In this episode we look at the early inquiry into the shape and size of the earth by the Ancient Greeks (note there were contributions by the Indians, Chinese and other Cultures as well). We see the beginning of the geocentric vs heliocentric debate.
The geometric proofs of Aristarchus of Samos (my favorites):
https://www.youtube.com/watch?v=99PjF6HxD2A
https://www.youtube.com/watch?v=yprjO0_3nvos
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have you started your astrophysics classes yet?
Just a clarification. The great pyramids were constructed closer to 2500 BCE than 3000 BCE. Not that it matters for your north star point, just a nitpick for nitpickers. Loving the series btw.
Very much enjoying this series, many thanks for sharing!
I made a video about the geocentric epicycles and why the cycles are just over 365 days for planets far out like saturn, uranus and neptune.
Great A'tuin rules!!!
So will the next one mention Bruno who died at the stake?
Enjoying this series. Thanks for presenting this information in such an interesting manner.
Thanks Bob!
That Map is really incredible for the time. Amazing.
According to the late, wonderful author Terry Pratchett, the four world elephants, Berilia, Great T'Phon, Jerakeen, and Tubul, ride on the back of the great A'tuin, the world turtle, and support Discworld on their backs. And that makes more sense than any flerf model
Fascinating. I'm really bad at math but would love to see how they calculated the dustances to the moon and sun znd theur sizes, and hiw you did it with a sextant.
I have to think that the flatties have trouble with a 27,000 year cycle. When we say there is a 27,000 year "wobble" to the earth's movement around the sun, they seem to think it is wobbling like an eccentric car wheel at ~50mph.
The Greeks saw the ships appear mast first because they didn't have Nikon P1000's to zoom in on them.
This series is fantastic. Really interesting And in nice size time scales. Thank you.
This video alone should convince flerfs to realize just how ignorant they are. I learned a bunch. Thanks.
The thing behind you is the discworld from Terry Pratchett the greatest author ever. Maybe I’m biased 😉 cos we’re both English
"It is turtles all the way down."
The world turtle and elephants is a concept from Hindu cosmology which Sir Terry Prattchet used, in the shape of Great A'tuin, as the basis for his amazing Discworld series.
In regard to Terry holding up a mirror to the ancient Greeks "Ephebians" and the shape of the world, check out his book "Small gods" discussing Christian dogmatism "Omnianism" which has (incorrectly) a globe as part of their belief system 😊
"You can't believe in the Great A'Tuin," he said. "Great A'Tuin exists. There's no point in believing in things that exist."
"Someone's put up their hand," said Urn.
"Yes?"
"Sir, surely only things that exist are worth believing in?" said the enquirer, who was wearing a uniform of a sergeant of the Holy Guard.
"If they exist, you don't have to believe in them," said Didactylos. "They just are." He sighed. "What can I tell you? What do you want to hear? I just wrote down what people know. Mountains rise and fall, and under them the Turtle swims onward. Men live and die, and the Turtle Moves. Empires grow and crumble, and the Turtle Moves. Gods come and go, and still the Turtle Moves. The Turtle Moves."
From the darkness came a voice, "And that is really true?"
Didactylos shrugged. "The Turtle exists. The world is a flat disc. The sun turns round it once every day, dragging its light behind it. And this will go on happening, whether you believe it is true or not. It is real. I don't know about truth. Truth is a lot more complicated than that. I don't think the Turtle gives a bugger whether it's true or not, to tell you the truth."
The account of Eratosthenes’ measurement is not accurate. His own account not survived, but is summarised centuries later by Cleomedes. Cleomedes’s version does not mention an obelisk, nor a well, but rather a gnomon, i.e. the part of a sundial that casts the shadow.
The idea of professional pacers or bematists is suspect, because the straight line path from Alexandria to Syene is across sand dunes, making any pacing highly inaccurate. Most likely, Eratosthenes used early maps. His estimate of the circumference apears reasonably accurate, but was one of many such estimates which varied considerably. Possibly his fame arises because of a lucky guess.
Eratosthenes’ map as pictured is not his, but a reconstruction almost entirely reliant on the information, testimonia and citations preserved by later authors. His *Geography*, together with his map, has long since been lost.
The one behind you is from a Terry Pratchett novel.
I really like that old Greek map of the known world. The Med is appropriately very accurate with lots of little jutting pieces of land. Then the further away edges of landmasses get smoothed out because they just don’t know. Even with how wrong it is I’m still impressed by how relatively accurate parts of it are. Especially how Africa/Libya and India taper off into tips. The ancients got a lot further abroad than we give them credit for.
The geocentric model lasted so long because Aristotle's physics made good intuitive sense, even if it was flawed.
I've studied this subject a bit, but I'm still confused how exactly Aristotle knew it was the earths shadow that caused the eclipse in the first place. Yes, if he knew it was the earths shadow, he could deduce that the earth was round from that. But I'm not seeing the intermediate step.