The denial of sci­ence suf­fus­es Amer­i­can soci­ety, and no mat­ter what the data says, some con­ser­v­a­tive forces refuse efforts to cur­tail, or even study, cli­mate change. Astro­physi­cist Katie Mack calls this retrench­ment a form of “data nihilism,” writ­ing in an exas­per­at­ed tweet, “What is sci­ence? How can a thing be known? Is any­thing even real???” Indeed, what can we expect next from what Isaac Asi­mov called the Unit­ed States’ anti-intel­lec­tu­al “cult of igno­rance”? A flat earth lob­by?

Welp… at least a cou­ple celebri­ty fig­ures have come out as flat-earth­ers, per­haps the van­guard of an anti-round earth move­ment. Notably, [Dal­las Mav­er­icks] guard Kyrie Irv­ing made the claim on a pod­cast, insist­ing, Chris Matyszczyk writes, that “we were being lied to about such basic things by the glob­al elites.” Is this a joke? I hope so. Neil DeGrasse Tyson—who host­ed the recent Cos­mos remake to try and dis­pel such sci­en­tif­ic ignorance—replied all the same, not­ing that Irv­ing should “stay away from jobs that require… under­stand­ing of the nat­ur­al world.” The weird affair has played out like a sideshow next to the main­stage polit­i­cal cir­cus, an unset­tling reminder of Carl Sagan’s pre­dic­tion in his last book, The Demon Haunt­ed World, that Amer­i­cans would soon find their “crit­i­cal fac­ul­ties in decline, unable to dis­tin­guish between what feels good and what’s true.”

Sagan devot­ed much of his life to coun­ter­ing anti-sci­ence trends with warmth and enthu­si­asm, park­ing him­self “repeat­ed­ly, arguably com­pul­sive­ly, in front of TV cam­eras,” writes Joel Achen­bach at Smith­son­ian. We most remem­ber him for his orig­i­nal 1980 Cos­mos minis­eries, his most pub­lic role as a “gate­keep­er of sci­en­tif­ic cred­i­bil­i­ty,” as Achen­bach calls him. I think Sagan may have chafed at the descrip­tion. He want­ed to open the gates and let the pub­lic into sci­en­tif­ic inquiry. He char­i­ta­bly lis­tened to unsci­en­tif­ic the­o­ries, and patient­ly took the time to explain their flaws.

In the very first episode of Cos­mos, Sagan addressed the flat-earth­ers, indi­rect­ly, by explain­ing how Eratos­thenes (276–194 BC), a Libyan-Greek schol­ar and chief librar­i­an at the Library of Alexan­dria, dis­cov­ered over 2000 years ago that the earth is a sphere. Giv­en the geo­g­ra­ph­er, math­e­mati­cian, poet, his­to­ri­an, and astronomer’s incred­i­ble list of accomplishments—a sys­tem of lat­i­tude and lon­gi­tude, a map of the world, a sys­tem for find­ing prime numbers—this may not even rank as his high­est achieve­ment.

In the Cos­mos clip above, Sagan explains Eratos­thenes’ sci­en­tif­ic method: he made obser­va­tions of how shad­ows change length giv­en the posi­tion of the sun in the sky. Esti­mat­ing the dis­tance between the cities of Syene and Alexan­dria, he was then able to math­e­mat­i­cal­ly cal­cu­late the cir­cum­fer­ence of the earth, as Cyn­thia Stokes Brown explains at Khan Acad­e­my. Although “sev­er­al sources of error crept into Eratos­thenes’ cal­cu­la­tions and our inter­pre­ta­tion of them,” he nonethe­less suc­ceed­ed almost per­fect­ly. His esti­ma­tion: 250,000 sta­dia, or 25,000 miles. The actu­al cir­cum­fer­ence: 24,860 miles (40.008 kilo­me­ters).

No, of course the Earth isn’t flat. But Sagan’s les­son on how one sci­en­tist from antiq­ui­ty came to know that isn’t an exer­cise in debunk­ing. It’s a jour­ney into the move­ment of the solar sys­tem, into ancient sci­en­tif­ic his­to­ry, and most impor­tant­ly, per­haps, into the sci­en­tif­ic method, which does not rely on hearsay from “glob­al elites” or shad­owy fig­ures, but on the tools of obser­va­tion, infer­ence, rea­son­ing, and math. Pro­fes­sion­al sci­en­tists are not with­out their bias­es and con­flicts of inter­est, but the most fun­da­men­tal intel­lec­tu­al tools they use are avail­able to every­one on Earth.

Note: An ear­li­er ver­sion of this post appeared on our site in 2017. This ver­sion has been light­ly edit­ed and updat­ed.

Relat­ed Con­tent:

Carl Sagan Pre­dicts the Decline of Amer­i­ca: Unable to Know “What’s True,” We Will Slide, “With­out Notic­ing, Back into Super­sti­tion & Dark­ness” (1995)

Hear Carl Sagan Art­ful­ly Refute a Cre­ation­ist on a Talk Radio Show: “The Dar­win­ian Con­cept of Evo­lu­tion is Pro­found­ly Ver­i­fied”

Carl Sagan Presents His “Baloney Detec­tion Kit”: 8 Tools for Skep­ti­cal Think­ing

Josh Jones is a writer and musi­cian based in Durham, NC. Fol­low him at @jdmagness

It would be clichéd to describe Leonar­do da Vin­ci as a man ahead of his time. But in the case of the quin­tes­sen­tial Renais­sance poly­math, it may well be one of those clichés firm­ly root­ed in truth. In fact, that root­ing has just grown even firmer with the dis­cov­ery of a tri­an­gle that Leonar­do sketched in one of his note­books, the Codex Arun­del (cir­ca 1478–1518). That tri­an­gle, as the New York Times’ William J. Broad writes, had “an adjoin­ing pitch­er and, pour­ing from its spout, a series of cir­cles that formed the triangle’s hypotenuse.” This image sounds sim­ple, but it reveals that Leonar­do approached an under­stand­ing of the laws of grav­i­ty before Galileo, and well before New­ton.

This find­ing is the work of Morteza Gharib, a pro­fes­sor of aero­nau­tics at the Cal­i­for­nia Insti­tute of Tech­nol­o­gy. Cap­ti­vat­ed by this sketch, he “used a com­put­er pro­gram to flip the tri­an­gle and the adja­cent areas of back­ward writ­ing,” which clar­i­fied what Leonar­do was attempt­ing to do.

His dia­gram turned out “to split the effects of grav­i­ty into two parts that revealed an aspect of nature nor­mal­ly kept hid­den.” The first part was grav­i­ty’s “nat­ur­al down­ward pull”; the sec­ond was the move­ment of the pitch­er itself along a line. That Leonar­do drew “the pitcher’s con­tents falling low­er and low­er over time” implies his under­stand­ing that “grav­i­ty was a con­stant force that result­ed in a steady accel­er­a­tion.”

Along with co-authors Chris Roh and Flavio Noca, Gharib has pub­lished a paper on “Leonar­do da Vinci’s Visu­al­iza­tion of Grav­i­ty as a Form of Accel­er­a­tion” in this mon­th’s issue of Leonar­do — an appro­pri­ate­ly named jour­nal in this case, though one ded­i­cat­ed less to the study of Leonar­do the man than to the study of the inter­sec­tion of art and sci­ence he occu­pied. As Gharib and oth­ers see it, Leonar­do “was far more than an artist and sug­gest­ed that his fame as a pio­neer­ing sci­en­tist could sky­rock­et if more tech­ni­cal­ly knowl­edge­able experts probed the Codex Arun­del and oth­er sources” — the kind of experts who can tell that, with his pitch­er and tri­an­gle, Leonar­do man­aged to deter­mine the strength of gravity’s pull to an accu­ra­cy of about 97 per­cent. Which leads us to won­der: What else about the nature of real­i­ty must he have worked out in the mar­gins of his note­books?

via Art­net

Relat­ed Con­tent:

Leonar­do da Vinci’s Vision­ary Note­books Now Online: Browse 570 Dig­i­tized Pages

Leonar­do da Vinci’s Ele­gant Design for a Per­pet­u­al Motion Machine

How Leonar­do da Vin­ci Made His Mag­nif­i­cent Draw­ings Using Only a Met­al Sty­lus, Pen & Ink, and Chalk

Down­load the Sub­lime Anato­my Draw­ings of Leonar­do da Vin­ci: Avail­able Online, or in a Great iPad App

A Com­plete Dig­i­ti­za­tion of Leonar­do Da Vinci’s Codex Atlanti­cus, the Largest Exist­ing Col­lec­tion of His Draw­ings & Writ­ings

The Old­est Known Globe to Depict the New World Was Engraved on an Ostrich Egg, Maybe by Leonar­do da Vin­ci (1504)

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. His projects include the Sub­stack newslet­ter Books on Cities, the book The State­less City: a Walk through 21st-Cen­tu­ry Los Ange­les and the video series The City in Cin­e­ma. Fol­low him on Twit­ter at @colinmarshall or on Face­book.