Both sections took place in the planetarium. They consisted of 2 parts. In the first part, the "Cosmology Statements" of the students were discussed. Many very fascinating points came up (hopefully this is not just the opinion of an overly enthusiastic TA!!!). Among them, the fact that it is equally difficult to comprehend the concept of a finite or infinite universe. Infinity appears to be just an abstract mathematical concept, yet it is very possible that the universe really is infinite, and not just VERY large. Furthermore, if it is infinite now, it has always been infinite, even immediately after the Big Bang. Since there is an infinite number of galaxies etc. in an infinite universe, everything that has even the smallest probability to occur will occur - an infinite number of times. So there will be an infinite number of solar systems just like our own with an infinite number of earths, cities just like Seattle, Astronomy 201 classes which discuss cosmology in a planetarium and so on. It is equally hard to comprehend the concept of a finite universe in which 3-dim space "curves back onto itself", similar to the way the 2-dim surface of a basketball does. Both are neither infinite nor do they have a boundary.
We also discussed the fact that while we are talking about all these cosmological concepts, we would not even be able to figure out that the Earth is not at the center of the universe just from naked-eye observations of the motions in the sky. Hundreds of years of scientific inquery where necessary to get to this point. This led to the second part of the sections, in which we used the planetarium to observe the diurnal (daily) and annual motions of the stars, the sun, and the planets from different lattitudes, and confirmend that it makes sense that the Milky Way really is a disk-shaped galaxy and we are located somewhere in the disk. It became apparent that while almost everything we know about the distant universe comes from observations of galaxies, there is only one galaxy (Andromeda) that can be seen with the naked eye from the northern hemisphere. It is much too close to be useful for cosmological purposes (its spectrum is actually blue-shifted, which means that Andromeda is coming towards us).
P.S.: In case this did not become clear from the fact that I never mentioned the word "constellation" in this summary of the sections: It is absolutely NOT important for this class to remember any of the constellations we identified in the planetarium. I could, however, come in handy in certain romantic situations...
:)
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