What would happen if a teaspoon of neutronium crashed through Earth's atmosphere? Pretty self explanatory hypothetical.  I realize this is probably an impossibility and maybe it'd be more likely to be hit by a small black hole or primordial black hole. I'm just curious, because we always talk about how much a teaspoon of neutronium would weigh on earth.
 A: The teaspoon of neutronium would have a mass of about $10^{12}$ kg.
Due to it's small size (and area), the pressure caused by the impact would be very high, so it's likely to plough straight through the earth and out the other side.
It depends on the velocity, but things coming from space are usually moving fast.
As the earth has a mass of $6\times 10^{24}$ kg the orbit of the earth wouldn't be changed much.
A: You haven't specified the speed of impact but it is reasonable to assume that it wouldn't be much less than the escape velocity of the Earth - about 25,000mph. I've just done a calculation of the kinetic energy based on 5 cubic centimetres and the result wouldn't be good for the nearby inhabitants. I make it about $3.1$x$10^{19}$ joules, which is equivalent to a 7400 megaton nuclear explosion. i.e. about 150 times the most powerful bomb ever detonated (the Tsar Bomb). However, the impact of the meteorite that was responsible for the extinction of the dinosaurs is believed to have been equivalent to 100 million Tsar Bombs.
