In the absence of news about The Controversy between evolution and creationism, we’ll zoom out a couple of clicks and look at an astronomy item we found at PhysOrg — The Great Debate over whether the universe is small or large.
It’s a fascinating look at some science history, and it demonstrates how science works when there’s a controversy between competing theories. We’ve added some bold font to the following excerpts:
The visible universe is vast. It is 93 billion light years across, and contains more than 100 billion galaxies. The average galaxy contains about 100 billion stars, and untold numbers of planets. Yet a century ago there was serious doubt among many astronomers that the universe was much more than 100,000 light years across. Arguments about whether the universe was small or large became known as the Great Debate.
A lot of controversies have been referred to by the opposing sides as the “Great Debate.” We have no doubt that the showdown between Bill Nye and ol’ Hambo is being called that. But the dispute about the size of the universe was worthy of the name. We’re told:
It is often known as the Shapley-Curtis debate, so named after Harlow Shapley and Heber Curtis, and a public debate they had in 1920.
Wikipedia has a brief article about it — see Great Debate. Back to PhysOrg:
The debate centered on the distance to certain nebulae. At the time, “nebula” referred to anything (excluding comets) that appeared “fuzzy” rather than distinct like a star or planet. So things like the Orion nebula (a stellar nursery), the Crab nebula (a supernova remnant) were considered nebulae just as they are today, but what we now call galaxies were also known as nebulae. The Andromeda galaxy, for example, was known as the Great Andromeda Nebula.
Curtis argued that Andromeda and other spiral nebulae were in fact “island universes”, similar in size to our own Milky Way “universe”. This would mean that not only were these nebulae 100,000 light years across or more, they must be millions of light years away.
This was in 1920. Did Curtis have any evidence? Let’s read on:
He based this argument on the fact that more novae were observed in Andromeda alone than were observed in the entire Milky Way. Why would that be the case if Andromeda were small and close. He also noted that some spiral nebulae had rather large redshifts, meaning that they were moving much faster than other objects in the universe.
Obviously a crazy man. Here’s the other side of the Great Debate:
Shapley argued that what we now call the Milky Way galaxy was the bulk of the universe. Spiral galaxies such as Andromeda must be relatively close and small. He based this view on several points. In 1917 Shapley and others observed a nova in the Andromeda nebula. For a brief time the nova outshined the central region of Andromeda. If Andromeda were a million light years away, as Curtis contended, then this nova (we now know it was a supernova) would need to be far brighter than any known mechanism could produce.
Shapley had other evidence too, which the article mentions. We notice, however, that no one was arguing for a bible based view of things. So how did the debate work out? PhysOrg informs us:
After the debate the general opinion was that Shapley had won. His own observations of the shape of the Milky Way and the 1917 supernova, and [other evidence we skipped] gave the small universe model solid footing. Besides, the idea that objects could be millions of light years away seemed patently absurd.
So there you are. The Milky Way, our galaxy, is the whole universe. Oh wait — there’s more:
In 1912 Henrietta Leavitt discovered that Cepheid variable stars vary at a rate proportional to their brightness. … In 1925 Edwin Hubble used Leavitt’s period-luminosity relation to precisely determine the distance to the Andromeda galaxy. He demonstrated conclusively that Andromeda was about 2 million light years away.
Aha! Curtis was right after all. You can read about the significance of Hubble’s work in Wikipedia — Hubble’s law. Here’s the end of the PhysOrg article:
Thus we came to know that our Milky Way is an island galaxy in a much larger universe.
Curtis had the unpopular idea. Prevailing opinion and most of the evidence seemed to be against him. His model of a gigantic universe was regarded as absurd. Yet his theory prevailed. Surely there’s a lesson the creationists can learn from this.
Well … no, there isn’t. But that shouldn’t stop them from using Curtis as an example of how a fringe idea can become mainstream. They’ll never explain how the big universe became mainstream, but don’t be surprised if they adopt Curtis as an encouraging example of an underdog who eventually achieved success over a dogmatic consensus.
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