TPO 14 Lecture 3 Astronomy
Narrator:
Listen to part of a lecture in an astronomy class.
Professor:
OK, last time we talked about ancient agricultural civilizations that observed the stars and then used those observations to keep track of the seasons. But today I want to talk about the importance of stars for early seafarers, about how the fixed patterns of stars were used as navigational aids.
OK, you've all heard about the Vikings and their impressive navigation skills, but the seafaring people of the pacific islands, the Polynesians and the Micronesians, were quite possibly the world's greatest navigators. Long before the development of, uh, advanced navigational tools in Europe, pacific islanders were travelling from New Zealand to Hawaii and back again, using nothing but the stars as their navigational instruments.
Um, the key to the pacific islanders' success was probably their location near the equator. What that meant was that the sky could be partitioned, divided up, much more symmetrically than it could farther away from the equator. Unlike the Vikings, early observers of the stars in Polynesia or really anywhere along the equator would feel that they were at the very center of things, with the skies to the north and the skies to the south behaving identically, they could see stars going straight up in the east and straight down in the west. So it was easier to discern the order in the sky than farther north or farther south, where everything would seem more chaotic.
Take the case of the Gilbert Islands, they are part of Polynesia, and lie very close to the equator. And the people there were able to divide the sky into symmetrical boxes, according to the main directions, north, east, south and west. And they could precisely describe the location of a star by indicating its position in one of those imaginary boxes. And they realized that you had to know the stars in order to navigate. In fact there was only one word for both in the Gilbert Islands, when you wanted to the star expert, you ask for a navigator.
Um, islanders from all over the pacific learned to use the stars for navigation, and they passed this knowledge down from generation to generation. Some of them utilized stone structures called stone canoes, ah, and these canoes were on land, of course, and you can still see them on some islands today. They were positioned as if they were heading in the direction of the points on the sea horizon where certain stars would appear and disappear during the night, and, um, young would-be navigators set by the stones at night and turned in different directions to memorize the constellations they saw, so they could recognize them and navigate… by them later on when they went out to sea.
One important way the Polynesians had for orienting themselves was by using zenith stars. A zenith star was a really bright star that would pass directly overhead at particular latitude…at a particular distance from the equator, often at a latitude associate with some particular pacific island. So the Polynesians could estimate their latitude just by looking straight up, by observing whether a certain zenith star passed directly overhead at night, they'd know if they have rates the same latitude as a particular island they were trying to get to. Um, another technique used by the Polynesians was to look for a star pair, that's two stars that rise at the same time, or set at the same time, and navigators could use these pairs of stars as reference points, because they rise or set together only at specific latitudes. So navigators might see one star pair setting together. And, uh…would know how far north or south of the equator they were. And if they kept on going, and the next night they saw the pairs of stars setting separately, then they would know that they were at a different degree of latitude. So looking at rising and setting star pairs is a good technique. Um… actually it makes more sense with setting stars; they can be watched instead of trying to guess when they'll rise.
Uh, OK, I think all this shows that navigating doesn't really require fancy navigational instruments; the peoples of the pacific islands had such expert knowledge of astronomy as well as navigation that they were able to navigate over vast stretches of Open Ocean. Uh, it's even possible that Polynesian navigators had already sailed to the Americas, centuries before Columbus.
TPO 14 Lecture 4 Archeology
Narrator:
Listen to part of the lecture in the archaeology class
Professor:
When we think of large monumental structures built by early societies and Egyptian pyramid probably comes to mind. But there are some even earlier structures in the British Isles also worth discussing, and besides the well-known circle of massive stones of Stonehenge which don't get me wrong is remarkable enough, well, other impressive Neolithic structures are found there too. Oh, yes, we are talking about the Neolithic period here, also called new Stone Age, which was the time before stone tools began to be replaced by tools made by bronze and other metals.
It was about 5000 years ago, even before the first Egyptian pyramid that some of amazing Neolithic monuments---tombs, were racketed at the very size around ironed Great Britain and costal islands nearby.
I am referring particular to structures that in some cases, look like ordinary natural hills. But we definitely build by humans, well-organized communities of human's to enclose a chamber or room within stone walls and sometimes with a high, cleverly designed sealing of overlapping stones. These structures are called Passage Graves, because in the chamber, sometime several chambers in fact, could only be entered from the outside through a narrow passage way.
Michael:
Excuse me, professor, but you said Passage Graves. Was this just monument to honor the dead buried there or were they designed to be used somehow by the living?
Professor:
Ah, yes! Good question, Michael. Besides being built as tombs, some of these Passage Graves were definitely what we might call Astronomical Calendars, with chambers they flooded with some light on the certain special days of the year, witch must see miraculous and inspired good dealer of they really just wonder. But research indicates that not just light but also the physics of sound help to enhance this religious experience.
Michael:
How so?
Professor:
Well, first the echoes. When religious leaders started chanting with echoes bounced off the stonewalls over and over again, it must seem like a whole chorus of other voices, spirits of God maybe join in. But even more intriguing is what physicists called Standing Waves. Basically, the phenomenon of Standing Waves occurs when sound waves of the same frequency reflect off the walls and meet from opposite directions.
So, the volume seems to alternate between very loud and very soft. You can stand quite near a man singing in loud voice and hardly hear him. Yet step little further away and voice is almost defining. As you move around chamber, the volume of the sound goes way up and way down, depending on where you are and these standing waves. And often the acoustic makes it hard to identify where sounds are coming from. It is powerful voices that are speaking to you or chanting from inside your own head. This had to engender powerful sense of all Neolithic worshipers.
And another bit of physics I played here is something called Resonance. I know physics, but well I imagine you have all below near of top empty bottles and heard sounds it makes. And you probably notice that depending on its size--- each empty bottle plays one particular music note. Or it is the physics might put it, each bottle resonates at a particular frequency. Well, that's true of these chambers too. If you make a constant noise inside the chamber, maybe by steadily beating drum at certain rate, a particular frequency of sound will resonate. We will ring out intensely, depending on the size of chamber. In some of large chambers though, these intensified sound may be too deep for us to hear, we can feel it. We are mysteriously agitated by a….but it is not a sound our ears can hear. The psychological effects of all these extraordinary sounds can be profound, especially when they seem so disconnected from human doing drumming or chanting. And there can be observable physical effects on people too. In fact, the sounds can cause headaches, feelings of dizziness, increase heartache, that sort of thing, you see.
Anyway, what is we experience inside one of these Passage Graves clearly could be far more intense than everyday reality outside which made them very special places.
But back to your question, Michael, as to whether these Graves were designed to be used by the living. Well, certainly, we have got to ask economical or calendar function. That seems pretty obvious, and I wanna go into more detail on that now.
