physics doesn't say...

[sanctus]

Today in my course about dynamical system the prof said something quite interesting:
"physics doesn't justify its laws, it verfies the consequences".
What do you think about this?

[Tormod]

I think it is an interesting statement. It is at least partially true - the laws of physics are not made but deducted. They are reached by observation and prediction using the scientific method. When the laws don't fit the methods then either our physics are wrong or our understanding of nature is wrong (although these two are closely related...).

But it is also partially false. Physics has to justify it's laws. If it only verifies the consequences then the physicist has no responsibility to verify that the laws are understood correctly. As observed in our discussions with James about his new non-mechanistic physics, there are many ways to understand nature and one way to express them is by formulating laws of physics. So when phycisists realize that something is not right they need to find out why (is it their data, their method, their bias - or the law?) and then be able to prove that.

Interesting topic, Sanctus.

[Qfwfq]

"physics doesn't justify its laws, it verfies the consequences"

I find this a somewhat limited pov, although many a physicist entertains it, simply because they carry out the role of verification. Without attempts to justify laws, we would have discovered a lot less of them. Examples plentiful.

[Biochemist]

Originally Posted by sanctus

"physics doesn't justify its laws, it verfies the consequences".

I think this is semantically correct. I do not disagree with the points offered by Tormod or Q, but the use of "justify" in normal english is only suggesting that the "laws" themselves are only as good as their validity, as verified by predictablility of consequences. That is, if a law does not accurately predict a consequence, we would modify or jettison the law.

Physicists have no prolem throwing out "laws" that don't fit observed results.

[Qfwfq]

Originally Posted by Biochemist

the use of "justify" in normal english is only suggesting that the "laws" themselves are only as good as their validity, as verified by predictablility of consequences

It can mean a host of things. Justification of the laws has always been an essential part of the process. Without it, just for example, nobody would have worried about that tiny little 'c' in Maxwell's equations. M & M, Lorentz and many others would have found better things to do and Einstein wouldn't have published "Zur Elektrodynamik Bewegter Körper". Without it, natural philosophers would be mere tax inspectors.

The professor of my advanced Field Theory course, when drawing a conclusion by reasoning that wasn't mere calculus, would say: "and this, if Justice exists, must be equal to..."

[Fishteacher73]

This is along the lines of a discussion I had that involved laws of nature vs the laws of science. The discussion was about whether the laws of science are the laws if nature or if the laws of science are aproximations of the laws of nature. We really did not get anywhere, but it was interesting. Both camps have some valid points.

[UncleAl]

Physics is a collection of mathematical models not falsified by observation. It only predicts the "how." It is spectacularly good at it. Physics does not speculate about the "why." That is religions' balliwick - and a right proper mess of it religions make.

Any axiomatic system must be based upon unjustifiable postulates and is therefore fallable. Many models are facile heuristics rather than exact. Newton was wrong for tacitly approximating c=infinity and h=zero, but he's usually good enough. No predictive theory we can imagine to date allows c=c, h=h, and G=G simultaneously.

Completion of physics is allocated to the interested reader.

[paultrr]

Originally Posted by Biochemist

I think this is semantically correct. I do not disagree with the points offered by Tormod or Q, but the use of "justify" in normal english is only suggesting that the "laws" themselves are only as good as their validity, as verified by predictablility of consequences. That is, if a law does not accurately predict a consequence, we would modify or jettison the law.

Physicists have no prolem throwing out "laws" that don't fit observed results.

Actually, outside of say the laws of thermodynamics and a few others which where all examples of being well varified by observation and experiments almost all the rest is what we term theory. SR & GR are both considered theories. They are well tested theories to say the least. But with theory there always remains the chance that further investigation or experiments might expose some problem that requires a rework or something more drastic. Theory, when it comes to physics, requires in a sence the test of time to see if that theory is fully correct or not. Nature in that sence of the word remains the ultimate authority. One area we are testing the bounds of our constructs at the present is by more exact obervations and testings on the constancy of C, by searching for that quark soup that was in the News, etc. Our constructs, the theories, are generally things that can and do evolve with time. Laws of nature are things generally so tested out that they are considered laws after a point.

Evolution is itself a theory that has evolved since the time of Darwin. Its a more general theory in that it covers the scope of a lot of fields far more than pure physics theories tend to. Yes, it concerns Biology. But chemistry, physics, etc all enter in with evolution also. QM out of physics has bearing on how the universe first started, what elements where present, etc. What chemicals can arrange themselves into certain groups has bearing on say the DNA of living organisms. Also the type of atmosphere the early earth had has effects on the exact way life evolved.

[paultrr]

Originally Posted by UncleAl

Physics is a collection of mathematical models not falsified by observation. It only predicts the "how." It is spectacularly good at it. Physics does not speculate about the "why." That is religions' balliwick - and a right proper mess of it religions make.

Any axiomatic system must be based upon unjustifiable postulates and is therefore fallable. Many models are facile heuristics rather than exact. Newton was wrong for tacitly approximating c=infinity and h=zero, but he's usually good enough. No predictive theory we can imagine to date allows c=c, h=h, and G=G simultaneously.

Completion of physics is allocated to the interested reader.

Physics does try at certain levels to answer the why question with trying to determine what the real origin of the BB and the Universe really was. But here we follow the path of theory also. We rely upon observations and rather accepted hows to try and figure out the why. Religion relies upon faith at its core and little other to come to its conclusions.

[Qfwfq]

Originally Posted by UncleAl

Physics is a collection of mathematical models not falsified by observation.

This is what phenomenology is about. It is part of the process. Physics is more than just mathematical models, despite some tendency in modern times to limit it to such.

Originally Posted by UncleAl

Physics does not speculate about the "why." That is religions' balliwick - and a right proper mess of it religions make.

Speculating about the 'why' is not religion's but philosophy's balliwick, including natural philosophy.

If it hadn't been for the asking about many whys, there wouldn't have been so much progress. Who would have ever worked out and proposed the quark-lepton model if nobody had asked about the why of the subatomic zoo? Who would have investigated atomic structure at all without asking the whys about the different elements, of radioactivity and of electric fluid? If people had been content verifying the consequences, for instance, of beta radiation Fermi would never have published "Versuch einer Theorie der Beta-Strahlung" and, without asking the whys about the different forces, why would Einstein have contrived GR and why would Goldstone, Higgs and Weinberg have ever worked out the standard model?

Somebody didn't just find them in a drawer of the Burana monastery and say "Hey, boys, try verifying these laws!".

Originally Posted by UncleAl

Any axiomatic system must be based upon unjustifiable postulates and is therefore fallable.

Physics sometimes makes use of axiomatic systems but this isn't the brunt at all.

Originally Posted by UncleAl

Many models are facile heuristics rather than exact. Newton was wrong for tacitly approximating c=infinity and h=zero, but he's usually good enough. No predictive theory we can imagine to date allows c=c, h=h, and G=G simultaneously.

What's that got to do with Tibetan penguins?