Curiosity 3 of 10
3. Sunlight takes 8 minutes to reach us
Light takes about 8 minutes and 20 seconds to travel the 150 million kilometers between the Sun and the Earth. Every ray of sunlight that reaches you shows the Sun as it looked a few minutes earlier.
Looking at the sky is looking into the past
Light travels at about 300 thousand kilometers per second in a vacuum. It is fast, but distances in space are so vast that this delay becomes noticeable. If the Sun suddenly disappeared, the Earth would keep shining for just over 8 minutes.
With the Moon, the delay is just over a second. With the stars, it ranges from years to thousands of years. The light from the nearest star after the Sun, Proxima Centauri, takes about 4.2 years to reach us here.
The trip to Earth is the short part. The Sun's energy is born in the core, through nuclear fusion, and takes tens of thousands of years to reach the surface. Inside, matter is so dense that light is absorbed and re-emitted countless times, following a zigzag path. A widely cited estimate puts it at around 170 thousand years.
In other words, the energy warming the Earth today began leaving the Sun's core long before writing existed. Only the final 8 minutes of the journey were in a straight line, through empty space.
Did you know? Never look directly at the Sun, not even for a moment, and especially not through binoculars or a telescope without a proper filter. Concentrated light can cause permanent damage to the retina.
