As you may have gathered from the intro of my previous post, I've been at a conference, preceded by a winter school, this week. I had planned to have a post prepared before I left, but it was not to be. Instead you get a post inspired by said winter school. (And incidentally, this was written entirely on an iPad soft keyboard. It wasn't a bad experience, if you're wondering.)
One of the talks I attended spoke about where we are today in understanding galaxies. As part of the talk the presenter also went over the history of the scientific study of galaxies, which got me thinking about how a scientific field evolves in time and what we need to consider when we're inventing a fictional scientific field. Then, obviously, I decided this would make a good blog post and here we are.
This isn't really going to take many societal effects into account, which could be very important in some fields, especially when religion disagrees with scientific discoveries. What I am instead going to talk about is how the scientific progress gets made using examples from galaxy astronomy/astrophysics and a few other fields.
Breaking it down
The way I see it, the development of a scientific field can be broken down into four stages:
The field first has to be discovered. This is a pretty basic requirement. In the case of galaxies, it was thought a hundred or so years ago that the Milky Way was the entire universe and contained everything we could see in the night sky. Then other galaxies outside of our own were discovered or, more accurately, it was realised that that "spiral nebula" in Andromeda was not actually within the Milk Way) and a field was born.
Once a bunch of galaxies had been discovered, Hubble and others started classifying them based on obvious characteristics of appearance. We actually still use a classification system based on Hubble's. However useful it is to be able to say, "Well, that galaxy there is elliptical, that one is a late-type* spiral," it wasn't quite giving us more information just yet.
This is the part where instead of just collecting things, we start analysing them in different ways. While Hubble was looking at galaxies with optical telescopes, he also took their spectra. It was at approximately this point when he noticed that all the far away galaxies were moving away from us (looping back to the discovery point) and the field of modern cosmology was born.
Since Hubble, of course, many other people have studied galaxies. As new data became available, thanks to the progression of technology, we discovered dark matter (from studying the dynamic properties of galaxies), we learnt that galaxies can interact and merge and we have been able to observe them at all sorts of different wavelengths leading to the discoveries of a variety of properties of galaxies and other things. We have started mapping the universe (which, if you hadn't guessed, is significantly larger than just the Milky Way), inventing models like hierarchical assembly (sorry, I couldn't find a sufficiently lay link for this one) to fit our data and we are now much better equipped to study the evolution of galaxies.
The last few points I made in the previous section are tied in with starting to really understand galaxies. This is the stage when we start to understand what's going on and become able to make predictions. As technology develops further, we can test our predictions more and more precisely and, sometimes this leads to discoveries of discrepancies and, again, we loop back to analysing and trying to explain these.
As hinted above, these aren't distinct stages. There is almost always going to be some overlap and a considerable amount of looping as the field progresses. And during the development of the field of galaxies, a whole lot of other (sub-) fields were born such black hole physics (well, more specifically, AGN), dark matter and dark energy (which are actually completely unrelated to each other).
*Don't get me started on why Hubble's ideas of "late-type" and "early-type" galaxies irritate me greatly.
I mentioned above that some of the new discoveries were made when new technology made new data available. In the absence of new data what sometimes happens is that more and more elaborate theories are invented to explain bits of observations that we just don't have enough information to address.
An obvious example that springs to mind is the celestial spheres rotating in the sky which were once used to explain orbital mechanics. The idea was that the stars were embedded in a sphere made of ether or quintessence (or insert fifth element of choice here), surrounding the Earth which rotated around the Earth, accounting for the motions of the stars across the night sky. Then more spheres, with each of the planets, sun and moon embedded in one each, were added to explain the motions of the nearer celestial objects. As observations and measurements improved, more spheres were added to account for things like the precession of the equinoxes/solstices. Even Copernicus, when he came along, kept the celestial spheres and just changed them so that, other than the moon, they rotated around the sun rather than the Earth.
It wasn't until Kepler came along and developed his laws of planetary motion that we moved from celestial spheres to orbits and then, shortly after, Newton came up with gravity and proved Kepler's laws. Kepler was able to do this thanks to the more precise measurements of planetary motions made by Tycho Brahe. New observations made it possible to move forward and, indirectly, contributed to a new field (Newtonian gravity) to be born.
Now we have absolute proof of a lot of things in astronomy and astrophysics (and many other areas of science). Basically, we know stuff now. But we don't know everything, not by a long shot. Remember, just over a hundred years ago, scientists thought that we knew almost everything and only a few small details were left to be filled in. Then quantum mechanics was discovered.
I like to think of the pool of human knowledge as fractal; the more we know, the greater the area of the fractal and the more branches of knowledge we develop, the larger and more visible the infinite perimeter between knowledge and known unknowns becomes.