The speed of light is meatsured by the time it takes a beam of light to travel a certain distance. There are light seconds, light minutes, and light years.
Shelby Lin Erdman
Cox Media Group National Content Desk
Stars and galaxies in outer space are just so far away, it’s hard to comprehend the staggering distances.
Scientists have come up with ways to measure space distance that are easier to understand.
A light year is one of those space measurements and is similar to how a mile or kilometer measures distance on Earth. Distances in space are so vast, though, that a mile or a kilometer is just too small a number to be useful, because of the huge numbers involved in space travel. Light years work better.
A light year is measured by the time it takes a ray of light to travel a given distance.
The moon is a little over one light second from Earth, meaning it would take a beam of light on Earth a little more than a second to reach the moon. The sun, which is 93 million miles from earth, is measured in light minutes and is some eight light minutes away.
Mars is under 25 light minutes from Earth, depending on its orbit around the sun, and the other planets in the solar system are several light hours from Earth.
The Milky Way galaxy, for example, measures about 150,000 light years across. The Andromeda galaxy, the nearest large galaxy, is more than 2 million light years away.
How long does it take to travel a light year? Here’s an example. The next closest star after the sun, is called Proxima Centauri. It is just over 4 light years away. If a spacecraft were traveling 38,000 miles per hour, it would still take 80,000 years to reach the star, according to the University of Virginia Physics Department.