Caltech Astronomy Public Lecture Series - Dark Matter: The Elusive Fibers of the Universe - Xuejian Shen - 06/23/2023

Despite being effectively invisible, dark matter is believed to compose 85% of the material of the universe--but what is it? Join us for a 30-minute lecture investigating the true nature of dark matter, followed by a panel Q&A consisting of several astrophysicists to answer your questions about astronomy, astrophysics, and space science. Timestamps below: 00:00 Announcements 04:52 Intro to Dark Matter Presentation 05:49 Dark Matter Presentation 37:08 Q&A for Dark Matter Presentation 37:19 "What assumptions go into dark matter simulations?" 40:09 "Does dark matter evolve over time?" 42:21 "Is dark matter connected to dark energy?" 44:39 "Is there evidence for dark matter vibration or spin?" 46:58 Intermission 52:43 Q&A Panel Introductions 55:02 "What is the mass of an eV (electron volt)?" 57:20 "How are dark matter halos observed for dwarf galaxies?" 58:38 "Do JWST observations change our view of bottom-up galaxy formation?" 59:28 "How are the distributions of dark matter and ordinary matter different?" 1:01:13 "Does dark matter not make disks?" 1:03:21 "Can particle collider experiments rule out certain dark matter candidates?" 1:05:13 "Can we gain insight about dark matter from gravitational wave observations?" 1:07:08 "What is the limiter in understanding dark matter: theory or observations?" 1:10:08 "Are there any galaxies without dark matter?" 1:13:34 "Is there a topological relation between dark matter and normal matter?" 1:15:15 "Tell us more about Pluto and friends!" 1:17:35 "Is dark matter represented as a particle or a field in simulations?" 1:19:27 "Can the observations be explained without dark matter?" 1:27:24 "Does dark matter have different phases: solid, liquid, gas?" 1:29:16 "Are there dark forces which only apply to dark matter?" 1:31:28 "Why do we simulate astrophysical systems?" 1:35:38 "Are there many types of dark matter?" 1:36:11 "Why do stars oscillate and are they observable?" 1:39:16 "Do scientists still hold to MOND as an alternative to dark matter?" 1:41:53 "How do we believe the Kuiper Belt formed?" 1:45:58 "What is the consensus on phosphene gas in Venus' atmosphere?" 1:51:55 "What does dark matter do?" 1:54:15 "Has dark matter changed its overall amount over time?" 1:56:08 "How can one succeed at learning math (or anything)?" 2:00:39 Concluding Remarks Title: Dark Matter: The Elusive Fibers of the Universe Speaker: Xuejian Shen Abstract: Scientists believe that most of the mass of the universe is composed of dark matter, a hypothetical material with no (or extremely weak) interactions with the normal matter we encounter in our daily lives. Despite being effectively invisible, dark matter is essential for the formation of large structures, like galaxies, in the universe. The fundamental nature of dark matter is one of the biggest question in modern physics. Could it be black holes? Could it be some new particles that have so far eluded detection in collider experiments? In this talk, I will discuss the compelling evidence for dark matter from astrophysical observations and introduce several hypotheses about the true nature of dark matter.