"Destroying" the earth with nuclear weapons

[Nephtys]

Question: someone suggested Asteroids, but what happens if nuclear warhead were accelerated to relativistic velocities then set off? Assuming the warhead survives the trip and doesn't blow up prematurely because the plutonium got too energetic?

At above 3000 km /s relative difference, your 150kt block of lead is going to have about as much energy as a 150kt nuclear bomb. (http://www.projectrho.com/rocket/rocket3x.html). At such a velocity, you don't need a warhead. Especially not on something as massive as an asteroid. It'll probably be nastier as well, given the various inefficiencies of a nuclear blast.

Are you sure it is not 3000 m/s ?

Ah right. It is. Whoopsie. 3000km/s would make a 1 ton block of lead have something like 900kt of energy.

[lance]

One famous idea that started a lot of this 'we can nuke ourselves to death' talk is the old notion that mankind has enough nuclear weapons to 'kill everyone on earth five times over'. We've all heard of that one. It's of course, based on not one or two, but many many silly notions.

First, it assumes all 6 billion people will gather in circles precisely in the same population density as 1945 Hiroshima. Then, the number of kilotons in all the combined world arsenals will be divided by 15 (the yield of the Hiroshima bomb) and multiplied by how many people died. The end result is about 30 billion, thus the 'we'll kill everyone 5 times over' spiel.

Of course, this is unrealistic. a 100 kiloton bomb does not have a destructive radius of 10 times a 10 kiloton bomb. It's about twice. Not to mention getting populations in that distribution is intensely unrealistic, or how exactly you divide a single megaton bomb exactly into so many 15 kiloton ones.

I imagine if we had the people stand in spheres it would be easier.