cerenkov

7

Scientists Catch The Highest Energy Particles By Making Them Go Faster Than Light

“If you want to catch particles as they were before they ever reached Earth, you need to go to space to see them. But that’s expensive; the Fermi gamma-ray telescope (which detects individual high energy photons, not cosmic rays directly) cost approximately $690 million total. For less than half that cost, you can catch the particles that result from cosmic rays hitting the atmosphere in more than 100 locations across the globe, all because we understand the physics of particles that move faster-than-light through the atmosphere. More than that, the science prospects include understanding the origin of relativistic cosmic particles, the acceleration mechanisms around neutron stars and black holes and might even improve astrophysical searches for dark matter.”

It’s true that nothing can move faster than the speed of light, but only if you’re in a vacuum. Once you’re in a material, like water, glass, or even the atmosphere, all you need to do is make your particles move faster than the speed of light in that medium and all the rules change. By moving faster than light, you force these relativistic particles to emit photons in all directions – Cherenkov radiation – which forces them to slow down. This Cherenkov radiation can be detected by an observatory designed to do exactly this! Since very high energy cosmic rays strike our world and move through the atmosphere, we can detect these Cherenkov photons as their signature, and work to reconstruct where they came from and what caused them.

Ground has been broken just this year on the first telescopes as part of the massive Cherenkov Telescope Array (CTA); come find out what science we’re poised to learn from this massive undertaking!

2

[blue nights]

“In certain latitudes there comes a span of time approaching and following the summer solstice, some weeks in all, when the twilights turn long and blue…

You notice it first as April ends and May begins, a change in the season, not exactly a warming–in fact not at all a warming–yet suddenly summer seems near, a possibility, even a promise. You pass a window, you walk to Central Park, you find yourself swimming in the color blue: the actual light is blue, and over the course of an hour or so this blue deepens, becomes more intense even as it darkens and fades, approximates finally the blue of the glass on a clear day at Chartres, or that of the Cerenkov radiation thrown off by the fuel rods in the pools of nuclear reactors…

The French called this time of day "l'heure bleue,” To the English it was “the gloaming.” The very word “gloaming” reverberates, echoes–the gloaming, the glimmer, the glitter, the glisten, the glamour–carrying in its consonants the images of houses shuttering, gardens darkening, grass-lined rivers slipping through the shadows…

During the blue nights you think the end of the day will never come. As the blue nights draw to a close (and they will, and they do) you experience an actual chill, an apprehension of illness, at the moment you first notice: the blue light is going, the days are already shortening, the summer is gone…

Blue nights are the opposite of the dying of brightness, but they are also its warning.“

-Joan Didion 

[listen]