英语类的考试中一般都会涉及听力的考察，也是检验考生对于英语的应用能力，尤其
Lecture 1 (science class)
Narrator
Listen to part of a lecture in the history of science class.
Ok. We’ve been talking about how though out history, it was often difficult for people to give up ideas which have long been taken from granted as scientific truth, even if those ideas were false. In astronomy for example, the distinction between the solar system and the universe wasn’t clear until modern times. The ancient Greeks believed that what we call the solar system was infect the entire universe, and that the universe was geocentric. Geocentric means earth centric, so the geocentric view holds that the sun, the planets, the stars all revolve around the earth, which is stationary. Of course we now know that the planets, including earth, revolve around the sun and that the solar system is only a tiny part of the universe. So why do the ancient Greeks believe that the earth was the centre of the universe. Well it makes sense to them. Observations of the sky made it appear as the sun and the moon and the stars all revolve around the earth every day while the earth itself is stay in one place. And this feel was also supported by their philosophical and religious beliefs about the origin structure of the universe. It was presented in the worlds’ well known Greek philosophers as released in the 4th century B.C.E. and the geocentric theory continue to prevalent western thought for almost 2000 years until the 17th century. Now what’s especially interesting is that when astronomical observations were made that seems to be in consistent with geocentric view, the ancient Greeks did not really consider alter the theories. It was so intuited, so sensible that the earth was the centre of the universe that astronomers found way to explain those seemingly inconsistent phenomenon within the geocentric feel. For example, Greek astronomers made excellent very accurate observations of the movement of the planets. But the observations revealed that be a problem, the geocentric theory said that the planets would move around earth in one direction. However, astronomers noticed that at times several planets seem to start moving in one direction and start moving backward in their orbits around the earth. And they came up with the theory that these planets themselves moved in small circles called epicycles as they travelled around the earth. Here’s a picture of what they imagined, you see how these epicycle theory could count for the seeming backward motion of the planet. Of course today we know that this appearance of backward motion is cause by the fact that earth as well as other planets or move in their own orbits around the sun and the relative movements of the planets with respective to each other can get quite complex.
However, there were a few astronomers agrees in other places who didn’t agree with the geocentric view. For example, a Greek astronomer who lives in the third century B.C.E., he proposed the theory that our planetary system might be heliocentric, his name was Aristarchus. Heliocentric means sun centric that the earth revolves around the sun. Aristarchus recognized from his calculations that the sun was much larger than the earth and other planets, it was probably this discovery that let him to conclude that the universe is heliocentric. I mean is it more sensible to think that a smaller heavenly body would orbit a larger one rather than the opposite However, his proposition was rejected largely based on other scientific believes held at that time which all make sense in a way even if they were incorrect.
Let me mention two objections Greeks made to Aristarchus’ theory. First, they believe that everything that moves create its own wind so they speak. Everyone has this experience when you’re running, right So they thought that if the earth itself was moving there would have to be a consistent wind blowing sweeping them all of their feet and of course there wasn’t. And second, the idea of the earth that moved didn’t fit in with the ancient Greeks understanding of gravity. They thought that gravity was basically on natural tendency of all things to move towards the centre of the universe, which was the earth or the centre of the earth. So that explained why apples and other falling objects for falling straight down. If the sun was at the centre of the universe, things would fall toward the sun and away from the earth which of course they didn’t. so these were some of the reasons they rejected the heliocentric theory.