10 things that would happen if the earth was really flat

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learning
Posts: 406
Joined: Tue Jul 11, 2017 4:57 pm

Re: 10 things that would happen if the earth was really flat

Post by learning » Sat Mar 09, 2019 5:06 pm

camera footage of the earth
https://youtu.be/2aCOyOvOw5c

neighbor
Posts: 515
Joined: Sun Jul 09, 2017 6:06 pm

7 ways to prove the earth is round

Post by neighbor » Thu Oct 03, 2019 11:18 am

http://crosstalk.cell.com/blog/seven-wa ... h-is-round

1. Watch a ship sail off to sea
2. Watch a lunar eclipse
3. Climb a tree
4. Travel through, or even within, different time zones
5. Watch a sunset
6. Measure shadows across the country
7. Google "International Space Station photos"



solarguy
Posts: 140
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Watch the test and results in real time

Post by solarguy » Thu Oct 03, 2019 7:09 pm

https://youtu.be/YaPa4esJJx4

Well, that nails it. The earth is round.

learning
Posts: 406
Joined: Tue Jul 11, 2017 4:57 pm

Re: 10 things that would happen if the earth was really flat

Post by learning » Sat Oct 12, 2019 7:14 pm

The al-Biruni method for calculating the radius of the earth, done in 1000AD. The whole video is worth a watch, though. Excellent example of how high school trigonometry is used in a practical way. To be scientifically rigorous about it, I'd recommend anyone trying to replicate this experiment that they do it on different sea-side elevations at different locations on different days and in different atmospheric conditions to eliminate refractive errors as much as possible. With good equipment and careful measuring, you should get a result within 5% of the measured value as given by national geographic / geologic studies organizations, government agencies, and world-renowned universities, despite the fact that you don't have their budgets.

The theodolite app will work, but a large cardboard protractor, spirit level, and some string should be sufficient if they are accurately marked.

The calculation starts at 5:31, but the first bit discusses Erastothenes.



He cites this video from a certified surveyor, which goes into the rigorous math behind horizon drop and how to do the measurements yourself:

solarguy
Posts: 140
Joined: Wed Jul 12, 2017 3:29 pm

Re: 10 things that would happen if the earth was really flat

Post by solarguy » Sat Oct 12, 2019 7:15 pm

Not to over simplify the problem (although it really is simple) the oldest objection that I know of for flat earth versus round earth comes from the shape of lunar eclipses. If the earth was a sphere then its shadow in any direction such as onto the moon would be round. If it was a disk then the orientation of disk to moon and sun would have to be just perfect to get a round shadow. Take a frisbee, a basketball, and a bright flashlight into a dark room and look at shadows. If the light hits the frisbee from the edge you get closer to a line segment looking shadow. Then rotate it slightly and see how it changes without becoming a circle until the light is directly perpendicular to the frisbee.

The lunar eclipse problem is why ancient greek gave up on flat earth and went spherical earth models about 600 B.C.

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