Artifacts from the Future: Problems with Time Travel

In the book "a sound of Thunder" by Ray Bradbury, a time-traveler accidentally stepped on a butterfly in the past.  That step on changed the food chain multiple times over billions of years, and when the traveler returned to the present, the entire world was changed drastically.  This was known as the Butterfly effect.  After watching the scientific film clip "Through the Wormhole" many pros and cons about time travel were brought up.  The question of is time travel even possible due to the laws of life was the biggest question that caught my attention.  I do not think it is possible AT ALL.  Although time traveling into the future or past would be cool, it is not possible and I predict that it will not ever be done.