“And just to get this out of the way, we’re in no danger from this explosion. It’s far too far away.”
Also, it happened 12 million years ago, so I think we are pretty safe.
Also, it happened 12 million years ago, so I think we are pretty safe.
That said, it also means we can probably skip that half of galaxy M82 in our search of extraterrestrial intelligence. For the planets that were within a few light years of the supernova, they probably lost anything that wasn't bolted down in terms of atmospheric gases :-).
You are correct that we are safe because of energy dispersion - or, put another way, because it is 12 million light-years away. But nmc thought we were safe because it was 12 millions years ago, and gabipurcaru tried to show by analogy why that is not true.
EDIT: For the follow-up questioning the correctness of my comment:
https://en.wikipedia.org/wiki/Inverse_square_law#Light_and_o... https://en.wikipedia.org/wiki/Radiative_flux
Speaking of archivists:
http://sci.esa.int/rosetta/31242-rosetta-disk-goes-back-to-t...
http://blog.longnow.org/02009/05/21/what-13500-pages-micro-e...
(this is the object of yesterday's HN story https://news.ycombinator.com/item?id=7092313)
But worry not! A bullet fired from 12 million light years away would probably be ablated into nothing by the interstellar dust.
Stop and think about the fact that starlight can travel that distance. Therefore the accumulated dust along that path is not enough to block light. That little dust won't stop a bullet either.
I can see starlight from the bottom of a pool, but the water in the pool will still stop a bullet.
(I am not a scientist, I could be entirely wrong, but it seems like the collective dust of 12 million light years would surely ground down a bullet, while being intermittent enough to let starlight pass through in aggregate.)
The collective dust of 12 million light years of intergalactic space does not seem likely to grind down a bullet very much.
That said, the whole calculation is flawed because first you have to get out of our galaxy, which is much higher density. Though that also wouldn't stop a bullet. But then you have our atmosphere, and that most definitely would destroy a bullet that tried to pass through it!
But the moral remains. Space is empty. Really empty. Unimaginably so.