How funny would it be to watch Cleopatra sing “Happy Birthday” to President Kennedy? Or how remarkable would it be to domesticate a dinosaur? And how wonderful would it be to relive the proudest moment of your life, or to save yourself from the most humiliating?
Time travel, a long-time speculation of scientists and dreamers alike, would open the door to such unlimited possibilities. However, what most fail to realize is that before we can accomplish time travel, we have to define time.
“Time,” as we are taught in school, is a simple measurement. We speak about it in both specific and abstract terms, whether it’s in exact “seconds” or merely “the other day.” In our daydreams, we often visit the “past” and “future.” However, as definitions grow more complex, the philosophy of time condenses to two main theories: that of a linear time, and that of an unreal time.
Linear or “real” time, as we are more familiar with, involves a past, present, and future. You have memories which you remember in the present; and you can project expectations to create a future. We believe there was a beginning for everything, and there will be an end for most things. According to Sir Isaac Newton, time can be described as a dimension of sequential events.
The opposing view suggests time is real to us only when we measure it; so time might not actually exist at all. In fact, time may just be a human construct. This idea dates as far back as the 5th century BC, to the Greek philosopher Antiphon. He believed “time is not a reality, but a concept or a measure.” Moreover, J. M. E. McTaggart pointed out in 1908 that “since every event has the characteristic of being both present and not present, time is a self-contradictory idea.” In truth, all we can really prove is the present, while the past exists solely in our memory.
If this is the case, time travel would be a moot point.
Since plausible evidence exists on both sides, scientists continue to argue. While some believe time exists as positively as space does, physicist Julian Barbour argues that quantum equations take their truest form when expressed outside of time. Outside of time, the equations can consider every possible momentary configuration of the universe. (Though this lends to alternate universes, we’re only going to have one psychedelic travel today.)
But maybe, if we can also define what the present is, we can figure out a way to manipulate that reference point. In the general theory of spacetime, time and space are one in the same (such speaks the name). Imagine a star in the night sky. You might have heard before that the stars you see may not actually exist in the instant you see them. What you do see, is the light that left the star many years ago. This is the best example of spacetime and understanding the speed of light: the past is a set of events that sends light to the present, and the future is a place to where the present sends its light.
Even if you were to travel at the speed of light, however, you still would not escape time. An astronaut aboard a ship moving at the speed of light would perceive himself as still and Earth as moving away from him at the speed of light. In the same regard, a stationary observer on Earth would see himself still and the astronaut traveling away at the speed of light. If this is the case, then who ages faster?
Traveling at this speed does not seem to be a plausible solution to time travel unless the two decide to meet at a very distant place in space.
With distance incorporated, we can say that it takes 20 years for the astronaut to travel somewhere 20 light years away. For someone moving at a general spaceship’s speed, it would take a good number of generations. If you’d like to rendezvous with your extremely distant (pun intended) relative, this is an option.
Someone once said to me that rather than getting hung up on the past or future, focus on the present. It’s a common thought, but he followed by saying that every object is in a constant state of change. You and I have not “aged,” but rather “changed.” Our particles are constantly rearranging, as well as the particles around us. Your computer used to be basic elements in rock, and now they have changed. Someday, they will be changed again. Perhaps the universe itself is simply in a constant state of change, and we have completely invented the notion of time.
Unfortunately for now, you’ll have to ignore your most embarrassing moments into oblivion.
-Navratil, Gerhard (2009). Research Trends in Geographic Information Science. Springer Japan. p. 217. -http://www.foundalis.com/phi/WhyTimeFlows.htm
-Markosian, Ned. “Time”. In Edward N. Zalta. The Stanford Encyclopedia of Philosophy (Winter 2002 Edition).