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Re: starship-design: Fermi's Paradox - Drake's Equation will have to be rewritten

Hi Group...

----- Original Message -----
From: L. Clayton Parker <lparker@cacaphony.net>
To: Starship-Design <starship-design@lists.uoregon.edu>
Sent: Thursday, January 28, 1999 12:16 PM
Subject: starship-design: Fermi's Paradox - Drake's Equation will have to be

>This was published last week and presents an interesting solution to the
>discussion we once had regarding drake's Equation....
>Gamma-Ray Bursts May Explain SETI Silence
>Published: 1999 January 21
>11:31 pm ET (0431 UT)
>Powerful blasts of radiation from an enigmatic astronomical phenomenon may
>explain why we have not yet seen evidence of extraterrestrial intelligence,
>one scientist has concluded.
He's not the first - I thought of it over a year ago... but if you don't
publish you can't claim priority. Damn.

>In an article to be published in the January 23 issue of the magazine New
>Scientist, Fermilab astrophysicist James Annis explains that gamma-ray
>bursts (GRBs) may have inhibited the development of intelligent life in the
>early universe.
Has been published, it's on the Web... very interesting - is it enough?

>"If one [GRB] went off in the Galactic center," Annis said, "we here
>two-thirds of the way out on the Galactic disk would be exposed over a few
>seconds to a wave of powerful gamma rays." Such radiation would be lethal
>life on land, he believes.
Consider when it might have happened last near enough to affect life on
Earth... ? Like when? I have a couple of suggestions - about two billion
years ago, quite close; and about 250 million, not so close. The first
relates to a study which dated the divergence of life from a common ancestor
~~ 2 billion years ago - that conflicts with every fossil from prior to that
time. But what if a GRB had wiped out all but one species? The other date is
the great Permian extinction, which wiped out most life on land and in the
sea. It's been tied to a catastrophic overturn in the ocean that released
huge amounts of CO2. Earth at that time had one continent and a global
ocean. If the GRB hit the ocean side then life wouldn't notice it much - but
what if that acted as trigger for the overturn? Some change in acidity or
greenhouse processes from massive amounts of upper atmospheric chemistry,
which changed the thermal balance of the ocean...

>GRBs occur in galaxies only once every few hundred million years today, but
>some theories suggest GRBs were more common in the early universe. Since a
>single GRB is powerful enough to sterilize nearly an entire galaxy, it may
>be only now that conditions have permitted the development of intelligent
>life here and elsewhere in the universe.
>"The GRB model essentially resets the available time for the rise of
>intelligent life to zero each time a burst occurs," Annis said.
>Such an explanation may be a solution to a half-century-old question on why
>we have not seen evidence of extraterrestrial life. The problem, proposed
>Nobel laureate physicist Enrico Fermi and dubbed the "Fermi Paradox", notes
>that a civilization traveling at only one-thousandth the speed of light
>could traverse the galaxy in 100 million years, far less than the age of
>galaxy or the universe. "Where are they?" Fermi was said to have asked
>GRBs, which may be caused by the collision of neutron stars or black holes,
>can release as much energy in a few seconds as a supernova. That short
>timescale could work against the theory, British physicist Paul Davies
>points out. "If the drama is all over in a few seconds, you only zap half
>the planet," he said. "The planet's mass shields the other side."
>Secondary effects from the blast, such as the destruction of the ozone
>layer, may be enough to wipe out life on the rest of the planet, Annis
Probably not, but it'd disrupt a hell of a lot enough to cause a mass
extinction in one hit.
>Lee Parker
If anything is a strong argument for a galaxy-spanning civilisation it's a
GRB - if you want to think in the long term and survive then GRBs need your
attention. How do you stop them? By knowing how they form for starters. No
one is still too sure.