I didn't use to think very much about time. When you're younger, you don't have to think about time except as something you need to keep track of so you're not late.
Funny how growing old can alter your perception of even the most fundamental of life's experiences. The passage of an hour or a day is noticed far more when I'm 71 than when I was 51 or 21.
When we think about time, we usually think of the "flow" of time — slow or fast — and our perception of that flow. The fact is, the "flow" of time is an illusion.
"When we say something flows like a river, what you mean is an element of the river at one moment is in a different place of an earlier moment. In other words, it moves with respect to time. But time can’t move with respect to time—time is time," writes physicist Paul Davies
It's called "temporal perception," or "chronoception," and it's revolutionizing our concept of the universe. Our perception of time isn't based on any objective reality but can be influenced by everything from our emotions and the intensity of our focus to our state of mind, even our age and experience.
For example, boredom can be perceived as making time pass very slowly, while excitement can cause the perception of the passage of time to speed up.
"A watched pot never boils" isn't true, but the suggestion of how time's passage is perceived is accurate. When you're intently waiting for something, your focus on the desired outcome can make the waiting period feel prolonged.
"A lot of people make the mistake of thinking that the claim that time does not flow means that there is no time, that time does not exist," Davies says. "That’s nonsense. Time of course exists. We measure it with clocks. Clocks don’t measure the flow of time, they measure intervals of time."
But the idea that time is fundamental to the creation of the universe may not be entirely accurate. Is there such a thing as "pre-time"?
This dichotomy between space-time being emergent, a secondary quality—that something comes out of something more primitive, or something that is at the rock bottom of our description of nature—has been floating around since before my career. John Wheeler believed in and wrote about this in the 1950s—that there might be some pre-geometry, that would give rise to geometry just like atoms give rise to the continuum of elastic bodies—and people play around with that.
From a scientific point of view, there is no way to measure or quantify anything that might be described as "pre-time."
The problem is that we don’t have any sort of experimental hands on that. You can dream up mathematical models that do this for you, but testing them looks to be pretty hopeless. I think the reason for that is that most people feel that if there is anything funny sort of underpinning space and time, any departure from our notion of a continuous space and time, that probably it would manifest itself only at the so-called Planck scale, which is [20 orders of magnitude] smaller than an atomic nucleus, and our best instruments at the moment are probing scales which are many orders of magnitude above that. It’s very hard to see how we could get at anything at the Planck scale in a controllable way.
According to Wikipedia, the Planck scale is "a set of units derived from fundamental physical constants that defines the smallest meaningful units of length, time, and mass." At the quantum level, the laws of physics change, meaning that any attempt to conduct an experiment proving a theorem would be futile. The smallest measurable unit of time, roughly 5.4 x 10⁻⁴⁴ seconds, is currently beyond our ability to read it.
For the time being, the fundamental aspects of time and the passage of time will remain tantalizing mysteries. But science is already looking at ways to slow the perception of time, perhaps looking forward to a time when we won't be such slaves to the clock.
