"Tim Killian" wrote in message
...
You're forgetting the effects of charged particles and neutrons that
would arrive after some years after the initial burst of neutrinos and
photons. These particles travel slower, but when they arrived at Earth,
the effect would be serious.

Atmospheric gasses would be transmuted into radioactive isotopes with
half lives of decades or more and because of the high, persistent
radiation levels, there would be little chance of survival for many
species. On a more positive note, since we'd have at least 10-50 years
warning, we could gather up asteroid belt material and build a 2
km-thick shield with a diameter of 15000 km (+/- !) to shadow the Earth
from the stream of particles ;-)

Bottom line is a supernova would have to be 50-100 ly distant for
minimal effects from the heavier particles.

Good points here and that's what I was thinking about initially- the long
terms effects. Yes, we would survive initially, but for how long
afterwards?

Jason


Michael Barlow wrote:
I asked a similar question probably about a year ago. I was given a
link to a site that described all the variables and came to a conclusion
that a star would have to be something like three light years or closer
before any possible damage could occur to us. If I find that link I'll
post
it.