that the Earth is round? We all know those photos taken out in space showing a round Earth could have been faked.

So how do we know the Earth is round?

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~AstroMike

Because it just defies reason that it could be a cube. :-?

Ptolemy's experiment. Measure the difference in the angle of insolation with reference to a gravimetric vertical. Do this simultaneously in two places on earth. Note the variance. Ptolemy not only proved the world was round that way, he fairly accurately computed its radius.

Circumnavigate it.

Observe other celestial objects and generalize.

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"Facts are stubborn things." --John Adams
Clavius Moon Base

I guess it depends on how much leg work you're willing to do, and how much you're willing to depend on other people's word.

If you need to prove it to yourself, then there are a few things that come to mind.

If you're near the ocean or other sufficiently large body of water, you can see ships disappear bottom first as they go over the horizon, and appear mast first as they come back.

The shadow of the Earth on the Moon during a lunar eclipse is round.

If you go high enough, say in an airplane, on a clear day you can see the curvature of the Earth.

I know I've seen this covered before on BABB, but I haven't checked the search function yet.

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Jeff Schwarz
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Argh!! They booby-trapped their sun!!****--Invader ZIM

The altitude of Polaris changes in a regular way with latitude which is inconsistent with a flat Earth. Remember, Polaris can be used as a navigation tool for that reason.

You misspelled Eratosthenes. :-)

Here is something that is bound to stir things up.

The ancient Greeks KNEW that the earth was round (as in, like a sphere, not like a pancake) because of a series of experiments where the sunlight cast shadows at different angles at the same time during the day at different locations. Did you follow that? Sorry, I might have done a drive by here. Let me put it another way. The ancient Greeks did the following experiment:

(#1) First, they assumed that the sun was far enough away that the light -- for the purpose of the experiment -- would be considered to be parallel. Although it is NOT -- they figured it was close enough in order to determine the curvature of the earth.

(#2) Using plumb lines -to make a vertical line towards the ground they set up a number of test sites where they would have a vertical line that would cast a shadow on the ground.

(#3) They set up areas miles away from each other and a means to measure the length of the shadows at the same time of the day.

(#4) If the earth was flat -- and if the sun was far enough away to be considered a source of parallel lines -- the shadows would all be the same length. But, alas, they were different lengths and even sometimes pointing in different directions.

From this, they made a fairly accurate of the curvature of the earth and even its size.

Now, I know a lot of people are going to say "blah blah blah that is not true because of Columbus and at Columbus' time most people thought the earth was flat bla blah blah blah" well, before you do, look it up, ok? You can do an easy Google on this and get all the details.

The fact is, there were educated people who knew the earth was spherical even before Christ.

You misspelled Eratosthenes. :-)

Either way, beware Greeks bearing plumb-bobs.

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"Facts are stubborn things." --John Adams
Clavius Moon Base

Besides, the Earth casts a round shadow on the Moon. It couldn't be a disk because no matter what time of the night the lunar eclipse occurred, the shadow was still a circular arc.

We had a nice long thread on this topic back when the new board first came up. Lots of good stuff there:

http://www.badastronomy.com/phpBB/viewtopic.php?t=12

(Wow! t=12? Only the twelfth topic posted, it seems!)

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...And that, my liege, is how we know the Earth to be banana-shaped. --Sir Bedevere

I guess I should of mentioned I brought this up because of this:

What did happen, according to conventional historians, was that Russia and the U.S. began space programs. After the Russians sent up Sputnik in 1957, the space race was on in earnest. The high point came in 1969, when the U.S. landed men on the moon.

That, according to Johnson, is nonsense, because the moon landings were faked by Hollywood studios. He even names the man who wrote the scripts: the science-fiction writer Arthur C. Clarke. But he acknowledges that the moon landings were at least partly successful.

"Until then," he says, "almost no one seriously considered the world a ball. The landings converted a few of them, but many are coming back now and getting off of it."

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~AstroMike

Yeah there are still some people out there that think the world is flat but most people just tend to ignore them.

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"Eternal vigilance is the price of supremacy"
------------Mark Twain

"Women are like Voltron. The more you can hook up, the better it gets."

That's a very sad article AstroMike. I believe there was a Straight Dope article a while back in which it related HBers to Flat-Earthers. They said that Flat-Earthers assume fakery because the Apollo photography shows a round Earth, which of course has to be false.

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Freedom For Fission A breath of fresh Iodine-131

Their basic reasoning from some of them anyway is that the earth can't be round because the people on the bottom would fall off! With such a misconception of gravity it is no use arguing with them.

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"Eternal vigilance is the price of supremacy"
------------Mark Twain

"Women are like Voltron. The more you can hook up, the better it gets."

Maybe I'm just optomistic, but I think the Flat Earth Society today is just running off of SARCASM.

Well in response to Johnson (whoever that is).

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If ten million people belive a stupid thing...its still a stupid thing. The mother of fools is always pregnant

What proof the world be round?

Pay Russians 20 million and go see for ones own self?

But since space flight is a hoax, you would just be seeing a movie set. So in reality, the Earth is really flat. :roll:

Which reminds me, you can't have different seasons like winter on a flat Earth because the Sun would be shining the same place everywhere and with the same intensity when directly overhead.

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~AstroMike

Sure you can. Australians are a hoax too. :wink:

Magic? [HB thought(?) mode] Between it, aliens, and government conspiricies you can answer a lot of questions without proving a thing.... [/HB thought(?) mode] :wink:

The wonderful thing about science is that everything is built on previous work. With suffeciont research, you can logically build a chain of connection from, for example, the HST all the way back to the discovery of fire and the wheel, although some documentation would be a real pain to come up with...don't know if Og the caveman ketp that great a notebook on his research into fire...

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"Light thinks it travels faster than anything but it is wrong. No matter how fast light travels it finds the darkness has always got there first, and is waiting for it." — Terry Pratchett, Reaper Man

441!!!! :)