actually i found an easier way.... unimportant are you prepared to take a driving trip?
you live in Washingtion DC right?
go to this place in New hampshire: Dartmouth College, Hanover, NH
then drive to one of these places in Florida:
* The Brevard Museum, Cocoa, FL
* Florida State University, Orlando, FL
* John Young Museum, Orlando, FL
* Miami Dade Junior College, Miami, FL
* Midland Centre for the Arts, Midland, FL
* Museum of Science and History, Jacksonville, FL
* University of South Florida, Tampa, FL
preferably the one that is furthest south from you
at both of them is a Foucault Pendulum, the one in the north in (new hampshire) will transverse round its arc faster than the one in Florida.
then you can come back to me and explain this using a flat earth.
and if you want to see it change direction, i'm afraid you're going to have to go to austrailia (or set up your own in the south of brazil)
but i feel that the florida and the New Hampshire trip should be enough proof.