In the 1990s a group of astronomers measured the rate of expansion of the Universe, and how that rate of expansion has changed over the lifetime of the Universe. The results were startling, and led astronomers to propose the theory of Dark Energy. This group of astronomers was later rewarded the Nobel Prize in Physics. What about the observed expansion of the Universe drove astronomers to propose Dark Energy, and what does the existence of Dark Energy mean about the future of the Universe (will it eventually collapse back in on itself, or will it expand forever? If it expands forever, what does that expansion look like?) Write a paragraph