"The mean free path in air is 68nm, and the mean inter-atomic spacing is some tens of nms about 30, while the speed of sound in air is 300 m/s, so that the absolute maximum frequency is about 5 Ghz."

[–] intensely_human@lemm.ee 1 points 6 months ago (1 children)

The term “mean free path” sounds a lot like an average to me, implying an distribution which extends beyond that number.

[–] Blue_Morpho@lemmy.world 1 points 6 months ago* (last edited 6 months ago)

One cubic centimeter of air contains 90,000,000,000,000 atoms. In that context, mean free path is 68nm up to the limits of your ability to measure. That is flip a coin 90 million million times and average the heads and tails. It's going to be extremely close to 50%.

Not to mention that at 5ghz, the sound can only propagate 68 nm.