The sun and the moon appear to be the same size. They are close. You can feel the warmth from the sun. You see the sun spots and the spreading rays, the long and straight reflections on a lake or sea. You can read by the light of the full moon. Sometimes the sun and moon are in the sky at the same time. Day and night are always equal. The same stars I watched as a child in the heavens are still there and always revolve around the fixed north star.
In my early years as an artist, I learned how to draw perspective. All lines converge on the horizon line. Train tracks, or a straight highway with telephone poles, meet at an apex on the horizon. This is how you draw it, but you know that the lines continue in reality. If you follow the train tracks or the highway, you will continue towards the horizon but never reach the meeting lines, as there are no lines.
That is how I know, when I am watch the sun move across the sky, that it appears to sink towards the horizon line and vanish beneath the surface. But it is travelling away across an extended plane beyond my field of vision.