Caltech Astronomy Public Lecture Series - Astronomical Discoveries of the Ancient Greeks - Michael Zhang - 09/04/2020

Far surpassing all other ancient civilizations, the Greeks used the scientific method to discover Earth's shape, measure its circumference, calculate the size and distance of the Moon, and debate whether Earth orbits the Sun. Timestamps, links and Q&A panel questions are included below. Welcome & Announcements: 00:00 What's up in the sky right now?: 04:05 Lecture: 10:21 Q&A Panel Introductions: 44:01 Why were the ancient Greeks so intelligent? 51:00 What about discoveries by ancient Indian astronomers? 55:07 Were there any noteworthy ancient Roman astronomers? 58:55 Which came first: supermassive black holes or galaxies? 1:01:02 How massive is the accretion disk around the Milky Way's supermassive black hole? 1:05:25 When two black holes merge, is there energy given off in electromagnetic waves? 1:08:00 What are the different formation mechanisms for black holes? 1:12:27 Why do researchers look for helium in the atmospheres of exoplanets? 1:22:36 How does the gas around a galaxy affect its evolution? 1:28:34 Is the total energy of the universe constant or variable? 1:32:52 Did ancient Sumerians make significant astronomical discoveries? 1:39:01 What do we know about our Milky Way's supermassive black hole? 1:42:42 What x-ray telescopes are there? 1:45:48 Why are there x-ray telescopes at all? 1:48:55 What inspired you to study astronomy? 1:53:10 Closing remarks: 2:08:08 Date: September 4, 2020 Lecturer: Michael Zhang Title: The Exceptional Astronomical Discoveries of the Ancient Greeks Abstract: In 800 BC, the Greeks were eking out an existence in impoverished city states and infertile fields, the illiterate remnants of an apocalypse that destroyed their civilization 400 years prior. They could not have imagined that they would rise from the ashes to become the premier civilization of the Mediterranean, spreading their new culture from Spain to India. Greek innovations in politics, philosophy, and art would form the foundation of Western civilization. Perhaps the most impactful Greek contributions were in science. Far surpassing all other ancient civilizations, the Greeks used the scientific method to discover Earth's shape, measure its circumference, calculate the size and distance of the Moon, and debate whether Earth orbits the Sun. I will tell the story of this remarkable civilization, discuss how they learned about the cosmos, and summarize the pivotal role their achievements played in kickstarting the Scientific Revolution and ushering in modernity. Participants: Michael Zhang is a graduate student in Caltech Astronomy. He studies the atmospheres of small planets orbiting other stars by a combination of simulation and observation. Currently, he is trying to measure helium in these escaping atmospheres. Michael is not a professional historian and has no formalized history education, but he is an enthusiastic history buff who has read extensively about the history of science and the history of Rome. Roma invicta! Nikita Kamraj is a PhD candidate in observational high-energy astrophysics at Caltech. Her PhD thesis focuses on the study of accreting supermassive black holes, known as Active Galactic Nuclei. She uses spectroscopic data from various X-ray telescopes to investigate the nature and geometry of material surrounding these supermassive black holes. Outside of academic research, she is heavily involved in student advocacy initiatives and is strongly committed to improving gender representation in STEM fields. She also loves Japanese culture and enjoys learning Japanese, watching anime and reading manga. Dr. Amruta Jaodand is a postdoctoral researcher in observational astronomy at Caltech. She works with various manifestations of neutron stars specifically to understand how they evolve towards later phases of their lives especially on account of their companions. She combines multi-wavelength data from both space-based and ground-based observatories spanning radio, X-ray, Gamma-ray and optical wavelengths. She is also an expert in afterglows of neutron stars and black hole mergers. Outside of academic research her passion is outreach and communicating science to marginalized students (especially from developing worlds). She enjoys hiking and spends weekends restoring post-burn forests with Tree People. Dr. Cameron Hummels is a postdoctoral researcher in theoretical astrophysics at Caltech. He creates supercomputer simulations to study the formation and evolution of galaxies since the Big Bang. In addition to astrophysics and public education, he is really enthusiastic about trail-running, backpacking, chess, and the astronaut program. http://chummels.org Stargazing Tools: Desktop Sky Visualization Software: Stellarium: https://stellarium.org/ Phone Apps: Sky Guide: https://www.fifthstarlabs.com/#sky-guide Star Walk 2: https://starwalk.space/en