if time travel was possible, it is virtually impossible that we would not know it already, because if we discovered time travel in the future, how likely is it that every time traveler didn't screw up and tell someone when they came back? also, time travel to the future is impossible, because it isn't there until it happens... it is theorized that we might find ways to speed up time or slow down time, which would be the closest to time travel we could physically come to