Odd O'blography

How High is Up?

Much like looking for your shadow on Groundhog Day, it's a matter of perspective. It depends on where you're standing, what you're looking at, how you measure, and where you measure from. I can look up to Mt. Rainier from sea level and say 'Wow, that's high!" Others might look up at the Matterhorn, Mt. Fuji, Mt. Kilimanjaro, Mauna Kea, or Uluru with similar awe. And everyone agrees that Mt. Everest is the highest, but is it really?

Everest may be the highest point above sea level, but the sea is neither fixed nor level. It's subject to tidal forces and the whims of weather. And it wraps around a lumpy world that isn't a perfect sphere (science guys call it an oblate spheroid). Earth's rotation produces a centrifugal force that causes an outward bulge at the equator. When measured from the center of the earth, this bulge accounts for a nearly 14-mile difference in sea level between the poles and the equator.

What? Sea level isn't level! How can that be?

Well, take a look at a globe. Why doesn't all the water run down to Antarctica? The answer, of course, is gravity. Gravity pulls the oceans toward the center of the earth and that causes the water to spread out more or less evenly. But the equatorial bulge also means that there's about a 1% difference in gravity between the poles and the equator. For example, a bag of potatoes that weighs 100 pounds at the north pole weighs only 99 pounds at the equator. Centrifugal force and the gravitational gradient allow the oceans to conform to the earth's equatorial bulge instead of draining 'down' to the poles.

So, how high is up? It really is a matter of perspective. Is sea level our reference point, or do we measure from the center of the earth? The accepted standard of sea level makes Everest the highest point at 29,000 feet. But Everest's peak is only 3965.8 miles from the earth's center. Ecuador's Mt. Chimborazo is only 20,500 feet above sea level, but it sits directly atop the earth's equatorial bulge. So, at 3967.1 miles, Chimborazo's peak is actually the highest as measured from the Earth’s center.

Does this definition of high actually matter? Well, try looking at it from a different perspective. Look down instead of up. Like a ship sailing over a reef, you're most concerned about what sticks up furthest. If you're in a UFO making an extremely close orbit of earth, then you're more likely to hit Chimborazo than Everest.