Wednesday, September 29, 2010

Driving Fast....fountain of youth?

Dan just turned me on to an article that is a real fun way to look at Einstein's predictions on relativity. The funny thing is in this discussion is I often made these same observations, when I was much younger, on time dilation, mainly from observing common occurrences while riding in a car. Relativity of course says that two object traveling at different speeds relative to each other will experience time differently. Today it is widely accepted that an object traveling at a substantial fraction of the speed of light will experience time much more slowly, relative to someone or something that is stationary (relatively speaking)

Even though a speeding car will not slow time down by much, the observational example can, however, still be very striking. This is how I would explain it. You're sitting in a car and a friend is standing outside the car and neither is moving. Time is experienced by the both of you the same. Now your friend starts walking and walks for an hour (at a normal pace he should now be about 2.5 miles ahead) Now for both, 1 hour has passed and you both have experienced it but at slightly different frames of reference. Now you accelerate your car to 60mph. You will cover the same distance in 2 minutes 30 seconds. You now continue to drive for an hour. Your friend has managed to now cover 5 miles and you 60. Speed relative to each other was vastly different, but this is where I would loose people. When you catch up to your friend at the end of that first hour you both start listening to a song that is four minutes long. At the end of the song your friend has covered roughly 900 feet. In your car, after the same 4 minutes you have covered 21120 feet or 4 four miles. Relative to your friend (or at least observationally) time would appear to be going 23 times slower (of course it isnt really, but relativity uses basically the same thought experiments ) If you put speakers outside your car, your friend would hear the sound being stretched to a lower / slower frequency which is much the same as what happens to light at the vast speeds needed to make relativity's time dilation work.

The story Dan brought me from the Los Angeles Time was the fact that even small changes have a dilation effect. Clocks at sea level run slower than counterparts on top of mountains which proves out Einstein's theory that gravity fields affect time and it has been documented since the Apollo age that clocks on high speed rockets run slower than fixed clocks.

Of course astrophysicists have long seen the effects of gravity on light and time. They have been using the gravity of suns or whole galaxies to slow time and therefor bend light allowing them to see further into the universe.

Is there really any uses past thought experiments that these effects can be useful towards? Mostly likely not in the near future. However as data streams become vastly more dense and complex, timing will become even more crucial in the future. Knowing that time runs faster off planet and slower in high speed craft could be very important to maintaining accurate timing of data streams etc.

wikipedia article on time dilation

Wikipedia article on Special Relativity

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