Things you don't know about the speed of light

The speed of light, (more generally, the rate of propagation of electromagnetic radiation) in a vacuum, denoted by c, is an important fundamental physical constant for many physical areas. It is exactly equal to 299,792,458 meters per second, because meter length units are redefined based on this constant and the standard second.

Light moves at a speed of nearly 300,000 km / sec (about 1 billion km per hour). It only takes more than a second to reach the Moon and about 8 minutes to reach the Sun. For a second, light can circulate around the earth 7 times. But it took years to overcome the gap between us and the nearest stars.

When passing through water, air, glass or all other transparent materials, the speed of light is reduced.

Radio and television waves, radar waves, infrared and ultraviolet rays move at the same speed as the speed of light. It is the highest possible speed in the universe.

Light moves at a speed of nearly 300,000 km / sec.

How to measure the speed of light

The first person who wanted to measure the speed of light was Galileo. He placed two observation points a few miles apart with two covered lanterns. The first observation point opens his lantern, the second observation point after seeing light from the first observation point opens his lantern. The time between the lantern opening + the distance between the two lanterns will help Galileo calculate the speed of light. However, in fact, this scientist knows that light goes too fast and the distance of several miles is not enough to do the experiment.

Must wait until 1676, the Danish astronomer named Ole Roemer did the first accurate experiment and gave the number 309,000 km / s (the number does not deviate much from the real speed) by How to observe Jupiter's moon.

In the nineteenth century, two French scientists Hippolyte Fizeau and Leon Foucault used complex mirror systems to calculate the speed of light and also achieved 298,000 km / sec.

Subsequently, a great student of Foucault, Albert Michelson, continued this work to make measurements more accurate.

In 1924, Michelson did experiments at different peaks of California with a distance of 140 km between experimental sites. In 1926 he announced the speed of light was 300,000 km / s. Today, experimental scientists assume that the speed of light is exactly 299,792,450 m / s.