It's a cloudy night, a good night to keep the scope covered and instead join the many other amateur astronomers in the Tucson Amateur Astronomy Association for the monthly meeting at Steward Observatory. We missed the Basics lecture (had to deliver one of my sons to a scouting activity) but Larry and I made it shortly before the main lecture began. There were a lot of people there tonight, several hundred by my estimate. It was worth going just to see a lot of friends there.
First on the agenda was a farewell to club member Andrew Cooper, who has taken a job at the Keck telescope. Andrew has been a significant force in the Tucson astronomy community and he'll be sorely missed around here. He maintains an amazing website about astronomy called Silicon Owl, I highly recommend a visit if you have not seen it before.
The main lecture was presented by Dr. Chris Impey of the University of Arizona, who spoke on "The Nature of Dark Energy". Dr. Impey is a famous professional astronomer and he is an animated speaker. I respect him greatly, but to be honest I don't get too excited about cosmology. My astronomical interests are more rooted in observations, and while theories certainly interest me, I find many of the theories in cosmology to be so tenuous that they seem to be more accurately described as science fiction, not science.
With that said, I am completely willing to consider the possibility of the existence of dark energy (and dark matter). The prevailing theory seems to suggest that the Universe is composed of about 23% dark matter and 73% dark energy. In other words, less than 5% is composed of things that we can see. This may sound like fantasy, but it also provides a possible path to an explanation about certain unexpected observational results, or results that cannot yet be explained with conventional theory. For example, some observations of supernova at very high redshifts seemed to be fainter than the accepted models predicted; dark energy may solve this problem by allowing a modification to expansion rates of the Universe.
Dr. Impey isn't a strict theorist, as many astrophysicists these days are. He has done many observation runs using the Hubble Space Telescope and other telescopes as well. In fact he described his interest in dark energy as a "sideline". He and a couple of students have done an observational project to attempt to detect dark energy by geometric means. They used data from quasar pairs and their results seem to support the 73% dark energy theory.
One thing I was pleased about was that Dr. Impey was quite open about the apparent absurdity of the idea that astronomers cannot explain 95% of the Universe; several times he emphasized that these are theories and may be completely wrong. It's true that scientists need to be bold enough to consider radical ideas, but it's also dangerous to jump onto a wave of popular opinion without facts to back it up. I think Dr. Impey is working on possible forms of evidence to test these theories, but it may be a long time before we will have enough to fully accept or reject them.
By the way, the picture is rather poor in quality, it was taken with the camera built in to my phone.
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