TPO 3 Lecture 3 Art History
Narrator
Listen to part of a lecture in an Art History class. The professor has been discussing the origins of art.
Professor：Some of the world's oldest preserved art is the cave art of Europe, most of it in Spain and France. And the earliest cave paintings found to date are those of the Chauvet Cave in France discovered in 1994. And you know, I remember when I heard about the results of the dating of the Chauvet paintings, I said to my wife, “Can you believe these paintings are over 30,000 years old?” And my 3-yearold daughter piped up and said, “Is that older than my great-grandmother?” That was the oldest age she knew. And you know, come to think of it. It's pretty hard for me to really understand how long 30,000 years is too. I mean, we tend to think that people who lived at that time must have been pretty primitive. But I'm gonna show you some slides in a few minutes and I think you will agree with me that this art is anything but primitive. They are masterpieces. And they look so real, so alive that it's very hard to imagine that they are so very old. Now, not everyone agrees on exactly how old. A number of the Chauvet paintings have been dated by a lab to 30,000 or more years ago. That would make them not just older than any other cave art, but about twice as old as the art in the caves at Altamira or Lascaux, which you may have heard of. Some people find it hard to believe Chauvet is so much older than Altamira and Lascaux, and they noted that only one lab did the dating for Chauvet, without independent confirmation from any other lab. But be that as it may, whatever the exact date, whether it's 15,000, 20,000 or 30,000 years ago, the Chauvet paintings are from the dawn of art. So they are a good place to start our discussion of cave painting. Now, one thing you've got to remember is the context of these paintings. Paleolithic humans - that's the period we are talking about here, the Paleolithic, the early stone age, not too long after humans first arrived in Europe - the climate was significantly colder then and so rock shelters, shallow caves were valued as homes protected from the wind and rain. And in some cases at least, artists drew on the walls of their homes. But many of the truly great cave art sites like Chauvet were never inhabited. These paintings were made deep inside a dark cave, where no natural light can penetrate. There's no evidence of people ever living here. Cave bears, yes, but not humans. You would have had to make a special trip into the cave to make the paintings, and a special trip to go see it. And each time you'd have to bring along torches to light your way. And people did go see the art. There are charcoal marks from their torches on the cave walls clearly dating from thousands of years after the paintings were made. So we can tell people went there. They came but they didn't stay. Deep inside a cave like that is not really a place you'd want to stay, so, why? What inspired the Paleolithic artists to make such beautiful art in such inaccessible places? We'll never really know of course, though it's interesting to speculate. But, um, getting to the paintings themselves, virtually all Paleolithic cave art represents animals, and Chauvet is no exception. The artists were highly skilled at using, or even enhancing, the natural shape of the cave walls to give depth and perspectives to their drawings, the sense of motion and vitality in these animals. Well, wait till I show you the slides. Anyway, most Paleolithic cave art depicts large herbivores. Horses are most common overall with deer and bison pretty common too, probably animals they hunted. But earlier at Chauvet, there is a significant interest in large dangerous animals, lots of rhinoceros, lions, mammoth, bears. Remember that the ranges of many animal species were different back then so all these animals actually lived in the region at that time. But the Chauvet artists didn't paint people. There is a half-man-half-bison creature and there is outline of human hands but no depiction of a full human. So, why these precise animals? Why not birds, fish, snakes? Was it for their religion, magic or sheer beauty? We don't know. But whatever it was, it was worth it to them to spend hours deep inside a cave with just a torch between them and utter darkness. So, on that note, let's dim the lights, so we can see these slides and actually look at the techniques they used.
TPO 3 Lecture 4 Astronomy
Narrator
Listen to part of a lecture in an astronomy class.
Professor：Now astronomy didn't really bloom into the science it is today until the development of spectroscopy. Spectroscopy is basically the study of spectra and spectral lines of light, and specifically for us, the light from stars. It makes it possible to analyze the light emitted from stars. When you analyze this light, you can figure out their distance from the earth, and identify what they are made of, determine their chemical composition. Before we get into that though, it's probably a good thing to back up a bit. You all know how when you take a crystal prism and pass a beam of sunlight through it, you get a spectrum, which looks like a continuous band of rainbow colors. The light that we see with our human eyes as a band of rainbow color falls in a range of what's called visible light. And visible light spectroscopy is probably the most important kind of spectroscopy. Anyone want to take a stab at the scientific term for visible light? And I'm sure all of you know this because you all did the reading for today.
Student：Optical radiation. But I thought being exposed to radiation is dangerous.
Professor：Yes, and no. If you are talking about radiation, like in the element Uranium, yeah, that's dangerous. But radiation as a general term actually refers to anything that spreads away from its source. So optical radiation is just visible light energy spreading out. OK, so we've got a spectrum of a beam of sunlight and it looks like the colors bleed into each other. There are no interruptions, just a band flowing from violet to green, to yellow, to… you get the idea. Well, what happens if the sunlight's spectrum is magnified? Maybe you all didn't do the reading. Well, here's what you'd see. I want you to know this that this spectrum is interrupted by dark lines called spectral lines. If you really magnify the spectrum of the sunlight, you could identify more than 100,000 of them. They may look like kind of randomly placed, but they actually form many distinct patterns. And if you were looking at the spectrum of some other star, the colors would be the same. But the spectral lines would break it up at different places, making different patterns. Each pattern stands for a distinct chemical element, and so different sets or patterns of spectral lines mean that the star has a different chemical composition.
Student：So how do we know which spectral patterns match up with which elements?
Professor：Well, a kind of spectroscopic library of elements was compiled using flame tests. A known element, say a piece of iron for example, is heated in a pure gas flame. The iron eventually heats to the point that it radiates light. This light is passed through a prism, which breaks it up into a spectrum. And a unique pattern, kind of like a chemical fingerprint of spectral lines for that element appears. This process was repeated over and over again for many different elements, so we can figure out the chemical makeup of another star by comparing the spectral pattern it has to the pattern of the elements in the library. Oh, an interesting story about how one of the elements was discovered through spectroscopy. There was a pretty extensive library of spectral line patterns of elements even by the 1860s. A British astronomer was analyzing a spectrograph of
sunlight, and he noticed a particular pattern of spectral lines that didn't match anything in the library. So he put two and two together, and decided there was an element in the sun that hadn't been discovered here on the earth yet. Any guesses about what that element is? It actually turned out to be pretty common and I'm sure all of you know it. OK. Let's try something else. Any of you happened to be familiar with the Greek word for “sun” by chance?
Student：Something like “Helius” or something like that. Oh it must be “Helium”. So you are saying that elium was discovered on the sun first.
Professor：Yes, and this is a good example of how important spectroscopy is in astronomy.
