Not now, but back then...

How did the ancient greeks find out what the physical dimensions of the earth were? How accurate was their attempt?

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Manu Narayan

That's a good question. But I bet it didn’t have anything to do with dumb luck. http://discussanything.com/Ubb/smile.gif

Probably using the sun, moon and geometry, I would guess. (there were close to the equator)

The way that Eratosthenes measured the circumference of the earth used simple geometry. He knew that at Syene (near Aswan in Egypt), a pillar would cast no shadow at noon on a certain day, meaning the sun was directly overhead. At ALexandria, also in Egypt, a pillar would cast a shadow at that time, meaning the sun was not overhead. He then assumed that the rays of light from the sun were parallel (this is an approximation). Then he measured the angle of light that would produce the shadow of the pillar in Alexandria, usin trigonometry. He walked the distance from ALexandria to Syene, meauring about 500 miles. The angle measured in Alexandria corresponds to the angle from the center of the earth. So, if d is the arc length (500 miles) and C is the corcumference of the earth and a in the angle meaured,

a/360 = d/C

C = 2*pi*radius = pi*diameter

That is how it was done. It is an ingenius experiment, and pretty accurate too. There is controversy over how the unit of measurement, the stadia, translates inot modern units. There are many conversions, it is unknown which definition of stadia Eratosthenes used. However, the estimate of the earth's diameter was about accurate to 15%, which is very good given that he walked 500 miles, measuring it along the way.

Nate

Originally posted by Thutmose:
The way that Eratosthenes measured the circumference of the earth used simple geometry. He knew that at Syene (near Aswan in Egypt), a pillar would cast no shadow at noon on a certain day, meaning the sun was directly overhead. At ALexandria, also in Egypt, a pillar would cast a shadow at that time, meaning the sun was not overhead. He then assumed that the rays of light from the sun were parallel (this is an approximation). Then he measured the angle of light that would produce the shadow of the pillar in Alexandria, usin trigonometry. He walked the distance from ALexandria to Syene, meauring about 500 miles. The angle measured in Alexandria corresponds to the angle from the center of the earth. So, if d is the arc length (500 miles) and C is the corcumference of the earth and a in the angle meaured,

a/360 = d/C

C = 2*pi*radius = pi*diameter

That is how it was done. It is an ingenius experiment, and pretty accurate too. There is controversy over how the unit of measurement, the stadia, translates inot modern units. There are many conversions, it is unknown which definition of stadia Eratosthenes used. However, the estimate of the earth's diameter was about accurate to 15%, which is very good given that he walked 500 miles, measuring it along the way.

Nate

Hit me with some math and riddle me this!

How long would it take to walk 500 miles and measure the whole way do you think?


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The only thing that saves us from the bureaucracy is inefficiency. An efficient bureaucracy is the greatest threat to liberty.
Eugene McCarthy

I have no idea, Ogre, but I am sure it is different for you than it is for me, seeing that you have almost an extra foot of height.

Nate

Wow thanks Nate!

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Manu Narayan

Heres an interesting thought. How long have we known the size of our planet? How long ave known the earth was round? How long have we known the complex astrology?

Not sure how familiar every one is about Global precession. The idea is relatively new to your civilization. There is a slight wobble to the axis of out planet. In order to get a precise calculation as to what degree the wobble moves at you need to know the diameter of the earth. It works out to a full 360 degree rotation about every 26,000 years or to be exact 1 degree of precession every 72 years. This in effect, very slowly changes the location of the stars in our sky. Here’s where it gets kind of interesting. The civilization of ancient Egypt is known to be about 5,000 years old. I’m sure we are all familiar with the great pyramids of the Gisa Plateau. Remarkably enough the 3 pyramids are an exact duplication of the 3 stars in Orion’s belt, down to the exact degree. However, this alignment didn’t exist during the time of the ancient Egypt. This exact alignment would have existed in 10,500bc, or about 12,500 years ago, thanks to precession. The sphinx, points due east and in the time of the Egyptians, would have stared straight at the constellation of Taurus the bull on the horizon. Logically speaking, why is the sphinxs, in the shape of a lion, not a bull? There was on time when the sphinx would have pointed to the horizon, facing Leo, the lion, that would have been 10,500 BC. Hrmmm. Now this puzzle moves on to Ancient Cambodia. The ruins on Anchor, more great pyramids. A civilization which existed only about 3 thousand years ago I believe. Interestingly enough, when looked at from above, Anchor is an exact representation of Draco, the Dragon. But again not how it would have appeared on the horizon in the time of ancient Anchor. Draco would have been upside down. In order to get a match, you would have had to turn back the processional rotation to 10,500 BC. Draco also sits exactly opposite Leo in the zodiac. These attempts to line up earth and sky also find their way to the Mayan temples, Easter Island, the Aztecs and quite a few other lost civilizations, which are all separated by oceans and thousands of years. 10,500 BC just keep popping up all over the place when they are aligned with precessional calculation. Here another interesting item. Easter island and Anchor are exactly 72 degrees from each other if viewed from the earth’s poles. The pyramids at Gisa are exactly 144 degrees from both Easter Island in the pacific and Anchor in Cambodia. These are all precessional numbers. 72 is years is one degree of precession and 144 years is 2 degrees of precession. Is it perhaps a bit ignorant of our civilization to say that we were the first to figure this stuff out? How can these coincidences be so precise and calculated both astrologically and geographically? What I find most interesting is that all of this happened with no supposed communication between continents.

Hmmm, what I have heard about the Orion/Giza stuff is slightly different. First of all, I do not think that precession changes the relative location of stars to each other. In fact, I am almost sure that it doesnt, since precession is simply a different location of the observer. So, even during egyptian times, Orion would look essentially the same, except in a different point of the sky. What I had heard was that the pyramids mimic Orion's belt, and if you run back 5000 years (about when we think they were made), the shaft in the great pyramid points directly to Orion's belt. When looking at the pyramids, they look alot like Orion's belt NOW, I think it would be wrong to say that they havent looked like Orion's belt since 12500 years ago. I think it is alot more reasonable to assume that Orion's belt simply moved through the sky, rather than changed its actual appearance, and since this is supported by logical analysis of precession, I think it is the explanation that I would choose. As for multiple cultures, if one culture could figure somehting out, why couldnt someone else?

Nate

I am familiar with percession, and I'd have to agree with nates analysis of the situation.

I mean, the contellations are constantly moving through the sky as we rotate around the sun. At what time of year are these measurments taken? Cause clearly without a given time of measurement, Orion sometimes isn't even visible!

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Manu Narayan

I would walk 500 miles and I would walk 500 more...

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That's Just My Humble Opinion.

Interesting facts, all of you, bravo. But when you mentioned all of those sites being related, I couldn't help but think about Atlantis. I mean, there are so many little connections between the American, Asian, and European/African continents that are so consistent with the theory of there being a global trading post. For instance, why were there dolls of distinctly African looks found in South America dated some thousands of years before even Erikson landed on America? I don't know, just something I was thinking about

I dig, definately! There are a lot of weird/errie connections.

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Manu Narayan