On Fri, 24 Jan 2025, Frank Leonhardt via cctalk wrote: A simple home experiment: Find two points, such a hill/mountain-tops that are visible from each other, but 10 or 20 miles, at least apart east/west.. Set up a vertical tube or slot. When the sun is directly overhead, tell the other person, and see how long it takes before the sun is directly overhead at the other location. if you don't want to use cellphones, since that would not have been available in the past, use smoke signals. I found about a minute to go 15 or 20 miles. 15 or 20 miles in a minute is about 1000 miles an hour. Since the sun's cycle is 24 hours, that would mean that it travels 24,000 miles in a day. And therefore, the circumference of the earth is about 24,000 miles. If you make up some jigs for measuring, and average the readings over a few days, you can get a fairly accurate estimate of the circumference of the earth. Divide by PI if you want the diameter. With visual signaling, instead of cellphones, you might lose a little accuracy, but it was well within the reach of technology for thousands of years. And, it would was close enough to make it obvious that if you want to sail west from europe to the indies, you are going to run out of supplies long before you get there! Unless you are dumb lucky, and happen to bump into some land on the way. Columbus had a bad idea that the earth was MUCH smaller, so he thought that he could make it. He did not prove that the earth is round; that would have to wait for Magellan. And, except for "flat-earthers", educated people knew that the earth was round, and even had a reasonable estimate of how large.

On 1/25/2025 1:04 AM, Fred Cisin via cctalk wrote: Or, he knew how big the earth was, but based on maps older than he was, he knew there was another continent between Europe and Asia traveling west and bilked the Spanish royalty into financing his boondoggle. :-) That was never his intention. bill

This is not sufficient to prove the earth is spherical. This method was used to calculate the diameter of the earth, already knowing that it was a sphere and the sun was very far away. To prove it was not flat, one has to use 3 locations. Using just two only helps to prove the stupid flat earther's thought that the sun was much closer to the flat earth. 3 locations prove that it can't be flat because the angle changes too much over distance. It can be done in any direction but is easier to do North to South because time of day only needs to be at high noon and distance known. Dwight

Can this stop already? Sellam On Fri, Jan 24, 2025, 9:33 PM Frank Leonhardt via cctalk < cctalk(a)classiccmp.org&gt; wrote:

On 1/25/2025 5:55 AM, Sellam Abraham via cctalk wrote: Will the circle be unbroken? (Except that some people maintain it's a square)

Other shapes go boing, boing, boing, boing. Reuleaux triangle goes Hmmmmmmmmmmmmmmmmmmmmmmmmmm. https://www.youtube.com/watch?v=oHzeGEHWMjo

On 23/01/2025 23:00, Paul Koning via cctalk wrote: All science is the best working theory until proven otherwise. However, theories can and disproven, and that's the history of science. No proper scientist believes any theory is the final word. However, they build on theories that have yet to be proven wrong. The theory that the earth is flat is clearly disproven. Aristotle worked it it was basically spherical, yet crackpots believe it's flat to this day - often because their scripture said otherwise.