[Raybooth]

There is actually a very simple experiment that we can do to prove the earth is flat.
But it requires a few people to make a measurement at the same time and a bit of trigonometry.

The experiment is this.

At noon on March 20, (when the sun id directly over the equator) measure the length of a shadow that a vertical post casts on a horizontal surface.
knowing that and the location of the measurement. you can use the formula   tan A = post height / shadow length
Then you can use the Angle you calculated and the distance to the equator to calculate the height of the sun
tan A = height of sun / distance to the equator

Now if the earth is flat EVERYONE will get the same height.  if the earth is round everyone on different latitude will get a different answer.

Can I get any volunteers?

[StinkyOne]

I'll participate if we get flat Earth volunteers, as well. I'm guessing they have a reason why this experiment will fail to prove anything.

[douglips]

People will observe the same size shadow only if the sun is infinitely far away. If the sun is a near distance, then you will get different sized shadows.

However, by collecting this data and then doing the math to see how far away the sun is, you will get conflicting distances for the sun. This contradiction has not been explained away.

[Dr David Thork]

Wilbur Voliva already did this experiment on behalf of the flat side. This is how we arrive at the sun being 3000 miles above the flat earth.



Good luck measuring the globe earth version. If you aren't deadly accurate, you won't even be close. Your readings need to be so accurate as you follow virtually parallel lines as to make your permissible margins of error tiny.

[Curious Squirrel]

Wilbur Voliva already did this experiment on behalf of the flat side. This is how we arrive at the sun being 3000 miles above the flat earth.



Good luck measuring the globe earth version. If you aren't deadly accurate, you won't even be close. Your readings need to be so accurate as you follow virtually parallel lines as to make your permissible margins of error tiny.

But if you take any other point pair you end up with sun heights with more than a 50% difference. This is just like the Eratosthenes experiment. You can get either A) The circumference of the globe if you assume it to be spherical or B) The height of the sun if you assume it to be flat. The problem with B is that no two points agree on the final answer without a fudge factor, when there should be agreement no matter where you take the measurement.

[Bart B]

How many of the flat earth folks see the earth surfaces at both points (45 deg North and South latitudes) are 90 degrees apart?  And in opposite directions?

If the earth is flat, wouldn't they be level and in the same horizontal plane?

[Raybooth]

@Baby Thork 
>>Good luck measuring the globe earth version. If you aren't deadly accurate, you won't even be close. Your readings need to be so accurate as you follow virtually parallel lines as to make your permissible margins of error tiny.

what are you talking about?

at 500 miles from the equator a 1/4 inch measurement  error is +-130 miles
at 1000 its 63 miles
at 2000 its 31 miles
at 3000 its 20 miles
at 4000 its 15 miles

are you telling me normal people can't measure a shadow of a yard stick to within a 1/4 inch?
you'd probably get more error from people not measuring at exactly noon when the shadow is shortest.

In any event the error from measurements would be a lot less than is needed to prove one way or the other. There is a huge difference between the 2 models.    3000 miles compared to 93 million miles.     who cares if the numbers people get are even 500 miles off?  granted that's a 15% percent error but we are not trying to get the exact distance, just enough to determine which model explains the numbers measured.

[Raybooth]

Adding link to round earth model for reference.

Seems to me that it should be fairly easy to prove one way or the other.

https://en.wikipedia.org/wiki/Eratosthenes

[round earth][/https://upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Eratosthenes_measure_of_Earth_circumference.svg/300px-Eratosthenes_measure_of_Earth_circumference.svg.png]

[brinnbry022]

could the results also be skewed if the sun is above a dome? ( the reason sun dogs make me think a dome / firmament is actually possible )

As a side note, I saw a sun dog last weekend in the sky, Using my sons camera I zoomed in 105x optical zoom, and it was no illusion

Or would it not matter i.e dome or not?

[Raybooth]

I've been playing around with excel to model the shadows for both flat earth and round earth.
With the sun at 3000 for flat earth and 93,000,000 for round earth  there is a delta of about 4 inches in shadow length at around 2000 miles from the equator (Miami, Dallas, Orlando, San Antonio, Atlanta, Las Vegas)   
Then decreases to 0 difference around 3000 Miles  (Seattle)
Finally increasing back to 15 inches difference at 4000 Miles  (Anchorage)

So yeah, it should be very easy to see which is correct.  We just need volunteers in
1) southern US
2) northern US
3) Calgory or further north