The most common way to become infected with giardia is after swallowing contaminated water. Giardia parasites are found in lakes, ponds, rivers and streams worldwide, as well as in municipal water supplies, wells, cisterns, swimming pools, water parks and spas.
Andreas Cellarius's illustration of the Copernican system, from the Harmonia Macrocosmica (1708). Heliocentrism, or heliocentricism, is the astronomical model in which the Earth and planets revolve around the Sun at the center of the Solar System. The word comes from the Greek (á¼¥Î»Î¹Î¿Ï helios sun and ÎºÎ­Î½ÏÏÎ¿Î½ kentron center).
For orbits around the Earth, see Geocentric orbit. In astronomy, the geocentric model (also known as geocentrism, or the Ptolemaic system) is a superseded description of the universe with the Earth at the center. Under the geocentric model, the Sun, Moon, stars, and planets all circled Earth.