How long does it take light leaving the sun to reach earth?
The published figure is 499.0047864 seconds. This represents the time it takes light travelling at 299,792,458 metres per second to cover one “astronomical unit” of 149,597,871,500 metres. The astronomical unit is the long term average distance between Earth’s centre and the Sun’s centre. At perihelion (the point in our orbit when we are closest to the Sun): January 2, 2008 at 23:00 UT (6 pm New York time) centre to centre distance = 147,096,448 km Sun’s radius = 696,265 km Earth equatorial radius = 6,378 The light leaving the surface of the sun closest to us and reaching the surface of Earth at the sub-solar point would only have to travel 146,393,805 km. At the speed of light in a vacuum, this would take 488.3 seconds (8 min. 8.3 sec.). Because the vacuum is not pure all the way, it could take a fraction of a second longer. Your mileage may vary…