## April 13, 2004

### The Elegant Universe: an excerpt

I'm reading a pretty cool book right now called The Elegant Universe by Brian Greene, and I must say it is a mind bender. In this book Mr. Greene tries to explain a relatively new theory called "string theory" which may, or may not, be the famed Theory of Everything that Einstein spent the last 35 years of his life trying to figure out. I'm not very far into the book, but in the beginning Greene spends a fair amount of time trying to explain the theories that string theory is trying to add upon. One of those is Einstein's special theory of relativity (not to be confused with the general theory of relativity). This is the theory that science fiction writers love. It is where we get the idea that someone travelling at the speed of light will come back younger than the people he left behind. It is so mind boggling, as Green says "Special relativity is not in our bones -- we do not feel it."

It is very difficult to understand how speed of motion can affect time since we never really move that fast. However, that doesn't mean that time isn't affected. Take this example from the book:

"To get a sense of the scales involved, imagine the year is 1970 and big, fast cars are in. Slim ... goes with his brother Jim to the local drag strip to give [a new Trans Am] the kind of test drive forbidden by the dealer. After revving up the car, Slim streaks down the the mile-long strip at 120 miles per hour while Jim stands on the sideline and times him. Wanting an independent confirmation, Slim also uses a stopwatch to determine how long it takes his new car to traverse the track. Prior to Einstein's work, no one would have questioned that if both Slim and Jim have properly functioning stopwatches, each will measure the identical elapsed time. But according to special relativity, while Jim will measure an elapsed time of 30 seconds, Slim's stopwatch will record an elapsed time of 29.99999999999952 seconds -- a tiny bit less."

Holy guacamole! That boggles the mind! But it doesn't stop there, special relativity contends that speed will also affect measurements of length. If Slim was to travel at 580 million miles an hour (about 87% the speed of light) "the mathematics of special relativity predicts that Jim would measure the length of the car to be about eight feet, which is substantially different from Slim's measurement [of 16 feet, since his measurement will be relative to the fact that he is also traveling 580 million miles an hour].

So, how is that for a good morning for ya? Like I said, I am only a couple of chapters in, and I don't feel very confident that string theory will make any more sense to me than special relativity. You can never stop learning though. I will continue to claw my way out of the abyss of ignorance.

Posted by snackeru at April 13, 2004 10:14 PM | Books