The only one argument I've ever thought of against time travel is the fact that we have not been visited by the future. This alone would suggest to me that at least humans will never travel through time.

And forget about Einstein. He's already been proved wrong. His theories simply explain a certain set of phenomena and fail to apply when used for more exotic scenarios. This is much the same way as Newton's laws appear to break down near the spped of light. They were never broken in the first place, but the margin of error was too small to notice. The same is true for Einstein's laws. They are not correct, however they are accurate enough to operate a nuclear reactor.

Einstein's laws were never meant to explain the possibility of time travel. People simply saw a law they could not understand and assumed that they did, much like people fail to understand the nature of self-awareness and therefore attribute it to God.

Also, when stating that something is travelling at or near the speed of light, what is it travelling relative to? The entire founding principle of Einstein's theories is that there is no absolute frame of refernce in the universe. Nothing can simply be travelling at the speed of light (or any other speed) without anything to compare it to. Nothing moves relative to the rest of the universe. It moves relative to the objects in it.

Objects also compress as they approach the speed of light. If we were moving towards each other near the speed of light, each would appear to the other to be compressed. However, if we were moving across the ground at the same speed, we would only appear compressed to an observer on the ground. We would not be moving relative to each other, and therefore would not appear compressed.

The belief that mass increases as one approaches the speed of light is incorrect. Density does. As an object is compressed near the speec of light, it's relative density must therefore increase. Theoretically, if we extrapolate this observation and apply it to objects travelling at the speed of light, they would compress to the point where they have no width in thier direction of travel, however thier mass would remain constant. They would therefore have an infinite density. In most cases, an infinite density would also mean an infinite mass, however this is not the case with zero volume.

Einstein did not define the laws of the universe. He simply made a set of laws to explain a finite set of conditions. Two common misconceptions are that Einsteins laws apply to a)Travel at or beyond the speed of light, and b)Time travel.

Einstein disagreed with the Uncertainty Principle, stating that "God does not play dice with the universe". This had nothing to do with his personal beliefs; he found a way to fit God into everything. He simply knew that this law and his laws of relativity cannot both be correct. They contradict each other. However, each are used to explain different phenomena. Quantum mechanics are used in the production of Microprocessors, and Einstein's laws in Nuclear reactors. If we tried to govern a nuclear reactor by the laws of quantum mechanics, we would all be dead by now thanks to nuckear winter. However these laws work fine for the production of microprocessors, because in that case they are accurate enough. If we tried to prodce microprocessors by the laws of relativity, we would still be counting on abaci. However, these laws work fine to run a nuclear reactor, but still break down at the speed of light. Each set of laws describes a different finite set of phenomena, however, they cannot both be correct. There is no scientific law that proves or disproves the possibility of time travel, or even produces a theory either way, as we have not yet made any observations with which to make such a law.

Einstein may have said that superluminous travel is impossible. He also said that the Uncertainty Principle is impossible, which we now know to be false.

When people speak of time travel, they assume that only one point in time exists for a given time and date. What if everthing that can happen does happen, and we are only experiencing one of an infinite number of possibilities? (Steven Hawkings belives this fiercely)