The heliocentric theory suggest that the sun is the central body of the solar system and perhaps of the universe. Everything else (planets and their satellites, asteroids, comets, etc.) revolves around it. The first evidence of the theory is found in the writings of ancient Greek philosopher-scientists.
When we fill a shallow pan with water and place a drop of red ink in one end of the pan and a drop of green ink in the other end we see that the red nd green inks are uniformly distributed throughout the pan.
This is due to the Diffusion of red ink and green ink in the water. Diffusion is the process where the movement of particles takes place from the region of higher concentrations to the region of lower concentartions.
Until the concentration of substances is uniform throughout, this phenomena continues.
