There is some exceptional science writing in the blogs. Over at Brent Rasmussen’s Unscrewing the Inscrutable, DarkSyd has posted Cosmology 101: Somewhere Over the Rainbow. With grace, style, rigor and admirable concision, and with some fine illustrations, Syd retells one of the classic tales of science:
The old story goes that he who follows the rainbow to the end will find a pot of gold. It is but a legend of course, there is no end to find. Rainbows we now know are an artifact of optics. But metaphorically we can make such a journey. It will be a quest in mind only, fueled by burning curiosity, and it will end in a treasure immeasurable by the dollar or the Pound Sterling. Our guide will be a brilliant rebel, a Rhodes Scholar, turned Lawyer, turned scientist. And what he found, somewhere over the rainbow, was and remains perhaps the greatest single, scientific discovery of all time.
The hero of the story, of course, is Edwin Hubble, and the story concerns his discovery of the fact that our entire universe is expanding, rapidly.
Hubble had the benefit of two new analytic techniques previous astronomers did not have. He had both the distances of several Galaxies from the Cepheid Variable Technique, and he had the redshifts of those same galaxies using the spectrum he obtained form the Wilson Observatory. And, when he correlated those two sets of data, he found that the further away a galaxy was from us, the more it was red-shifted!
The conclusion is pretty easy to visualize. The galaxies were moving away from and the velocity with which they were receding was a function of their distance form us: Either our Milky Way Galaxy is the center of the universe and every other galaxy was hauling ass away from it. Or all the galaxies were moving away from each other, ours included.
The only bone I have to pick with DarkSyd’s otherwise excellent article is in his first sentence, in which he dismisses the Pot of Gold Hypothesis as “only a legend of course”. As evidence otherwise, I present the following photograph, taken a couple of years ago from the deck of Fairview, the cabin we stay in at Hiram Blake Camp, on Penobscot Bay in Maine. It was an early morning double rainbow, and it was entirely contained within the small cove on the shore of which our cabin sits. One leg of the rainbow entered the water in front of the pine trees on the farther shore, and the other leg ended exactly at the stern of our little sailboat Anjana. And while a quick investigatory row out to the boat found no literal gold, still, Anjana is worth her weight in the stuff, and the rainbow, we like to think, was a confirmation of her true worth.
