Who am I? Where is here? When is now?
Uploaded by [Digital^Dude] on May 02, 2006
Often when I look at the stars when I’m in bed at night I shudder to think of my insignificance in the immensity of the Universe.
The distances in the Universe are inconceivably huge, so we measure them in light-minutes or light years. A light minute is the distance light travels in one minute, and that’s a long way, because light travels through space at 300,000 km a second. So in a minute it would travel 18,000,000 km.
The distance of the Sun from the earth is about eight light-minutes__which means that the light falling on us has travelled eight minutes through space before it reaches us. When we look at the Sun it is actually what it was like eight minutes before. Same is the case with other planets, e.g. if Mars is ‘x’ light-hours away from us, and someone goes on Mars and looks at the earth with a powerful telescope he would see the earth as it looked x hours before. If we could reach Mars in x hours, may be, we, on Mars looking at the earth, would watch our rocket taking off!
It’s really hard to believe that the nearest star we see on a starry night is 50,000 light years away from the earth. Actually, the star may not be there at that instant, but it surely was some 50,000 years ago! Thus we can never know what the Universe looks like right now, we only know how it looked like then.
Assuming that man was able to devise a space-craft which could travel with the speed of light, and could land at a station in space, like Mars, or even the moon, that would work as a time machine using the principle described above. Watching the situation on the earth at whichever point in history would be possible, we could even investigate murders, look at the lifestyle of the early man, we could even see who was responsible for the attacks on World Trade Centre, for instance!! But the problem is that if we have to go 3 hours back in time, we would land on Mars, and if we want to go 6 hours back in time, we would land on Pluto. Provided we have powerful telescopes enough to give a good view of the earth from a place as far as 2 light-years! Which is quite impossible. That is why the idea of a...