OT: Galactic sterilisation

[JurijD]

Originally posted by oleg:
Even if these calculationa are correct, you underestimate the effect of 100 LY. Simple calculation reveals 10^30 attenuation factor. At worst it will be like radiation 1000 km away from the bomb. Extensive hydrogen bomb tests in 50s and 60s proved that there is nothing to fear

Besides, the time duration odf star collapes is surely much longer than H-bomb explosion and the _intensity_ of the radiation will be very small indeed.

You are so wrong Oleg... As I said they calculated that the intensity of the radiation over a couple hundred light years will be enough to kill us. I didn't underestimate the distances and neither did they. You on the other hand seem to have underestimated the ammount of gamma radiation that is released when all the outer material of a star if transormed into pure energy...

And u obviously didn't do those simple calculations you mentioned either. Lets assume this:

1. at a distance of 10km from the center of an explosion of an H-bomb the radiation IS LETHAL (we can all agree to that).

2. Lets say that the density of radiation comming from that H-bomb explosion at 10km distance is J1 = P/S1 (J1 being the density, S1 the surface area of a sphere at 1km and P the power output of the bomb)

3. At a distance of 100 Light years from the H-bomb the Density of radiation would therefore be J2=P/S2 where S2 is the surface of the radiation sphere at (9,4608*10^14 km = 100 light years)

As J2*S2=J1*S1, J2=J1*S1/S2, J2=J1*R1^2/R2^2
R1=10km
R2=9,4608*10^14 km

J2 is about 10^28th smaller than J1. that means that if we had an explosion 10^27 biggeer than that H-bomb we postulated could kill us at 10km, our dosage at 100 light years would be something like 10% of the dosage we get standing 10km from an H-bomb explosion.

To put it another way... if a back hole goes off somewhere in the distance of 100 light years we get the same ammout of radiation as if we were standing 30km from the center of a H-bomb explosion. (do the math yourself if you want).

And we musn't forget that these explosions don't stop in a few hours or days but can Last up to several decades or even more... The cumulative effect of that kind of radiation on the biosphere over so long would be devastating to say the least. And I was calculating for 100 light years... the systems at less than 50 or so would get totally fried anyway.