Stockcoach's Corner

Up 0.4 percent today. I am always struck by stories like these that remind us just how small (though not necessarily insignificant) our world is in the great scheme of things. There are at least 100 billion stars in our galaxy and at least 100 billion galaxies in the visible universe. And standard cosmological models of inflation suggest that if the entire universe were reduced to the size of our solar system, the visible universe (the part that we can see with our telescopes, which is about 26 billion light years across) would be smaller than a grain of sand. And on top of that, our entire universe, which string theory suggests may have 9 spatial dimensions, may itself just be one in an infinite number floating in a larger "hyperspace". You see how small one feels when one think in these terms.

When I was a teenager, I remember being enthralled by the notion that time can not be measured in absolute terms. If a light bulb goes off in the middle of a train that zips by you at high speed, the light from the bulb will be seen instantaneously by passengers at the front and back of the train. But from your perspective, the light will reach the back of the track before it reaches the front. Everyone has a "now list". But my "now list" may be different from yours, especially if you happen to reside in another galaxy. Indeed, if you live in a distant galaxy that is moving away from ours, you may legitimately claim that it is not the year 2006 on earth, but 1006!

I was also struck just by how malleable time is. If you get into a rocket that is constantly accelerating at a comfortable 1G (the gravity here on earth) not only will you have a smooth journey (the force of acceleration will make it feel as thought you never left earth) but you will be able to travel one trillion light years (as measured on earth) in about 55 years in the rocket (try this applet for fun)!

Indeed, once one realizes that space and time are so intricately linked that you can not really understand one without understanding the other, the notion of something as basic as life and death gets a bit blurry. In some sense, none of our loved ones have really died. They just live in a different corner of spacetime. And since general relativity does not prohibit traveling back in time, who knows what amazing things await for humanity.