Originally Posted by
oneant
Actually, a great circle (or segment thereof) IS a straight line. It's just in curved space-time.
you are right! if you point a laser beam in SFO toward the direction of SYD, and if someone is looking at the beam from moon, that person would see the laser beam "bending around" the earth surface to SYD, although to laser beam itself, it's going a straight line in its curved space-line!