How can you explain the speed of sound vs. the speed of light?


Quick Answer

Although both sound and light are fast by human standards, light is far faster than sound because waves of sound must propagate through a medium, while the speed of light is tied to fundamental universal constants. Light travels at about 300,000 kilometers per second, and the speed of sound is usually around 300 meters per second.

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Full Answer

The speed of sound is conditional on the medium it propagates through. Sound is just the repeated compression and rarefaction of the medium, which can be air, water or a solid, and different materials allow these waves to pass at different rates. In general, the denser the medium, the faster vibrations can travel through it.

Light is different. Waves of light travel at their highest speed in a vacuum and are only slowed by passing through a medium. While the speed of sound is a property of material density and temperature, the maximum speed of light is intrinsic to the way matter and energy interact. Einstein's famous equation, E = mc^2, provides an example of why the speed of light must be what it is. If the speed of light, usually written as "c," had a different value, the energy released by nuclear forces would also have to be different, and the universe would likely operate in a fundamentally different way. Unlike sound, therefore, the speed of light is closely tied to the way the universe works on its most basic level.

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