What is Time?

Time is something that everyone is familiar with: 60 seconds is one minute, 60 minutes is one hour, 24 hours is one day, and so on. This is known as Linear Time and is something that everyone is familiar with and agrees upon. But consider this: if someone came up to you on the street and asked you to draw time, what would you draw? You might draw a clock or a watch ticking every second. Or you might draw a calendar with X's over each day to represent the passing of time. But that's all those drawings would be: just physical representations of the passing of time. Those drawings would just scrape the surface of the Enigma that is time. Something that seemingly runs our lives and is unavoidable can't be explained by even the smartest people on Earth.

So what is time, and can we prove that time even exists? Aristotle once said, "Time is the most unknown of all unknown things." That was nearly 2,500 years ago, and it still stands true today. If you were to go to Google and type in, "What is time?", you would find that it says time is a dimension, and in many ways it is. When you text a friend and ask them to meet for coffee, you wouldn't give them a place without a time. However, there's a flaw in that definition of time; it leaves too many doors unopened—because time is also a measurement. For example, I was born in the 1990s. That was over 20 years ago. If I were to say I was born 18 billion kilometers in the past, that wouldn't make much sense, and people would probably look at me like I'm crazy.

With spatial dimensions—the 3D world that we live in—it's very easy to go back and forth between places because these things are essentially fixed in space. If I went to the store to buy groceries and I forgot milk, I could easily go back and buy some milk. However, the time that it took to do that is unable to be retrieved. It is lost forever into the past. An object placed in 3D space will stay there almost indefinitely. If I place a bottle on the table, it will just stay there, but that bottle still falls victim to time. See, time is like an arrow—it moves in one direction: forward. Scientists fittingly called this the arrow of time.

If you one day woke up and found yourself floating in the middle of empty space, would you be able to tell which way is up, down, left or right? Probably not. However, time is a much simpler ordeal. See, time comes from the past, originating at the Big Bang, where our history lies and is fixed, through the present, where we are essentially prisoners of, towards the unknown and turbulent future. We can remember things from the past, like how I can tell you that this morning I went to the store, bought groceries, and then forgot to buy milk. But at the same time, I can't tell you what I ate for breakfast next Thursday.

The arrow of time originated at the Big Bang and has been moving forward ever since. We used the second law of thermodynamics to represent this. It is known as entropy. Think of entropy as a measure of disorder in the universe. At the Big Bang, all the matter in the universe was compacted into an infinitely small point. This is considered a very low entropy situation; a very orderly situation. It would be similar to stuffing every sock that was ever made into one drawer. In that situation, you know with 100% certainty where your socks would be. Ever since the Big Bang, all the matter in the universe has been expanding away from each other, making the universe a higher entropy system.

Because of entropy and because of the arrow of time, we have galaxies, stars, planets, and even life. Entropy is the reason that you can tell the difference between the past and the future. It explains why every human is born and then lives and then dies, always in that order. If there were no entropy—if there were no change in the universe—you wouldn't be able to tell the difference between the year 2017 and the year 1 billion. No matter what you do, time moves forward and doesn't stop for anyone or anything. At least on the macro scale. See, the arrow of time works and is extremely noticeable on l...