Giant's shoulders

30th December 1994 at 00:00

Newton's Cradle Series, Three videos, Pounds 29+VAT and pamp;p. Viewtech Film and Video, Bristol BS4 3NJ.

The problem with Newton's laws is that they run contrary to everyday experience, and sometimes even common sense. When did you last see an object moving in a straight line at a constant speed? Don't say "the M1".

In real life, there are a number of forces at play including, most commonly, friction of some sort. For this reason, most people hold the Aristotelian view that you need to apply a force to keep something moving.

As these videos point out, it took Sir Isaac's genius and non-conformity to begin to overthrow the ideas about motion which had been around for over 2,000 years. The video includes Newton's famous line that he was only able to see the truth by "standing on the shoulders of giants".

The first video sketches the history of ideas about motion. In 23 minutes we learn about Galileo's observations of the solar system which landed him in deep trouble with the Church (he was forgiven in 1980); and the work of Tyco Brahe and Kepler who "solved the riddle of planetary motion" with the idea of elliptical orbits and the original ideas of Aristotle. The story is told by an actor portraying Sir Isaac, who sounds like an American trying to speak with an Olde English accent. This is extremely distracting and reduces the value of an excellent historical account.

The second video explains Newton's first and second laws fairly clearly and succinctly. Several comparisons are made between Newton's ideas and those of Aristotle, in the hope of showing that Newton's make more sense. However, research in the past 10 years on children's ideas has shown that it will take a lot more than this to shift people from supporting the ancient Greek. A useful demonstration of two children dropping a water melon and an apple off a bridge will help, but the subsequent explanation given by the Newton actor is too long and complicated to make an impact.

The third video goes over the first two laws and introduces the most famous concerning action and reaction. The examples used are useful (skateboards, basketball and running) but again the language will be difficult for some pupils. My main complaint about thevideos is that they use feet, yards and miles as their units. Consequently, "g" is expressed in feet per second, and escape velocity in miles per second, so the quantitative parts will confuse as much as clarify.

The videos will generally be helpful in explaining some very difficult concepts, particularly if students have experience of them before. For revision purposes they will be valuable at key stage 4 and to a lesser extent key stage 3, but they will need supporting with plenty of practical work and discussion, if teachers really hope to shift ideas towards Newton rather than Aristotle.

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