2023-01-16 6 min read


NOTES, 2023-01-16.

The monochromatic room at the Exploratorium is a surreal space. The room is lit using low-pressure sodium vapor lamps, which were commonly used in streetlights from the 1980’s through the 2000s, but are now mainly used near observatories and turtle nesting sites where light pollution is a concern. These lamps produce light exclusively at 589.0 and 589.6 nanometers, making them – and everything in the monochromatic room – *really* orange.

Inside the monochromatic room, life feels completely flat. It is a space devoid of the nuance and meaning that comes from color, as if somebody hit pause. You can’t see someone blush with embarrassment, or the shade of their lipstick, or the rainbow pattern on their new kicks. It was in that room where the relationship between light and lived experience clicked for me.

The monochromatic room is, of course, simply a heightened version of what most human-constructed spaces are like. Although LEDs and fluorescents perform better than sodium lamps, they fall short of the spectrum and intensity of sunlight. Illuminating your home with flat, uninspiring light, will make the home cooked meal you put so much effort into also look flat. By lighting your spaces with full-spectrum lights and sunlight, the richness, depth, and quality of your visual experiences also benefit.

For a dimension of our life that has such big psychological and physiological effects, we often forget about the importance of light. We design dorms with no windows, spend almost all our time indoors, and ruin our sleep by staring into bright screens before bed. As stewards of our built environment, I think it’s time for us to think about light as a primary design element instead of an afterthought – and to work time into our schedules to get outside a bit more.

-Harrison Lin

The most clicked link from last week's issue (~4% of opens) was a video about pipe-freezing kits – but be wary: when they fail, they fail spectacularly. In the Members' Slack, the #community-hiring channel isn't just a good tool for filling open roles, it's also a place for open-ended conversations determining what skills are needed in your org and thinking through how to find the right people.


  • When the sun’s light reaches the earth’s outer atmosphere, its intensity is a fairly consistent 1,353 watts per square meter. About 30% of that is reflected back into space; the rest continues down towards the earth’s surface, though much of it – about 23% – is absorbed by water vapor and dust before it reaches earth. The more atmosphere the light goes through, the more energy is absorbed, and the result is that the sun is dramatically weaker at the poles than it is at the equator.

    In order to quantify the intensity of solar radiation at a particular place and time, engineers calculate the air mass coefficient, which is essentially a measure of how much atmosphere lies between the sun and a given point on earth. Air mass depends on latitude and time of year, and by convention we say that the air mass is equal to one when the sun is directly overhead (as it would be on the equator on the equinox, or on the tropic of cancer on the summer solstice). Air mass increases when the sun is lower in the sky, as it is for me today: the sun will peak at around 30° on 2023-01-16 in San Francisco, making the air mass coefficient around AM1.16.

    When estimating how solar radiation will affect the things we build (and characterizing the performance of solar cells), ASTM G-173-03 recommends that engineers use AM1.5, which corresponds with the sun being at a 48° angle and results in an energy density around 1,000 watts per square meter. A *lot* of the world’s population experiences AM1.5 at some point during the year; at home in San Francisco, I see it in mid-April and again in early October.
  • Pixar *really* understands how to make their characters look alive. One thing that affects how humans perceive living objects is subsurface scattering: When light hits skin, some of it reflects, some of it is absorbed, and some of it actually bounces around under the surface, scatters, and comes back out, giving it a translucent appearance. This in-depth paper from Pixar describes the math they use to model subsurface scattering in their films.
  • By placing optical elements like lenses, mirrors, and point sources on a blank canvas, this ray optics simulator allows you to play with how light scatters, diffuses, and concentrates.


  • In U.S. Patent 251,551, issued 1881-12-27, Thomas Edison proposed running electricity through gas piping. To quote Edison, “In a system of furnishing light and power by electricity it may be sometimes convenient to utilize the system of gas pipes and fixtures already existing in a house as conductors for the current without interfering, if so desired, with their legitimate use.”
  • A new favorite curio of mine is the Crookes Radiometer, which consists of four pieces of painted paper that somehow convert light into rotation. Invented in 1873, it took until 1879 for scientists to propose the now-dominant theory of how it works – though that theory is still being debated today. Easily mistaken for another banal desktop toy, the radiometer is one of the simplest examples of a heat engine; it also introduces the concept of blackbody absorption, which is how light converts into heat.





  • Google has deployed its operating systems on 3 billion mobile devices – a staggering amount of hardware and data. Using federated learning, they could in theory be used to train a machine learning model – without any (personal) training data being shared. This interactive site lets you tinker with a federated model; the authors claim that “This framework has the potential to enable large-scale aggregation and modeling of complicated systems and processes like urban mobility, economic markets, energy use and generation patterns, climate change and public health concerns.”
  • Anybody can propose an emoji. Mark Bramhill brings you through the emoji industrial complex for his proposal for “Person Meditating.” Unicode’s technical document registry contains every technical document, application, and meeting minute since 1991, representing decades of sustained effort to standardize the way we communicate. Also, a handy Unicode fraction creator.

A building made of 60,000 seeds embedded in fiber optic rods.

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