Thursday, April 10, 2008

Standing on the shoulders of giants

As mentioned before, since getting an IPod for christmas I am a huge fan of podcasts. I find it's like listening to the radio but you decide what they talk about. Currently, my favourite feeds are Chaos Radio Express (in German) and the In Our Time BBC programme.

Recently, I was listening to an episode about Newton's Principia that discussed the scientific trends of the time when Newton published his seminal book. In Cambridge, I had learned before that Newton's remark that he was standing on the shoulders of giants was not meant as modest as it might sound. In fact, it's meaning was rather sarcastic as it was referring to Robert Hooke whose bad posture mad it obvious that Newton was in fact saying that he did not learn anything from him.

To me, that had always sounded rather reasonable given that the law that carries Hooke's name does not sound particularly deep from a modern perspective: It states that to leading order the elastic deformation is linear in applied force, basically a statement saying that no surprise happens and the first order does not vanish. Formulated this way quite a minor contribution compared to Newton's axioms and his inverse square law for gravity.

From the BBC programe, however, I learned that the situation is not that simple: In fact, Hooke had already found an inverse square law for gravity experimentally and suggested to Newton in a letter that that might me responsible for the elliptic motions of the planets. Hooke himself did (could?) not prove that and was asking Newton for his opinion.

Later in their life, the two men both of difficult character had an ongoing dispute about scientific priorities and this is where the famous quotation is from. The wikipedia page contains more information about it and buts it in the context of (wave) optics rather than gravity.


theoreticalminimum said...

I recently read the best concise biography of Newton I've come across so far, by Gale E. Christianson (which I heartily recommend). I quote from pp 63-64:
" ...Halley suggested that the force of attraction between the planets and the sun decreases in inverse proportion to the square of the distance between them. If this were true, then each planet’s orbit should take the form of Kepler’s ellipse, a shape like a football, though somewhat more rounded.

Halley recalled that Hooke immediately “affirmed that upon that principle all the Laws of the celestial motions were to be demonstrated.”[1] Wren, who was also deeply interested in the new science, claimed that he, too, had reached the same conclusion. The problem, as all three admitted, was to find the mathematical means of proving it.

Anxious for a solution, Sir Christopher [Wren] offered to give a valuable book to the friend who could deliver solid proof within the next two months. Hooke, to whom modesty was a stranger, claimed that he already possessed the required proof. However, he would keep it a secret for the time being so that his friends “might know how to value it, when he should make it public.”[2]

The deadline came and went without a word from Hooke, and spring soon turned to summer ... "

My understanding is that this is a slightly different version of the story from the BBC programme, or what is written in the wikipedia article. By the time that Halley, Wren and Hooke were thinking about the inverse-square distance dependence of the gravitational force, Newton had already proved mathematically that such a dependence would produce the elliptical orbits of Kepler.

I think you have been rather seriously misunderstanding Hooke's contributions to science, although the guy was no saint.

Given what you think as Hooke's "minor contribution", I can already easily imagine Motl going so far as calling Hooke a string theorist of his time. ;-)

[1] Isaac Newton, Corres., II, 433–35.
[2] Ibid.

Robert said...

All this is likely true. I have to admit I am a complete ignoramus of the history of science.

That goes as far as me failing to give the names of the "different" gas laws when teaching the physics part of a scuba diving course. I can never remember which names are associated with pV=const (for T const) or p/T=const (for
V const) etc since to me they are all consequences of the ideal gas law (which comes without the name of a physicist).

And of course it's true that Hooke was the founding father of string theory as a string is not much different from a spring (even if the potential energy of a string is proportional to the length rather than the length squared).

Anonymous said...

“Nearly three and a half centuries of scientific study and achievement is now available online in the Royal Society Journals Digital Archive.
This is the longest-running and arguably most influential journal archive in Science, including all the back articles of both Philosophical Transactions and Proceedings.”

Anonymous said...

a film with an other physics giant:

CLH Hoodies said...

Interesting. I did not know this about Newton.