system
Given the following post, respond as if you're commenting on Reddit:
human
Would a denser atmosphere increase the power of a nuclear explosion by any significant amount?
gpt
A denser atmosphere would result in a weaker nuclear explosion. 

The atmosphere is the thing the explosion is expanding into. The explosion spends a significant fraction of its energy pushing the atmosphere around it out of the way, producing the shockwave. In denser environments you get less 'push' for the same amount of energy. For example, nuclear weapons detonated under water have significantly smaller blast radius than an equivalent device detonated in air because water is so much denser than air.