| 8 | | Chemistry has always played a critical role in modern astronomy. Before we knew about nuclear reactions, many astronomers and other scientists believed that the Sun was powered by chemical reactions and gravitational energy. However, both energy sources are woefully inadequate for powering the Sun over billions of years. While we now know that chemical energy plays no appreciable part in powering the Sun, we do know that the Sun consists of the same chemicals we find on Earth. How did the Sun come to have the chemicals it has? I will answer this question by explaining the processes that go in to creating the chemical make-up of our Milky Way Galaxy and how we can use the chemical signatures of stars to reveal the history of formation and evolution of the Milky Way. |
| | 7 | Physicists and astronomers have been pondering the above question for |
| | 8 | 40 years. Far from being a mere theoretical curiosity, it may hold |
| | 9 | the key to understanding the nature of gravity, the history of cosmic |
| | 10 | expansion, the origins of supermassive black holes, and the physics of |
| | 11 | quasars. I will describe (i) why astronomers expect supermassive |
| | 12 | black holes to collide, and (ii) the history, current status and |
| | 13 | future prospects of the scientific quest for the answer to the title. |
| | 14 | |
