Time Machine

23 Time Machine Do you know that there is a way to look into the past right in your own house? It's true. It's called a mirror. You see, everything that moves has a speed-even light. Although it travels incredibly fast, light still has a speed, and you can measure it. When you look into your mirror, you are seeing the light that is reflected off your face. It travels to the mirror, then back to your eye so you can see it. Although that light travels really fast, it still takes time for it to get to your mirror, and then back to you. The time it takes is unbelievably small. How small? Well think about this. Light moves so quickly that it can travel around the earth seven times in one second! “ What has all of this got to do with looking into the past?" you might ask. Good question. Here's the explanation.

There is a measurement called a light year. The strange thing is that it doesn't measure time. It measures distance- the distance light travels in one year, which is a very long distance: 10 trillion kilometres. So if we took your mirror and moved it back the distance it takes light to travel in one year, how far in the past would we be seeing? Well, the light has to come from something in the past, travel 10 trillion kilometres to the mirror, and then another 10 trillion kilometres back to you. So the answer is two years. But there is a problem with using your mirror to see the past. The light would have to be as bright as a star for you to see it because it must travel 20 trillion kilometres back and forth. That would be a very powerful light! Isn't science interesting?