Letter: Nuking asteroids

From David Giles

We cannot push asteroids away with nuclear explosions (26 September, p 30).

A nuclear explosion on Earth heats up and vaporises everything around it, producing a powerful shock wave. Space is a vacuum, so there is nothing to vaporise and heat except the bomb casing. All the energy from the nuclear explosion stays as electromagnetic radiation, which doesn’t push.

It may heat up or even vaporise part of the asteroid, though, if it’s close enough.

The editor writes:

• A nuclear bomb detonated above the asteroid will vaporise its surface, thereby changing its momentum and nudging it onto a safer trajectory.

Ulverstone, Tasmania, Australia