Before I explain why time travel is impossible, I first need to describe what this elusive word ‘time’ refers to. Well, if we look at a dictionary, then what we discover is that the word time has many conflicting definitions.

http://www.merriam-webster.com/dictionary/time

But what all of these definitions have in common is that they all ultimately refer to motion. Time is a dynamic concept, not a static one. Time is a measurement of motion. Time either refers to “past, present and future” (an abstract description of objects moving from their ‘past location’ to their ‘present location’) or to our measurements of “seconds, minutes, hours, days, weeks, etc, etc.” (Which is based off of the earth’s motion around the Sun). We used this concept to invent sundials, hourglasses and clocks.

Time is an extremely common word. In fact it’s one of the most commonly used words in the English language. Yet this word is actually defined very sloppily and inconsistently. Time is a vague word that has very little meaning. A much better word to use when discussing this subject is ‘motion’. The word motion refers to the changing locations of objects. Unlike ‘time’ the word motion has a very clear meaning.