Light Travel Time
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Transcript: Since light has a finite speed, three hundred thousand kilometers per second, there’s an inevitable consequence called light travel time. In terrestrial environments light essentially travels instantly or appears to travel fast. The finite speed of light, three hundred thousand kilometers per second, has a consequence called light travel time. On the Earth, light essentially travels instantly. It takes light eight minutes to reach us from the Sun, so technically we are seeing the Sun as it was eight minutes ago. In the solar system it takes light hours to travel through the solar system. However, the distance to nearby stars is hundreds of thousands of times larger than the size of the solar system. Even the nearest star, Proxima Centauri, has a distance of 4.3 lightyears. This means we see Proxima Centauri as it was four and a third years ago. Polaris, the pole star, is at a much larger, distance 650 lightyears. Thus, we see Polaris as it was in the 1300s. If Polaris exploded we would not know about it until after 2600 A.D.
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