instead of asking for others to perform experiments, you could perform a simple one yourself and not have to take anyone's word for it: just make a straight line with a taut length of string. then, set that line perpendicular to the moon's phase. then, see where that straight line path leads. be careful to wear eye protection because it absolutely is gonna point at the sun.
this whole thread is based on a premise that isn't true, and it would cost you virtually nothing in terms of money or time to see that for yourself. and yet for some reason you simply refuse. idgi no one's asking you to fund a trip to the ice wall, just hold some twine in front of you for like 10 seconds.
The corners and edges of my ceiling are straight lines.
stand in front of the midpoint of a wall in your room. look directly in front of you at the top edge of your room, the straight line formed by the intersection of the wall and the ceiling. notice that this bit of edge directly in front of you has no slope. it looks like a horizontal line.
now turn your head to the right and look at the corner of the room. notice that this line appears to point up from the corner and to the left. it appears to have a negative slope.
now turn your head to the left corner and notice that the line appears to point up from the corner and to the right. it has a positive slope.
since the slope of this line appears to change from one end of the room to the other, then by definition it does not appear to be a straight line.
ipso facto ergo sum ad infinitium (that's latin for "i proved it my dude").