Question: could the earth be destroyed by a black hole and what would happen to us as it neared

Susan Cartwright answered on 16 Jun 2015:

It could be, in principle, but the odds against it are phenomenally large. Stars are a very long way apart, and black holes are the remnants of massive stars, which are very uncommon (the vast majority of stars are less massive even than the Sun, whereas the stars that make black holes are about 20 times more massive than the Sun). Based on the population of stars near the Sun, the average time it would take for ANY star to get near enough to the Sun to make a collision probable is about a million billion years, which is 100000 times the age of the universe. The time for a black hole to do so is at least 100 times longer.

So, not going to happen. If it did happen, since black holes are extremely small (typically about 50 km across, although weighing 10x the Sun), the likeliest mode of destruction is not a direct hit, but a near miss. This would break the Earth apart through tidal forces (the gravity on the side of the Earth closer to the black hole would be much larger than on the further side, with the result that the two sides would try to pull themselves apart). It would also wrench us out of our current orbit around the Sun and probably fling us off into deep space, where we’d freeze (if the encounter wasn’t close enough to tear the Earth to pieces).