Light from Alpha Centauri, which is the nearest star system to our own, requires roughly 4.3 years to get here, so Alpha Centauri is 4.3 light-years away. Sunlight takes about 8 minutes to reach our eyes, so the sun is about 8 light-minutes away. Light travels from the moon to our eyes in about 1 second, which means the moon is about 1 light-second away. So far no one's been able to demonstrate a real warp drive, but that hasn't slowed our collective hurtle toward new stories, new inventions and new realms of physics. Through some crafty equations, it also helps define the kilogram and the temperature unit Kelvin.īut despite the speed of light's reputation as a universal constant, scientists and science fiction writers alike spend time contemplating faster-than-light travel. National Institute of Standards and Technology (opens in new tab), it is used to define international standard measurements like the meter (and by extension, the mile, the foot and the inch). The speed of light is so immutable that, according to the U.S. That means the speed of light functions as a speed limit on the whole universe. The theory states that as matter approaches the speed of light, the matter's mass becomes infinite. According to physicist Albert Einstein's theory of special relativity, on which much of modern physics is based, nothing in the universe can travel faster than light.

Speed of sound in miles per hour