@NickSeam My understanding is that while in the "galaxies colliding" scenario above, it would be possible for an astral body of significant enough mass to end up much closer to us in an absolute sense, there's just so much *space* in space that the odds are still very good there'd be only a negligible effect.
If, for instance, an entire solar system somehow passed within half the distance to our current nearest neighboring system, that would put its star ~2x10^12 miles away. But Neptune's orbit is only ~3x10^9 miles from the Sun, so the rogue system would still be ~700x father away. Yes, the Oort cloud(s), etc. would extend well beyond that, but still have more than a light year between them in this back-of-the-napkin example. And the inverse square law of gravitational fields means we wouldn't feel pulled skyward, as cool as that sounds.
I agree, it sure *looks* like impending doomsday, but I think that's mostly the unimaginably distorted physical and time scales.
That gif's field of view is maybe 400,000 light years, or 2.4x10^18 miles, across, and I'd guess 1 sec. = 1 billion years. So we've got a) room and b) time.
What we should be worried about are local NEOs, and the fact that we've got less than 2% of the sky under watch for them. Remember Chelyabinsk? Imagine that, or an actual big one, happening over London, New York, Tokyo, etc.
http://www.nasa.gov/mission_...
If, for instance, an entire solar system somehow passed within half the distance to our current nearest neighboring system, that would put its star ~2x10^12 miles away. But Neptune's orbit is only ~3x10^9 miles from the Sun, so the rogue system would still be ~700x father away. Yes, the Oort cloud(s), etc. would extend well beyond that, but still have more than a light year between them in this back-of-the-napkin example. And the inverse square law of gravitational fields means we wouldn't feel pulled skyward, as cool as that sounds.
I agree, it sure *looks* like impending doomsday, but I think that's mostly the unimaginably distorted physical and time scales.
That gif's field of view is maybe 400,000 light years, or 2.4x10^18 miles, across, and I'd guess 1 sec. = 1 billion years. So we've got a) room and b) time.
What we should be worried about are local NEOs, and the fact that we've got less than 2% of the sky under watch for them. Remember Chelyabinsk? Imagine that, or an actual big one, happening over London, New York, Tokyo, etc.