Bruce Marlick wrote:
I once attended a lecture by the head of a university's astronomy department. He said that astronomy was a very exciting field because massive changes in beliefs were relatively frequent. I kept quiet my opinion that that might be because astronomers (and cosmologists in particular) seems relatively happy to jump to conclusions!
You may be right that cosmologists are happy to jump to conclusions, at least sometimes, but my personal opinion is that cosmologists have often been too happy to "anthropomorphize". That is, cosmologists, like most of the rest of us, have been happy to think that the universe should make sense in human terms. And it should, preferably, put ourselves in the center of it all.
It is a misunderstanding that cosmologists in the past clung to the belief that the Earth is flat. The roundness of the Earth was well known by astronomers of antiquity.
However, those cosmologists of yore did stick to the idea that the Earth is the center of the universe. It took a long time to discard that idea. Copernicus stated that the Earth is orbiting the Sun rather than the other way round, and was later proven to be right about that. (Technically the Sun and the Earth orbit one another, but the size of the Sun's orbit "around" the Earth is about a meter or so, so the Sun is just wagging back and forth around its own center.)
But the Sun-centered universe just meant that our own dear Sun became the center of the universe rather than the Earth. By the time it had become understood that there was a galaxy around the solar system, astronomers first believed that our solar system, and therefore the Sun, was the center of the galaxy. William Herschel, discoverer of Uranus, championed this idea. It took the studies of globular clusters by Harlow Shapley to prove that the solar system was nowhere near the center of the Milky Way. But Harlow Shapley still believed that the mysterious "spiral nebulae" that had been discovered, and that bore names like M51
, were just rotating gas clouds in our own galaxy, and that the Milky Way comprised the entirety of the universe
It took the studies of galaxies and redshifts by Edwin Hubble to prove not only that those "spiral nebulae" were galaxies of their own, independent of the Milky Way, but also that almost all of them were moving away from us. The expansion of the universe had been proved. The expansion of the universe suggested a violent birth of the universe at a moment in time in the past, but this idea sat uncomfortably with some astronomers, who preferred the unchanging "serenity of the night". So astronomers fought over whether the universe had been born violently or whether it had always existed and looked pretty much the way it does now. It took the discovery of the cosmic microwave background radiation, the echo of the Big Bang, to convince astronomers that our universe had been fundamentally different in the past.
After astronomers had become convinced that the universe had been born in the past and had been evolving ever since, the idea that the universe would reverse its expansion and fall back on itself and disappear in a "Big Crunch" became popular. This idea quickly evolved into the concept of the "Big Bounce", where the Big Crunch immediately leads to a new Big Bang, making the universe rise from the ashes like a phoenix. Astronomers diligently began searching for evidence that the universe was destined to collapse, which was of course the necessary prerequisite for a Big Bounce. The astronomical community was absolutely stunned when studies of distant supernovae appeared to prove that the universe wasn't slowing down, like it "should". It was speeding up instead.
I think I see a lot of anthropomorphism in the way cosmologists have been thinking about the universe. So far, the universe has always proved to be bigger and stranger than most cosmologists would have guessed. Perhaps it couldn't have been different. What we humans can think and imagine is limited by our human experiences.
As for black holes, there is a lot of evidence that huge gravity wells do exist. What's at the center of those enormous gravity wells is, so far, beyond the realm of science.
Personally I'm sure that many of us are doing a lot of anthropomorphizing when we think of them.