Geocentric model and planets were holes in invisible wheels surrounding Earth; through the holes, humans could see concealed fire. About the same time, Pythagoras thought that the Earth was a sphere (in accordance with observations of eclipses), but not at the center; they believed that it was in motion around an unseen fire. Later these views were combined, so most educated Greeks from the 4th century BC on thought that the Earth was a sphere at the center of the universe. In the 4th century BC, two influential Greek philosophers, Plato and his student Aristotle, wrote works based on the geocentric model.
Umbrella term Umbrella term An umbrella term is a popular metaphorical phrase that covers a wide range of concepts belonging to a common category. For example, "cryptology" is an umbrella term that encompasses cryptography and cryptanalysis, among other fields. Similarly, an umbrella organization is a central and coordinating body representing a number of smaller, separate bodies. A blanket term is a closely related word or phrase that is used to describe multiple groups of related things. The degree of relation may vary or have a minimal relationship, but blanket terms often trade specificity for ease of use. In other words, a blanket