But the sheer size of the universe means that light carries information from the distant past into our present, showing us what the cosmos looked like long, long ago and far, far away. Here's how it works. Light, the speediest thing we know of, zips along at 186,000 miles a second in the vacuum of space.
Light leaves the surface of a star or planet, travels a great distance, and finally enters our eyes.
When light leaves the Sun, it takes 8 minutes to speed through space and reach Earth. If the Sun were to magically vanish, sunlight would continue streaming through our windows for 8 blissful last minutes, and the Sun would shine in its normal place in the sky. But over millions of years, stars do eventually become cold, dark cinders. So some stars that we see shining brightly through our telescopes may have actually burned out millions of years ago. We may see one star as it appeared in 1803, another as it was in 3100 BC, and the next shining with light that left it 100 million years ago, when dinosaurs roamed Earth.