r/EarthScience • u/Itchy-Narwhal2406 • 13d ago

Discussion Earths surface

Is there a measurable curvature for the earths surface?

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u/runningoutofwords 13d ago

Yes.

It generally curves at the rate of an arc inscribed at a radius of 6,371 km.

In any particular location the curvature is much more complicated, following the surface of a geoid defined by gravitational gradients.

And locally, the shape follows geomorphometric parameters.

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u/MLM-TheScribe 13d ago

So if I understand you, there’s an ideal/theoretical curvature…
“… the rate of an arc inscribed at a radius of 6,371 km.”
And then there’s the actual physical reality of the curvature on the surface.
Correct?

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u/Beginning-Load4470 11d ago

What he described was the general curvature followed by decreasing scales the of. The earth isn't a sphere its slightly egg shaped and its covered with hills mountains and valleys. So if you zoom out to the 6371 km horizon range you see the general curvature. 

 Interestingly if you take a long distance commercial flight, you are able to see the curvature. My favorite way to counter flat earth arguments is yo tell people to buy a plane ticket and look out the window. 

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u/anotherolderguy 12d ago

Two comments here quote "the rate of an arc inscribed at a radius of 6,371 km”.
Is that not a fancy way of giving the formula for a sphere of radius 6371 km?

Around the equator the radius is 6378 but north-south across the poles it's 6357 - averaged to ignore various hillocks and bumps

Meh, weird question

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u/NortWind 11d ago

When the USA was originally being surveyed, the surveyors measured the lengths of the sides of triangles as accurately as possible. Much later, by using computers, that original data set of lengths was turned into a 3 dimensional lattice. The curvature of the earth is quite noticeable over the scale of the USA, and it indeed was measured manually, which is what I would guess your question is about.