Explain to me nice and simply exactly how and why looking through two tubes set up on a slope so they are in line and level with each other proves in any way what shape the Earth is. I do love your little sketch of Bob the Builder by the way. Complete with Hi-Vis jacket and yellow hard hat so as to keep the HSE people at bay. Very cute!
If water level won't convince you then nothing will.
However, if your Earth is the globe you believe it to be then you understand that.... you..... looking level should clearly understand that your globe, underfoot will curve down and away from that vision with every inch, no matter how small the curve would be.
It would never rise up to meet your centre point of the tube (crosshair).
This is why standing on a downward gradient with level tube set up, shows there would be no view of the ground beneath and the ground beneath would change height over distance between that ground and tube end.
Basically you would never see any ground but would see into the distance, any ground that rose up from that downward gradient end if it rose up enough to get back into line of sight.
However, because I am are arguing against a globe and consistent downward curve over distance, you will never see anything merge, as in the convergence of shades of light, only sky itself, assuming it was magically possible to do it on a globe, which it isn't because a globe would not offer us anything of the sort.
Also explain what your cross-hairs were made of, and how you managed to get them both in focus from your eye point.
Cotton for tube and string from the hanging cross. Very simple and inexpensive or even free for ready to hand household bits and pieces.
What is that cross like structure hanging between you and the tubes?
Just a starter point for the eye focuse to the tubes.
It ensures there is no angled view and keeps a point to point level focus over a small distance over the downward gradient.
I get it that the tubes have crosshairs mounted in them. If there is 5ft between the tubes then you would be standing about 30ft away from the tubes based on your diagram. You wouldn't be able to see the crosshairs clearly enough to see when they were exactly in line from that distance.
You can do this experiment over 12 feet, no problem.
A one foot tube and 5 feet gap plus one foot tube, plus a 3 foot cross and a two foot distance to eye from that.
Drawing lines and circles on a screen is one thing but actually setting up this sort of experiment would be hard and essentially pointless in relation to what you could learn from it. I'd love to see some photos of your set up if you actually put in the time and effort to do this.
Go and do it. Simple stuff and you are welcome to actually use a cheap scope to view through the set up if your eyes are a bit dodgy over a small distance.
a cheap bird watching scope or whatever...it doesn't matter just as long as your start focus is through all crosshairs.
All your 'experiment' does in an almost cartoon like way is explain very loosely how theodolites work. Which is well known in architectural circles.
I could've told anyone to go and use a theodolite. How many people do you know that pown one?
I put out a simple experiment and a back up to ensure no cheating.
If you have a theodolite then by all means use it....but here's the key.
If you take JJA's set up and use a theodolite on that, knowing you have to set up the measuring stick to gain a level over distance, how high do you think that measuring stick would be as you moved down that gradient from a level set up?
Soooo, how in the hell would anyone expect to see the ground from thats et up?
The only way you can do that is to set up your sights on an angle down that gradient, which would obviously show the actual slope itself.....but that's not what the argument is about.
The horizon (theoretical) line is your very own eye converging light and shade over a level distance, meaning below and above atmosphere meet.
I agree with you that the horizon is a theoretical line. Although I wouldn't use the word theoretical. I would use apparent instead. If I look out towards the horizon I will see a 'line' which separates the sky from the sea or land. The horizon is the border between surface and sky. If I see a buoy floating on the water apparently sitting on the horizon and then swim up to it the buoy will no longer be on the horizon. The horizon will have 'moved'.
It is theoretical. It does not exist as a real line.
If you want to call it apparent then fine, as long as you accept it does not exist as a real line.
The horizon does not use a surface, it uses a convergence of shades from the surface and sky, not a physical hit on the surface.
Asfor seeing abuoy on your horizon. You never will. You would see it as an obstacle to your view of your theoretical horizon line or as a stand up above your theoretical horizon line.
The theoretical line is your convergence from your view over distance. The second you move forward the very second your theoretical horizon line moves away...because it's specific to your eye level sight over that distance.
In the same way if I look along a disused straight length of railway track the rails will seem to converge to a theoretical or apparent point in the distance. I know they don't in reality but it just looks like they do due to perspective.
Just convergence and no real angles are used.
I could travel along an infinitely long and straight railway track at whatever speed I wanted and I would never reach the 'point' along the track where the rails actually converge.
Yep, the very same as the horizon. It's all specific to you and every other individual has their own based on their own sight convergence..