system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why is it more devastating to detonate a nuclear bomb at a distance above ground, as opposed to directly at ground level (upon impact) ?
gpt
If you detonate a bomb at ground level then a lot of the energy is spent digging a hole which is useless. You want the bomb to have a clear line of site to a large area for effective destruction

It's also important to note that if a 10 PSI overpressure will collapse most reinforced concrete structures then there isn't much value in hitting them with a 50 PSI overpressure, they're collapsing either way. Nuclear bombs are generally detonated at a height that maximizes the range of their 5 PSI overpressure which will knock down most structures and is almost universally lethal

There's also an interesting effect where the shockwave hits the ground and then bounces back up still expanding. This means that the edges of the shockwave are extra strong because they're the combination of the initial shockwave coming outward from the bomb and the shockwave reflecting off the ground. This results in extra damage and increases the radius of the 5 PSI overpressure.