> I object already! Knowledge does not reside in society. [...] You and I can know. It is not a societal exercise.

Knowledge may or may not reside in society, but all practical effects and consequences of knowledge reside in society. A concept does not exist in an abstract and metaphysical world where you can go and find. And it's not possible to develop any concept, including scientific concepts, without social interactions. Thus, some (not all) Social Constructionists believe the process of scientific investigation is largely a societal exercise, and I don't find it's an unreasonable argument (I didn't say I agree, I say it's not unreasonable). For example, when one use the language of math to describe the physical phenomenon, some will represent it in terms of vectors, others will show it using complex numbers, or alternatively explaining it by a matrix. In practical, all are valid and useful, but their mental pictures are different. These concepts only exist in a society (an interesting article on this issue is Would Aliens Understand Lambda Calculus? [0]). Of course, if experimental physics is something to be accepted, it must explain observed phenomena and makes predictions. But how you exactly imagine the concept of "force" (or even this concept itself) and how you describe it in language depends on the history and culture of your society. Thus, I think it's fair to say that societal exercises are at least one part of any scientific investigations.

> Well, having given a bunch of detailed examples to show why it is not possible to prove a spherical earth, why do you call it an 'absurd' theory?

First, I didn't show it is impossible to prove a spherical Earth. I simply showed examples that some experiments are not as "obvious" as many have thought, and there exists practical problems. I also showed how these problems can be fixed and a spherical Earth can be demonstrated, by taking additional phenomena or concepts into accounts, which makes the experiment more difficult and non-obvious. But just because you cannot solve a problem for once doesn't mean the problem is impossible to solve. Speaking of atmospheric refraction, you can repeat the experiment in different time of the day, in different seasons, or try adjusting the heights of the objects, and you'll find strong evidences of atmospheric refraction, and how Flat Earth results are experimental errors.

> why do you call it an 'absurd' theory?

As I already mentioned in the original comment, arguments by Flat Earth advocates are 100% cherry-picked. They say the experiments are unable show a spherical Earth, not because they're serious experimenters, but that other experiments or additional concepts that would show a spherical Earth are intentionally ignored. For example, under some conditions, optical observations can show a spherical Earth, but it's not published by Flat Earthers. On the other hand, results show a flat Earth is published as a definite conclusion, and the concept of atmospheric refraction is rejected for being unnecessary and too complicated. However, if I use the same standard, I, too, can publish a single spherical Earth result and call it the definite conclusion, but this time, Flat Earthers will suddenly start rejecting my results on the basis of atmospheric refraction! Also, suggestions of improvement of the experiment that would clarify the problem will be intentionally ignored.

[0] http://tomasp.net/blog/2018/alien-lambda-calculus/