A question with regard to Hooke's and Kepler's laws

Florian Geyer said:

I have been studying some physics and I have the mentioned laws, but I have understood that the first law (elasticity modulus equals the stress over strain) ##e=\frac{\sigma}{\epsilon}## is valid only to limited range,

Florian Geyer said:

[Kepler's laws are] just a result of Newton's second law.

Florian Geyer said:

TL;DR Summary: Shall we consider the previous "laws" as physical laws? why?

laws must be general and not resulted from another law, and they must have adequately large range of validity

Florian Geyer said:

TL;DR Summary: Shall we consider the previous "laws" as physical laws? why?

Hello esteemed members,
I have been studying some physics and I have the mentioned laws, but I have understood that the first law (elasticity modulus equals the stress over strain) ##e=\frac{\sigma}{\epsilon}## is valid only to limited range, and the second one is just a result of Newton's second law.
Thus I concluded that they shall not be considered as laws since laws must be general and not resulted from another law, and they must have adequately large range of validity, which I do not think is the case of any of these laws.

Thanks in advance for reading/considering replying.

Hill said:

No, Kepler's laws cannot be derived just from Newton's second law.

Florian Geyer said:

cannot we consider it as a derivation of Kepler's law?

Vanadium 50 said:

OP. what do you think a "law" is? It is certainly not something alwasy true - Ohm's law describes ideal resistors, but not everything is an ideal resistor. Or even a resistor.

Hill said:

Yes, it is a derivation of the Kepler's law, but as you see, it is not derived just from the Newton's second law but requires applying the gravitation law.

Florian Geyer said:

since we have derived it from them, is not it better to call them laws, and to call it a relation? or results?

Dale said:

I have never heard those requirements.

Most laws are just called laws because historically they have been called laws. I guess you could make some rigid definition and exclude Hooke’s law under that definition, but people will still call it Hooke’s law.

Most laws are just called laws because historically they have been called laws.

Hill said:

I don't think so. IMO, they are results, relations, and laws. I don't see why one is better than another.

Florian Geyer said:

Do you mean they are arbitrary names? just something like this?

topsquark said:

Personally, I really don't care what they are called... "laws" works just fine for me. We have ro refer to them by some means, however. In their ranges of validity I see no reason not to call them laws. And not all of the principles that Physics is based on are called laws anyway. Some are "theorems" and others are just names of equations or concepts that we use.

From your statement, I guess you don't feel that we have any Laws in Physics? I mean, not even Newton's 2nd Law always holds. You seem to be reaching for some kind of Axiomatic development of Physics, I take it? So far we don't yet know enough to make a list of the most basic "laws" that govern the Universe, so the list of laws could be constantly changing as we learn new things. Again, I really don't care what they are called, in the end. But we have to call them something to give them some kind of Historical label so we can refer to them by a consistant name for more than a decade or so. Just out of curiosity, what would you prefer us to call them by?

-Dan

So far we don't yet know enough to make a list of the most basic "laws" that govern the Universe, so the list of laws could be constantly changing as we learn new things.

Hill said:

Yes, pretty much. Other names are "equation" (as in "Dirak equation"), "inequality" (as in "Bell's inequality"), "transformation" (as in "Lorentz transformation"), even "diagram" (as in "Feinman diagram").

Florian Geyer said:

Do you mean they are arbitrary names? just something like this?

Florian Geyer said:

Some last things to conclude:
1- I think we need to use some resources, is there a comprehensive dictionary for physics concepts?
2- Do think these names are "arbitrary" even when we are talking about physical principles?

PeroK said:

I suggest it's a waste of time!

Florian Geyer said:

Can you suggest to me a resource for this?

PeroK said:

It might be an interesting exercise for a student of the history of physics to look at the different "laws" and find a plausible reason why some key things are called a "law", others a "principle" and others an "equation".

For everyone else, I suggest it's a waste of time!

"Philosophy of science is about as useful to scientists as ornithology is to birds."

Florian Geyer said:

I am not sure if this also is a waste of time, I look forward to hear from you.

Florian Geyer said:

I want to extend this a little further and ask if you also consider all the study of history or philosophy of physics as a waste of time for those who aspire to be physicists and do research.

PeroK said:

There is nothing stopping you researching it yourself. You could rename Newton's laws to Newton's humble suggestions for the advancement of science. That doesn't change anything. Not to a scientifically-minded person.

The history of science is a fascinating subject. Whether you have time to study it while doing a degree is a different matter.

The philosophy of science to science is a contentious subject. As are Popper's views on science.

Hill said:

For the history and philosophy of science for physicists I'd recommend THE EVOLUTION OF PHYSICS BY ALBERT EINSTEIN & LEOPOLD INFELD.

Florian Geyer said:

I want to extend this a little further and ask if you also consider all the study of history or philosophy of physics as a waste of time for those who aspire to be physicists and do research.