FactSentinel

Sunlight takes about eight minutes and twenty seconds to travel from the Sun to Earth. The figure comes from a simple calculation. The average distance between Earth and the Sun is roughly 149.6 million kilometers (93 million miles), a value known as one astronomical unit. Light travels at about 299,792 kilometers per second in a vacuum. Dividing the distance by the speed gives approximately 499 seconds, or just over eight minutes.

The numbers behind this are well established. The speed of light is a defined constant in physics, and the Earth-Sun distance has been measured precisely using radar ranging of planets and tracking of spacecraft. Because Earth's orbit is slightly elliptical, the travel time varies a little through the year, from about 8 minutes 10 seconds when Earth is closest to the Sun in early January, to about 8 minutes 27 seconds when it is farthest in early July.

A common misconception is that the eight-minute figure describes how long it takes energy to emerge from the Sun. In reality, photons created in the Sun's core spend thousands to hundreds of thousands of years bouncing through dense solar material before reaching the surface. Once they escape, the trip to Earth takes only about eight minutes. Another misunderstanding is that sunlight arrives instantly, when in fact everything seen in the Sun is about eight minutes old.