"What caused the planets to aggregate as they did? What are the dynamics of gravity, that caused the plantets to evolve, progressively larger from Mercury to Jupiter and then progressively smaller Jupiter to Pluto? What are the dynamics of gravity, that caused the inner plantets to aggregate solid and not gaseous? Newton law states that mass (a bird or its feather) accelerates at the same speed towards a gravitational center, if there is no air resistence. A science demonstration popular for centuries had a coin and a feather dropped simultaneously inside a glass tube from which air had been pumped: the two are always seen to drop equally fast. Such a demonstration was also made on the surface of the Moon by David Scott, one of the Apollo astronauts. Not only has the Moon no atmosphere, but its gravity is several times weaker, making the fall slower and easier to observe. Space is a near vacuum, does dark matter or energy have a play in what has happened?