Light-years
⭐ MasteredA light-year is the distance light travels in one year, about 9.5 trillion kilometres. It's used to measure distances between stars.
Light-years measure distance, not time.
All about Light-years
A light-year is the distance that light travels in one year, which is about 9.5 trillion kilometres. Light moves at about 300,000 kilometres per second, so it can cover the distance between Earth and the Moon in about 1.3 seconds.
Light-years are used to measure distances between stars and galaxies. The nearest star to our Sun, Proxima Centauri, is about 4.2 light-years away. Because light takes time to travel, when we look at distant stars, we see them as they were long ago.
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Real-life uses of Light-years
- Measuring distances to stars and galaxies
- Understanding that looking far away means looking back in time
- Comparing the scale of the universe
Frequently asked questions about Light-years
Is a light-year a measure of time?
No. It is a unit of distance, even though it contains the word year.
How long does sunlight take to reach Earth?
About 8 minutes and 20 seconds.
Can anything travel faster than light?
According to our current understanding of physics, nothing with mass can travel faster than light.