The Call, Column 88 – Keep the Sun in Mind

14 01 2018

(January 14, 2017)

The Urban Farmer

Keep the Sun in Mind

Last time, we started talking about this idea of the Sun as the Earth’s “passive clock”. Each place on Earth typically gets more sunlight (read: solar energy) during the day and less at night, and more sunlight during the summer and less during the winter. This is because of the Earth’s rotation about its own axis – which forms the 24-hour, daily “clock” – and because of the Earth’s rotation around the Sun – which forms the 365-day, yearly “clock”. This predictable, periodic ebb and flow in solar energy over the course of each day and each year influences basically every aspect of the climate and Earth’s geochemical cycles, especially the hydrological cycle.

I want to make a quick aside about my terminology before we continue. I’m using the word “passive” in a similar way to how it is used in engineering. The aspects of the Earth-Sun spatial relationship that form the clock I’ve described are just that…“passive”. Nothing on the Earth is making a decision, or anything like that, to heat up the air during the summer, or increase precipitation during the winter and spring. These happen because the Earth is the passive recipient of solar energy, and its geochemical cycles are driven directly by the ebbs and flows in this energy, and all of this correlates with the periodic clock of the day and the year. The Earth responds to the changes in solar energy because it is a passive relationship – because that’s just how its atmospheric and surface chemistry works.

In stark contrast, there exists something called an “active” relationship. In engineering, a thing’s behavior is active when it is able to make decisions about how to behave, based on some sort of “knowledge” of something else. If some aspect of the Earth were somehow able to adjust its behavior in response to the daily or yearly solar clock, it would be actively-controlled. That sounds odd, right? No part of the Earth is able to actively control its behavior based on the perceived position of the Sun, right? The “active solar clock” doesn’t exist, right?

It actually does! This type of control exists in a lot of different organisms on Earth, which are able to align their internal clock to the active solar clock – the perceived, relative position of the Sun, as it changes over the course of the day and the year – and make deliberate adjustments to their behavior based on this. Plants, fungi, some bacteria, and of course, animals (including human beings) have biological mechanisms within themselves that are able to keep track of the position of the Sun over time, and use – use, not just passively respond to – that information to maintain a regular, predictable time-base, upon which to shape their characteristics and behavior accordingly. How unbelievably cool is that?!

This process is called “the Circadian Rhythm”, and getting you all to geek out about it, as much as I am right now, is what prompted these two columns in the first place. If the discussion last time focused on the cosmological, physical, and chemical aspects of the solar clock, then today’s will be the biological and…shall we say, “computational” aspects.

Bacteria, fungi, and plants maintain their circadian rhythms using complex processes, wherein hormones and other chemicals are produced and consumed in their body tissue. They need to know when nighttime is coming, or when the seasons are changing, in order to affect various aspects of their reproduction, nutrient intake and assimilation, “sleep” cycles, and all sorts of other behaviors. This is arguably more impressive than animals’ circadian rhythms, because 1) it was evolved much earlier in these more primitive organisms, and 2) is done successfully without a central nervous system…without a real brain to regulate the process, like more highly-evolved animals have at their disposal.

But for the sake of maximum wow-factor, I want to limit the rest of the column to the animal (and mostly, mammal) circadian rhythm, which is easily the most interesting. Forgive the impending excited rant, but I want to make sure you understand how awesome this really is.

Our (mammals’) brains use actively-controlled chemical reactions, well-placed sodium and potassium ions, and cellular biology to maintain an internal clock that is synchronized with our eyes’ perception of the Sun’s position in the sky! This internal clock arose via evolution like two billion years ago, and forms an incredibly intricate feedback loop between us and our environment, which can be maintained even if the information about the Sun’s position is cut off for some period of time, which all takes place in the background of our logical and emotional thought, judgment, and free will.

It was optimized over time to both drive the performance of certain behaviors – feeding, breathing, sleeping, reproduction, etc – as a function of time, and also somehow utilize these behaviors to help keep the clock in sync. Our brains are able to do this by making chemicals and eating them, and storing it all with tiny bits of electricity!

This system is so finely tuned that it could be used to calculate the actual length of a solar day and solar year (which are a little longer than 24 hours and 365 days, respectively) better than human math and inventions could, up until relatively recently in our history. If you think about it one way, the very understanding of “time” and its passage is reliant on our circadian rhythms, and this understanding underwrote the invention of a mechanical clock. Rocks and algae didn’t invent timekeeping devices, because they don’t actually know what “time” is.

We only do, and were only able to, because our brains can somehow use melatonin and cortisol, our eyes’ light receptors, nerve endings and body temperature, and metal ions and neurons to keep track of and predict where the Sun is in the sky, even when it’s cloudy or nighttime. I hope you agree with me, when I say that this might be the coolest thing about biological life that I’ve ever heard.

So here’s a basic explanation of how this works. As an embryo, your genes were used to construct your central nervous system with the implicit expectation that there was a clock that needed to be maintained, and an as-of-yet unrevealed master clock with which it needed to synchronize. Your mom’s womb probably helped with this, and created an initial synchronization even though you couldn’t yet see the Sun. But shortly after birth, your brain used the photoreceptors in your eyes to start keeping track of the Sun – its brightness, its position, and the relative amounts of different colors of light – as well as things like air temperature, to gain an intuitive, neurological understanding of the periodic motion of the Sun, and aligned that happily-awaiting internal clock that your brain was constructed with, exactly to it. And using hormones and ions and electrical signals, it has endeavored and (mostly) succeeded to maintain this clock to this very day.

You get tired at night and awake in the morning, you sleep more during the winter and less during the summer, you get hungry and thirsty and even get the urge to use the restroom at certain times, your hormone levels fluctuate…all according to this clock. Even chickens lay far fewer eggs during the winter, because their brains understand it as a sub-optimal time to be reproducing and slow that biological process down as a result.

And, in my amateur understanding, how well each of these processes are able to be performed at the expected optimal time, gives feedback to your brain that further helps to entrain your circadian clock. When your brain thinks that it is sunrise, and spikes your cortisol to wake you up, there are cues that it looks for to check whether this assumption was right…and adjusts your circadian rhythm accordingly.

It is incredibly important that your brain is able to maintain this circadian rhythm, lest it not be prepared for stressors that may challenge your wellbeing. It has been proposed that obesity and some cancers are at least partially caused, or triggered, by “circadian dysrhythmia” – the mismatch between your brain’s internal clock, and the actual time of day and year.

Circadian dysrhythmia is not a biologically-normal state, and is actually caused by the way we live in modern, Western society. Bright, blue lights at night – from phones, TVs, and other screens, as well as some light bulbs – trick our brains into thinking it’s daytime; not sleeping enough and being woken up by an alarm, drinking too much coffee and messing with our cortisol levels, spending literally all day in a climate- and light-controlled building…all of these habits create the circadian dysrhythmia with which our species has found itself plagued.

My column appears every other Sunday in The Woonsocket Call (also in areas where The Pawtucket Times is available). The above article is the property of The Woonsocket Call and The Pawtucket Times, and is reprinted here with permission from these publications. These are excellent newspapers, covering important local news topics with voices out of our own communities, and skillfully addressing statewide and national news. Click these links to subscribe to The Woonsocket Call or to The Pawtucket Times. To subscribe to the online editions, click here for The Call and here for The Times. They can also be found on Twitter, @WoonsocketCall and @Pawtuckettimes.

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