Why doesn't sound travel at the speed of light?

Question

Since soundwaves are massless, why doesn't sound travel at the speed of light?

In that case, does sound travel at the speed of light through a vacuum? Or is sound unable to move through a vacuum?

Answer 1

You are right that the 'wave' is massless, but you must remember this:

The sound wave is caused by the displacement of molecules (in air, water or whatever) and those molecules do have mass. If the sound was the displacement of massless molecules (that do not and cannot exist) then yes, sound would travel at the speed of light. However, because the molecules being periodically displaced have mass (technically the inertial mass) the force that moves them produces a finite acceleration (F = ma) which means that the velocity change occurs in a given time and does not occur instantaneously (as would be the case for a zero-mass molecule).

This is why light can travel at the highest-possible speed (the speed of light): there is no displacement inertial mass because the displacement is of the electromagnetic field and not of any molecules.

ASIDE: Interestingly, if you do consider a molecule of zero-mass the formula F = ma breaks down (the acceleration would need to be infinite). Instead, you must take into account the relativistic effects of accelerating bodies.

PS: Jerry P, there is a 'quantum of sound' called the phonon. It relates to the lowest possible energy state of lattice vibration that a solid (or indeed a liquid but not a gas) can support.

PS: Arnie, you are right that phonons were transmitted at light speed BUT this was in a superconductor and, in this case, the phonons were coupled with the electron-electron pair such that, essentially, the lattice wasn't vibrating at all but the momentum change was being carried in the virtual exciton. It isn't quite the same as getting 'sound' to travel at light speed.

Answer 2

i've got self assurance the explanation why sound waves holiday slower than easy waves is by technique of their mechanics, and that they way they holiday. Sound waves are regularly varieties of severe and/or low speed vibrations that holiday by a medium, be it air, wood, water, steel or bone. with a view to holiday, it may desire to have some thing in which it vibrates (think of molecules). the cost at which the wave travels is set by skill of ways the molecules are arranged - the greater tightly-packed the molecules are, the less they vibrate, and the slower the sound travels. Molecules circulate quickest as a gasoline, so the quickest that sound can holiday is the quickest a particular gasoline's molecules circulate. watching easy, that's the two an electromagnetic wave, and a particle (do no longer ask, it extremely is complicated). It would not want a medium to holiday by, so even interior the vacuum of area easy travels (that's additionally why there's no sound in area!). easy waves have not any truthfully mass, and as a result holiday very, very rapid. in fact, no longer something can holiday swifter than easy, (with a view to holiday swifter, it may could desire to have detrimental mass, it extremely is, weight below 0). as a result, sound won't be able to holiday on the cost of light, because of the fact the cost of sound is constrained by skill of the will for a medium to holiday by.

Answer 3

Because only electromagnetic waves travel at the speed of light, sound is a mechanical disturbance and usually only travels as fast as the vibration that causes it, and slower in some cases because it cannot propagate that fast ... as in the waves building up to create a sonic boom because the first waves go slower than the jet plane that keeps piling the waves up on the leading edges of the plane.

Answer 4

Sound waves require a medium for propagation. Light does not.
In a real manner of speaking, sound waves *are* a property of the medium in which they propagate. For example it is air that moves the tympanic membrane to transduce sound waves in the human ear. Sound waves do not have a wave-particle duality; there is no smallest quantum of sound. Masslessness is irrelevant.

Answer 5

Sound doesn't travel through a vacuum.

'In space, nobody can hear you scream'

Remember? Sound is a wave of pressure, if there's no air there's nothing to pressurise.

Answer 6

Sound waves are carried in a medium that does not respond at the speed of light.

Answer 7

Just last month some research sceintists has done that.
Please search it on internet.

Answer 8

for the same reason waves on the ocean don't

Answer 9

because most sound is offensive and gathers more friction