charge.)
If you remember your physics (I just barely know enough to get all this,) antimatter is rare, and on contact with normal matter, they react and annihilate each other with a tremendous burst of energy for their mass. Science fiction back from the fifties to the seventies was full of uses for antimatter, but it’s not exactly easy stuff to handle, and it takes a lot of energy to produce in decent quantities – we generally use cyclotrons and particle accelerators (like the Large Hadron Collider) to create just a smidgen of it, at a ridiculous cost that makes it impractical to consider for those uses.
Here’s the cool part. The Fermi telescope registered it all because the antimatter followed Earth’s magnetic lines, and just so happened to be whipping past in this natural highway just as Fermi was. The antimatter contacted Fermi and reacted with electrons orbiting atoms that made up Fermi’s structure. The resultant burst of energy, also a gamma ray, registered on Fermi’s own detectors. In other words, Fermi detected its own “blood” as it was shot by a positron stream. And not once, but twice, as most of the stream whipped past/through, hit a “mirror” point someplace downstream in the magnetic field line (I don’t pretend to understand this,) and came back past again milliseconds later. Fermi was shot coming and going, struck by both the initial round and the ricochet. In true movie hero style, Fermi is plugging away with two infinitesimal bulletholes in it (actually, more than that – Fermi has detected antimatter five times now, and the collision was likely from a stream of positrons rather than a single antibullet.) Don’t let me give you the wrong idea – we’re still talking teeny tiny here, and Fermi has undoubtedly taken more damage from colliding with interstellar dust than those antimatter bursts.
It’s startling the amount of energy that’s routinely being discharged here, and interesting to consider the process. Atmospheric temperature differences and humidity create charged areas within storms that discharge as lightning (it’s still not really known exactly how this works,) and this can create an electron flow upwards. The electrons accelerate, and contact with atoms emits gamma rays. Subsequent contact with atoms by these gamma rays creates an electron/positron pair, and subsequent contact of those positrons with electrons again creates gamma rays, again. And we detect the gamma rays by the energy they dump into electrons. It seems very circular, but really, electron interaction with energy is key to damn near everything – you’re reading this through a much more convoluted path utilizing a few trillion electrons. We should have a National Electron Day…
Thanks to Jen at Skepchick for the link.