The value of G was first determined by Henry Cavendish in 1798 while the Greek mathematician/scientist Hipparchus (190 BC - 120 BC) found that the radius of the moon's orbit was between 60 and 80 Earth radii. (It is actually about 59 Earth radii). The period of the Moon's orbit is about 29 days. From the period and radius you can find the speed of the Moon in its orbit. What can be determined if the radius and period of the Moon's orbit and the value of G are known

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 -

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