Gamma Ray Bursts

February 18, 2004 11:38 AM

Arthur C. Clarke once proposed that gamma ray bursts could be a sign of interstellar warfare (he later changed his mind). What would happen if a GRB struck Earth?
posted by Termite to science & nature (10 comments total)

It depends. According to this gamma radiation can penetrate meters of air or centimeters of flesh. There's around 1500 kilometers of air above the earth's surface. You'd need a tremendous amount of gamma radiation to cause damage so it's unlikely to be a concern. If something happened that caused an alarming amount of radiation to reach the earth's surface then the cause of the radiation would be the most immediate concern.

I guess the easiest way to put it is this: Don't worry about radiation if you're at ground zero when the bomb goes off.
posted by substrate at 12:17 PM on February 18, 2004

From reading hard SF books by the likes of Greg Egan, I recall that a GRB originating from as far as a few thousand light years away from Earth would essentially sterilise the entire surface. Here's a link to talk about whether a GRB killed the dinosaurs (probably not, but if one was nearby it could've done the job). Here's another article from Scientific American attesting to the potency of GRBs.
posted by adrianhon at 12:23 PM on February 18, 2004

Not just the surface.

Stephen Baxter wrote (in "Manifold: Space") that gamma rays from GRB detonations could penetrate "several hundred meters of concrete or lead," and the whole book is premised on the assumption that supermassive GRBs represent sterilization events for volumes of space many tens of lightyears across.
posted by adamgreenfield at 12:48 PM on February 18, 2004

BTW, I believe I've read that, due to their low but unpredictable frequency and off-the-top-of-the-scale lethality, you technically have a higher chance of being killed by a GRB than by a domestic accident, homicide, etc.

A thought.
posted by adamgreenfield at 12:49 PM on February 18, 2004

Sweet. I'm going to go strip naked and max out my credit cards
posted by keswick at 12:55 PM on February 18, 2004

From the Scientific American article Adrianhon posted, "If the burst radiated its energy equally in all directions, it must have had a luminosity of a few times 10(45 power) watts, which is 10(19 power) times as bright as our sun."

off-the-top-of-the-scale indeed.
posted by jazzkat11 at 1:14 PM on February 18, 2004

Statistically, assuming isotropic emission, the observed event rates and fluxes imply that one event occurs per 10^4- 10^6 years per galaxy, with about 10^51- 10^53 ergs in gamma-rays emitted per event. Unless the Milky Way is unusual, a gamma-ray burst should occur within 10^2 - 10^3 pc of the Sun in a time span of order 10^8 years.

There's an interesting calculation waiting to be done here which incorporates these estimates, star density distributions in a galactic disk, and the expected time it takes for intelligent life to form (~10^9) which should show that Life has almost no chance to develop too close to the dense galactic core but exists on the fringes, like us, in the outer arms.

I'd do it, but i gotta run...
posted by vacapinta at 1:28 PM on February 18, 2004

Wouldn't we all turn into The Hulk?
posted by jpoulos at 1:54 PM on February 18, 2004

Not answering the question here-perhaps this is what originated the question- but Clarke has a current short interview in the Onion A.V. Club where he says he thinks that they are a sign of something else:
"No, no, I've changed my mind. I think they're industrial accidents."
posted by superchris at 4:39 PM on February 18, 2004

But who will think of the man-in-the-moon marigolds?
posted by dhartung at 9:19 PM on February 19, 2004