Dave you posted this picture as a diagram of the flat earth model.
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In that picture neither the sun nor the moon would sink behind the horizon. Instead they would only get smaller as they got further away from my point of view. Yet everyday I see the sun set at night as it drops entirely behind the horizon and then it rises the next morning peaking up from behind the horizon.
Furthermore what I see is the opposite of your model. When the sun sets (and when it rises) it appears much larger than in the middle of the day when (according to your model) it would be the closest to me.
In your own words can you tell me why the sun would set behind the horizon in a flat earth model?