How Compton computed Latitude, direction to North, and length of a day

Thanks to @FlatSlugbrains for finding this one on the Copasetic Flow blog.

How would you do such a thing on a non-rotating Flat Earth with no gravity?

You couldn't even reliably find "down" because, if density determines motion as Flat Earthers claim (and which NO Flat Earther has ever actually shown evidence for, and we know this isn't true from experiments such as observing a density tube in absence of gravity), then changes in lateral density should cause lateral forces on a body making it impossible to reliably find "down".

Arthur H. Compton built such a device and published his results in Phys. Rev. 5, 109 (1 February 1915) entitled "A Determination of Latitude, Azimuth, and the Length of the Day Independent of Astronomical Observations" (DOI) [backup link, Google Scholar Search]

His paper details the methods and calculations but for the purpose of this exercise it would be sufficient to simply observe the water consistently rotating in the direction consistent with a rotating spherical Earth.

He also publish an article about it in Scientific American, March 27, 1915 entitled "Watching the Earth Revolve".

The apparatus is astonishingly simple - a round tube of water containing a mixture of coal oil and carbon tetrachloride of the same density as water in a constant temperature environment near freezing to minimize thermal influences and a microscope mounted for observing the motion of the fluid (one configuration projected the image on a screen).  The tube was made more narrow at the point of observation as this amplifies the speed of the water moving past that point (the speeds in question are on the order of watching a minute hand on a watch move so proper care must be taken).

You set the tube in a plane and let it rest -- over a period of time the motion of the water in the tube will stabilize, once everything is completely stable you measure the rate of motion of the water, then turn the tube 180° and observe the rate again. You do this in all three planes (OX, OY, and OZ) and you get three component vectors of the Earth's rotation.

Earth rotates around P*

I wonder what imaginary new forces (like 'Magical Flat Earth Density') Flat Earthers will invent to explain this one away?

I'm posting this in part to gain wider exposure to this and in the hopes that we can replicate it both for fun and personal education.


See Also:

Copasetic Flow: Compton's Water Based Foucault Pendulum
The Effect of the Coriolis Force on the Flight of a Bird
A. A. Michelson, H. G. Gale and F. Pearson (1925) Astrophysics J, 61, 137-145 (Part I, Part II)
Compton, "A Laboratory Method of Demonstrating the Earth's Rotation", Science, V 37, #960, 1913