Re: MEDIA: NOVA on Gamma Ray Bursters

From: Robert J. Bradbury (
Date: Wed Jan 09 2002 - 23:18:30 MST

On Wed, 9 Jan 2002 wrote:

>        John K Clark      wrote
> "I don't see how Gamma ray Bursters could explain the Fermi paradox.
> A burst only lasts a few seconds so half of the planet would be
> shielded by 8000 miles of rock. There would be survivors."
> Yea, I thought the same thing, gammas are absorbed by meters of rock and iron
> etc, so why would it torch everything? They implied in their graphic that
> the atmosphere would all be ionized, perhaps around the globe.... someone
> has modeled this?

Go read the daXn paper. I think its only come across the list
3 times at this point.

The gamma rays, which I think are put out spherically only
cause severe damage to "nearby" planets -- and you are right
the shielding would help on the far side of the planet.

Its the cosmic ray "jets" that pack a larger effective radiation
dose and arrive over a much longer period (so the planets get
fully irradiated as they rotate into the "wind") that are the
*real* problem. As their radiation dose is higher they harm
planets further away -- but because they are directional
they only harm systems in directly in their path.


This archive was generated by hypermail 2.1.5 : Fri Nov 01 2002 - 13:37:33 MST