Sorry for the confusion on this earlier post. I mixed up bulge height as a rise in height when I should have described it as a drop in height. But, as you will see getting the bulge right is important. I have made a number of word revisions and added more commentary on what the "bulge" is to clear up any misunderstanding.
Earth's Curve Horizon, Bulge, and Drop
If you put 3 miles distance and 6 feet for viewer on the chart at this website you will get this:
View attachment 26536
Go to the interactive illustration on this site and drag the blue dot on the curved earth (it will probably have the word "Hidden" in red to the left of it) right on top of the X marked as "Horizon" and the word hidden will disappear. This is the bases for my argument that follows.
On the interactive illustration at Metabunk the earth "bulge" is located in relation to "eye level", and "surface level". Eye level is looking straight forward parallel to the ground as if the surface level is flat and not curved. The bulge of the earth is below the surface level of the curved earth. For a viewer with his eye at 6 feet above the ground the horizon is 3 miles away. At the three mile distance to the horizon, eye level remains 6 feet above the flat surface level. The flat surface level is 6 feet above the horizon point of the curved earth 3 miles away. So, from my eye to the actual horizon point, is a 12 foot drop.
1. Eye level---------------6 foot above surface
2. Surface level---------0
3. Horizon point--------6 foot below surface
A 6 foot drop from eye to surface level plus a 6 foot drop from surface level to horizon point equals 12 feet. So, though it may seem that we are looking straight ahead at the horizon we are actually looking down on a curved earth with a 12 foot drop from my eye to the horizon. But the author of the video says the change in "vertical height" from where we stand at 6 feet on a beach looking three miles to the horizon is a 1.5 feet drop.
How can there be a vertical drop of only 1.5 feet when there is an actual drop of 6 feet from surface level and a 12 foot drop from eye level?
According to the interactive illustration from the Metabunk website, the "bulge" is determined by drawing a line from the point on the surface where we are standing to the horizon. The bulge height is calculated from this imaginary straight line that runs under the actual curved earth surface. The bulge height of 1.5 feet is the distance from the imaginary line up to the actual earth surface midway between the viewer and a 3 mile horizon. It seems this 1.5 foot bulge is used to determine "the change in vertical height", (the distance in drop at three miles distance from viewer) that the author in the video refers to. Which makes no sense.
But there is another bulge point (not mentioned in the Metabunk site) created "at" the three mile horizon, but that is a bulge half way between a 6 mile distance. As ships sail past the three mile horizon they begin to gradually sink below this bulge until they are entirely hidden from view 6 miles away.
So, we have two different points we call "bulge", one is a midway point, 1.5 miles, between the point where we are standing at 6 feet to the horizon three miles away, and the other is the horizon itself, the midway point from where we are standing at 6 feet to a point six miles away where anything under 6 feet in height becomes entirely hidden
So, saying there is only a 1.5 foot drop in a three mile horizon is inaccurate and misleading. There would be an actual 6 foot drop on a curved earth at 3 miles from where we stand plus 6 more feet from eye height. Where as a 1.5 foot drop three miles away would be unnoticable a 12 foot drop would be.
This is where I see the failure of globe model in respect to the horizon.
--Dave