WITH JUST TWO STICKS AND A BRAIN
In the mid-20th century, we began launching satellites into space that would help us determine the exact circumference of the Earth: 40,030 km. But over 2000 years earlier, a man in Ancient Greece came up with nearly the exact same figure using just a stick and his brain, putting a stick in the ground. That man was Eratosthenes. A Greek mathematician and the head of the library at Alexandria.
Eratosthenes had heard that in Syene, a city south of Alexandria, no vertical shadows were cast at noon on the summer solstice. The sun was directly overhead. He wondered if this were also true in Alexandria.
So, on June 21 he planted a stick directly in the ground and waited to see if a shadow would be cast at noon. It turns out there was one. And it measured about 7 degrees.
Now, if the sun's rays are coming in at the same angle at the same time of day, and a stick in Alexandria is casting a shadow while a stick in Syene is not, it must mean that the Earth's surface is curved. And Eratosthenes probably already knew that.
The idea of a spherical Earth was floated around by Pythagoras around 500 BC and validated by Aristotle a couple centuries later. If the Earth really was a sphere, Eratosthenes could use his observations to estimate the circumference of the entire planet.
Since the difference in shadow length is 7 degrees in Alexandria and Syene, that means the two cities are 7 degrees apart on Earth's 360-degrees surface. Eratosthenes hired a man to pace the distance between the two cities and learned they were 5,000 stadia apart, which is about 800 kilometers.
He could then use simple proportions to find the Earth's circumference — 7.2 degrees is 1/50 of 360 degrees, so 800 times 50 equals 40,000 kilometers. And just like that, a man 2200 years ago found the circumference of our entire planet with just a stick and his brain.
-
3:30
Elena Danaan
1 year agoCONTACT Ep 27 ~ Ea & Thor Han ~ Aug 28 2023
11.1K49 -
52:02
Josh Pate's College Football Show
3 hours agoWeek 7 Upset Alerts | Repeat Of 2007 Season? | Bama Culture Questioned | Cole Cubelic Joins
4.57K -
DVR
Lee Camp
2 hours agoLIVE: Piers Morgan Destroyed, Israel Strikes Beirut, Much More!
4.38K -
1:09:57
Russell Brand
6 hours ago“Trump Will END THE WAR In Ukraine” Col Douglas Macgregor On Ukraine, Iran, The Border & WW3 – SF471
120K254 -
1:32:43
The Quartering
4 hours agoHurricane Milton Aftermath, Kamala Harris Tries To Appeal To Gamers & Fails & Today's News
67.7K8 -
2:52:11
The Dana Show with Dana Loesch
4 hours agoHURRICANE MILTON AFTERMATH | The Dana Show LIVE On Rumble!
49.9K8 -
2:57:42
The Charlie Kirk Show
4 hours agoThe Crumbling Blue Wall? + Dem Border Bluster | Underwood, Hari, Lake, Prager | 10.10.24
114K41 -
54:19
Ben Shapiro
4 hours agoEp. 2064 - PANIC At Kamala HQ
61.7K58 -
1:23:56
TheAlecLaceShow
5 hours agoGuest: A.J. Rice | The White Privilege Album | Woke Professor Axed | The Alec Lace Show
27K6 -
LIVE
LumpyPotatoX2
6 hours agoWelcome to Off The Grid - #RumbleGaming
193 watching