Posted: Sat Apr 17, 2004 11:38 am Post subject: What About Time Travel?
The theory of relativity states that time is relative. As we approach the speed of light time slows down. Stephen Hawking's book, A Brief History of Time delves into the subject a little bit. If we could transcend the speed of light we could, theoretically, travel back in time, but our mass increases the closer we get to the speed of light, and we would reach infinite mass long before we could travel one second back in time.
Joined: 15 Mar 2005 Posts: 8 Location: Baton Rouge, LA
Posted: Tue Mar 15, 2005 1:35 pm Post subject: Re: What About Time Travel?
dan wrote:
The theory of relativity states that time is relative. As we approach the speed of light time slows down. Stephen Hawking's book, A Brief History of Time delves into the subject a little bit. If we could transcend the speed of light we could, theoretically, travel back in time, but our mass increases the closer we get to the speed of light, and we would reach infinite mass long before we could travel one second back in time.
Exceeding the speed of light would mean your clock would be measuring time in imaginary time.
Gamma = (1/(1 - v^2/c^2))^1/2
If v > x, we are taking the square root of a negative number, so gamma is an imaginary number. Hence so will measurements of time, mass, and length. So its not physically possible to exceed the speed of light - imaginary numbers are not physically real. Its only possible to exceed the speed of light in math. Even then - its not possible to be exactly at the speed of light.
Note that the above only applies to particles with inertial mass.
Joined: 15 Mar 2005 Posts: 8 Location: Baton Rouge, LA
Posted: Tue Mar 15, 2005 1:38 pm Post subject:
Arquais wrote:
what if you had the earth moving at half the speed of light and yourself moving at half the speed of light, plus 1?
First off, you need to define a reference frame for your velocity measurments.
So I assume you mean that there is a third observer, measuring your velocity to be 50% the speed of light, and measuring the velocity of the earth to be equal in magnitude but opposite in direction.
You would each measure your velocities to be less than the speed of light due to length contraction and time dilation effects. I forget the actual equation but you'd measure the earth to be moving away from you at around 70% the speed of light
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