Everest the highest? (APOD 08 Apr 2007)

TimLong · Post by **TimLong** » Sun Apr 08, 2007 12:48 pm

Just heard on NPR that if one measures from the center of the Earth, that there is a mountain in Ecuador that is actually taller than Everest. This is caused by the bulging of the Earth at the Equator.

JohnD · Post by **JohnD** » Sun Apr 08, 2007 3:28 pm

Mt.Chimborazo's summit is further from the centre of the Earth than Mt. Everest's, but by the same measure, so are the beaches of Ecuador! This is due to the 'oblateness' of the Earth, and was calculated by Isaac Asimov, in a 1966 article to which I would be grateful for a reference.

Another point, about this photo. I had always assumed that an object seen to project above the horizon of the observer was higher than the observer's eye. There are several peaks in this picture, both near and far, that show higher than the horizon. Am I wrong?

JOhn

TimLong · Post by **TimLong** » Sun Apr 08, 2007 9:14 pm

I was told that also a long time ago. But I think it may have to do with how far away the horizon is. In the case of being on top of Everest, and I haven't done the math, I would think the horizon would drop away from the true horizontal. Just a guess.

BMAONE23 · Post by **BMAONE23** » Mon Apr 09, 2007 4:49 am

This is the article about this. http://www.npr.org/templates/story/stor ... Id=9428163
There is a mistake in the article though.
It states that:

"Mathematicians call this an "oblate spheroid," which means there is a bulge that circles the Earth just below the equator, so anyone standing in that part of the world is already standing "higher," or closer to outer space, than people who aren't on the bulge.

Therefore people in Ecuador, Kenya, Tanzania and Indonesia are all a bit closer to the moon (not much, only about 13 miles closer) than people standing at the North and South poles."

The obvious problem with this statement is that the Moon orbits roughly around the equater and the Poles sit over 4000 miles further away at what would be the central axis point of the earth.

Andy Wade · Post by **Andy Wade** » Mon Apr 09, 2007 10:32 am

BMAONE23 wrote:This is the article about this. http://www.npr.org/templates/story/stor ... Id=9428163
There is a mistake in the article though.
It states that:

"Mathematicians call this an "oblate spheroid," which means there is a bulge that circles the Earth just below the equator, so anyone standing in that part of the world is already standing "higher," or closer to outer space, than people who aren't on the bulge.

Therefore people in Ecuador, Kenya, Tanzania and Indonesia are all a bit closer to the moon (not much, only about 13 miles closer) than people standing at the North and South poles."

The obvious problem with this statement is that the Moon orbits roughly around the equater and the Poles sit over 4000 miles further away at what would be the central axis point of the earth.

I'm not surprised they made a mistake, their thinking is flawed in measuring from earth's centre.
Water finds its own level, this is why mean sea level is used as the daturm for measuring heights.
Heights are relative to our perspective as humans, and since we can't stand at the centre of the earth its a bit daft measuring heights from there as the measurements have no real meaning.
That teacher drawing a perfect freehand circle is pretty cool though...

iamlucky13 · Post by **iamlucky13** » Mon Apr 09, 2007 11:31 pm

Andy Wade wrote:I'm not surprised they made a mistake, their thinking is flawed in measuring from earth's centre.
Water finds its own level, this is why mean sea level is used as the daturm for measuring heights.
Heights are relative to our perspective as humans, and since we can't stand at the centre of the earth its a bit daft measuring heights from there as the measurements have no real meaning.
That teacher drawing a perfect freehand circle is pretty cool though...

Perhaps less anthropocentrically, sea level gives us a measure of even gravitational potential, which is certainly a factor in the rise and subduction of all these mountains.

orin stepanek · Post by **orin stepanek** » Tue Apr 10, 2007 4:06 pm

iamlucky13 wrote:
Andy Wade wrote:I'm not surprised they made a mistake, their thinking is flawed in measuring from earth's centre.
Water finds its own level, this is why mean sea level is used as the daturm for measuring heights.
Heights are relative to our perspective as humans, and since we can't stand at the centre of the earth its a bit daft measuring heights from there as the measurements have no real meaning.
That teacher drawing a perfect freehand circle is pretty cool though...
Perhaps less anthropocentrically, sea level gives us a measure of even gravitational potential, which is certainly a factor in the rise and subduction of all these mountains.

http://antwrp.gsfc.nasa.gov/apod/ap070408.html
Also; if you use the basic surface of the Earth; than Everest is the top dog.

Orin

makc · Post by **makc** » Wed Apr 11, 2007 10:51 am

oh, this is one of those respawning APODs they pull out when there's nothing better to show

the page has same defunct author email as the old one (and I know because I had to contact him to get his permission for my Everest stellarium landscape).

NoelC · Post by **NoelC** » Thu Apr 12, 2007 5:16 pm

LOL, the concepts of "closer to outer space" and "closer to the moon" have me laughing here. And while at first blush seeming descriptive, neither is accurate. "Further from the center of the Earth" is the only measure that works in this context.

Someone standing on the pole is something like 4000 miles further from the moon than someone on the equator, and it has nothing to do with the bulge. The moon never orbits above the poles!

And is the Earth's atmosphere thinner at the equator? I don't think so, yet that measures the "distance from outer space" in my thinking.

Just the other day I was marveling at how Microsoft Streets and Trips showed me traveling at 70 feet below sea level (in Georgia). This "Earth isn't flat after all" stuff sure is complicated for a lot of folks!

-Noel