I was walking back to my dorm at my prep school on a cold winter evening when I saw a point of light moving fairly rapidly directly from west to east across the clear sky on a track passing somewhat to the north of me. I had long enough to say to myself that it seemed to be faster than a satelite, but much slower than a meteor.
When it got directly north of me it made an instantaneous 90° turn to the north without changing velocity. Then it accelerated over the horizon, New Hampshire, in what seemed like an instant.
I was dumbfounded that an object could seem to make a 90° turn in the air, or space, which seemed to defy the physics I was learning in school.