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ericmazur / PnPbook

Tracking of typos, errors, and improvements for "The Principles and Practice of Physics"
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Cavendish & gravitational constant #13

Open ericmazur opened 9 years ago

ericmazur commented 9 years ago

From Josip Slisko: Cavendish did not measure either the gravitational constant, nor the mass of the Earth. He determined the mean density of the Earth.

JohnDenker commented 9 years ago

That seems awfully nitpicky to me. At the time of Cavendish's work, the size and shape of the earth had been known with precision for 50 years. So by measuring the mean density, he could instantly infer the mass, and thence the gravitational constant ... and everybody involved knew this at the time.

It would make equally much sense (i.e. no sense at all) to say JJ Thompson did not discover the electron; all he did is measure some temperatures that allowed him to "infer" the existence of electrons. Similarly Penzias and Wilson merely "inferred" the existence of the cosmic microwave background. Similar words apply to virtually every experiment ever done. I strongly recommend NOT playing such games.

JohnDenker commented 9 years ago

One might consider including a few words about how science is done, namely a multi-step multi-dimensional chain of inference:

cavendish-inference

Throughout their schooling, students are all too often assigned exercises that focus on only one link in the chain. They don't get nearly enough practice with complex, multi-stage reasoning. This is a fixable problem. Not fixable overnight, but fixable.

I have no patience with the claim that students can't handle the complexity. A high-school football team runs plays more complicated than this.