Links and Comments: Science Matters, 18 Mar 2021

Catching up on things that have caught me eye the past week or two. How humans have remade the Earth; about Daylight Saving Time; Dark Matter; How time might flow in two directions; the Nature of mathematics.

Washington Post, 12 March 2021, Jedediah Britton-Purdy: Humans have rapidly remade the Earth — and imperiled its future

(I have a book by this writer, from 1999: For Common Things. Then his last name was just Purdy. I glanced through it without reading thoroughly; he struck me as a traditionalist without being a reactionary conservative. Beyond that one book, I haven’t followed his career. Wiki. He wrote a book on the Anthropocene in 2015.)

This piece is basically a book review, of a book on a significant topic, one of the most significant of our era: Grand Transitions: How the Modern World Was Made, by one Vaclav Smil. (Amz.)


How dramatically do humans dominate the Earth? As late as 1800, the total weight of wild mammals was greater than that of all domesticated species. By 1900, with the bison gone and cattle herds roaming the plains of the Americas, cows alone bulked twice as heavy as all remaining wild mammals. A century later, domesticated animals outweighed wildlife by a factor of 20. In less than the life span of the U.S. Constitution, the Earth has gone from half-wild to a global farm.

The greatest change by far is in the energy sources that make us the dominant species. To stick with farming a little longer: During the 20th century, harvested cropland expanded about 40 percent worldwide to feed a population that grew almost fourfold. In that time, the energy consumed by farming increased to 90 times its level in 1900, as fertilizer, tractors and factory farms replaced sunshine and muscle with carbon-based fuel. How vital is all that carbon? In “Grand Transitions: How the Modern World Was Made,” Vaclav Smil estimates that without the energy-intensive process that produces nitrogen fertilizer, nearly half of today’s population would starve.


If we can find a way to throw collective effort against the very fossil fuel system that has brought us so far, and put it to rest 50 years sooner than current trends would do, we might face fewer disasters, and along the way we might grow less fragmented and more concerned with shared survival than our own comfort. Our greatest transition yet might be from tragic ecological fate into an economy that would be both sustainable and fair. Or so it is possible to hope. Alas, in politics as in engineering, we would have to do better in the very near future than we have ever managed in the past.

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Slate, 15 March 2021, Molly Olmstead: Why a Standard Time Activist Thinks Losing an Hour Is Actually a Big Deal.

I’ve already linked this on Facebook, with the comment “I agree.” As it happens, the “activist” discussed here is a “software engineer and amateur astronomer,” almost exactly like I am/was. He says:

A lot of people say time is a social construct. That’s not true. There is an actual objective meaning to time. Noon is supposed to be when the sun is halfway across the sky at its highest, most southerly point. But with daylight saving time, we just completely obliterate the connection to nature. Within the software engineering community, we call it biohacking, but it’s circadian health—it’s looking at how you can listen to your circadian rhythm and get optimal rest and optimal performance.

My take: Daylight Saving Time is living a fantasy reality. Noon is when the sun is highest in the sky; midnight is 12 hours later, the middle of the night-time; that’s what those words mean. If the changes in the amount of daylight throughout the year bother some people, because of their fixed schedules, then *change their schedules*, don’t change the meaning of the clock to indicate something that’s not true.

–At the same time, I’ll admit, our situation of time zones, established as late as 1883 in the US, are to some extent a fiction, or a rounding off of reality. (Before that, every small town had its own local time, until the railroad schedules forced them to cohere.) That is, unless you’re in the exact center of your time zone (or along the line of longitude that defines the time zone), the sun isn’t precisely overhead at noon, and so on; but it’s close. And because of seasons, and precession, at any given place on the world, sunrise and sunset are not exactly 12 hours apart, or equally distanced from noon and midnight, even at the equinox, depending on lines of latitude. (Reality is complex.) But such minor deviations from idealistic time are trivial compared to the redefinition of the clock that DST presumes.

(Yes I know that it’s Daylight Saving Time, not Daylight Savings Time.)

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Vox, 10 March 2021, Brian Resnick: Dark matter holds our universe together. No one knows what it is.

Vox is a great “explainer” website. Here is its science reporter, in the first of a series of podcasts apparently, summarizing what we know. (Basically, dark matter is whatever generates the gravity that seems to hold together far-away galaxies and galactic clusters, in the absence of any visible matter. [Whereas dark energy is the force that is increasing the expansion of the entire universe, and we don’t “know” what that is, either.])

It turns out all the stars in all the galaxies, in all the universe, barely even begin to account for all the stuff of the universe. Most of the matter in the universe is actually unseeable, untouchable, and, to this day, undiscovered.

Scientists call this unexplained stuff “dark matter,” and they believe there’s five times more of it in the universe than normal matter — the stuff that makes up you and me, stars, planets, black holes, and everything we can see in the night sky or touch here on Earth. It’s strange even calling all that “normal” matter, because in the grand scheme of the cosmos, normal matter is the rare stuff. But to this day, no one knows what dark matter actually is.

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New Scientist, 3 March 2021, Julian Barbour: Did time flow in two directions from the big bang, making two futures?

Subtitle: Why time only flows forwards is one of the great mysteries of physics. A new idea suggests that it actually went in two ways from the big bang – and, even more radically, that time emerges not from entropy, but from the growth of structure.

I noticed this because I just read about it in Alan Lightman’s new book Probable Impossibilities: Musings on Beginnings and Endings (Amz, which I’ll summarize here shortly.

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The New Yorker, 2 March 2021, Alec Wilkinson: What Is Mathematics?, subtitled, Mathematics has been variously described as an ideal reality, a formal game, and the poetry of logical ideas.

I was a math major in college, though it was because I couldn’t handle the physics courses to become an astronomer, my initial dream — but I’ve always had an intellectual fascination with the frontiers of mathematics. I have one shelf of a bookcase of books about mathematics and its philosophical implications. This article teases my fascination with mathematics. This is a beautiful take (I’ve inserted some para breaks):

Mathematicians know what mathematics is but have difficulty saying it.

I have heard: Mathematics is the craft of creating new knowledge from old, using deductive logic and abstraction. The theory of formal patterns.

Mathematics is the study of quantity. A discipline that includes the natural numbers and plane and solid geometry. The science that draws necessary conclusions. Symbolic logic. The study of structures

The account we give of the timeless architecture of the cosmos. The poetry of logical ideas. Statements related by very strict rules of deduction.

A means of seeking a deductive pathway from a set of axioms to a set of propositions or their denials. A science involving things you can’t see, whose presence is confined to the imagination. A proto-text whose existence is only postulated. A precise conceptual apparatus.

The study of ideas that can be handled as if they were real things. The manipulation of the meaningless symbols of a first-order language according to explicit, syntactical rules.

A field in which the properties and interactions of idealized objects are examined. The science of skillful operations with concepts and rules invented for the purpose.

Conjectures, questions, intelligent guesses, and heuristic arguments about what is probably true. The longest continuous human thought. Laboriously constructed intuition.

The thing that scientific ideas, as they grow toward perfection, become. An ideal reality.

A story that has been written for thousands of years, is always being added to, and might never be finished. The largest coherent artifact that’s been built by civilization. Only a formal game. What mathematicians do, the way musicians do music.

And how mathematics is older than scripture, and all science.

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