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A wise man in ancient time did this by comparing shadows in different places. Can't remember his name though. But he was quite close with his calculations. It d

A wise man in ancient time did this by comparing shadows in different places. Can't remember his name though. But he was quite close with his calculations. It doesn't need to be expensive. Just wait for noon. Then hop in a car/bus/train/whatever and do the same at the same time next day somewhere else. It helps if the shadow-casting thing is the same height.

YeGoblynQueenne 5y ago
That was Eratosthenes of Cyrene: The simplified method works by considering two cities along the same meridian and measuring both the distance between them and the difference in angles of the shadows cast by the sun on a vertical rod (a gnomon) in each city at noon on the summer solstice. The two cities used were Alexandria and Syene (modern Aswan), and the distance between the cities was measured by professional bematists.[16] A geometric calculation reveals that the circumference of the Earth is the distance between the two cities divided by the difference in shadow angles expressed as a fraction of one turn. https://en.wikipedia.org/wiki/Eratosthenes#Measurement_of_Earth's_circumference https://en.wikipedia.org/wiki/Eratosthenes#Measurement_of_Ea...
eesmith 5y ago
Here's Philip Morrison showing how to do a similar experiment, from the 1980s TV series "The Ring of Truth". https://youtu.be/yRY2SkMTafc?t=567 https://youtu.be/yRY2SkMTafc?t=567 They found a road that was almost due north and south (US 183 from Bassett, NE to 370 miles south in Coldwater, KS). They measured the elevation of Antares at its zenith one night, then again the next. From that they get the change in latitude. Combined with odometer data and some estimates for wiggles, and end with a result about 5% larger than the best-known solution. Their measuring instrument was a Ryder van dubbed "The Van of Eratosthenes." As an aside, later in the same episode is when I learned about GPS. https://youtu.be/yRY2SkMTafc?t=2968 https://youtu.be/yRY2SkMTafc?t=2968 . "This is the future of mapping."
elsjaako 5y ago
What I don't like about this argument is that it assumes the sun is very far away, which I've heard flat-earthers claim it isn't.

YeGoblynQueenne 5y ago

That was Eratosthenes of Cyrene: The simplified method works by considering two cities along the same meridian and measuring both the distance between them and the difference in angles of the shadows cast by the sun on a vertical rod (a gnomon) in each city at noon on the summer solstice. The two cities used were Alexandria and Syene (modern Aswan), and the distance between the cities was measured by professional bematists.[16] A geometric calculation reveals that the circumference of the Earth is the distance between the two cities divided by the difference in shadow angles expressed as a fraction of one turn. https://en.wikipedia.org/wiki/Eratosthenes#Measurement_of_Earth's_circumference https://en.wikipedia.org/wiki/Eratosthenes#Measurement_of_Ea...

eesmith 5y ago

Here's Philip Morrison showing how to do a similar experiment, from the 1980s TV series "The Ring of Truth". https://youtu.be/yRY2SkMTafc?t=567 https://youtu.be/yRY2SkMTafc?t=567 They found a road that was almost due north and south (US 183 from Bassett, NE to 370 miles south in Coldwater, KS). They measured the elevation of Antares at its zenith one night, then again the next. From that they get the change in latitude. Combined with odometer data and some estimates for wiggles, and end with a result about 5% larger than the best-known solution. Their measuring instrument was a Ryder van dubbed "The Van of Eratosthenes." As an aside, later in the same episode is when I learned about GPS. https://youtu.be/yRY2SkMTafc?t=2968 https://youtu.be/yRY2SkMTafc?t=2968 . "This is the future of mapping."

elsjaako 5y ago

What I don't like about this argument is that it assumes the sun is very far away, which I've heard flat-earthers claim it isn't.