Of those time traveling fictions that you’ve read for the years of your life, you may still wonder, is it really possible? Despite most of these fictions contradict to themselves. In this essay I’m going to demonstrate that it is, at least logically and conceptually, possible. However, before introducing our subject, I should remind you that travelling to the past does not mean you could change history.
What is time, exactly?
“For what is time? Who can easily and briefly explain it? ...If no one asks of me, I know; if I wish to explain to him who asks, I know not.” –St Augustine of Hippo
Across the fields of science, religion and philosophy, no unique and non-controversial definition of ...view middle of the document...
The first thesis is the flow of time thesis which matches the A series perception, or ‘Heracliteanism’, named after the ancient philosopher Heraclitus. Another name of the thesis is Presentism, as the name suggests, the concept maintains that events are constantly changing and flux and that there is an objective notion of the present. Events only exist in the present, past events may also exist but certainly not future events. The active moment brings about events from future to present and then past. Imagine the universe as a sausage machine, the present brings about the existence of events similar to the extruded stuff from the machine, and goes off to past.
Another thesis is the block universe thesis, or ‘Parmenideanism’ named after the ancient Greek philosopher Parmenides. It is also called 4 Dimensionalism, this theory argues that time is one of the four fundemental structure of the universe, along with the spacious (3D) world that we’re familiar with. An event is constructed of 3D objects matched with a unique time along the time dimension. Time is measured by the qualitative change between two different 3D stages. Their respective assignments of time along the time dimension manifest their sequence. It is in 2010 when you have physically and mentally changed compare to 2006 that explains time. In this thesis, the universe is like a tape with everything written. However, it is not determinism and further explanations are not within the scope of this essay.
David Lewis, a 20th century American philosopher discussed about time travel in his essay ‘The paradoxes of Time Travel’. Conventionally when we talk about time travel, we mean travelling to one’s past or future within the same ‘world’. This means time travel is impossible under the flow of time thesis, since past or future does not exist.
We will then have to turn to the Block universe thesis to examine the possibility of time travel. A time travel inevitably involves a discrepancy between time and time. It takes a zero or positive duration of time between the departure and arrival when the time traveler travels. For example, if it takes one hour for the time traveler to travle from 2010 to 2020, two different independent time dimensions must exist. This would result in having a pair of events located in different times. In graph one, the plane (T1, T2) indicates two-dimensional time, a given point in space (3D world) would have to be assigned to different times. Same conclusion would be drawn if he travels back to the past. However, this is not what we called time travel since it is not the same 4D universe that we’re concerning, he may have travelled to another possible 4D world or whatever, but certainly not his past.
What we are now left with is one-dimentional time travel. As things develop, some of our common sense will be challenged and we may discover some peculiar but still coherent circumstances.
For a time traveler to travel back to his past, time must be...