I heard a story, once, about a man who sat down in the final exam for his phsycology class and found one question staring up at him. "Prove the existence of the chair you're sitting on." He thought for a few moments, scribbled a quick response, and then got up and left the room. Curiosity getting the better of him, the instructor looked to see what the student had written. He chuckled at the response..."What chair?"
This story has helped to expand and further solidify, in my mind, the definition of truth. Some question the nature of truth based on one or another theory of reality. They believe that truth must be taken, reexamined, and redefined based on changes in perception, speed, dimension, or some other modifier.
Again, think of truth in terms of reality...the way things actually are, and apply it to the story. Most will see a chair and accept it as being real. Some will not. In the case where the chair is not real, is it truth that is changed or is our perception of truth limited?
You see, even if what we perceive is false there still exists a reality that has been, is, and will remain unchanged. If, in reality, several dimensions exist then this is the truth and our lack of understanding or of seeing these other dimensions is merely a question of perception.