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?
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.)
Would it be possible to tell when such events happened far into our past? I'm curious if such an event could trigger a mass extinction [1] on Earth ... and if any of the 5 previous mass-extinctions [2] might coincide with one.
Probably not from one of these magnetar quakes. The one described in the articled released 10^39 J of x-rays; the typical gamma-ray burst is estimated to be 10^44 J, and moreover, concentrated in a narrow beam. If you're in the path of a GRB, it's looks as bright as a 10^45 - 10^47 J isotropic source.
So, if the article you link to estimates a GRB would be an extinction event within <6,000 light years or so, you could extrapolate that a magnetar quake, 10^7 times weaker, would need to be 10^3.5 times closer, that is, within 2 light years. There's zero magnetars in that range for sure.
Then again, Phil Plait is taking about much lesser effects like damaged satellites. He calculates this could happen at 5,000 light years from a magnetar; that implies (flipping my calculation around) that a GRB could do that all the way from another galaxy (..if it's a "nearby" galaxy).
Does this imply that the 1806-20 event occurred ~50,000 years ago and only just reached us ten years ago?
"In December 2004, the magnetar SGR 1806-20 underwent such a starquake." <- Makes it sound like the effect on Earth was instantaneous but I imagine that is impossible.
Relativity kind of messes with our notions of time.
Any event that happens outside of our lightcone (http://en.wikipedia.org/wiki/Light_cone) cannot have any casual effect on us, even theoretically, until it enters our lightcone. Before then, the event literally doesn't exist from our point of view. Because of this, it's reasonable and valid to take the position that distant events "happen" when we're first able to see them happen. It's not the only perspective you could have, of course, but it can be a useful one and astronomical events are often discussed this way.
That's not true if faster than light travel is possible (e.g. wormholes, warpdrives, any form of time travel, etc.) And even so, it doesn't make a lot of sense to redefine time that way. It would be like a pre-electricity civilization declaring that things outside their mail-cone (how fast mail can travel) haven't actually happened yet.
Civilization destroying starquakes, wow! It's amazing to consider that since such a thing could theoretically happen, then in the infinite stretch of time and space, then such a thing certainly has happened, many times over.
Doesn't the fact that we have actually observed this happening anywhere in the universe mean it's basically a "regular every day" event?
The universe is seriously incredibly hostile to life... and yet here we are!
But then again, how about another way to try to gauge the treat in terms we can actually comprehend... What percent of the known universe would be within the 'kill zone' of a starquake over the course of, let's say, 1 billion years?
