Sunday, June 07, 2009

Five things about time travelling

I have tried to understand time traveling and relativity for several years and had several attempts to learn it from the web.

I think I finally got a good hold of it after reading "About Time" by Paul Davies. The book has hundreds of theories which have continued to be speculation rather than successfully proven facts. The first 3 or 4 chapters of the book are useful though. Here's the 5 things i took away from the book.

1) There's no universal time. There's Earth time which most of us follow and there's other more dynamic time which changes like another physical dimension in space due to gravitation and velocity.

2) Time can be slowed down by both gravitation and by velocity. Gravitational time dilation and Velocity time dilation.

3) You can travel to the future but you CANNOT travel to the past. For example you can travel on a spaceship at high speeds close to the speed of light starting in 2010 for five years of your local time measured by your clock on space ship and when you return to earth you could find that you are 2030 earth time. Twin paradox is a good example for this

4) Experimental results have proven time dilation and therefore its not science fiction but real physical phenomenon.

5) Maximum speed that can be achieved is the speed of light and this precludes traveling to the past and also prevents from causality violations like the grandfather paradox in which you travel to the past and kill your own grandfather and therefore prevents your own existence etc.

There are other interesting things in the book but I think I have covered the important ones here.