Tuesday, March 07, 2006

(21) Questioning Newton´s third law

On May 20th 1987 I smiled at the memory of Byron’s observation in Don Juan; that people must have been pretty dull for it to have been necessary for an apple to fall on Newton’s head before the law of gravity was thought of.

I had heard several comedians also make jokes about that.

(Further to the notion of "ideas coming of their time", do not forget Charles Fort’s observation that for centuries the rattling of kettle lids proclaimed steam power, but it was only when people decided that we were ready for it that that power was harnessed.)

That made me think of some of Newton’s other laws.

The only one that I could recall precisely was "To each action there is an equal and opposite reaction."
This did not strike me as anything like as self-evident as the law of gravity, and I did not see how one could make fun of mankind for not having thought that one out before him.
(In fact pages from Leonardo´s notebooks show that he devised two Perpetual Motion machines. Neither worked and he had concluded that this must be because "To every action there is an equal and opposite reaction". That was one hundred and seventy-five years before Newton´s birth.)
And I started to think more about this law: it is not obvious at all!

I had seen rows of metallic balls where the letting go of the extreme ball at one edge caused the furthest ball to swing outward as its distant brother bashed into the mass.

O.K. But does that mean that we can be certain that every action, be it animal, human or naturally caused leads to an equal and opposite reaction?
Rows of metal balls may reveal very precisely the forces at play, but can we be so certain that we can pick out all of those produced by a typhoon?

I have no Physics qualifications and last had a lesson in that subject in 1974. All the same, I began to think that this Newtonian law could be wrong.

Three days later I bought a copy of The Times.
This article was at the bottom of page two -

GYROSCOPES CHALLENGE LAW OF MOTION By Rodney Cowton Transport Correspondent

British experimenters have developed propulsion systems that could revolutionize space travel. Whether they might also overthrow Newton’s law of motion, that to every action there is an equal and opposite reaction, is a matter for argument. Mr Sandy Kidd, aged 49, a toolfitter, has moved to the department of mechanical engineering at Dundee University, to continue his investigations after working for four years in his garden shed in Dundee to produce his system.
Unknown to him, Mr Peter Greed, a Swindon schoolteacher, had been working on the same subject and had taken out a patent in 1974.
Both have used spinning gyroscopes to convert rotary momentum into spinning momentum.
Mr Greed said that he had used a simple device which showed in principle that in low gravity it was possible for the device to reduce the weight of the object being propelled until there was an upthrust which would lift it against the gravitational field. Mr Kidd’s device, which is about 18 inches high, uses two gyroscopes, an electric drill and a model aircraft engine to demonstrate the principle.
Professor Eric Laithwaite, of Imperial College, London, the leading British academic in the field, said:
"What he has to do now is to make a machine which develops a bigger force in relation to weight."
It was lectures by Professor Laithwaite which first stimulated Mr Kidd’s interest.

"What Mr Kidd has achieved so far, he has achieved by pure intuition. I want to see what more his intuition can turn up. He might just turn up something that the experts miss. We need all the help we can get."
If the principle could be developed it would be possible to travel great distances in space largely unconstrained by the quantities of fuel that could be carried.

Professor Stephen Salter, head of engineering design at Edinburgh University, said that he suspected that Mr Kidd’s device had achieved its effect through some form of friction; otherwise it appeared to be contrary to Newton’s law.

Mr Greed, who used pieces of wood and string and two gyroscopes to demonstrate the principle, denied that it was contrary to Newton’s laws.

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