Thursday, 17 March 2016

188) “Over the years NASA has twice changed their story regarding the shape of the Earth. At first they maintained Earth was a perfect sphere, which later changed to an “oblate spheroid” flattened at the poles, and then changed again to being “pear-shaped” as the Southern hemisphere allegedly bulges out as well. Unfortunately for NASA, however, none of their official pictures show an oblate spheroid or pear-shaped Earth! All their pictures, contrary to their words, show a spherical (and clearly CGI fake) Earth.”

The fact that the earth is not quite a sphere is another finding of science. However, you won’t see it in a photo of the earth. That is because the “bulge” is so tiny compared to the size of the globe that it would be smaller than a pixel in a standard size photo.  Its so small  that it rarely makes any difference to mapmaking.

It is about 5 miles extra width, in a diameter of nearly 8000 miles. Can you detect a difference of 1 in 1583 by eye?  We are talking about a difference in shape that takes enormous precision to detect it. Which you would have known already if you’d tried to find out, instead of blindly repeating a talking point.

Oblateness is the very slight bulge at the equator. The answer is that water is subject to the same forces that the rest of the earth is. The equator is very slightly further from the centre than the poles because the Earth’s spin makes it bulge.

Ever watched pizza dough being spun out into a disk?  Same principle, with very much less stretching in proportion to size.

As a matter of fact, it's almost impossible to see the flattening at the poles (the diameter of the earth along the polar axis is approximately  1/300th of a diameter shorter than the diameter through the equator). This has been accepted fact since at least 1910. On the other hand, the "pear shaped" quality is described as "a subject of much discussion" in a page called "Geodesy for the Layman" published in 1983, and then dismissed as being too small to make any difference in normal geodesy (surveying/map making) practice.

Pear shaped" is a bit of an exaggeration. The amount the earth varies from a ellipsoid at any point on the earth's surface is minuscule compared to the size of the earth, so you wouldn't see it if you were far enough away to see the whole earth.

The Earth is only approximately spherical, so no single value serves as its natural radius. Distances from points on the surface to the center range from 6,353 km to 6,384 km (3,947 – 3,968 mi). Several different ways of modeling the Earth as a sphere each yield a mean radius of 6,371 kilometers (3,959 mi). Regardless of the model, any radius falls between the polar minimum of about 6,357 km and the equatorial maximum of about 6,378 km (3,950 – 3,963 mi)
Exactly how round is the Earth?
The shape of the Geode, as it is called, is nearly a perfect sphere, but because the earth is spinning, it is about 21.5 kilometers flatter at the poles, and bulged-out at the equator by about the same amount.
There are also other 'higher-order' shape deviations which make the Earth slightly pear- shaped with a larger southern hemisphere surface area than in the northern hemisphere, but at a level of a kilometer or so in radial girth. The biggest effect, though, is its polar flattening. If you had a basketball to represent the Earth's spherical average shape, the flattening would be 21/6500 = about 1/300 the radius of the basketball or 1/32 of an inch...give or take.

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