Physics
Refraction of Sound Waves
Quick fact
On a cool, overcast night, sound can refract downward and travel twice as far as on a hot, sunny day—explaining why trains or distant conversations seem unusually loud then.
Why this is interesting
Ever noticed how a straw looks bent in a glass of water? Sound does something similar when it passes through air of different temperatures—except instead of seeing it, you hear it. Could this bending explain why sound sometimes seems to disappear or travel surprisingly far?