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Comment by TeMPOraL | Hacker News Reader

I read once about gamma ray bursts [0] which happen pretty frequently out there; we detect them every day in other galaxies. If any such event occurred near us (by near I mean anywhere in the vicinity of our galaxy) and the Earth was in the path of the beam, it could do anything from destroying the ozone layer to burning away every trace of life from the surface.

The scary thing is that, like with starquakes, we can't dodge it. The effect moves with the speed of light; when we detect it, it's already too late for us.

So between GRBs and starquakes, what else is there that can snuff us out without warning?

[0] - http://en.wikipedia.org/wiki/Gamma-ray_burst

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If you're into worrying about catastrophic existential threats, you'd be hard pressed to do better than Vacuum Instability: http://en.wikipedia.org/wiki/Vacuum_instability#Vacuum_metas... ...especially worrying because the recently confirmed mass of the Higgs puts us firmly in the realm of "well, it could happen".

It is worth noting, however, that a region of lower vacuum energy does not actually expand at lightspeed- merely near the speed of light (and exactly how near depends on the details of the vacuum inside the bubble), due to the fact that domain walls have mass-energy. So, if it happens sufficiently far away, we could in theory actually notice it happening before it killed us, unlike a gamma-ray burst.

Yes, but unlike a gamma-ray burst, there is literally no hope of survival. With a gamma-ray burst one could, in theory, survive given an ultra-shielded structure with full life support (to offset the lack of atmosphere and any other life on the surface once the burst passed). If a region of lower vacuum energy were headed our way, it would completely change the very physics we know of down to the sub-subatomic level. Ain't nothin' standing in the way of that...

So supposing it happened a billion light-years away, based on our best guess at the relevant physics, how much warning would we have and what would that warning look like? (Not that it would do us any good in any event, of course. I'm just asking out of morbid curiosity.)

... "Welp, all of existence will be totally annihilated in 2 years".

Yeah, that's not better.

I thought I recognised that from the Stephen Baxter/Arthur C. Clarke book "Time" - well worth reading.

I thought you might like this: http://qntm.org/destroy

From the very page you linked:

most GRBs are billions of light years away from Earth, implying that the explosions are...extremely rare.

There are things to worry about, and things not to worry about. GRBs seem to be fairly squarely in the 2nd camp.

Even if they were a possibility near here, they're so far beyond our capabilities that it doesn't matter. We'd never be able to do anything about it.

The strength to change what I can, and to accept what I can't...

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