Most people here have heard about the Grandfather Paradox. Most people here have also read at least one time-travel story in which people either take out or attempt to take out Hitler. But if we have one, can we possibly do the other?

What if all the Large Hadron Collider's recent woes are more than bad luck and technical problems? Two noted physicists speculate that the future may be pushing back on the LHC to avert the disaster of observing the Higgs boson.

The moment we learn how to time travel, the first thing we're all going to want to do is go back in time and kill our own grandparents as children. It's like picking at a scab, you can't resist. A big part of the temptation comes from the fact that we don't know what'll happen when you do that — it's the great unknown, …