Jingszo !

Light is electromagnetic radiation: basically, an electric wave and a magnetic wave coupled together and traveling through space-time. It has no mass. That point is critical because the mass of an object, whether a speck of dust or a spaceship, limits the top speed it can travel through space.

But because light is massless, it’s able to reach the maximum speed limit in a vacuum – about 186,000 miles (300,000 kilometers) per second, or almost 6 trillion miles per year (9.6 trillion kilometers). Nothing traveling through space is faster. To put that into perspective: In the time it takes you to blink your eyes, a particle of light travels around the circumference of the Earth more than twice.

As incredibly fast as that is, space is incredibly spread out. Light from the Sun, which is 93 million miles (about 150 million kilometers) from Earth, takes just over eight minutes to reach us. In other words, the sunlight you see is eight minutes old.

Alpha Centauri, the nearest star to us after the Sun, is 26 trillion miles away (about 41 trillion kilometers). So by the time you see it in the night sky, its light is just over four years old.