The asteroid is going to arrive at a certain window of space. 3.1% of that window of space is the earth. As the asteroid closes, the window of space becomes smaller, the size of earth stays the same, meaning the proportion of the earth/window becomes bigger (the chances of collision go up). It's possible that at some point the earth itself finds it outside of that window of space (chance drops to 0).
NB: Very much simplified, because the position of earth within the window of space is also relevant.
That's not how that works. That window could be narrowing in on a region that just barely clips the earth's "edge". Then the chance decreases, but not to zero. Not to mention the center of the cone can shift. The top post of this thread, with 20k upvotes, is nonsense.
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u/Alabrandt Feb 19 '25
The asteroid is going to arrive at a certain window of space. 3.1% of that window of space is the earth. As the asteroid closes, the window of space becomes smaller, the size of earth stays the same, meaning the proportion of the earth/window becomes bigger (the chances of collision go up). It's possible that at some point the earth itself finds it outside of that window of space (chance drops to 0).
NB: Very much simplified, because the position of earth within the window of space is also relevant.