How long does sunlight require to traverse the distance equivalent to one Astronomical Unit (1 AU)?
Answer
About 8 minutes and 20 seconds
The time it takes for light emitted by the Sun to reach Earth is intrinsically linked to the definition of the Astronomical Unit (AU), as 1 AU is defined as the average Earth-Sun distance. Since the speed of light is known and constant, measuring this travel time provides a direct measurement of 1 AU. This duration is consistently cited as being approximately 8 minutes and 20 seconds. For context, light reflecting off the Moon takes substantially less time, merely just over one second, to cover the distance to Earth.
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