51–60 of 90 posts
Either there is an abundance of life out there, or we are most likely just experiencing a brief period of lucky safety in a tiny corner of the Universe.
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It is, but on a side note: If you actually had the technology to accelerate to a speed close to light, time dilation might actually allow you to make an intergalactic journey as long as you were okay with leaving behind your home forever... Since a few years for you might be tens of millions of years elsewhere. There is also little matter between galaxies, so the hyper velocity particles problem would be less severe.…
The issue with Fermi's Paradox is the fact that it's not a paradox at all. It relies on assumptions and presumptions that are now dated (we have explanations for). For starters, let's begin with the first point it makes; If there are a bunch of civilizations out there, why haven't we heard them yet? That's the wrong question. It makes an incorrect presumption; Why should we have heard them? Do you think a highly adva…
It does no such thing. Your objections are in fact a possible answer to the "why" posed by the Fermi Paradox, but they are pure guesswork.
The entire point of the paradox is to illustrate that the common (at the time it was formulated) ideas about the likelihood of life elsewhere were clearly wrong in some way or other, but we don't know what we got wrong.
We still don't know what's wrong with them.
I wonder if 500 million years is long enough for an intelligent civilization to come up with some sort of early warning system such as figuring out which stars might be turning dangerous. The article doesn't say how long the bursts last.
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To survive a mass extinction from gamma-ray bursts, a smart species would build a self-sustaining subterranean city with 1 million humans in residence at any one time, perhaps rotating in and out on tours. I'm sure the Chinese will have one within 50 years even if no-one else does. And such subterranean cities are also likely how humans will be living on Mars for thousands of years before it's terraformed.
A subterranean city won't protect your from a GRB.
Is the gamma-ray burst a spherical field, or is it a narrow, directed cone? If the latter, I wonder how the burst spreads/diffuses as it travels and what sort of equation governs the energy flux with respect to distance and initial conditions.
Great question! Since they're emanated in jets, the GRBs travel in a conical shape that spreads out as it travels. Check out page 19 of this paper, it has a histogram of the jet opening angle; http://arxiv.org/pdf/1101.2458.pdf Then you can figure out the flux from the area of a circle on a sphere, which is something like 2πr^2(1−cosθ) Where theta is the opening angle and r is the distance from point of emanation of…
e.g. in a spiral galaxy, do they tend to align with the axis of rotation and so do less damage locally (spray out "up and down" from the galaxy)?
Earlier quoted context omitted.
Great question! Since they're emanated in jets, the GRBs travel in a conical shape that spreads out as it travels. Check out page 19 of this paper, it has a histogram of the jet opening angle; http://arxiv.org/pdf/1101.2458.pdf Then you can figure out the flux from the area of a circle on a sphere, which is something like 2πr^2(1−cosθ) Where theta is the opening angle and r is the distance from point of emanation of…
Do you know if there is any bias to the orientation of the jets? e.g. in a spiral galaxy, do they tend to align with the axis of rotation and so do less damage locally (spray out "up and down" from the galaxy)?
Greg Egan's fantastic Disaspora begins with a GRB hitting earth. It isn't pretty. Hence the title. Best scifi I've ever read.