Time is a funny old thing. First and foremost, time is difficult to define (but not to rhyme). As Saint Augustine of Hippo (A.D. 354-430) famously said: “What, then, is time? If no one ask of me, I know, but if wish to explain to him who asks, I know not” (see also In Search of Time: The History, Physics, and Philosophy of Time by Dan Falk).

For most of us, time is predominantly a subjective experience. When I was a kid, and there were two weeks to Christmas, and I looked at one of the big analog clocks that were everywhere, the second hand would go sooooo slowly. Not Tick, Tock, Tick, Tock, like it usually did, but more like Tick… … … … … … … … Tock… … … … … … … … Tick… … … … … … … … Tock…

Oh, the suspense. By comparison, at my current age, when there are still two weeks to Christmas, all I need to do is blink to find myself already embroiled in the New Year.

And then there’s objective time, which can speed up and slow down in the presence of cosmological bodies with different masses and velocities. This means a second on the surface of the Earth does not necessarily have the same “duration” everywhere in the universe. For example, unless corrections are applied, the clocks in GPS satellites will drift by 45µs a day as compared to their ground-based counterparts. My current understanding is that, as a function of their masses and velocities, different areas of the universe (think galaxies and galactic clusters) may be at different ages.

As John Lennon famously noted, “Reality leaves a lot to the imagination.” I wonder what John would have thought if he’d got to read Reality Is Not What It Seems by Carlo Rovelli and Is Time Truly an Illusion by your humble narrator. If I were to boil this down to its quintessence, I’d say: “It now appears that there really isn’t such a thing as space that contains things, and there isn’t really such a thing as time during the course of which events occur.” And then things start to get complicated.

Of course, this leads to all sorts of cogitations and ruminations, like when I posed the age old question Is Dust in the Wind All We Are?

Solstices and Equinoxes (Click image to see a larger version — Source: Max Maxfield)

My wife (Gina the Gorgeous) often says that I’m oblivious to whatever is going on around me (and that’s when she’s in a good mood). For example, I used to do a lot of camping when I was a boy scout. We often watched the sun rise in the morning and set in the evening. Gina’s comment leads me to think that, if I had been born a caveman (well, cavekid), I probably would never have noticed that the sun rose or set a little more to the right or left each day until it reached the summer or winter solstices, at which point it reversed direction. But some cavemen did notice these things, leading them to build stone structures like Stonehenge to mark the longest and shortest days of the year.

It’s one thing to wait for your stone structure to tell you that you’ve just arrived at the winter or summer solstice and to then take things from there. However, problems start to arise when you learn to count the days from one winter solstice to the next and you come up with 365, and you start basing everything you do (like planting and harvesting crops) around this number, not realizing that a year is actually closer to 365.25 days (well, 365.2422 to be a tad more precise).

Solstices and Stonehenge (Click image to see a larger version — Source: Pixabay.com)

I wonder how long it took before people started to notice that they had a problem. The solution we eventually adopted was to have leap years in which we add an extra day on February 29 approximately once every four years (I’m glad that’s not my birthday present-wise, but it would be nice to be only a quarter of my present age). The reason for the “approximately” qualifier is that the year isn’t exactly 365.25 days long, which requires us to introduce a “fiddle factor.”

I remember once seeing an advert for something in an electronics magazine. They quoted the number of seconds from a specific date that year to another date tens of thousands of years in the future. “Hmm,” I thought to myself, “I wonder if they accounted for leap years?” I checked. They had. This made me happy.

There’s also the fact that the Earth’s rotation is slowing over time due to tidal effects caused by the Moon. As a result, days today are about 1.7 milliseconds longer than they were 100 years ago. So, 1.7 x 365.25 x 100 = ~62,093 milliseconds = 62 seconds slippage over the course of the past 100 years. Taking all of this into account is why scientists occasionally make leap second (that is, one second) adjustments to the time being maintained on their atomic clocks (it gives them something to do, bless their little cotton socks).

I could waffle on about this stuff for hours. Fortunately for both of us I don’t have to because those clever chaps and chapesses at SiTime recently posted a blog: Decoding Time: Why Leap Years Are Essential for Precision. Since they’ve taken the time to write it, I think the least we can do is bounce over to their website and read it. In the meantime, I would be interested to hear your thoughts on time, ideally in a timely manner, but only if you have the time.