Time travel:


Special relativity:

Einstein's theory of special relativity describes the motion of objects at near-light speed. It says that the speed of the light is constant whatever the relative speed of the observer, and the laws of physics are the same in all frames of reference. Its called the theory of special relativity because it has to do with relative motion.

Will it work: (why or why not)

According to special relativity, time slows as an object approaches the speed of light. So far it isn't known how to make an object go faster than light, because as it approaches the speed of light it's mass increases infinitely and therefore requires infinite force. Physicists believe that if it were possible for an object to travel faster than light, it would travel through time.


Heisenberg uncertainty:

The Heisenberg uncertainty principle says that the position and velocity of a particle cannot be measured at the same time. By measuring the velocity of a particle using photons, the velocity of the particle is altered, and therefore makes it impossible to measure accurately. When measuring the velocity of large objects the difference is insignificant. But measuring a subatomic particle greatly affects it's velocity and there is a high percentage of uncertainty.

Sources:

http://www.bbc.co.uk/dna/h2g2/A408638
http://www.pbs.org/wgbh/nova/time/think.html