So, if we think about that, this is certainly a shame, because there are a few things that are more magnificent than a view of the night sky.
But we should also think about what is this doing to our health if we’re flooding ourselves with this amount of light pollution?
So I want to I tell you that all throughout your bodies, in all of your organs, you have biological clocks that keep you in sync with the light-dark cycles of your environment that result from the Earth’s rotation. And in your heads you have a master clock, a main clock that synchronizes all of these other clocks in your bodies.
The way that this works is that light travels from a source, such as the Sun, or an artificial light source, through your eyes, and that light information is then conveyed to the brain, to the master clock that’s in a part of your brain called the suprachiasmatic nucleus, or the SCN.
So in your eyes you of course have cells that help you see the stars, that help you form visible imagery. But you also have cells that are not a part of the visual-forming pathways, but rather their role is to capture light information and basically convey it to the brain, to tell the brain what time of day it is.
So, how can I convince you that you have this clock?
Well, if I closed you in a dark room where you would have no external source of light, no alarm clocks, no clocks of any kind, you would still retain rhythmic sleep and wake patterns at least for a little while, because your clock was previously trained to light-dark cycles. And one of the main functions of the clock is to regulate behavioral rhythmicity.
This, of course, is not an experiment that many of you would be willing to subject yourselves to, but, fortunately, there’s an experiment that most of us have participated in, which is traveling across time zones.
So, I like this quote that says:
“When you travel from America to Europe, your soul takes about three days longer to get there.”
And I know this is certainly true when I travel from here to Serbia, my home country. It does take me several days basically, to feel normal, to feel aligned with the population that’s living there. And this is because your clock takes a few days to get realigned with this new schedule.
And, if you think about this, this makes sense, right? So, for pretty much all of our history, except for a blink of an eye, in our evolutionary history, nobody had a way of hopping from one continent to the other in a matter of hours. We’re changing time zones so quickly, and in this case, nature’s not really keeping up with what we are capable of doing.
So, what is this clock? And why is it important to think about light?
The clock is a molecular oscillator, the details here are not important at all, I don’t want you to look at the names of these things on the board. But I want to point out that the clock is essentially the same in animals such as fruit flies, which my lab uses in our studies, and in mammals like mice or humans.
And the first glimpses of the clock, the components of the clock, and the way that it ticks were gained in the fly, actually. What I want to stress here is that the clock is tuned by light.
Some of the components of this clock are actually degraded, directly degraded by light. So, that results in the state of the clock essentially oscillating throughout the day and night.
You can imagine if the composition of the clock, if some of the components are degraded, the composition of the clock will change between day and night. And then the outputs of the clock between day and night will be different.
So, for instance, during the day, the state of your clock is such that you are suppressing production of melatonin, which is the hormone that helps you fall asleep, but also has other functions, such as anti-cancer and antioxidant properties.
So light. Let’s talk about blue light a little bit. When you’re outside during the day, you’re, of course, exposed to sunlight which consists of different wavelengths of light.
But the one that’s particularly important is blue light, because of its effect on our clock. Blue light also directly elevates your mood, it boosts your attention and your alertness.
So blue light during the day is very, very good, and I’d say that most of us don’t spend enough time in a bright light outside. You should be for 30 to 60 minutes outside in bright light, so put some sunscreen on and go outside.
The flip side of this is that when you come home at night I would dare guess that pretty much none of us spend the rest of the day when we come home, in darkness, and we’re not in tune with the natural light and dark cycles, right?