It was, I admit, far from the worst falsehood in Donald Trump’s inauguration speech:

And whether a child is born in the urban sprawl of Detroit or the wind-swept plains of Nebraska, they look up at the same night sky, they will [fill?] their heart with the same dreams, and they are infused with the breath of life by the same almighty creator.

This is roughly what the child in Detroit sees on a clear moonless night. The photo was taken in suburban southern California, which surely has less light pollution.

Credit Wikimedia

At a plausible inner city star visibility cutoff of magnitude 2, about 70 stars are visible from anywhere on the Earth, or at most 35 stars from a given point.

This is what the same night sky looks like from unpolluted and bone dry Death Valley:

Credit Grant Kaye (a fine professional photographer but I couldn’t find copyright info – I’ll replace if he objects)

At the limit for the naked eye on magnitude 6.5, the Yale Observatory has catalogued 9,096 stars visible from the globe, or a maximum of 4,500 from a single point. That is roughly what you get in Death Valley. Of course there is a reason nobody lives there. But a habitable deep rural site like Crater Lake still shows a very large number:

Credit

It is simply untrue that the child in inner-city Detroit (Bortle scale 8/9) and Nebraska (Bortle scale 3) see the same night sky. The country girl sees up to a hundred times more stars. QED.

Why did Trump and his speechwriter, believed to be Bannon, make make this simple mistake of fact? First, they don’t care and just put in a rhetorical flourish that sounds good. Second, it’s possible that as city slickers they have never really seen a sky full of stars. That would be odd, as Trump owns rural golf courses. But then, they would have had to look up not ahead or over their shoulders. Either way, the phrase is just more lying pixie dust.

Does this matter, independently of the Trumpery? Yes.

First, as a textbook externality. It works better for teaching than a critical issue like climate change, where deniers fear the loss of their liberty to drive a car and live in a suburban McMansion and realists fear for the lives of their children and think about “Second Amendment remedies”. Light pollution is not an existential threat. But everybody agrees that a full starlit night sky is beautiful, and its loss by city dwellers is a pity. It also illustrates the policy problem. A Coasian solution via property rights is infeasible, especially as much of the pollution comes from the provision of competing public goods like safe streets. A purely technical fix seems out of reach: LED street lights are even worse than sodium, and their cheapness will encourage proliferation.

As with other externalities, a balance has to be struck through GOVERNMENT REGULATION hiss hiss. It is possible to require lighting downwards, for streets and building façades. Much more security lighting could be triggered by sensors. Indeed, modern digital cameras are so sensitive that they can operate without night lighting – that costs more, but you save on the lighting.

Light pollution is also a complementary externality of outdoor (mainly urban) air pollution, whose main harm is in causing illness and death on a massive scale: at least 3 million premature deaths a year worldwide according to the WHO. Vehicle exhausts and the chimneys of factories, offices and homes spew out chemicals that form aerosols, responsible for much of the light reflection back to earth. I haven’t been able to find an estimate of the percentage of the responsibility, as water droplets also scatter light, but in dry cities like Los Angeles it must be high.

At first sight, a strategy to cut light pollution seems to have three elements.

1. Recognize the problem and the harm. It’s not gigantic, but it’s real.
2. Cut unnecessary upward lighting through regulations requiring downward and sensor-driven lighting where possible. This should not cost much if anything net.
3. Replace ICEVs (starting with diesels) with electric vehicles in the city, through purchases of electric buses and other public-service vehicles, and progressively tighter low-emission central zones. This will need real money and political effort, and is mainly justified by very large public health and climate change costs and benefits.

Why bother?

Trump or Bannon got one thing right. We look up to the stars in awe. Their apparently unchanging majesty reminds us of our smallness in the universe, and raises theological and scientific questions. At first sight, the starfield is random. Early efforts to see patterns resulted in the rather specious constellations, which may just have been a way for our distant ancestors to orient themselves in the night sky and track the seasons. We can’t see the beautiful and ordered spiral arms of the Milky Way galaxy because we are in one, and so it took till the late 18^th century for humans to realize that we live in a galaxy like millions of others. (BTW, the evil tyrant George III of American revolutionary propaganda also paid a salary to early galaxy-hunter Caroline Herschel, the sister of the Astronomer Royal, and possibly the first woman in the modern era to have earned a wage as a recognized scientist.)

From above, our Milky Way galaxy looks like this.

Hubble image of the Pinwheel Galaxy (M101), credit: NASA/ESA/Wikipedia, and galaxy hunter Pierre Méchain, 1781. Distance from Sol 21m ly; the image corresponds roughly to a naked-eye view from 2/3 diameters, or 350,000/500,000 ly

We now have another reason to look up at the night sky. That’s where we come from. Of the atoms in our bodies, 10% are hydrogen and are ± 13.7 billion years old, all born simultaneously in the Big Bang. All the rest - the 10 other elements in macroscopic quantities, oxygen, carbon, nitrogen, calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium, about a dozen more trace elements in tiny quantities, and unwanted passengers like lead, uranium and aluminium – were created later in the fusion fires of giant stars just before they went supernova and blew their ashes violently into space. Gravity, assisted by shock waves from other supernovae, compressed these huge dust clouds  into the accretion disk from which our sun and the planets formed.

As Genesis says, man is born of dust, and returns to it. But it is the dust of stars. Give children back the sight of their home.