Mapping the universe with galaxies
In the lecture, the ultimate motivation is to explain the power of the upcoming large galaxy surveys and the revolutionary science which they will bring about. I will start off by covering (or reviewing) the highlights of the hot big bang, with attention to kinematics, time and distance scales, and important cosmological epochs. Then we're ready to tackle linear perturbations in the density field and the ensuing instability due to gravity. We'll trace these perturbations from decoupling to the present, and show how structure in the universe today is the current work in progress of gravity and time.
Materials: Overheads and maybe slides
Video or computer hookup to show numerical simulations: e.g., this page
In the lab, we will utilize a cosmology workshop WWW page setup at the University of Oregon. This environment is ideal for the following reasons: 1) everyone can work at their own pace, 2) the Web can be used to download or locate other useful or auxiliary informaion, 3) the virtual workshop can then be used by the teachers at their own institution. The site is here.
Although we will mainly focus our attention on the Hubble expansion law, many of the concepts (like light, atomic spectra, and other physics laws) can quickly be reviewed to refresh ones perspective.
Ideally, everyone would have his or her own computer. And I would like to have one at the front to lead them through as a group at the beginning. I should have some extra sites or computer projects ready for the fastest participants.
Limited to 10 people 320 Kersten Physics Teaching Center (corner of Ellis & 57th St.; enter north door on 57th, under bridge)
I will walk the participants through a new lab project for undergraduate non-science majors, the first trial course of which will have just been completed. I will report on the real world successes and problems that we encountered in this class. The project should be exportable to other sites with little difficulty because the equipment is generic, off-the-shelf. More extensive writeup.
The idea is to demonstrate the phenomenon of the expansion of the Universe using data obtained with small telescopes on the rooftop of the Kersten Physics Teaching Center, and, moreover, to measure the value of the Hubble Constant and thus the age of the Universe. Besides the telescopes, other equipment includes digital cameras and analysis computers and software.
The first goal (demonstrating the expansion) is addressed by imaging a number of rich clusters of galaxies over a range of redshifts, some of which were in Hubble's original paper. We will not attempt to measure the redshifts; those data we will take from the literature (as did Hubble!). Students will need to figure out how to order the clusters by relative distance, using some combination of angular sizes of the member galaxies, the angular size of the whole cluster, or apparent brightnesses.
The second goal (measuring the Hubble Constant) starts with measuring the size of something of galactic dimensions, namely the thickness of the disk of the Milky Way. This is large enough that the corresponding angular size of another galaxy with (presumed) similar dimensions can be detected. In this case, students will need to figure out how to relate the measurement of the thickness of the Milky Way (done via star counts) to the thickness of edge-on disk galaxies (done via surface brightness contours).
Another approach that may be feasible is to measure the light curve of a Type Ia supernova, and use the flux at maximum as a standard candle. This requires that others discover a good candidate supernova at some convenient time during the course.
If the weather is clear, we will use the same equipment to demonstrate the process of taking digital images of galaxies and star fields in the Milky Way. Regardless of the weather, we will look at the archived data from the course and re-trace at least some of these steps.