On reading through
Earth Not a Globe, I've spotted a few misunderstandings and faulty assumptions. I plan to start up individual threads on some of these, so that they can be discussed and, hopefully, clarified.
I've decided to start with the section on spherical excess, found
here.
Spherical excess is the theory behind the 'triangle with three 90 degree angles' thought experiment, which has been proposed on this forum before. This experiment is a bit impractical, due to the distances involved, but "...the excess of three spherical angles above two right angles..." has been observed and recorded on smaller scales already.
Rowbotham contends that this excess is due to collimation, which he mistakenly compares to refraction: "...the influence of refraction or "collimation" in their instruments...". Apparently, he did not know that collimation is "the accurate adjustment of the line of sight of a telescope". Even then, if there were an error present in the measurements being made, it would be either left or right, but
always the same way, and always the same amount, which would mean that the angles would still be accurately measured, and any excess found would be real.
So, given that spherical excess has been accurately measured as long as 150 years ago, despite Rowbotham's assertions to the contrary, I would consider it a reasonable contribution to the evidence supporting a round earth.
What are your thoughts?