I've recently seen a Flat Earth trend in describing Flat Earth as a movement. (i.e. from Pete)
But, in other descriptions such as this site and Wiki, it is described as a theory.
A movement is very different than a theory and so just wanted to check.
I don't see why it can't be both.
Movement:a group of people working together to advance their shared ideas.
Then I think the phrase flat earth movement is an appropriate thing to say based on the definition above.
Theory:a supposition or a system of ideas intended to explain something
Then I think the phrase flat earth Theory is ALSO an appropriate thing to say based on the definition above.