Q:

# How fast is the speed of light in mph?

A:

The speed of light in mph (miles per hour) is 6.702 x 108 mph or more precisely 670,616,629 mph. In metric units, the speed of light in a vacuum is 2.998 x 108 m/sec.

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Theoretically, nothing can travel faster than light. The average distance from Earth to the Moon is 238,854 miles and light crosses that distance in about a second. The distance from the Sun to Earth is 92,955,817 miles and light only takes about 8 minutes to travel that distance.

Light travels in waves and can be slowed like sound, depending on the medium where it is traveling. Through the atmosphere of Earth, light moves almost as fast as it moves in a vacuum. The passing speed of light through a diamond is less than half of its vacuum speed.

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## Related Questions

• A:

The speed of light in a vacuum is measured at 186,282 miles per second, which is 670,616,629 miles per hour. The speed of light is denoted mathematically by the symbol "c."

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• A:

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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• A:

The speed of light in water is approximately 225,000 km per second. While enormously fast, this is notably slower than the speed of light in a vacuum, which is 300,000 km per second.