Topics Time

Question After a discussion about time travel, I asked my high school science teacher, “How can we be sure time even exists? How do we know it’s a tangible thing that can be traveled through?” His simple reply was to say that time can be measured. Therefore, it exists. That answer was never enough. As I’ve grown older, I still believe that time doesn’t exist, because all it is, is a term used to describe the interaction between matter. As matter interacts, the physical world changes, thereby creating one’s perception of ‘time’. The more gravity one has, the slower matter interacts and the inverse. One can’t go back in time, because one can’t rewind all the infinite physical changes that have taken place. However, one can speed up the interactions. So, I pose you the same question. How can we be sure time exists?

Accepted:
November 19, 2005

Comments

Newton proposed that there is "absolute time", over and above the motions of clocks and pendulums and celestial bodies that (to some degree of accuracy) measure absolute time. Newton did so in the context of a scientific theory that aimed to account for some of our observations of the motions of material bodies. The tremendous success of his theory counted as good evidence for the existence of absolute time. Roughly the same situation exists today, except that our best current theories of how and why bodies do what they do fail to use Newtonian absolute time. Those theories (roughly, quantum mechanics and relativity theory) use other notions of time -- indeed, notions that are difficult to reconcile. Still, whatever evidence we have that time exists comes primarily from evidence for our best scientific theories, which use various concepts of time to characterize the universe.

Now those theories might be mistaken, or the evidence for their accuracy might not constitute very strong evidence for what they say specifically about time. Such turned out to be the case with Newton's theory. But in any event, although we cannot "be sure" that time exists, since scientific theories are never proved for certain, the question of whether time exists is tightly bound up with questions about what theories are accurate regarding the most fundamental physical processes and interactions.

By the way, I agree with you that the fact that we say that time can be measured is not very good evidence that it exists. We also say that the magnetic field at a certain point in space can be measured -- for instance, by sticking an iron filing there and watching how it aligns itself with the magnetic field. But this measurement is not very powerful evidence that there exists a magnetic field, over and above all of the material bodies, occupying otherwise empty space throughout the universe. The behavior of the iron filing is compatible with magnetic forces operating by action at a distance rather than by way of an invisible field.