This thread: I dOn'T wAnT tO aDmIt ThE sImPlE fAcT tHaT GpS dOeS nOt ReQuIrE SaTeLiTes.
I don't really see any need to address your strawmen. It has been well established at this point. You can take that knowledge or not. If you want to see more discussion on the matter, there are a ton of threads you can pursue using search or via google.
For the GPS devices you have (embedded into your phone, the GPS device in your car) to operate properly, satellites that are 20'000 kilometers up in the sky are needed. And there are multiple lines of evidence of that, including the fact that they can tell the elevation you are at with signal from 3 emitters and the fact that many of them have open-source software which obviously relies on receiving signal from emitters that follow the orbit which is 20'000 kilometers up in the sky. I thought we agree on that.
Assuming we agree on that, what's holding the satellites up in the sky? If the Earth is flat, it's not the centrifugal force. Do you think the non-Euclidean nature of the space we supposedly live in enables them to? Do you have some mathematical model which predicts that? The mathematical model, if we assume Round Earth, is rather simple. How is your model better than the Round Earth model? Can you make some falsifiable prediction based on your model that's different from what Round Earth predicts?
Yes, the satellites are traveling their inertial paths in straight lines. Rather simple I'd say.
Simple? Jesus Christ, I am having trouble believing you are serious. Why is the first cosmic speed finite if the Earth is flat? On a round Earth, the concept of the first cosmic speed makes perfect sense, it’s the speed at which the centrifugal force caused by you going around the Earth at certain speed matches the gravitational force. But on a flat Earth? How does it make any sense that, if you move horizontally at certain speed, you start accelerating upwards at the same rate as the Earth? It doesn’t. Show me the math that predicts that!
And that’s just the beginning. How it is that satellites that go faster end up flying higher? If the Earth is round, and there is gravity, that makes perfect sense, the gravity offsets the centrifugal force of a body moving at a certain speed at different heights, for gravity is weaker up in the sky. How does even the concept of gravity being weaker when you climb on a mountain make any sense if “gravity” is caused by the flat Earth accelerating upwards? It doesn’t. That fact significantly undermines that claim.
And you can test the fact that gravitational acceleration changes with height yourself, quite a few mobile phones today come with an accelerometer that’s precise enough that it can measure the difference in gravity on a high mountain and on the sea level. Or you can buy a more precise accelerometer and you don’t even have to climb a mountain, just climb a building to see that effect.
No, I mean, Flat-Earth Theory is obviously just a bunch of ad-hoc hypotheses. If you assume the Earth is round and things fall because of gravity, the fact that satellites are possible makes perfect sense, and the fact that gravity is weaker when you are at a higher elevation makes perfect sense. It follows from the Earth being round, if you assume the Newton’s laws are correct or approximately correct, as they obviously are. If you assume the Earth is flat, nothing makes sense, you need to add layers upon layers of ad-hoc hypotheses. And you end up with a “theory” that makes no clear predictions.
Similarly with the horizon, the Earth being round predicts there will be a horizon which will be visible from certain heights and at certain angles (that it will be significantly below your eye-level when you are on an airplane) that can be calculated using basic trigonometry. Flat-Earth theory doesn’t predict that, in order to explain those observations, you need to add layers upon layers of ad-hoc hypotheses, and again you can’t make any clear predictions.
Sorry, but any reasonable person would reject Flat-Earth theory because of that.