Audible Light

800pxpolarlicht_2 Jennifer Ouellette over at Twisted Physics, which has also moved to the Dicsovery News site:

A favorite pasttime in geek culture is pointing out scientific inconsistencies in film and TV shows — you know, like how when there’s an explosion on Star Trek, it shouldn’t make a sound because sound needs a medium through which to propagate, and deep space is pretty darn empty. (Sci-fi author/blogger John Scalzi has aptly dubbed this practice “nerdgassing.”) But a true nerd (ahem) would feel compelled to point out that, when it comes to sounds in space, this isn’t 100% accurate either. Space isn’t completely empty. There are pockets of hot ionized gas (called plasmas) lurking in the atmospheres of planets like Venus and Mars, or the moons of Jupiter, for instance.

And there’s the Earth’s atmosphere, which is a notorious emitter of something called Auroral Kilometric Radiation (AKR), a phenomenon first discovered by satellites in the early 1970s. It’s basically radio waves generated high above the Earth, caused by the same shower of solar particles that give rise to the aurora borealis (“northern lights”). So, if Captain James T. Kirk and the Enterprise crew were approaching the Earth (or Jupiter, or Saturn, which also have auroral displays and accompanying AKR) from space, most likely the first thing they’d hear would be these bizarre chirps and whistles.

For decades, astronomers monitoring the radio emissions assumed the signal propagated outward in an ever-widening cone, just like the light from a flashlight. But a new analysis by the European Space Agency’s Cluster mission shows that actually, the AKR is beamed into space in a very narrow path. Imagine placing a filter over your flashlight so the light could only emerge in a narrow slit. This is a boon to astronomers, since it enables them to trace the source of these emissions, according to Robert Mutel of the University of Iowa, a member of the three-year study. This, in turn, will make it easier to search for similar planets around other stars that might possibly harbor some form of life.