Carl Sagan Explains How the Ancient Greeks, Using Reason and Math, Figured Out the Earth Isn’t Flat, Over 2,000 Years Ago

The denial of sci­ence has entered the high­est lev­els of gov­ern­ment, and no mat­ter what the data says, the U.S. promis­es to cease all 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 a flat-earth­ers, per­haps the van­guard of an anti-round earth move­ment. First Cleve­land Cav­a­liers 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.”  Then, no less a bas­ket­ball wor­thy than Shaquille O’Neal weighed in with his own belief in flat-earth­ism.

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 in to 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, 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.

via 9Gag

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

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Comments (11)
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  • Mike Lowery says:

    Just to give you an update on the flat earth thing; Shack has already admit­ted it was a joke and peo­ple should not be so gullible.

    Kyrie Irv­ing is doing this for sev­er­al rea­sons;
    1. To make fun of this car­i­ca­ture of peo­ple that don’t put a lot of belief into sci­ence.
    2. To make fun of peo­ple who are so gullible and make such a big deal on social media about this stuff.
    3. To show how some­thing as insignif­i­cant, as some­one’s opin­ion, can be so news­wor­thy.
    4. To get his name out there; any pub­lic­i­ty is good pub­lic­i­ty, right? Seri­ous­ly, most peo­ple had nev­er heard of him before this. Plus, his shoe is now the top sell­ing in the Nike line! lol

    So I guess he did a great job of get­ting what he want­ed because you can pret­ty much check each one of these off of the list.

  • Gwil says:

    The far sight­ed Carl Sagan. I watched him week in and week out on TV. His series was won­der­ful. Sad­ly there are bil­lions in the world who still live in dark­ness.

  • E. Derksen says:

    Walk­er Per­cy has a very insight­ful com­ment about Carl Sagan’s approach to “sci­ence”, one wor­thy of con­sid­er­a­tion:
    What is to be deplored is not Sagan’s sopho­moric sci­en­tism — which I think bet­ter than its coun­ter­part, a sopho­moric the­ism which attrib­ut­es the won­ders of the Cos­mos to a God who cre­at­ed it like a child with a cook­ie cut­ter — no, what is deplorable is that these seri­ous issues involv­ing God and the nature of man should be co-opt­ed by the present dis­putants, a pop­u­lar­iz­er like Sagan and fun­da­men­tal­ists who believe God cre­at­ed the world six-thou­sand years ago. It’s enough to give both sci­ence and Chris­tian­i­ty a bad name.

  • Josh Jones says:

    @Mike: Fig­ured as much. Some smooth trolling, and a great excuse to talk about ancient Greek sci­ence.

  • mike hire says:

    As a true skep­tic I must ask if the char­ac­ter Eratos­thenes ( sup­posed geo­g­ra­ph­er, math­e­mati­cian, poet, his­to­ri­an, and astronomer ‑real­ly ? ) isn’t the fig­ment of “sci­en­tis­tic believ­ers” wish­ful think­ing- indeed, pure­ly made up like the ‘fly­ing saints’ and mir­a­cle work­ers of reli­gious believ­ers.

  • mike hire says:

    And do we real­ly know if Mike is telling the truth about Shaq — he gave no source ?

    late­ly I’ve been won­der­ing about all the false ‘facts’ every­where from the past-in books and news­pa­pers full of BS — made up just to sell papers .…. not unlike today’s TV

    yep, I can make up words like they make up facts .…

    The Truth is hard to find .…

  • Dario says:

    @mike Hire: con­sid­er that the term “sci­en­tist” did not mean the same thing in ancient times as today. As shown in Sagan video, Her­atostenes sim­ply had a genial idea and the will to prove it. No train­ing, no instru­ments nor the­o­ries were need­ed: just basic math and genius.
    Aris­to­tle was a biol­o­gist, psy­chol­o­gist, soci­ol­o­gist, the­ater crit­ic, logi­cian, gram­mar­i­an.
    Pla­to poet, math­e­mati­cian, politi­cian, psy­chol­o­gist, lit­er­ary crit­ic.
    Actu­al­ly even in more recent times Descartes, Leib­niz, Vico were all poly­maths.
    This is just to say that ordi­nary (sci­en­tif­ic) skep­ti­cism should­n’t go as far as to deny the data and the world, oth­er­wise it plays against and not for rea­son.
    Rad­i­cal skep­ti­cism (solip­sism, tran­scen­den­tal phe­nom­e­nol­o­gy, Carte­sian doubt) would not ques­tion empir­i­cal and mun­dane mat­ters as the exis­tence of Her­atostenes, because it would deny the rel­e­vance of such ques­tions them­selves: Her­atostenes, be one or many, would be an illu­sion any­way.

  • Jose A Amoros says:

    The ear­ly Greek philosophers–the atomists–had great faith in the exis­tence of the atom, with­out see­ing them and with­out empir­i­cal evi­dence too.

  • Jose A Amoros says:

    Iron­i­cal­ly that this arti­cle starts by ask­ing philo­soph­i­cal ques­tions and then goes into quot­ing Neil DeGrasse Tyson, who has dis­par­aged phi­los­o­phy, while try­ing to under­stand the “nat­ur­al” world.

  • Ifianassa Karabatsou says:

    Eratos­thenes, a Libyan-Greek ????how did you end up in this ??there was no Libya that time mis­ter !! all around Medit­er­a­nen sea were ancient Greek colonies ‚and the knowl­edge was writ­ten in GREEK „THANKS TO MY ANCESTORS .DR IFIANASSA KARA

  • Ian says:

    I’ll defer to those who have inves­ti­gat­ed the his­tor­i­cal evi­dence to com­ment on the verac­i­ty of Eras­tothene’s exis­tence & accom­plish­ments, but one of the beau­ties of sci­ence is that it does­n’t very much mat­ter, indeed *should­n’t* mat­ter who he was or what he did.
    What mat­ters are the exper­i­ments, and we can repro­duce those for our­selves & inde­pen­dent­ly ver­i­fy if the earth is indeed spher­i­cal (or near­ly so) or not, and see if we can derive a sim­i­lar fig­ure for the aver­age cir­cum­fer­ence.
    If we are instead able to show the earth is flat, then fame, for­tune and a place in his­to­ry are assured.

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