The simple proposal here - to advance the discussion - is to dispose of images and projections and simply talk about the paths of light rays in the REAL WORLD.
So here's the scenario - let me paint a pretty picture for a moment. This is all about the ACTUAL locations of things...nothing else.
I'm facing towards the sunset - with my eyes closed - blindfolded. We've banned all cameras, telescopes, pinholes, lenses and microscopes from the scene to avoid any risk of perspective entering into the discussion.
It's a cool fall day with a clear sky but the sun is hot. But there is a *big* mountain on the western horizon - it's six miles away and it's HUGE! It's a MILE HIGH and the sun is setting behind it. We know that in some distant city off to the west (which we're going to say is 6,000 miles away for the sake of keeping the math easy) the sun is vertically overhead - and Flat Earthers tell me it's 3,000 miles up in the sky and the Earth is FLAT.
I should be standing in the shadow of the mountain. The mountain is clearly blocking 100% of light from the sun...I don't feel the sun's warmth on my face at all. We should all be able to agree on that. If I cheated and peeked out from under my blindfold, I'd see it had set - but I'm not going to cheat.
Let's follow one of the photons coming out of the sun. Remember - we're not talking about images AT ALL - all eyes are blindfolded - all cameras are banned - there is just me, the mountain and the sun. This is just about where the photon goes in reality...just like where the train goes down the train tracks IN REALITY.
The photon starts out at 3,000 miles up and 6,000 miles away from my head at noon in some remote place - then, (as we agree) it travels in a straight line:
Simple geometry of straight lines says:
* Halfway to my head - the photon would be 1,500 miles up and 3,000 miles away.
* 90% of the way it would be 300 miles up and 600 miles away.
* 99% of the way it would be 30 miles up and 60 miles away
* 99.9% of the way - it would be 3 miles up and 6 miles away. <==== REMEMBER THIS!
* ...and then it's 3 feet above my head and 6 feet away.
* ...and finally, it's zero feet above my head and zero feet away. The photon hits my skin and gives up it's tiny packet of energy - and along with the trillions of others that followed the same route - it warms my face most pleasantly.
That's what the straight line path of the photon from the sun to my head is.
If the horizon was 6 miles away - and the photon crossed the horizon at an altitude of 3 miles - and COMPLETELY MISSED the mile high mountain!
But hold on a moment! Didn't the sun just set behind the mountain? I should be in it's shadow...but somehow I'm not! I'm feeling the sun's rays on my face!
Since we just established that the photon missed the mountain on the horizon COMPLETELY...and not by a little bit - it zoomed over it at a height of 3 miles...how is this happening?
Finally - having established that I CAN feel the heat of the sun...I take off the blindfold - Tom tells us that the sun is CLEARLY behind the mountain - I'm standing in shadow - but I can still feel the sun's rays warming my face? Eh?! What the heck?
This is impossible - but that's what this Flat Earth hypothesis is saying must be happening.
So - even without images - without eyes or anything that could remotely have ANYTHING to do with perspective...the sun should not be able to be blocked by the mountain and therefore didn't "set".
How on EARTH are you going to get around THAT one Tom?
(And just in case you're thinking of saying that heat travels in other ways - I sneakily had a photo-cell taped to my forehead the whole time - and that confirms that there is (or is not) sunlight shining onto it).