The speed of light in a vacuum is about 300 thousand kilometers per second. Here’s what it would look like on Earth
The speed of light in vacuum is exactly 299,792,458 meters per seconda universal constant known in equations as “c“. According to Einstein’s theory of special relativity, nothing in the universe can travel faster than light. The theory states that when matter approaches the speed of light, it becomes infinite. This means that the speed of light acts as a speed limit for the entire universe.
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How we calculated it
One of the first measurements of the speed of light was made by Rømer in 1676 while observing the moons of Jupiter. Rømer was able to measure the speed of light by observing eclipses of Jupiter’s moon, Io. When Jupiter was closest to Earth, Rømer noticed that eclipses of Io they occurred slightly earlier than when Jupiter was further away. Rømer then attributed this effect to the time it takes for light to travel a greater distance, when Jupiter was farthest from Earth.
10 trillion kilometers
A light year is the distance that light can travel in one year: approximately 10 trillion kilometers. It’s one way astronomers and physicists measure immense distances in our universe. Light travels from the Moon to our eyes in about 1 second, which means the Moon is about 1 light second away. Sunlight takes about 8 minutes to reach our eyes, so the sun is about 8 light minutes away. The light coming, the closest star system to ours, it takes about 4.3 years to get here, so Alpha Centauri is 4.3 light years away.
The speed of light and the past
When astronomers study distant objects, they see light that shows the objects as they existed when the light left them. This principle allows astronomers to see the universe as it appeared about 13.8 billion years ago. Objects 10 billion light-years away appear to astronomers as they did 10 billion years ago – relatively soon after the birth of the universe – rather than as they appear today. Below is the video:
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