[ExI] Panbiogenesis

Keith Henson hkeithhenson at gmail.com
Thu Jan 26 17:10:23 UTC 2012

On Thu, Jan 26, 2012 at 5:00 AM,  "spike" <spike66 at att.net> wrote:
> On 25/01/2012 14:45, The Avantguardian wrote:
>>> Well at 400,000 g's acceleration, I was thinking more about supernovae
>>> shockwaves than meteor impacts. But I agree that the evidence is tenuous.
>>Well, in supernovae the problem is heating rather than acceleration...
> I haven't done the calcs on this, but a supernova would also send out an
> enormous wave of neutrinos.  The tiny fraction of them that interact with
> the matter in the life forms would cause all manner of problems, ja?
>>...I wonder if anybody has run a hydrocode on what happens to a terrestrial
> planet subjected to its sun going supernova? It would be interesting to see
> if any material is ejected that is not subjected to extreme heating and
> radiation... Anders Sandberg
> Life on the night side at the time of the supernova might have a chance
> against everything except the neutrinos, which would pass through the planet
> and zap everything, regardless of the size of the planet.  I'm pretty sure a
> supernova sterilizes everything in the stellar neighborhood.

The distance is usually quoted as 30-50 light year.   Taking 10 gray
as lethal, i.e., 10 j/kg, the flux would be 1000 j/kg at 3 light year,
100,000 j/kg at 0.3 ly.  Taking the specific heat capacity of typical
stuff at 1 kJ/kg deg K, rocks and such would heat up by 100 deg out to
0.3 light year.

Three tenths of a light year is ~20,000 AU.  The energy dumped in a kg
of material at 1 AU would be 400 M times as that of at 0.3 light year,
or around 40 B j/kg or around 20 M kWh/kg, or something around a
million times the energy released in the formation of of the earth.
The reasonable assumption is that a planet at earth's distance from a
supernova would blow up spectacularly from the neutrino flux, if it
were not totally eclipsed by the supernova glare.


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