What were the 2 main factors that slowed the acceptance of the heliocentric model?

1. If the Earth is rotating about its axis, and orbiting around the Sun, then the Earth must be in motion. However, we cannot ''feel'' this motion. Nor does this motion give rise to any obvious observational consequences. Hence, the Earth must be stationary.

2. If the Earth is executing a circular orbit around the Sun then the positions of the stars should be slightly different when the Earth is on opposite sides of the Sun. This effect is known as parallax. Since no stellar parallax is observable (at least, with the naked eye), the Earth must be stationary. In order to appreciate the force of this argument, it is important to realize that ancient astronomers did not suppose the stars to be significantly further away from the Earth than the planets. The celestial sphere was assumed to lie just beyond the orbit of Saturn.