A question of Time: [Part 1: Understanding & Definition]
Time, one of the most important things [should I even call it a thing?] in our day to day lives. As far back as we can remember, humans have always had time. Everything we do or talk about or think about, at one point, we have to reference time.
But what is time?
Wikipedia defines time as the indefinite continued progress of existence and events that occur in apparently irreversible succession from the past through the present to the future. It goes on to define the past, present, and future as follows:
The past is the set of all events that occurred before a given point in time.
The present is the time that is associated with the events perceived directly and in the first time.
The future is the time after the present. Its arrival is considered inevitable due to the existence of time and the laws of physics.
All the above definitions are given from a particular human perspective of time being like a continuous line starting from the past and infinitely flowing into the future. To be frank and logical, this does make a lot of sense. We have been constantly traveling from the past into the future as far as we can remember. Our past we remember as those things and outcomes that happened before now and we are continuously experiencing our now which is always leading us to the next point in the line.
Coming back to the human perspective, it would be interesting to review our understanding and view of time and if and how it may have changed.
I’d say from my own opinion that the most way that people view time is like an SI unit of happening. We have this straight line that runs independently of anything else and we then have to measure everything we do against this constant line and assign a spot for everything. It is a perfect way for maintaining a chronology of existence. We use this method to measure how long it takes to complete a task, how old we are, how long certain events took etc.
Another perspective I’d say most have is that of time being like a circle just like the way a clock is. In this perspective, the relationship between the past, the present and the future is still a linear one progressing respectively. However, there is some sort of repetition. We have this 24-hour cycles that are always repeating themselves. We have these four seasons that are always following each other in a particular order. It’s like the whole universe is in a forward progressing loop of events but the occurrences within this loop are changing and hence the past, present and future are still possible.
Both these two perspectives operate on the notion that time is absolute. Time is the same everywhere. Originally introduced by Sir Isaac Newton, absolute time and space are independent aspects of objective reality. This means that time exists independently of any perceiver of factors and progresses at a consistent pace throughout the universe. This is an idea that most people I talk to seem to get behind.
Then came the theory of relativity. Now, before I even go on to define relative time, let’s play out some scenarios.
Imagine you are seated in a theatre somewhere. On the stage is fella sitting on a chair that is moving horizontally. The movement is illustrated below:
Then, after a while, the fella is given a tennis ball and instructed to start throwing it up and down while the chair still moves horizontally. Now to you who is seated in front of the stage, the movement of the ball will look like below:
Now imagine, that you are the fella sitting on the moving chair while throwing the ball up and down. The movement of the ball will look like:
Now, put that idea aside and let’s go back to defining relative time. To explain this we have to explain Time Dilation. Wikipedia defines time dilation as the difference in the elapsed time measured by two observers, either due to a velocity difference relative to each other or by being differently situated relative to a gravitational field.
Jesus Christ on a wooden scooter! What the hell is that?! In simple terms, time is not the same everywhere. We all experience time differently based on other factors like velocity, height, gravity etc.
One very popular experiment is the Hafele-Keating experiment to test the theory of relativity. These two built atomic clocks and flew with them twice around the world. When they came back, they compared the clocks to those that had remained in the US and the clocks seemed to be disagreeing with one another. In this experiment, a clock on the plane flying eastward [direction of the Earth’s rotation] had a higher velocity than the one left on the ground and thus lost time. The clock that was on the plane flying westward had a lower velocity than that on the ground.
This and very many other experiments go to show that time is not absolute. Time slows with speed but the time dilation is so small that in most cases, we can ignore it. This does not, however, mean that the difference is to be assumed. I believe that this fact is a very huge shift in terms of how we understand time and relate to it. It is not a preset environmental SI unit.
This finding leaves a bunch of questions in my head.
If time is not the same everywhere, How does this affect this the forever moving line of time? Is it even a line? Does nature basically assume those infinitesimal differences in time dilation?
Enjoyed the read? Check out A question of Time Part 2 on MindNinja where I’ll be diving into space-time and trying to answer my questions.
