Science
The history of our place in the universe
12/04/2012 09:12
To review some of the big milestones on this journey of discovery, Renaissance astronomer Nicolaus Copernicus published his heliocentric theory, De revolutionibus orbium coelestium, in 1543. Copernicus replaced the Earth with the Sun as center of the solar system, but the universe was still a smallish place, extending only to Saturn and the “fixed stars” which had been known since prehistoric times. The next planet, Uranus, was discovered by William Herschel in 1781, while his countrymen were fighting to retain their thirteen rebel colonies in America. Neptune was discovered in 1846, based on mathematical predictions made by Urbain Le Verrier to explain observed perturbations in the Uranian orbit (this was also a dramatic confirmation of Newton’s theories of gravity). But again, although our gaze had widened to include the solar system and the Milky Way, the background of more distant stars which had once been thought to all inhabit a single “sphere,” the
Although Immanuel Kant had speculated in the eighteenth century that the Milky Way might be an “island universe,” in April, 1920, Harlow Shapley and Heber Curtis debated the structure of the universe at the Smithsonian Museum of Natural History. Shapley insisted that the Milky Way was the whole universe, while Curtis argued that observations of the “Andromeda Nebula” suggested it was separate from and far away from the Milky Way, which he believed was only one “island universe” among many. The existence of galaxies was finally settled by Edwin Hubble in the early 1920s, and in 1929 Hubble published his Redshift Distance law of Galaxies (now called simply Hubble’s Law), which for the first time suggested the true physical scale and immense age of the universe.
In 1930, Clyde Tombaugh discovered Pluto, and in 2005 a team led by M. E. Brown discovered Eris, a Trans-Neptunian Object larger than Pluto that would certainly have been hailed as the tenth planet if Pluto had not already been demoted. By 1936, when Hubble published his classification system for galaxies, we understood that the universe was much larger and much older than we had ever imagined. But we were still unique and special, many believed, because we were the only known solar system and the only place in the universe that harbored life.
Nobel physicist Enrico Fermi, in an informal discussion in 1950, suggested what has come to be known as the Fermi Paradox: if the universe is so old and so big, where is everyone? Outside science-fiction circles, however, Fermi’s question has been largely ignored. It was still possible, until the last year or so, to believe that even in a nearly unimaginably big and old universe, Earth was the oasis of life. Very recent discoveries make this belief much less tenable.
The planet circling Alpha Centauri B is not Earth 2.0, however. It is too close to its star, so the surface temperature is much too high. In addition to believing the Milky Way was the entire universe, Harlow Shapley postulated “habitable zones” surrounding different types of stars, where liquid water could exist on a planet’s surface. Astronomers have generally regarded earth-like planets as the ideal places for life to develop, although some dissenters have pointed out that pressure as well as temperature influences the behavior of water, and there is ice on Mercury. So Shapley may have been wrong about this too, and the parameters for liquid water may be wider than just “Earth-like” worlds. But even if we restrict our search for possible havens of life to rocky planets in their stars’ habitable zones, these have now been located. And we’ve only scratched the surface.
Most of these revolutions in our understanding of our place in the universe have taken some time to filter out of scientific circles. But they have also been contentious, especially when scientific discoveries challenged widely held beliefs and dogmas. I wonder, in light of all the harm religion has done to our search for the truth (and to many of the individuals who searched!), why historians are currently so fascinated with the history of religion. It’s the hot new field, if books, articles, and professional blogs are any evidence. The Historical Society, which I’m a member of, for example, has received a grant of over $1 million to sponsor a program and book on “Religion and Innovation in Human Affairs.” Seems like somebody out there ought to say something about the ways religion has hindered innovation, to balance all the papers that are sure to be written about how faith and progress are the best of friends. But even aside from the history of science and religion, I wonder whether this underlying issue of where we see ourselves in the universe has influenced how we do history. I suppose (since it’s not my period) the change from a Ptolemeiac to a Copernican worldview altered the way historians approached their work. Maybe that’s all implicated in modernism, but I wonder about the relationship between an expanding view of the universe and how we think of history. And I wonder what effect the discovery of life (intelligent or not) off Earth would have. But yeah, I guess really what I’m wondering is what it will take for people to give up on their religious dogmas? Or is it really a case of Credo quia absurdum (“I believe because it is impossible”)?
