It's Just a Matter of Time

This week the Hong Kong University of Science and Technology research team led by Du Shengwang said they had proved that a single photon, or unit of light, "obeys the traffic law of the universe." What he meant was that Einstein was right and nothing can travel faster than light. This put the dampers on some theories which were counting on superluminal speed in order to travel back in time. Of course, this did not affect other time travel theories that use other exotic means such as worm holes to go back in time.

Personally, I think it is illogical to believe it is even possible to travel into our past, no matter what means might be developed. So consider for example that there might be other beings living among us who are so far technically advanced that they have developed the capability to travel back in time. It seems to me that it would be impossible for them to travel back in time without affecting the present. Suppose, for example, while you are talking to someone, a time traveler decides to visit the past. Suppose they accidentally kill or even just alter the direction in life of the person to whom you are talking. Suddenly that person would vanish before your eyes. There are many other examples in which the time travelers would alter the present and we would notice a sudden discontinuity in events. To my knowledge we never have noticed such discontinuities. That tells me that no one or no entity has traveled into the past or could ever do so.

This is not to say that any time travel is impossible. What if someone were to construct a spaceship propelled by a gravitational field? They could accelerate at very high rates and travel great distances into our galaxy. According to Einstein, time is altered for a traveler who is experiencing very high velocities and/or accelerations and/or gravitational fields. So that person may use their spaceship to travel out perhaps 100 light years from Earth. However in their time frame perhaps only one year elapses. They then turn around and return to Earth at high velocity and accelerations just as when they left. While according to their clocks they have aged perhaps two years the earth is now 200 years into the future. This then would be a form of time travel. Unfortunately, the traveler could not return to their original time as this would be the same as time travel into the past.