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How was the size of Earth first measured? (2015)

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Re: How was the size of Earth first measured? (2015)

#111

Post by MilStdJunkie »

thechao wrote: post #106
MilStdJunkie wrote: post #65

The Greeks (or, more precisely, the Eastern Mediterraneans, since a ton of these guys were Phoenician) were jaw-droppingly awesome at this stuff. I wish I could have seen it. It makes you wonder how much knowledge from other places - places with wetter climates, and/or further from the colonial powers of the 19th C - has been lost. One of the contributing reasons heliocentrism disappeared from view was that a large q…

I had a history prof address these feats-of-observation of these primordial scientists: you've got a group of totally idle wealthy, with up to 16 hours of day time to fill, across millions of people and thousands of years. Eratosthenes could've thought about this problem — and nothing else — for a thousand hours in just six months, with plenty of time off to pursue other hobbies. When's the last time you dedicated 10…

Absolutely! That's absolutely a prerequisite for these periods of very sudden advancement. Look at the 19th century! Very nearly the entire world's capacity was pulled into a very small geographic area, which then made the modern world.

It's a bit depressing because of the brutality that's involved, but let's not write off Europe and Greece quite so quickly. There's plenty of powers in world history that established a similar level of "excess capacity" re: labor but didn't engage in anything that could be interpreted as "societal advancement". England, during the rise of its supremacy, decided to end slavery. Yeah yeah yeah I know - there were very good realpolitik reasons for this, and England over the centuries has had some very good PR agents, but in the end, they did it. The Enlightenment was, compared to the theocratic/autocratic fusion of the early modern era, an advancement[1]. I'll die on that hill. It wasn't possible without the blood and labor of countless aboriginal peoples, who we should honor in the same proportion, of course.

[1] There's some disagreement about this in the current era, which I won't express an opinion on. "Palingenesis" is an applicable cautionary term.

Re: How was the size of Earth first measured? (2015)

#112

Post by pizzafeelsright »

soraminazuki wrote: post #110
mcmoor wrote: post #73

Earlier quoted context omitted.

Knowing this makes me perplexed whenever someone treats geocentrists as idiots. Sometimes science really can get only as far as our "eyes" can see.

If we had to prove which is right without access to prior wisdom, most of us would fail miserably. Our current understanding of the world can't be built in any single person's lifetime. But it's easier than ever to do your own research in the modern age. Heliocentrism vs. geocentrism is a well established topic. It doesn't take a genius to reach the right information. You can even conduct your own experiment if you w…

Try to correct people to say, "What a beautiful earth rotation" instead of "sunrise".

Doing research means believing works written by old dead men who held power. Sometimes, they are proven false. Other times, they were right all along.

Re: How was the size of Earth first measured? (2015)

#113

Post by zeroimpl »

kemotep wrote: post #84
jan_Sate wrote: post #82

This estimation method would only work under the assumption that earth is a spherical. Now that we do know that it's a sphere. But how could you figure that out back in 2000 years ago?

That’s the entire thing! He read an account of a city so many miles away from where he was that on a specific day of the year had no shadows at noon. On that day in his city, shadows still were cast. If there was no discrepancies in the shadows that would make sense for a flat earth. But the discrepancy made him determine it had to be sphere and then he went out and calculated the circumference.

Huh? If I put a lightbulb above something, the place it’s above won’t have shadows, but there will be shadows at places that aren’t directly underneath.

Re: How was the size of Earth first measured? (2015)

#115

Post by soraminazuki »

pizzafeelsright wrote: post #112
soraminazuki wrote: post #110

Earlier quoted context omitted.

If we had to prove which is right without access to prior wisdom, most of us would fail miserably. Our current understanding of the world can't be built in any single person's lifetime. But it's easier than ever to do your own research in the modern age. Heliocentrism vs. geocentrism is a well established topic. It doesn't take a genius to reach the right information. You can even conduct your own experiment if you w…

Try to correct people to say, "What a beautiful earth rotation" instead of "sunrise". Doing research means believing works written by old dead men who held power. Sometimes, they are proven false. Other times, they were right all along.

> Try to correct people to say, "What a beautiful earth rotation" instead of "sunrise".

That's just figure of speech. I don't see how it's relevant.

> Doing research means believing

The thing about good science is that it's verifiable, no need to believe. In this case, anyone with a cheap telescope can conduct their own experiment. There's just no excuse for believing in geocentrism in 2023.

As I mentioned, this is a well established scientific fact we're talking about here. People believing in geocentrism failed at multiple levels. For starters, they failed to distinguish trustworthy information from outright misinformation. They also failed to comprehend the details of the arguments being made, or haven't even bothered. On top of that, they also failed at critical thinking too.

That's more than enough reason to draw conclusions about one's ability to learn.

> works written by old dead men who held power

People so powerful that they were persecuted for their work by the church.

There are also countless people, currently alive, of various age and gender, independently verifying scientific facts and writing about it. Nobody gets their facts solely from "old dead men."

Re: How was the size of Earth first measured? (2015)

#116

Post by ahazred8ta »

jaggederest wrote: post #96
labster wrote: post #80

Earlier quoted context omitted.

The thing that stood out to me was the second rung of the ladder, the Moon. Having a large companion satellite is not a prerequisite for life (probably), so how would aliens without one bridge this gap? It seems like it would take a lot more physical theory beyond simple geometry to get there.

> Having a large companion satellite is not a prerequisite for life (probably) I don't know, there's a sibling comment to this one that brings up some proposed benefits to having a moon. It's possible that the foundation of life itself relied on having tidal variation of some kind, since AFAIK the equivalent of early amino acids were formed in tidal pools cut off from the main ocean and cooked under the stress of UV…

they may have found Darwin's 'warm little pond' - http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem... Common origins of RNA, protein and lipid precursors in a cyanosulfidic protometabolism

Re: How was the size of Earth first measured? (2015)

#117

Post by ahazred8ta »

zeroimpl wrote: post #114

Somewhat surprised the answer isn’t based on the angle to the North Star - that’s my preferred approach and it seems less explainable by a flat earth model under assumption the stars are further than the sun

One calculation (75 BC) used the angle of Canopus, which was conveniently near the horizon. https://en.wikipedia.org/wiki/Posidonius#Calculation_of_Eart...

Re: How was the size of Earth first measured? (2015)

#118

Post by kemotep »

zeroimpl wrote: post #113
kemotep wrote: post #84

Earlier quoted context omitted.

That’s the entire thing! He read an account of a city so many miles away from where he was that on a specific day of the year had no shadows at noon. On that day in his city, shadows still were cast. If there was no discrepancies in the shadows that would make sense for a flat earth. But the discrepancy made him determine it had to be sphere and then he went out and calculated the circumference.

Huh? If I put a lightbulb above something, the place it’s above won’t have shadows, but there will be shadows at places that aren’t directly underneath.

Only places near the equator will be parallel with the sun. Anywhere else, because the curve of the earth, there will always be an angle, and thus even at high noon on the summer solstice, there are still shadows in Alexandria. So I don’t understand your analogy. It doesn’t apply because the earth isn’t flat.

Re: How was the size of Earth first measured? (2015)

#119

Post by [deleted] »

whatshisface wrote: post #97
oxygen_crisis wrote: post #75

Earlier quoted context omitted.

He measured it in "stadia" and there was no consensus about exactly how long a stadion was. The definitions ranged widely, from ~150m to ~210m. The low error assessment comes from magnanimously (but baselessly) choosing to use the definition of a stadion which assigns Eratosthenes the lowest error. https://en.wikipedia.org/wiki/Stadion_(unit)

> An empirical determination of the length of the stadion was made by Lev Vasilevich Firsov, who compared 81 distances given by Eratosthenes and Strabo with the straight-line distances measured by modern methods, and averaged the results. He obtained a result of about 157.7 metres Sounds like there are other lengths given by Eratosthenes which could be used to tell what he meant by one stadion.

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