Ok I'm going to bring this back so that people can try to prove my evidence wrong. It would also be good if someone could move this to the flat earth debate & discussion thread.
I remembered today that I had in fact figured out the altitude of the sun during an equinox. I had forgotten about it because it didn't seem that important to me at the time I did it in earth science class last year. I don't really remember much of it, but throughout the day we went outside during the September equinox. We had these clear domes (representing the sky from our point of view), and a toothpick (held up with modeling clay) at the side. I don't remember what it looked like exactly, but we used markers to put the endpoints of the shadow on the dome, which represented the altitude of the sun at that time. We did this about 8 times that day. At the end of the day, in science class, we connected the dots and figured out the zenith (highest altitude of the sun). I live at about 42 degrees north, and the zenith was 48 degrees. This goes with what I said before - the altitude of the sun at an equinox is equal to 90 minus your latitude.
Now nobody can prove me wrong by saying that I didn't gather my own evidence.