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Description
Prof. Pentz discusses the background to Galileo’s inclined plane experiment and hypothesis. He describes the difficulties Galileo would have faced with the technology of the time and then carries
... out the inclined plane experiment himself.
Doing the second part of the experiment enables the student to prove Galileo’s circle/chord theory, which Prof Pentz demonstrates. He also points out the errors Galileo had made in his theory.
Prof. Pentz discusses how location and technology have no bearing on experimentation and that researchers have always been restricted by the limitations of the equipment available to them.
| 1 | 00:00:01,000 | 00:00:03,000 | Michael Pentz: Now I’m going to go over the main steps of this experiment… |
| 1 | 00:00:01,000 | 00:00:03,000 | (Michael Pentz) But this laboratory, which incidentally we shall be… |
| 1 | 00:00:02,000 | 00:00:04,000 | Michael Pentz: Even in the most modern laboratories, like CERN, |
| 2 | 00:00:03,000 | 00:00:06,000 | ..in case you’ve run into some difficulties with it. |
| 2 | 00:00:03,000 | 00:00:06,000 | ..visiting in a later programme, is a chemistry laboratory… |
| 2 | 00:00:05,000 | 00:00:09,000 | equipped with the most complex and costly apparatus and with instruments of… |
| 3 | 00:00:06,000 | 00:00:08,000 | But before we do that let’s just stop and think about… |
| 3 | 00:00:07,000 | 00:00:10,000 | ..and this man is a physical chemist. |
| 4 | 00:00:09,000 | 00:00:11,000 | ..the background to the experiment. |
| 3 | 00:00:09,000 | 00:00:14,000 | ..great precision and refinement, the research scientist is in essentially… |
| 4 | 00:00:11,000 | 00:00:17,000 | What he is doing is analysing an element with an instrument called a mass spectrometer. |
| 5 | 00:00:12,000 | 00:00:16,000 | What was the hypothesis that Galileo had that the experiment was meant to test? |
| 4 | 00:00:15,000 | 00:00:18,000 | ..the same situation as Galileo was, or for that matter, as you will be… |
| 6 | 00:00:17,000 | 00:00:20,000 | Well it was simply that falling bodies are uniformly accelerated, |
| 5 | 00:00:19,000 | 00:00:21,000 | ..when you do some of the home experiments in this course. |
| 7 | 00:00:21,000 | 00:00:23,000 | by which he meant that their speed increased by… |
| 6 | 00:00:22,000 | 00:00:27,000 | He is working in the unknown and near the limits of his instrumentation. |
| 8 | 00:00:24,000 | 00:00:27,000 | .. the same amount in each interval of time so that, for example, |
| 5 | 00:00:24,000 | 00:00:28,000 | An electronic instrument records his measurements. |
| 9 | 00:00:28,000 | 00:00:30,000 | if in one second they reached a speed of 10 metres a second, |
| 7 | 00:00:28,000 | 00:00:32,000 | He has to design his experiments so as to be able to test some hypothesis. |
| 10 | 00:00:30,000 | 00:00:33,000 | then in 2 seconds they reached a speed of 20 metres a second, |
| 11 | 00:00:33,000 | 00:00:36,000 | in 3 seconds, 30 metres a second, and so on. |
| 8 | 00:00:33,000 | 00:00:36,000 | He does so in the technological context of his time. |
| 6 | 00:00:36,000 | 00:00:40,000 | Both these scientists – the biochemist and the physical chemist, |
| 12 | 00:00:38,000 | 00:00:42,000 | Now to test that hypothesis he could simply have dropped some heavy object… |
| 9 | 00:00:38,000 | 00:00:43,000 | Technology sets the limit on what he can do - sometimes even sets the limit… |
| 7 | 00:00:41,000 | 00:00:45,000 | work in modern laboratories – but laboratories weren’t always like this. |
| 13 | 00:00:42,000 | 00:00:45,000 | ..from the windows on different floors of some tall building… |
| 10 | 00:00:44,000 | 00:00:49,000 | ..on what he can think of doing and he may be confronted with some… |
| 14 | 00:00:46,000 | 00:00:48,000 | ..and measured the time it took for the object to reach the ground. |
| 8 | 00:00:47,000 | 00:00:52,000 | This is one of the places where it all began, one of the earliest laboratories. |
| 15 | 00:00:49,000 | 00:00:52,000 | And he could have measured the speed that it had at the moment it hit the ground. |
| 11 | 00:00:50,000 | 00:00:53,000 | ..unknown phenomenon that drastically affects his experiments – |
| 9 | 00:00:53,000 | 00:00:57,000 | It’s the Octagon Room at the old Royal Observatory in Greenwich. |
| 16 | 00:00:54,000 | 00:00:56,000 | But he had no means of measuring the speed – even we'd find it… |
| 12 | 00:00:54,000 | 00:00:57,000 | as Galileo was, with rotational energy. |
| 17 | 00:00:56,000 | 00:01:00,000 | ..difficult to measure the speed of a falling object at the moment of impact, |
| 10 | 00:01:00,000 | 00:01:04,000 | As you can see, it is a most elegant room, |
| 18 | 00:01:01,000 | 00:01:03,000 | and for Galileo it was absolutely out of the question. |
| 19 | 00:01:04,000 | 00:01:07,000 | So he couldn’t test his hypothesis directly, |
| 20 | 00:01:08,000 | 00:01:11,000 | he had to translate it into another form which he could test. |
| 12 | 00:01:10,000 | 00:01:17,000 | Though would it be right to call this a laboratory? I think so. |
| 21 | 00:01:12,000 | 00:01:15,000 | And what he did was to turn it into the form which says… |
| 22 | 00:01:16,000 | 00:01:20,000 | ..the distance an object falls in a given time is proportional to the square of the time. |
| 13 | 00:01:18,000 | 00:01:22,000 | I think it was a laboratory in the sense that it was a place where… |
| 23 | 00:01:20,000 | 00:01:23,000 | He’s got rid of the speed you see, which he can’t measure, |
| 14 | 00:01:23,000 | 00:01:28,000 | ..a particular piece of nature could be observed in abstraction from all the rest. |
| 24 | 00:01:24,000 | 00:01:27,000 | and replaced it by a statement involving the distance which he can measure. |
| 25 | 00:01:28,000 | 00:01:31,000 | Now this is spelt out in detail for you in the broadcast notes that… |
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