In determining height of mountains, in a lay man's language, what does the phrase; 'center of the earth' mean?

Question

Please, educate me on the applications of terms like; tallest, highest, summit, sea-level, etc, as applied in this field.
What exactly does planet earth appear like in a simple example when you refer to the phrase; 'center of the earth'.
In my own idea of tallest / highest or any other term connected to it, i thought we are looking at the very first tip or point of touch on any part of the earth's surface whatsoever, if one descends vertically from the sky?
Now, given my own thinking as above, where (name of mountain etc) on earth is it highest?
I am yearning to go visiting, or is it 'summitting' the highest point on planet earth.
Thanks.

Answer 1

A good question.

The centre of the earth means just that: the point coinciding with the earth's centre of gravity. It is not quite the same as the geometric centre of the earth, because the earth does not have a uniform density or shape; but the difference would be slight.

Because the earth rotates about its axis at something like 2000 km/hr (which we don't feel, because we are rotating with it), it is not quite spherical, but is slightly flattened at the poles and bulges slightly at the equator. This shape is called a spheroid of rotation. Also, because the earth's crust is not uniform in density (the continental land masses being slightly less dense than the oceanic crust), and because the continents 'float' slightly on the denser mantle lying beneath the oceanic and continental crust; the gravimetric shape varies a little: It bulges with the equator, and is slightly elevated under the continents. This shape is called the geoid; and is roughly equivalent to the common term 'sea level'. There are slight variations, where denser rocks (eg, ore bodies) cause 'gravimetric anomalies', but these are local in effect.

The net result is that 'sea level' is further away from the centre of the earth near the equator than it is near the poles.. This has a curious effect, when talking about the height of moutains:
Although Mt Everest is the highest point above sea level, it is not the furthest point from the centre of the earth: That is the summit of Mt Chimborazzo in Ecuador, which is close to the equator, and therefore part of the equatorial bulge.

Answer 2

The center of the earth is the middle of the earth. If the earth was an apple, it would be the core.

The highest point on earth is the summit of mount Everest in the Himalaya mountains in Nepal. The height of landforms is usually measured from sea level, which (at the right tide) is the same level all over the earth. Mt. Everest is 8850m above sea level. Because water is pulled towards the center of the earth by gravity, this is the same as measuring it's height from the center of the earth. It's just easier to work with.

You could have a taller mountain that arises from the sea floor, but rises from a lower point than everest and so does not reach as high.

Answer 3

The center of earth is the center of gravity of all its mass. The center of mass causes all the oceans to seek a common level (affected a little by the spin of the earth and of course the tides caused by the sun and moon). Heights of mountain peaks are generally measured relative to average sea level and the diameter of the earth is the diameter of the average sea level around the globe. Mt. Everest is the tallest mountain above sea level (and is still growing). Except for volcanic mountains such as Hawaii, mountains are pushed up by tectonic plate collisions.

Answer 4

The earth is not a perfect sphere, mostly because it is spinning. If an imaginary perfect sphere is created about the center of gravity of earth at the average radius of earth, then at the north pole the ground and ocean will be lower than the perfect sphere and at the equator they will be higher.
http://en.wikipedia.org/wiki/Spherical_Earth#Geodesy
Thus the peak of a mountain near the equator is further from the center than one of the same height further north or south.
By your definition - if one had a special altimeter that measured the distance to the center of gravity, it would encounter different highest peaks than one looking up from sea level.

Answer 5

The "center" could be the center of gravity, or it could be the center of the Earth's shape. It is thought that the difference is only a few centimeters.

"... if one descends vertically from the sky" -- there are different kinds of vertical: astrometric vertical, gravitation vertical, ellipsoid vertical, etc. ...In some places, they can be as much as 0.4 degrees apart.