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Eight Inches per miles squared
I quite often see this “8 inches per mile squared” formula used by flat earthers to calculate the hidden height on a spherical Earth. There are several problems with that formula:
It’s simply the wrong formula. Why so?
- As often depicted, it calculates the drop height perpendicular to a horizontal tangent line, not the hidden height, or, to put it in other words:
- The biggest problem with that formula is that it does not consider the observer’s altitude. It is somewhat correct if you were to dig a hole on a beach so that your eyes would be at water level – something I, for my part, do not do that all too often.
In the image below, we can see the difference between the hidden height, according to the eight inches per mile squared, and the hidden height according to a line-of-sight model.
Then we have some minor issues, at least compared to the above.
- It does not take refraction into consideration.
- It is not accurate at long distances, but this is not a good argument against the formula, since the error even at 100 miles is less than one part in 1300 – if the intention is to calculate the drop height. The question, though, is, why on Earth would one need to do that particular value?
So, what would a more accurate formula be?
Let us have a look at that on the next page.
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