Bill Silvert writes: > I've posted too much on this topic, but can't resist responding to one > paragraph of Wirt's posting. One approach to looking at science is to ask > whether the general statements we make apply to all sciences. My favourite > counter-example to almost all assertions about prediction, controlled > experiments, replication, etc. is the oldest science, astronomy. Geology and > oceanography will also serve.
I too will quit after this posting, but I feel obliged to counter Bill's counter-example. All sciences become predictive as they mature, and no science has become more predictive, indeed some would say more speculative, than modern astronomy has. Multimillion dollar instruments are now built years or decades after the development of theories in the hope of chasing down the specific evidence that would prove or disprove a particular thesis. A century ago, the universe was seen as passive and unchanging, but all of that changed in the 1920's when a lawyer-turned-astronomer, Edwin Hubble, and his assistant, a muleskinner wagoneer who learned to work the telescope he helped deliver to the top of Palomar Mountain, Milton Humason, began measuring the distances and red shifts to the nearest "nebulae" (clouds). To their's and everyone else's surprise, some of the nebulae weren't localized gas clouds but were instead vast arrays of stars millions of light years away, alternate "island universes" to the Milky Way. But even more surprising, Hubble determined that every galaxy was receding from every other galaxy proportional to the distance between them. This implied only one conclusion: that the intervening space between the galaxies itself was expanding, a result no one could have possibly previously imagined. The notion of a steady-state universe did not die easily, and it was not put to rest until the 1950's. The obverse idea, that an expanding universe, when run backwards in time would have a singular point of origin, was so unpalatable that it required 30 years of argument before it was begun to be even tentatively accepted. In the interim, in 1937, Fritz Zwicky discovered that clusters of galaxies were not orbiting one another as they should. They apparently were missing an enormous amount of mass, mass that was non-luminous and which could not be detected by observation. Zwicky's conclusion was well-known but ignored until 1970 when Vera Rubin measured the rotational velocity of the disk of the nearest galaxy, Andromeda, and found that it too did not orbit the galactic center in a Newtownian/Keplerian fashion. If the dominance of gravity in the universe were to be preserved, something else must be present. All of a sudden, the universe was now believed to be filled with an enormous amount of mass that could not be otherwise observed, and was labeled "dark matter." The first response to Zwicky's/Rubin's findings was to presume the most prosaic explanations, MACHOs (massive compact halo objects) being most favored. In this hypothesis, the missing mass would be composed of brown dwarfs and large Jupiter-like planets orbiting above the planes of galaxies. These are perfectly ordinary galactic denziens, but after decades of searching, it was determined that there are not nearly enough of this low- or non-luminous material to account for the missing mass. The favored alternative at the moment, simply because in the best Sherlock Holmesian fashion, "when every other plausible hypothesis has been eliminated, what ever remains, no matter how strange, must be the truth," are WIMPs (weakly interacting massive particles), a form of subatomic matter that we have never seen in our detectors and for which we can only vaguely guess at its properties. We are now at the point of invoking ghosts to explain the universe we've measured and spending billions of dollars to seek out these spectres: http://cerncourier.com/cws/article/cern/29083 http://physicsworld.com/cws/article/news/24740 Nonetheless, in the most classically predictive manner, the observation of repeated patterns have lead to predictions which in turn have lead directly to the contstruction of that Large Hadron Collider at CERN in Switzerland in an attempt to seek some evidence of the existence of WIMPs: http://a1.vox.com/6a00c2251c28f3f21900cdf7e74979094f-500pi http://graphics8.nytimes.com/images/2007/05/14/science/15cern.xlarge1.jpg ...but it's not at all certain that even this machinery will do what's being asked of it. Ordinary matter (the stuff of you and me and everything that you know) is now believed to compose only 4% of the universe. Dark matter is estimated to represent another ~25%, but things have gotten even more strange in the last decade. "Dark energy," a quality for which we have absolutely no clue, is being invoked to account for the remaining ~70% of the universe. In 1964, the background microwave radiation left over from the big bang was discovered by accident at a Bell Labs facility in New Jersey. The two leading hypotheses for the source of this radiation were (i) it was cosmic in origin, and (ii) it was the product of bacterial decay of the pigeon droppings in the antenna. After assiduously scrubbing the interior of the antenna, it was decided that the source of the radiation could only be a radiation that filled the sky in every direction. In the intervening years, the measurement of this cosmic background microwave radiation has been refined to the point that its variation is now known to be only one part in a hundred thousand. A number of satellites were built in the 1980's, 1990's and 2000's to determine this number, most recently culminating in WMAP (Wilkinson Microwave Anisotropy Probe): http://map.gsfc.nasa.gov/m_mm.html Of greatest importance, we now have sufficient data to calculate the acoustic properties of the early universe, and from those properties, we can calculate that the "geometry" of the universe is "flat" (parallel lines remain parallel forever), something that was in doubt for decades. When this result is coupled with the discovery in 1998 that the universe is not only expanding, but recently greatly accelerating in that expansion, a repulsive force ("dark energy") has had to be re-invoked, and now represents most of the known universe, although "dark energy" is enormously more ghostly than "dark matter." Dark energy is the re-invocation of Einstein's cosmological constant, which Einstein put into his equations simply to prevent the collapse of the universe under its own gravitational pressure, and which he called his "greatest blunder." With the discovery of Hubble's expanding universe in the 1920's, he took it out, but it's back and on steroids now, and we haven't a clue about its true nature. The point of all of this is to argue that astronomy, which on its face appears to be an observational science much like ecology, has matured to become exceedingly predictive. Ecology will undoubtedly do the same as well. Indeed, at one time, that was ecology's goal too. I wrote yesterday that "the International Biome Program, in the decade following the development of the theory of systems ecology, attempted to measure the mass and momenta of bush, insect, horse and carriage in the various biomes of North America" in order to predict the future. That may have sounded like literary hyperbole, but it wasn't. I found this 1970 newspaper cartoon on Oak Ridge National Laboratory's webpage last night that says the same thing: http://daac.ornl.gov/NPP/html_docs/IBP_toon.html Ecology has retreated from this vision nowadays, but it's certain to retry this level of prediction again some time in the future, but in a more mature fashion. Wirt Atmar
