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Re: [Phys-l] Equations (causal relationship)



As I understand it, part of the debate about forces causing (or not)
acceleration hinges on the meaning of the equal sign. In fact, Newton's
Principia doesn't even say F = ma at all (it's closer to F = p-dot).
Furthermore, Newton wrote it out in words, not mathematical symbols. Do we
know that what Newton's meant by "is" is the same as what JD means by "="?
Out of historical curiosity, how would Newton weigh in on this debate?
Maybe only Newton himself knows this, but I'll accept speculation.

I ask this because, while JD recommends alternative symbols/notation for
causation, defining, and calculating, I don't believe they have been used
consistently historically. While JD is correct about the technical
mathematical distinctions, I don't think the notation has historically
always been adequate to the task. If I wanted to write a
mathematical/physics formula implying causal relation two hundred years
ago, how would I have written it? Or, how old is the definition symbol?
Or the assignment symbol := ?

Can we get intro physics textbooks to use different symbols for equality,
causation, defining, and calculating? Maybe not, because, as in the case
of Ohm's law, one man's definition is another man's causal relation, is
another man's equality.

Larry, who wonders if physicists will all agree on this in a hundred and
fifty years.