In the opening video for this chapter, we made an analogy between the expansion of the Universe and a ball in motion because in both cases we are dealing with the interplay of gravity and the energy o...In the opening video for this chapter, we made an analogy between the expansion of the Universe and a ball in motion because in both cases we are dealing with the interplay of gravity and the energy of motion. time resembles the Hubble diagrams in Figure 17.1 and Figure A.17.1, which show the position of galaxies on the x-axis and the velocity of galaxies on the y-axis.
