| Today: Reminders/Assignments | |
| Longair, Ch. 5-6 | |
| - Getting into Theory/GR (Ch. 5+) | |
| - Hogg papers | |
| Unless noted, all figs and eqs from Longair. | |
| Mini-Exgal-TAC on Friday | ||
| Any questions at this stage? | ||
| Try not to discuss with each other too much in advance, that will happen Friday | ||
| Register an account on MAST? | ||
| WIRO over spring break: | ||
| Camera on and working, clusters selected | ||
| I’ll go 1-3 nights – who else? | ||
| Discuss logistics | ||
| No class on Wed. March 26 | ||
| Next Friday in place of our usual astro-ph preprint discussion. | |
| 12 proposals, everyone has two primary proposals to lead the discussion about, plus two secondary proposals. | |
| Everyone must read all proposals and note strengths and weaknesses, and assign a preliminary grade (1=best, 5=worst), in accordance with guidelines. | |
| I’ll chair the meeting and evaluate performance. I expect this will be a challenging but very educational experience. |
| Section 5.1, the “Cosmological Principle” | ||
| Isotropic, homogenous, uniform expansion | ||
| Can write relativistic equations in different forms (famous names cited here…) | ||
| Weyl’s postulate: “The particles of the substratum (representing the nebulae) lie in space-time on a bundle of geodesics diverging from a porint in the (finite or infinite) past.” | ||
| Section 5.1, the “Cosmological Principle” | ||
| Geodesics are “world-lines” of galaxies and do not intersect except at a singular point in the past. Weyl’s idea predates Hubble’s law. | ||
| Fundamental observers on each world line, each with standard clock measuring cosmic time from that singular point. | ||
| “We are not located at any special location in the universe.” | ||
| Sections 5.1-5.4 cover underpinnings of GR (curved spaces, space-time metrics) and in particular the Robertson-Walker metric that we will need to describe the universe. | |
| Read and follow these sections, but we don’t have the lecture time to go into much detail with the perspective of observational astronomers in a mixed galaxies/cosmology course. |
| Section 5.5 covers observables. We’re going to jump to the chase momentarily and walk through Hogg (2000), which integrates this material with world models (Chapter 7, and a Sandage review article I will probably assign soon.) |
| Chapter 6 introduces General Relativity, which I won’t go over in class. Again, read through it. I expect to cover chapter 7 following spring break. | |
| WIRO and an observing manual are the “homework” over spring break…I hope! |