You actually did not read my post.
These sort of accusations do not belong here. If you didn't understand my response (or identical responses of others before me), ask for clarification. Do not make ungenerous assumptions, lest they turn against you.
My apologies, it seems I was the one who failed to read yours fully. Your argument, however, falls apart when considering your key statement, that EA makes the two situations indistinguishable. My answer: not quite. This has been argued over and over again, with neither side making progress, so I'll try to explain why EA doesn't affect precision assembly.
Straightness is derived from non-optical means at its base. 3 flat plates are rubbed against each other: A against B, A against C, B against C. The only surface shared by 3 surfaces is a flat plane, so this creates a gradually flatter surface on all 3. Once flatness is achieved, this can be used as a reference for easily creating other flat objects. If a measurement unit is decided on, a straight edge can be turned into a ruler, and from there we can use math to get angles, circles, everything. Everything comes from the flat plane. We of course use other methods two, and we are able to verify flatness with electron microscopes (at extremes of precision.)
So, we are capable of creating a round tube with a high degree of straightness, and with square ends. Importantly, we are able to do this without using optical means: no laser levels, etc. Can we assemble it without using optics, and more importantly would we? Because optical straightness verification isn't really used in machining: it's too imprecise, and most is done by referencing a straight plane. It's highly likely that optical straightness verification wasn't used in the creation process for the tube sections of LIGO. Even, therefore, if a laser level was used to assemble them, they still would have shown the gap.
Try it for yourself: get a couple of long things with square edges like Legos or blocks, really anything, so long as it has a slender form factor and square edges. (Square meaning perpendicular to the other edes, not square as in the shape). Then, put them in the straightest line you can. It should be fairly easy, because the square edges act as a guide for assembling them. Now, try and make a curve with them without altering the individual blocks or leaving any gaps between the edges. Difficult, huh? That's the problem facing the FE interpretation of LIGO.
You've seen how easy it is to make a straight line with straight blocks with square edges, and that it's impossible to make a curve without leaving gaps. So, let's look at LIGO construction, then.
On a flat earth: the concrete curves upward. This is because Caltech is trying to account for curvature that isn't there. They put in the first tube, and all is well. They put in the second tube, square it with the first, and weld it on. All is well, except for a slight dip towards the concrete. Fastforward, and the tube is all perfectly straight, but it's also notably lower than at one end than the other. So, let's say they mount each tube parallel to the concrete, which wouldn't be the smartest thing: concrete is by nature a less precise surface than steel, especially poured concrete. But let's say they do do that: each tube has a gap. A small gap, but a noticeable gap certainly (I calculated earlier that it would be half a centimeter. That's a conundrum: if they construct the tube referencing itself, it isn't square to the ground. If they construct it referencing the ground, it isn't square to itself. That's going to take some explaining to management.
On a round earth: the concrete counters the curvature of the earth and is flat. This is because Caltech is accounting for the curvature. They put in the first tube and all is well. They put in the second tube, square it with the first, and weld it on. All is well. Fastforward, and the tube is all perfectly straight and not lower to the concrete on either end. The scientists have a party!
Do you see? The round earth model just works, with no complications, while the flat earth model is going to take considerable explaining. Use the zetetic method, look at the two models, and find which one is truly more likely.
I eagerly await your replies.