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Visualizing Time: An Essay

If time were stopped, would this falling pen look blurry to us?
Time can be a very confusing subject. It has a past, a present, and a future, but the future keeps changing and the present is always moving, while the past grows larger. Although most people think they understand time, they often get confused when they try to describe it. To help visualize and understand time, many people compare it to a very familiar concept: a line.

This line, called a timeline, represents time as a whole. The current moment, or the present, is a single point which moves smoothly along the timeline. The part of the timeline behind the point is the past, and the part ahead of the point represents the future. The whole timeline, including the moving point that represents the present, is considered exactly the same for everyone. Although this whole approach may be a useful way to represent time, it is actually inaccurate in describing time.

First of all, the present does not have to be experienced in the same way for everyone. In many science fiction films, including Star Trek: The Voyage Home, the characters time travel to different time periods using various methods such as high velocity. Time travel may not seem possible, but according to Einstein's general theory of relativity, it actually is.

According to Einstein's theory, objects in a strong gravitational field experience time more quickly than objects in a weak gravitational field; this effect, called "time dilation," has been supported experimentally, and even has to be regarded when synchronizing the clocks on GPS satellites (1). In fact, the first GPS satellite was designed without regarding time dilation, and within hours the satellite was noticeably out of sync with clocks on earth.

Due to time dilation, if two people were both experiencing the same point on the timeline, one person could be placed in a high-gravity environment so that he would experience time faster than the other. He would then move more quickly along the timeline than the other person, effectively moving into the future until he is experiencing a different period of time than the other person. Therefore, the present is not necessarily the same universally, and is unique to each person experiencing it.

Furthermore, the present should be represented by a line at least 23 milliseconds long on the timeline, not a single point. It should be represented this way because humans perceive and experience multiple points of time simultaneously, due to their imperfect sensory processing, which not only blurs periods of time together but also delays perception time by varying amounts.

According to a study published by Michael Barnett-Cowan, PhD, and Laurence R. Harris, PhD, the perception time for a visual stimulus is 220 milliseconds, while the perception time for an auditory stimulus is 197 milliseconds (2). This means that a person would visually experience one point in time while simultaneously experiencing sound that occurred 23 milliseconds earlier.  Because the present is defined by a person experiencing it, the present should be represented by a period of at least 23 milliseconds on the timeline, rather than a specific point on the timeline, because that is the minimum range that each person experiences at a given time.

Even if humans had perfect senses, the present moment would still need to be represented as a small line on the timeline, not a single point. It should be represented this way because time has a smallest possible length. The smallest possible length of time, called the Planck time, is defined as the amount of time it takes for light to travel a distance of one Planck length, which is believed to be the shortest possible distance. Because nothing can travel faster than light, no event can happen in less than one Planck time (3). Admittedly, because the Planck time is such a short period of time, it would still be somewhat accurate to represent the present with a single point; however, it is more accurate to use a line of at least one Planck time in length.

To summarize, the commonly accepted model for time is incorrect; time is not universal, and the current moment cannot be accurately represented with a single point. In reality, time is different for every person, and the current moment is an interval of at least 23 milliseconds. This new model will seem a little strange to most people; it is certainly difficult to accept after living with the old one for so long. But it is probably the closest the average person will ever get to making sense of the mystery of time.


REFERENCES:

 1. Barnett-Cowan, Michael, and Laurence R. Harris. "Perceived Timing Of Vestibular Stimulation Relative To Touch, Light And Sound." Experimental Brain Research 198 (2009): 221-31. Print.

2. "Planck Time." Cosmos. Swinburne University of Technology, n.d. Web. Accessed 19 Sept. 2014. <http://astronomy.swin.edu.au/cosmos/P/Planck%2BTime>.

3. Wolfson, Richard. Simply Einstein: Reality Demystified. 1st ed. New York: W.W. Norton, 2003.

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