How Fast Does Light Travel?
Light travels very fast. In just one second, it goes 186,282 miles (229,792 kilometers), and at this speed takes about eight minutes to reach the earth from the sun.
In miles per hour, light speed is, well, a lot: about 670,616,629 mph. If you could travel at the speed of light, you could go around the Earth 7.5 times in one second.
The speed of light explains why we can see the glow of lightning the instant it flashes, even though it may be miles away. Sound travels much more slowly. It takes the sound of thunder nearly five seconds to travel one mile.
A light-year, the distance traveled by light in one year, is about six trillion miles. Light is a form of energy that travels in waves, in much the same way waves travel in the ocean and like sound, can be slowed depending on what it is traveling through.
Nothing can outpace light in a vacuum. However, if a region contains any matter, even dust, light can bend when it comes in contact with the particles, which results in a decrease in speed.
Light traveling through Earth’s atmosphere moves almost as fast as light in a vacuum, while light passing through a diamond is slowed to less than half that speed. Still, it travels through the gem at over 277 million mph (almost 124,000 km/s).