Which of the following statements correctly describes the models put forth by ptolemy and copernicus to explain the universe? a. the model developed by copernicus was simpler and had less inconsistencies than ptolemy’s model. b. the sun was in the center of ptolemy's model, but the earth was in the center of copernicus' model. c. through observations, both astronomers presented models where the earth remained stationary. d. both of the models were easy to understand and thus were well received by the public almost instantly.

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -