I’ve made mention of this before, but it bears repeating; when I was a little lad growing up in England, it seemed to me that, as soon as two or more adults huddled together, they had only three main topics of conversation. They started with the weather—how it was today, how this compared to the past 50 years, and what we might expect in the coming decades. Then they moved on to health—discussing their various ailments, trying to outdo each other, and—if we were unlucky—comparing scars from previous operations. Finally, they came to everyone’s perennial favorite—how time seems to go faster the older you get.

Now that I adorn myself in an older man’s attire, it’s gradually dawned on me that—and I find it hard to believe I’m saying this—my parents and their companions may actually have had a clue. These days, if I blink, I find another day has passed; if I sneeze, I’ve lost another week; and if I… but we digress.

Do you remember when we were at school and we were first introduced to the concept of a horizontal integer number line with zero in the middle, negative values presented to the left, and positive values marching off the page to the right? This concept seems obvious now, but it came as something of a surprise to the unwashed masses when the English clergyman and mathematician John Wallis included it in his Treatise on Algebra in 1685.

Much the same thing happened with the introduction of the timeline, which is a display of a list of events presented in chronological order. In this case, time is usually represented as a horizontal line with earlier events (the past) on the left and later events (the future) on the right. The concept of a timeline seems intuitively obvious to us now. However, when it was invented in 1765 by the English chemist, natural philosopher, and separatist theologian, Joseph Priestley, it was so radical that he was obliged to publish a small accompanying book to explain its underlying principles (see The Invention of Time, published in History Today, Volume 73 Issue 8 August 2023).

Joseph Priestley’s A New Chart of History, 1765 (Source: Wikipedia)

Looking at the above chart with time progressing from left-to-right triggered another thought with respect to the “arrow of time,” which is the concept positing the “one-way direction” or “asymmetry” of time that was conceived in 1927 by the British astrophysicist Arthur Eddington. It’s obviously convenient that we perceive and understand events as having a causational (“cause-and-effect”) relationship. On the other hand, why is it that time (if it exists at all) “flows” only in one direction?

Another possibly related question is why does our universe contain 99.999%+ regular matter and only 0.001%- antimatter? In modern physics, antimatter is defined as matter composed of the antiparticles (or “partners”) of the corresponding particles in “ordinary” matter and can be thought of as matter with reversed charge, parity, and time, known as “CPT reversal.” In his book Reinventing Gravity, John W. Moffat postulates that, in addition to creating our universe with regular matter and the arrow of time going “the right way,” as it were, the Big Bang may also have spawned a “mirror image” universe composed of antimatter with its arrow of time going “the other way,” if you take my meaning.

Unfortunately, I am a bear of little brain, and all these lofty concepts make my little brain ache.   

“What on Earth triggered your current cogitations and ruminations?” I hear you cry, “And why are you inflicting them on us?” I hear you whisper under your breath. Well, I was just reading a jolly interesting whitepaper on Intel’s website. The title of this paper is, Intel PTP Servo Solution for Time Synchronization Applications. Following the Executive Summary with its small words and short sentences (bless their little cotton socks), the first introductory section is titled (you guessed it), What Is Time, What Time Is It, and Why Do We Care?

On the one hand, it must be said that the authors make some excellent points. On the other hand, each of the points they make sets a bunch of related ideas ricocheting around my poor old noggin. As a result, I decided to expound, elucidate, and explicate (fear not, I’m a professional), so hold onto your hat because here we go…

What is Time?

Time is difficult to define (“I’m a poet and I never knew-it,” as they say). As Saint Augustine of Hippo (A.D. 354-430) famously noted: “What, then, is time? If no one ask of me, I know, but if I wish to explain to him who asks, I know not” (see In Search of Time: The History, Physics, and Philosophy of Time by Dan Falk).

In the first book of The Hitchhiker’s Guide to the Galaxy by Douglas Adams, one of the characters notes: “Time is an illusion. Lunchtime doubly so.” Although this was intended as an “off-the-cuff” remark, many contemporary physicists agree that time may well be illusionary. While some physicists (currently the minority) continue to believe that an objective, “universal time” is a fundamental aspect of the universe, others (currently the majority) no longer consider time to be an independent property or quality. There’s a convincing argument that, at its most elementary level, the universe is a “sea of quantum foam,” which leads to the argument that there really isn’t such a thing as space that contains things and there isn’t really such a thing as time during which events occur (see The Order of Time and Reality Is Not What It Seems: The Journey to Quantum Gravity by Carlo Rovelli).

At the macro level in which humans exist, of course, time is experienced as a subjective reality. Following Einstein’s publication of the general theory of relativity in 1915, it’s now understood that time can speed up and slow down in the presence of cosmological bodies with different masses and velocities. As a result, 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—which are travelling at roughly 8,700 mph (14,000 km/h) at an altitude of 12,550 miles (20,200 km)—will drift by 45µs a day as compared to ground-based stations.

This 45µs value is the result of two complementary effects. Time dilation associated with the speed of the satellite means that, if this was the only effect, the satellite would experience one day on Earth as one day minus 7µs. Countering this is the fact that the Earth’s gravitational effect is much stronger on the surface. If this was the only effect, then the satellite would experience a day on Earth as being one day plus 52µs. Taking both these effects into account gives (52 – 7) = 45µs. If not constantly corrected for, this would equate to positional errors on everyone’s GPS systems of approximately 8.4 miles (13.5 km) a day, which would be annoying, to say the least.

Just a couple of paragraphs above we noted that “a second on the surface of the Earth does not necessarily have the same ‘duration’ everywhere in the universe.” It’s worse than you think. In fact, a second on the surface of the Earth doesn’t actually have the same duration as a second in the Earth’s core. As reported by the New Scientist, The Earth’s Core Is Two-and-a-Half Years Younger than Its Crust (I tell you; I couldn’t make this stuff up).

It is generally agreed that time—whatever it actually is—is an emergent property that came into being with the rest of the universe 13.8 billion years ago as part of the Big Bang. That is, there was no space and no time prior to the Big Bang. With respect to the space-time continuum, both the standard model of quantum mechanics and the general theory of relativity remain incomplete, not least that they cannot be reconciled with each other; also, there are discrepancies between the universe we observe and the universe the general theory of relativity predicts. There is also the possibility that, as a function of their masses and velocities, different areas of the universe (think galaxies and galactic clusters) may be at different ages. And then things start to get complicated.

What Time Is It? 

Our need to know the time has evolved along with our sociological and technological requirements. Many ancient nomadic peoples migrated with the seasons, which required them to keep track of important celestial events like the summer and winter solstices and the vernal (spring) and autumnal (fall) equinoxes. Similarly, ancient farmers needed to know when to plant and harvest their crops.

As technology grew, so did people’s need to know the time with greater accuracy. Railroads provide a classic example. In England, up until the latter part of the 18th century, time was normally determined in each town by a local sundial. As a result, the time in a town or village could differ by as much as 20 minutes from the time in London.

This wasn’t a problem when travelling between towns and cities on foot or by horse-drawn carriage could take days or weeks. However, it did become problematic with the introduction of railroads circa the 1820s and 1830s, when even relatively small discrepancies in time could cause confusion, disruption, and accidents. Due to opposition by local factions, early railway stations often had two clocks—one showing “railway time” (i.e., “London Time”), while the other displayed “local time.” Eventually, everything was brought in line with London Time; that is, the time set at Greenwich by the Royal Observatory, which was already widely known as Greenwich Mean Time (GMT).

The situation was even worse in the United States when railroads were introduced circa the 1850s and 1860s. In addition to myriad local times, there ended up being 50 different railway times. As a result, anyone attempting to travel across the country by rail was required to perform substantial mental gymnastics to reconcile the various timetables.

Following several accidents involving trains colliding due to things like their guards having different times set on their watches, the railway companies agreed to divide the continental USA into the five time zones we employ to this day (Alaska, Pacific, Mountain, Central, and Eastern). However, although this scheme was proposed in 1870 and adopted by the railway companies in 1883, it wasn’t until 1918 that these time zones were incorporated into federal law.

Why Do We Care? 

When people wish to collaborate on some event, it is advantageous for everyone involved to share a common understanding of the current time. In order to catch an airplane, for example, it is necessary for passengers to arrive at the airport prior to the plane’s scheduled departure (I’ve tried doing things the other way and it doesn’t work nearly as well). Similarly, if a group of friends agree to meet at a certain time and location to hike up a mountain, it behooves them to all be aware of the correct time, otherwise someone is going to be left behind (once again, I speak from experience).

In the not-so-distant past, determining the precise time was no easy task for the average person, not least that household clocks and personal watches tended to gain or lose a few seconds each day. To address this problem, different countries introduced their own versions of a “Speaking Clock,” which was usually accessed by telephone. Such services started in the USA in 1934 (where it was known as the “Time of Day” service), the UK in 1936, Canada in 1939, Australia in 1953, and so forth. Users would call the service, which would report the correct time every 10 seconds using a recorded human voice saying something like, “At the third stroke, the time will be twelve forty-six and ten seconds…,” followed by three beeps. Most of these services have now ceased, although some continued long into the 2010s and a small number persist at the time of this writing (see also The Speaking Clock Speaks No More).

In addition to determining the correct time, programming it into electronic equipment was also problematic. Anyone who lived in the 1970s and 1980s will well remember the frustration that accompanied attempting to program the time into a video cassette recorder (VCR). Many people simply gave up. Even the ones who succeeded typically ended up recording the right channel at the wrong time or the wrong channel at the right time (recording the right channel at the right time was cause for celebration).

Things are a lot easier today. Devices like cable boxes and smart televisions automatically determine the correct time via the internet, as do computers, tablets, smartphones, etc. Sometimes they do this via hard-wired connections (coaxial cables or CAT5/CAT6 Ethernet cables); other times, they employ a wireless connection like Wi-Fi. As a result, it’s typically only unconnected devices like microwave ovens whose clocks need to be reset following a power outage or to accommodate transitions between standard time and Daylight Saving Time (DST). 

The point of all this is that, as our technologies advance, it becomes increasingly necessary for all the devices and subsystems forming a larger system to agree on a common reference of time in order to function correctly and optimally.

Yes, of Course There’s More

To coordinate the actions of disparate electronic systems potentially dispersed around the globe, all these systems must be synchronized in time. Take packet-based networks, like those employed by 5G Radio Access Networks (RANs), for example. Have you ever wondered how the various elements in the network manage to keep track of time?

Returning to the aforementioned Intel PTP Servo Solution for Time Synchronization Applications whitepaper, I was amazed to discover that networks achieve this by passing timestamped packets back and forth. This started with the Network Time Protocol (NTP), which can synchronize clocks with millisecond accuracy, and was superseded by the Precision Time Protocol (PTP), a.k.a. IEEE 1588, which can achieve accuracy in the sub-microsecond range. Suffice it to say that this paper opened my eyes to all sorts of nuggets of knowledge, tidbits of trivia, and juicy factoids with which I can bore my family and friends.

How about you? Do you have any thoughts you’d care to share regarding anything you’ve read here?