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Message: <blockquote data-quote="Umbran" data-source="post: 5280532" data-attributes="member: 177">Yes, but here is my point: those rocks did not come from outside our solar system.  They came from within our solar system.Our being hit by "debris" from outside our solar system isn't a realistic risk.  The materials of interstellar space are so diffuse, and our planet is so small compared to the space involved, that the statistics show a collision, even on geologic timescales is just not going to happen.  This is why I say you might not understand the scales involved.  Space is so incredibly huge, and there's so little matter in it, that this just isn't a concern.Now, if you want to say that our sun will be passing through a region in which there are more stars, and one of those passing nearby and might give a gravitational nudge to things in our own Oort cloud and that's a risk, you might have something.Except that the nearby stars are well charted, and their velocities relative to us are known.  None of them are on a path that's going to be an issue in the next few tens of thousands of years, as I understand it. Yes.  And all those rocks are within our solar system.  None are "extrasolar".I will say once more, just to be 100% clear.  Getting hit by something is a notable risk.  Getting hit by an object from outside our solar system is not a notable risk.  You've got the right general idea, but you're attributing a danger from the wrong place.I'm sorry if I seem to be harping on this.  I'm a physicist by training, and when I see policy-influencing misinformation, I feel a bit obliged to correct it.Yes, but objects moving at relativistic speed are few and far between.  More rare than even non-relativistic objects.  While it makes good theater, it is not a realistic risk.If you want death from outside our solar system, worry about gamma ray bursts.</blockquote>

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