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Comment by adrianmonk | Hacker News Reader

I suppose there are two types of people: those who would consider it fine if a night light is on continuously all night, and those who would not.

I'm firmly in the second category. I want my room to be as dark as possible while I'm sleeping. I don't have a night light right now, but if I did, I would get something that errs on the side of not being lit. For example, a motion-activated one.

If that is what this dim by default behavior is intended to accomplish, then it sounds like a wonderful idea to me. A night light is a hard sell for me in the first place, but this is the sort of thing that might convince me to consider it.

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I totally agree the dim to dark is an amazing feature before bed. I just wish they would use something better than a 2700K LED if it's supposed to be used in the 15-45 minutes before sleep.

In my opinion, if people are able to sleep in darkness, they should, and it's not a good habit to start kids out sleeping with the lights on.

>> and it's not a good habit to start kids out sleeping with the lights on.

Why? I usually see issues going the other way, where kids from birth get absolute quiet and dark, then can't get to sleep without those conditions for the rest of their lives (i.e. adults who need blackout curtains and ear plugs to sleep).

I've wondered about that -- my partner and her cousin both grew up in the Midwest and need white noise and eyeshades to sleep. For reference we live in the SF Bay. I grew up here and can sleep through damn near anything. I'm curious how much of the difference is due to childhood locality vs genetics vs child-rearing practices.

Have you ever tried sleeping with eyeshades?

It has been shown[1] that even small sources of light can inhibit the secretion of melatonin (the hormone that regulates the circadian rhythm and consequently sleep).

If you use eyeshades, you might feel more rested in the morning (if your bedrooms is not already pitch black dark, that is).

As a personal anecdote, I always feel less rested when I don't use eyeshades.

[1] https://www.ncbi.nlm.nih.gov/pubmed/3567262

I'm not a doctor, but we know about the negative effects of light on sleep. Our species evolved with little nighttime light, and we know the mechanism by which our circadian rhythms are tricked by artificial light.

Most sleep experts (including pediatric sleep experts) recommend blacking out your room, removing all electronics, etc.

Perhaps an expert in this area can chime in, but I don't think light during sleep is positive.

Did the moon not exist during evolution?

It did, and it actually does have a circadian effect. But it has much less illuminance than most artificial light sources. That's what I mean when I say "little nighttime light."

The full moon under the best possible conditions can reach about 0.3 lux illumination.

By comparison, phone and laptop screens start around 400 lux and go up from there.

The moon at its brightest is about 0.5 lux, and that's at its peak... once a month (waxes and wanes obviously).

Many nightlights I've tried are at least 0.5 lux depending on distance, but are often higher (1 lux or more)

”moon at its brightest is about 0.5 lux”

Given the wonders of dark adaptation of the human eye (https://en.wikipedia.org/wiki/Adaptation_(eye)#Dark_adaptati...), does that really matter? In my experience, the full moon is almost bright enough to comfortably read normal black on white printed text.

Many of the mechanisms for light impacting biological functions show a clear dose-response relationship - fewer photons hitting the retina leads to less effect.

As a rough estimate, one decade (10x) of the eye’s light adaptation, at most, comes from aperture variation - the pupil expanding and contracting. The rest comes from intensity-driven modification of the sensing and image processing systems in the eye - rods that are completely saturated with signal above a few dozen lux become the primary sensors in very low light.

In other words - just because the moon provides enough light to see and even read doesn’t mean that it will cause insomnia.

It’s interesting to think about the origin of the many ancient myths and legends about human behavior during full moons (i.e. insane behavior, sleepwalking, criminality,accidents, etc) and the possibilities of even that small amount of light (as generated by a full moon) having an affect on human behavior and emotion, especially during times of our evolution when the alternative was a nearly pitch black environment.

While not conclusive, it would appear that light and subsequent circadian disruption may increase chances of things such as breast cancer. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3002207/

From an evolutionary biology standpoint, I would expect being able to sleep through light and noise a negative for survival.

Absolute quiet provided by a white-noise sound machine, plus darkness provided by blackout curtains, was/is crucial in helping my toddler get healthy, successful naps. Without them, he would not be able to sleep with the afternoon sun pouring in the window while listening to Mom and Dad putter about the house.

It does make me worry how we'll wean him off the sound machine.

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