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Phildonnia3
2003-Nov-04, 10:03 PM
I'm trying to follow up on an interesting fact i heard, but I can't seem to find any figures on the exact shape of the earth. Can anyone spare a link?

The claim, incidentally, is that the headwaters of the mississippi river are closer to the center of the earth than the delta.

bobjohnston
2003-Nov-04, 10:46 PM
Here's one (it's .pdf though):

http://topex.ucsd.edu/geodynamics/14gravity1_2.pdf

You'll also need the altitude of the headwaters (plus the latitude of the headwaters and mouth).

Phildonnia3
2003-Nov-04, 11:47 PM
Thanks, that's all I needed. I'll put this one in the "true" category. True, but extremely weird to think about. The river flows uphill?!

The "geoid" is about 7100 meters lower at latitude 49 than 29. The elevation of Lake Winnibigoshish (what a cool name!) is about 400 meters above sea level.

I just used the slightly inaccurate ellipsoid formula; I assume that the more accurate model is not going to cover up the additional 6700 meters.

kilopi
2003-Nov-05, 12:34 AM
The river flows uphill?!
No, of course not (http://www.straightdope.com/mailbag/mgeoid.html).

SpaceTrekkie
2003-Nov-05, 03:38 AM
The river flows uphill?!

no, it flows downhill, which, in this case (as well as the Nile) happens to be North!

Musashi
2003-Nov-05, 04:03 AM
I'm pretty sure the Miss flows south.

Charlie in Dayton
2003-Nov-05, 06:45 AM
Thanks, that's all I needed. I'll put this one in the "true" category. True, but extremely weird to think about. The river flows uphill?!

The "geoid" is about 7100 meters lower at latitude 49 than 29. The elevation of Lake Winnibigoshish (what a cool name!) is about 400 meters above sea level.

I just used the slightly inaccurate ellipsoid formula; I assume that the more accurate model is not going to cover up the additional 6700 meters.

21000+ feet? Unless we're talking two different things here, that's nowhere near the Missisiippi drop.

And it's Lake Itasca, not Winnibigoshish...
Check here, and scroll down to the pix of the source of the Mississippi River (http://www.2havefun.com/Places/North-West/LakeItasca/). I have taken my shoes off and walked across the Mississippi - twice.

kilopi
2003-Nov-05, 07:02 AM
21000+ feet? Unless we're talking two different things here, that's nowhere near the Missisiippi drop.
For one thing, he claims that's the Mississippi rise. :)

The surface of the Earth at the equator is 20 kilometers farther from the center of the Earth than the poles.

Phildonnia3
2003-Nov-05, 04:18 PM
21000+ feet? Unless we're talking two different things here, that's nowhere near the Missisiippi drop.

And it's Lake Itasca, not Winnibigoshish...
Check here, and scroll down to the pix of the source of the Mississippi River (http://www.2havefun.com/Places/North-West/LakeItasca/). I have taken my shoes off and walked across the Mississippi - twice.

I think I said 400 meters, or about 1500 feet. I stand corrected on the source lake. Lake Itasca's elevation is approximately 420 meters.

Additionally, I should take back my tongue-in-cheek comment that the river flows uphill; it flows away from the center of the Earth.

The Nile flows North? That's impossible. North is up.

Eroica
2003-Nov-05, 05:33 PM
I have taken my shoes off and walked across the Mississippi - twice.
I knew it! When I saw your picture (http://www.badastronomy.com/phpBB/viewtopic.php?p=161877#161877), I thought to myself: Now, there's a man who can walk on water!"

Blondin
2003-Nov-07, 07:20 PM
Here's another good reference site:
http://hypertextbook.com/facts/2001/BeataUnke.shtml

The beaches of Ecuador are higher (further from the center of the Earth) than the peak of Mt Everest (even though they are at sea level).

:o