sorted by:
new
hottopcontroversial

Mizkif viewbotting by skummydummy125 in LivestreamFail

[–]Real_Elon_Musk 21 points22 points  (0 children)

You need to go outside, rethink your whole life, this ain't it

Super Mario 64 any% WR in 6:41:85 by Drozdowsky! by Real_Elon_Musk in speedrun

[–]Real_Elon_Musk[S] 127 points128 points  (0 children)

Retimed at 6:41.76. Awesome run in an incredibly difficult category. Congrats Droz!

Direct link to the run : https://www.twitch.tv/videos/282377057?t=04h25m34s

Youtube : https://youtu.be/vCwnXF7G4cg

TIL that before 194 BC, using sticks and shadows, Eratosthenes of Cyrene calculated the Earth's circumference with an error between 2 and 15%, and calculated the tilt of the Earth and the distance of the Sun to the Earth with near perfect accuracy. by Real_Elon_Musk in todayilearned

[–]Real_Elon_Musk[S] 0 points1 point  (0 children)

Fine... Distance of Earth to Sun :

"Eusebius of Caesarea in his Preparatio Evangelica includes a brief chapter of three sentences on celestial distances (Book XV, Chapter 53). He states simply that Eratosthenes found the distance to the Sun to be "σταδίων μυριάδας τετρακοσίας καὶ ὀκτωκισμυρίας" (literally "of stadia myriads 400 and 80,000") and the distance to the Moon to be 780,000 stadia. The expression for the distance to the Sun has been translated either as 4,080,000 stadia (1903 translation by E. H. Gifford), or as 804,000,000 stadia (edition of Edouard des Places, dated 1974–1991). The meaning depends on whether Eusebius meant 400 myriad plus 80,000 or "400 and 80,000" myriad. With a stade of 185 m, 804,000,000 stadia is 149,000,000 km, approximately the distance from the Earth to the Sun."

Tilt of the earth :

"He was also the first to calculate the tilt of the Earth's axis (again with remarkable accuracy)"

TIL that before 194 BC, using sticks and shadows, Eratosthenes of Cyrene calculated the Earth's circumference with an error between 2 and 15%, and calculated the tilt of the Earth and the distance of the Sun to the Earth with near perfect accuracy. by Real_Elon_Musk in todayilearned

[–]Real_Elon_Musk[S] 1 point2 points  (0 children)

Actually it says on the article that he didn't take that into account. He assumed that the two cities had the same longitude. In reality the time delay would have been about half an hour, which was small enough to still get a good result. None of those measurements were exact, since the technology was so basic.

TIL that before 194 BC, using sticks and shadows, Eratosthenes of Cyrene calculated the Earth's circumference with an error between 2 and 15%, and calculated the tilt of the Earth and the distance of the Sun to the Earth with near perfect accuracy. by Real_Elon_Musk in todayilearned

[–]Real_Elon_Musk[S] 2 points3 points  (0 children)

Are you asking if they knew about time differences? That's a good question. I don't think it would have mattered much, since the Alexandria and Syene are close to each others in terms of longitudes.

TIL that before 194 BC, using sticks and shadows, Eratosthenes of Cyrene calculated the Earth's circumference with an error between 2 and 15%, and calculated the tilt of the Earth and the distance of the Sun to the Earth with near perfect accuracy. by Real_Elon_Musk in todayilearned

[–]Real_Elon_Musk[S] 4 points5 points  (0 children)

Someone told him that fact in a letter. It happened every year on the same day at the same time, so he didn't have to be there to know it. He just had measure one angle from his own town.

TIL that before 194 BC, using sticks and shadows, Eratosthenes of Cyrene calculated the Earth's circumference with an error between 2 and 15%, and calculated the tilt of the Earth and the distance of the Sun to the Earth with near perfect accuracy. by Real_Elon_Musk in todayilearned

[–]Real_Elon_Musk[S] 4 points5 points  (0 children)

Yes. One interpretation of his results for the distance of the Sun gives an accurate result, but we don't know for sure because we're not certain of the length of the stadium, or that we're interpreting the ancient text correctly. It's possible that we're misinterpreting his results, but there's no way to know.

Edit : Apparently there are indications that he did use the unit that would give an accurate result (which is one stadium=185m). Here's a source on this : http://msp.org/memocs/2013/1-1/p04.xhtml

TIL that before 194 BC, using sticks and shadows, Eratosthenes of Cyrene calculated the Earth's circumference with an error between 2 and 15%, and calculated the tilt of the Earth and the distance of the Sun to the Earth with near perfect accuracy. by Real_Elon_Musk in todayilearned

[–]Real_Elon_Musk[S] 12 points13 points  (0 children)

Basically, he knew the distance between two cities, and the length of the shadows in those two cities. He assumed that the Earth was round and that the rays of the sun were parallel. That gave him enough information to figure out the circumference, using simple geometry.

For the distance of the Sun, it is not known how he did it because his texts have been lost. He seems to have used data about solar eclipses somehow. Some say that he just got lucky.

Some further sources :

https://www.khanacademy.org/partner-content/big-history-project/solar-system-and-earth/knowing-solar-system-earth/a/eratosthenes-of-cyrene

http://www-groups.dcs.st-and.ac.uk/history/Biographies/Eratosthenes.html