Goddu (381–84) has plausibly maintained that while the initial motivation for Copernicus was dissatisfaction with the equant, that dissatisfaction may have impelled him to observe other violations of uniform circular motion, and those observations, not the rejection of the equant by itself, led to the heliocentric theory. Blumenberg (254) has pointed out that the mobility of the earth may have been reinforced by the similarity of its spherical shape to those of the heavenly bodies. 