Why Is Light Faster Than Sound?

Light is composed of photons, which are discrete collections of energy with wave and particle properties, while sound travels as a wave through a medium, which makes it travel more slowly. While light and sound have some similarities due to wave-particle duality, their physical attributes differ significantly.

Most light comes from particles releasing energy in the form of a photon. Making something travel faster requires adding energy proportional to its weight. Since photons have no mass at all, their speed is not limited by this natural law. As a result, photons travel at the maximum speed possible: the speed of light.

Light doesn't need a medium to travel through, so it's able to travel through space unobstructed. Sound, on the other hand, needs a medium to spread, so sound doesn't spread in the near vacuum of space. When sound travels through air, its energy transfers from particles to other particles, and this transfer of energy limits its speed. Since air is primarily composed of nitrogen and oxygen, sound must push these particles in order to spread, further limiting its maximum speed.

Sound travels faster in dense substances; the speed of sound is faster through water than through air, and even faster through solid substances. However, sound dissipates as it travels, unlike light, which can travel from distant stars and galaxies to Earth if nothing gets in its way.