In terms of age and expansion Perlmutter explains they used a particular kind of supernova that has a known and uniformly proporitional peak brightness. The light as it travels to us undergoes the expansion effects and can be used to `measure' the rate of expansion in its spectral redshift.
He goes on to explain when they did their measures of supernova at great and in between distances, they found distances between galaxies was accelerating. This is the measure of a phenomenon without explanation, hence dark energy, or some source driving the expansion faster. The other possibility is that Einstein's theory of gravity needs modification.
He shows a pie chart where Atomic Matter represents 4%, Dark Matter represents 24% and Dark Energy 72%. That's pretty stunning. This means in effect the cosmological constant represents 96% of the stuff in the universe. Some whopping big fudge factor.
In good cheer, Perlmutter says they receive paper after paper of theory to explain what's going on and his next slide has a list: Quintessence, Supergravity, K-essence, Cyclic Universe, Phanton Energy, Extra Dimensions, Big Rip Cosmology, Ekpyrotic Universe, Photon-axion oscillations. He notes they average two to three papers every week for the past ten years.
If you ask these theorists do you know what's going on, and they say no, we hope you can come up with something...
Perlmutter turns it over to David Schlegel who ran the Sloan Digital Sky survey. He points out that before Sloan the only large maps of the universe were photographic plates dating from the 50s--70s. Then he shows a 3-D map (23:13/min). It looks like star trek's opening animation with stars and galaxies receding, except this is data and not illustration. The end result is a complex structure where most of the sources are concentrated and condensed in a kind of web-like curved column. It is composed of more than a million galaxies.
These maps combined with the earliest data map of the universe at 380,000 years, gives a standard ruler for expansion. The ruler is how far light travels in 500 million years. He shows the 380k map with a small circle in the lower hemisphere and then a companion slide of that same circle, slightly larger and what it looks like now.
Schlegel turns the talk over to Alexie Leauthaud who opens with a brief history of the idea of dark matter. She starts with Fred Zwicky n the 1930s who calculated the motion of galaxies within giant clusters and compared the motions to the luminosities and found there wasn't near enough mass by about 160 times more needed to account for the observed motions. Then up to 1970 when Vera Ruben looked at the motion of stars within galaxies. She found the stars were moving much too fast compared with the star that could be seen (mass-luminosity ratio). The only explanation was a large amount of matter that could not be seen.
The current hypothesis for dark matter is some kind of particle that does not absorb or emit light and makes its presence known through gravitational effect, hence lensing as the primary evidence. She then switches to an illustration for the textural picture of what a dark matter universe looks like at extreme scale 1 gigaparsec, or 3 x 10^12 light years. It's called the millenium simulation. Leauthaud (lah-toe?) then runs an animated zoom from a homogeneous picture into the closer view 105 megaparsec (over h, h -> hubble radius?) where the texture has turned into clumps connected with filaments.
This picture looks very much like the internal strut webs inside cells that hold their molecular systems together under a membrane.
Leauthaud explains that normal matter lays within these giant clumps, and the picture zooms again at about 15.6 Mpc/h. This shows a supercluster which contains thousands of galaxies. Normal matter is `resigned to stay within the scaffolding of the dark matter.' She then shows the Bullet Galaxy with its shock front, hot gas (x-ray) and visiable masses. The next slide is from COSMOS the Hubble space telescope survey with a proposed dark matter map. I've seen this slide elsewhere but can't locate it at the moment. It is a trace map of the dark matter contour around and between observed galaxies.
The point. The central point is, the proposal of dark energy and dark matter are driven by evidence and observed phenomenon, that contradicts the central dogma of big bang and general relativity. That means that these are not proposed answers drivend by an effort to prop up theory. Quite the contrary. They are observations that require a better and probably different cosmological theory. This is exactly contrary to what I thought while reading through papers and trying to figure out what was going on.
So, the central metaphor is not epi-cycles to preserve a Ptolemic theory, but the opposite, Tycho Brahe observation tables without explanation that do not fit current theory...waiting for Kepler. Tycho's system used a modified geocentric system. Tycho was not a Coperican.
There are other interesting parallels that have to do with calculation, something that I am terrible at. The central issue in Tycho's time was calculation using spherical angles and trig tables to perform approximations. They did not have log tables or the slide rule. Here is a little hint on what was involved:
http://en.wikipedia.org/wiki/Prosthaphaeresis
Behind the scenes of Perlmutter, Schlegel, and Leauthaud are tremendous numbers of calculations over thousands and thousands of motions and masses of statistical mechanics... using giant number crunchers. The statistical data sets have to be in the hundreds of thousands to even qualify as `data'. So, we are not talking about a few stars or galaxies that don't fit a model. We are talking about hundreds of thousands or millions of observations that don't fit.
Anyway another nice feature of this talk, is the ease and smooth confidence of Alexie Leauthaud who is obviously the central figure in this particular program. You know there is not a long list of women astronomers. Vera Rubin is about it.
CG