Despite the impression you get from watching Star Trek adventures, you can’t really zip around the Universe faster than the speed of light! Light always obeys the speed limit. In the vacuum of outer space, it hurtles along at three hundred thousand kilometres a second. The speed of light is nature’s speed limit – the fastest anything can travel!
Light can be slowed down by transparent materials like air, water, glass or diamonds, but it can never break the speed limit. The slowing down of light causes it to bend or refract. The more that light slows down in its travels from one material into another, the more it bends.
Diamonds are more brilliant than other substances because they are more effective at slowing light, causing it to bounce around inside and sparkle. The lens in your eyeglasses works by slowing light down to half of its air speed, bending it to focus on the eye’s retina.
Even though light travels at such fantastic speeds, it still takes significant time to go places. When you see the sun rise at 7 a.m. you are actually seeing something that happened at 6:52 a.m. If the sun suddenly exploded, you wouldn’t notice it for eight minutes.
So next time you see a space ship zipping between galaxies in a movie, remember that it would really take thousands of years travelling at nature’s speed limit to make the trip.