Air is a seething low-density molecular gas with constant collisions

Evidence

Then the golf balls will start moving with a velocity away from each other in order to get to the rarefacted state. Again the velocity toward the golf balls will become zero at the trough of the rarefaction. The velocity does not switch instantly from one direction to another, due to the inertia of the molecules involved; instead it accelerates smoothly from a stationary to a moving state and back again. The velocity component reaches its peak between the compressions and rarefactions, and for a sine wave displace­ ment component the associated velocity component is a cosine. — David Howard, Jamie Angus, coustics and Psychoacoustics, 144 (#expands, via linked claim)

What I am learning now is that far from being empty, space is full of stuff. And some of it even qualifies as sound. — George Michelsen Foy, Zero Decibels, 270 (#qualifies, via linked claim)

Categorization

• XREF: connects to: Molecular inertia makes air particle velocity change smoothly and continuously — David Howard, Jamie Angus, coustics and Psychoacoustics, 144; A barely audible sound moves air only a few atoms’ width; Coherent scattering among tightly packed molecules enables clear vision. — Eric J. Heller, Why You Hear What You Hear- An…, 2635 (+2 more)

Related

• Molecular inertia makes air particle velocity change smoothly and continuously (similarity 0.86)
• Air molecules collide billions of times per second yet occupy little volume (similarity 0.85)
• Interstellar space is not a true vacuum but full of particles (similarity 0.83)
• A barely audible sound moves air only a few atoms’ width (similarity 0.83)
• Sound wave molecules have zero velocity at compression peaks due to inertia (similarity 0.79)

Broader Connections

• Molecular inertia makes air particle velocity change smoothly and continuously #expands (0.90) — David Howard, Jamie Angus, coustics and Psychoacoustics, 144
• A barely audible sound moves air only a few atoms’ width #expands (0.85)
• Coherent scattering among tightly packed molecules enables clear vision. #expands (0.80) — Eric J. Heller, Why You Hear What You Hear- An…, 2635
• Interstellar space is not a true vacuum but full of particles #qualifies (0.80) — George Michelsen Foy, Zero Decibels, 270
• Molecular interaction prevents sound pressure from cutting off sharply at edges #expands (0.75)