Sound does not travel in vacuum as it needs a medium to carry it, unlike light which does not necessarily need a medium to travel. The denser the medium the faster the speed of sound in it. So sound travels faster in water than it does in air. By the same logic, the sound travels much faster in steel than in a less dense medium like air or water. The speed of sound also depends on the other properties of the medium, especially the temperature of the medium.

Under normal atmospheric conditions, at sea level at 21 degrees Centigrade temperature, sound travels at a speed of 344 m/sec. At high altitudes the sound travels slowly as the temperatures at those altitudes are generally low and the density of the air is also less. Hence having a conversation on the moon is impossible due to the absence of a medium there.

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