As far as I know, FET has not been able to explain aurorae- how they occur in FET and why they occur where the do. Please explain how this works in FET.
Erastosthenes of Greece was able to determine that the Earth was round using his simple "light in a well" experiment. If the Earth was flat, angles in wells would still be observed (possibly, depending on how large the Earth is supposed to be in FET) but the angles would increase as a linear function of distance. In reality, the angles are not a linear function of distance, and the difference in angles from point to point suggests a spherical Earth.
Also, in the Q&A thread I asked about a consistent model of the solar system in FET. No one has been able to provide me with a proper one, because it can't possibly be made.