Speed of Light: Calculate distance or time

Speed of light calculator for the distance per time or time per distance. The formula for calculation is the same formula as that for velocity, with the given value of the speed of light in a vacuum.

distance = speed of light * time, s = c * t

Please enter distance or time and select the units for both, the other value will be calculated. One year is counted as 31557600 seconds (365 1/4 days).

Examples: the average distance of the moon from earth is 384400 kilometers. The light takes just under 1.3 seconds to get there. The sun is at an average distance of about 150 million kilometers from the earth, which is one astronomical unit. It takes light about 8.3 minutes to travel this distance.

For one centimeter, light takes 3.3e-11 seconds. These are 0.000000000033 seconds (first digit ≠0 at the 11. decimal place), or 33 trillionths of a second.

Light is so fast that it took a long time to determine that it travels at a finite speed at all. There was speculation about this as early as ancient times. Galileo Galilei was the first one known to attempt to measure the speed of light. He was using a method similar to the one he had used to measure the speed of sound. However, he and others who followed him failed to measure the speed of light using earth-based methods. In 1676, Ole Rømer was able to show that the speed of light is finite when he took measurements as the moon Io orbited Jupiter, but he was unable to find a value. Two years later, Christiaan Huygens used his data to calculate the speed of light to be almost a third too low. Over the course of the 18th century, evidence for a speed of light of around 300,000 kilometers per second increased. The exact value was not determined until the middle of the 20th century.