In a vacuum, the speed of light is about 3 × 10⁸ meters per second, which is very, very fast. That’s so fast that a beam of light could travel around the whole world in only about 0.13 seconds!

It’s interesting to consider just how far away from the Earth stars really are. After the Sun, the next closest star to the Earth is over four light years away (a light year is the distance light travels in one year). This means the next closest star is over 20,000,000,000,000 miles away. Because light must reach our eyes for us to see anything, if that star exploded, we wouldn’t see it until over four years after it actually happened!