Are sun shadows only possible on a flat earth?

I found this claim that solar shadows are only possible on a flat earth. I remember their being a debunk vid but I cannot find it may I have some help?
 

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Nth

Member
Well, for one, that's Phuket Word in the screenshots, and he can't get anything right to save his life, so I'd consider it debunked right there. :p

Joking aside, we'd need more specifics on exactly what the claim in question is. Based on the screenshots, it looks like he's commenting on the "Eratosthenes experiment", which uses the lengths of shadows cast by sunlit objects to determine the shape of the Earth. If that's what it is, I'd consider Sly Sparkane's experiment on the subject to more or less be the definitive test. Very carefully gathered data, well presented, with a virtually inescapable conclusion.

Sly Sparkane - Flat Earth: Debunked

He first maps the shadow angles to their locations on an AE flat map. The result is shown below:

SlyFlat.PNG

If the situation is a small sun circling above a flat earth, all the lines should point directly at the sun, allowing it's altitude to be triangulated. This is quite clearly not the case, so the option is ruled out. Secondly, Sly mapped the data onto a sphere of 3959 miles radius, yielding this:

SlyGlobe.PNG

If the sun is very large (e.g., larger than Earth) and very distant, the incoming light rays should be effectively parallel. My brain is too tired to create the appropriate syllogisms, but the flat earth model w/ close sun doesn't accurately predict the observations, while a spherical earth of 3959 miles radius and a distant sun does accurately predict the observations.
 

Mendel

Senior Member.
FE generally has to warp the sun position, because otherwise the sun positions at sunrise and sunset being southeast and southwest in the Southern Hemisphere in the summer can't be explained away: if the sun is circling above the equator, between the two tropics, it should always be north of Australia Therefore, any triangulation towards the sun position that a FEer might make is moot right there, because on FE you can't be sure that the sun is where you see it.
FE triangulation similarly fails for Polaris: if you can get a FEer to agree that a degree of latitude equals 60 nautical miles, and that the North Star's elevation (more precisely: the elevation of the Northern Celestial Pole, the virtual center point of the star tracks, which is close to the North Star) equals Northern latitude, then a simple drawing for different latitudes shows that the North Star's position is not triangulable on FE.
image.png
Phuket Word knows this.
 

DavidB66

Active Member
Someone (sorry, I forget who) has pointed out on YouTube that if the sun moves in a circle parallel to the ground (the usual flat earth model), the tip of the shadow of a stick (gnomon) can only trace an arc of a circle on the ground. Which it never does in reality: it is either a straight line (at the equinoxes) or an arc of a hyperbola (if I recall correctly).
 

Mendel

Senior Member.
Someone (sorry, I forget who) has pointed out on YouTube that if the sun moves in a circle parallel to the ground (the usual flat earth model), the tip of the shadow of a stick (gnomon) can only trace an arc of a circle on the ground. Which it never does in reality: it is either a straight line (at the equinoxes) or an arc of a hyperbola (if I recall correctly).
You may be thinking of this thread https://www.metabunk.org/threads/does-sundial-disprove-flat-earth.7578/ or this post https://www.metabunk.org/threads/ho...-relying-on-nasa-or-photos.10557/#post-229547 (my favorite low-tech debunk #3).
You can probably do this experiment sometime during the next few days, weather permitting.
 

DavidB66

Active Member
You may be thinking of this thread https://www.metabunk.org/threads/does-sundial-disprove-flat-earth.7578/ or this post https://www.metabunk.org/threads/ho...-relying-on-nasa-or-photos.10557/#post-229547 (my favorite low-tech debunk #3).
You can probably do this experiment sometime during the next few days, weather permitting.

Thanks.
I was thinking of this video by Jos Leys, or something very similar:

Source: https://www.youtube.com/watch?v=OYZ-Ab9-WHI


For those who haven't seen Jos Leys's channel, do check it out: he does some outstanding work, mainly with computerised animations.
 
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