What is the Definition of Physics?

[Crosson]

Physics is the study of things and the way they move; in the sense that all there are are things, and all they do is move.

 

[Ratzinger]

how about this?

physics deals with the very small and with bulk of matter, that means time-reversible/ non-historical processes and purely statiscally processes

 

[pmb_phy]

Why do you guys like to make life difficult?

Physics is the study of nature - Period.

Pete

 

[Gokul43201]

Why do you guys like to make life difficult?

Physics is the study of nature - Period.

Pete

Then what are chemistry and biology ?

I say physics is the science that deals with things that are easy to calculate from first principles.

 

[Pi_314B]

Physics is the study of physical bodies and their motion. Unfortunately there are no physical bodies to study. Funny how that works. Someday in the not to distant future, physics will be scrapped in favor of the study of conceptual entities and their motion.


You heard it here first.

 

[Sir_Deenicus]

I feel physics is man's attempt to stuff infinity in a box.

Or perhaps, an attempt to give as a rigid structure the amourphous super-fluid.

 

[Nusc]

physics is mathematics constrained by objective observable reality.

It takes a whole lot more than mathematical logic to come up with such marvelous ideas.

What is wrong with an online dictionary version of the word physics?

The science of matter and energy and of interactions between the two, grouped in traditional fields such as acoustics, optics, mechanics, thermodynamics, and electromagnetism, as well as in modern extensions including atomic and nuclear physics, cryogenics, solid-state physics, particle physics, and plasma physics. - dictionary.com

Mathematics is a 'useful' tool physicists use in describing physics. But to say physics is mathematics is not quite accurate. He once said, "As far as the laws of mathematics refer to reality, they are not certain, and as far as they are certain, they do not refer to reality." However, the relevance of mathematics in the physical world is somewhat astonishing.

 

[PhysicsEnthusiast]

Study and analysis of nature.

In other words, the science of natural philosophy or the study of natural phenomenon that is the given universe.

 

[photons]

physics is the study of convertion of energy from one form to other

 

[Maxos]

Since our Galileo was the "inventor" of Physics, I think we should follow him:

Physics are a subject characterised by:

1. End: Describing nature i.e. our perceptions, putting order among them and being able to make predictions, understanding the notion of "cause" (Here, Newton takes the lion's share).

2. Method: It has been varying, from analytic (18° cent.) to synthetic (19° cent.), but it is always experimental, without pretending to be immune for our ideas, since the observer must operate choices and distinctions e.g. between "primary and secondary qualities" i.e. what affects the processes studied and what doesn't (One of the most important achievements of Galileo's work, since it implies quantifying)

3. Language: Maths and only Maths, we cannot translate Physics in other languages (such as that used in the Bible, even if Galileo did not know modern Maths, which were started by Descartes)

(For the first two points I would add that Newton called his Physics "Experimental Philosophy", this is not insignificant)

 

[pmb_phy]

Then what are chemistry and biology ?

I say physics is the science that deals with things that are easy to calculate from first principles.

Chemistry is quite often considered, by physicists, as a subset of physics and biology a subset of chemistry. Chemistry is the study of complex structures and how they interact etc. More and more often one utilizes the principles of physics to solve chemistry problems. I suppose I can answer your question better than that if I give it more than an "off the cuff" response. However if you have the Feynman Lectures on physics then the author directly responds to such questions and does so magnificently.

Pete

 

[NeutronStar]

Amorphous Definition

Physics originated as a quantitative study for the purpose of explaining cause and effect in the observable universe. Issac Newton was a bit embarrassed because he could explain the effect of gravity but not the cause.

Albert Einstein was praised when he was able to make more accurate calculations for the effect of gravity plus add a conceptual geometric explanation of the cause in terms of a warped fabric of space-time.

With the discovery of quantum mechanics, however, physics has been derailed from this cause & effect approach and has been reduced to the study of probabilities.

If anyone can ever explain the cause of these probabilities he will immediately be donned the greatest physicist of our time. Until then, physics will remain nothing more than a discipline for calculating the probability of effects without being able to make any statements whatsoever about their cause.

Half of physics has died. Whether it can ever be resurrected in full no one seems to know for sure. Although it does appear that most physicists have accepted that it will most likely never be resurrected. In other words, many of them believe that subatomic events genuinely are random and it is not possible to assign to them a definite cause.

Today physics basically states that the universe is a bunch of effects without causes. That’s where physics stands today. It’s the probabilistic study of causeless effects. Of course, they can still talk about macroscopic causes that change the probabilities, so cause & effect is not entirely absent. It’s just that on the smallest scale of things the precise cause of individual microcosmic events cannot be determined, and it even appears that they are absolutely indeterminable. So at the subatomic scale half of physics falls apart (the explanatory half). All that’s left is the probabilistic half that predict the probability of effects without offering any explanation for their cause.

This is the truest definition of physics at the current time. In short, classical physics breaks down at the subatomic level, but we all knew that right?

So really when asking for a definition for physics we should really ask for the definitions of both classical physics and modern physics because they really are two different beasts. Physics itself has become amorphous over time. In physics we are simply not studying the same world that people like people like Galileo and Newton were studying. We are studying the whole different world of the subatomic scale. It’s a whole new beast. So I don’t believe that there is anyone definition that would satisfy all of physics historically.

 

[Telos]

Wow. Everyone on the first page, and many afterwards, said "the study of..." I can study the world all I want and not be doing physics.

Try "the science of..." and go from there.

 

[NeutronStar]

Wow. Everyone on the first page, and many afterwards, said "the study of..." I can study the world all I want and not be doing physics.

Try "the science of..." and go from there.

I think everyone knows that physics is a science. Therefore if you are studying physics correctly you are using the scientific method.

However, what many people don't seem to realize is that mathematics itself is not a science. Mathematics does not use the scientific method and therefore is not a science. Ironically physicists use mathematics a lot even though mathematics itself is not a science. Moreover, the pure theoretical physicists are moving away from the scientific method even more drastically. String theory is a perfect example of this. Physics that is based solely on mathematics is not science.

 

[Telos]

NeutronStar, I don't want to spar with you on such a futile subject, but a case can be made for studying mathematics scientifically. You have an idea and then you test it (getting rid of the parallel postulate, for instance) and then you see what you get. You analyze the specifics of your "test," what paths you took and others you might have forgone, and then come to a conclusion, (i.e., whole new structured geometries can be made outside of the Euclidean perspective).

And I understand that the fact that physics is a science is immediately obvious, it is still a definitive aspect.

 

[Maxos]

Ne ne ne!

There is a fundamental difference between Maths and Physics:

The mathematician first gives a definition (properly characterizing a set), then he demonstrates theorems, starting from the definitions, thus in Maths you know without uncertainty the set on which the theorem will apply.

The Physicist has an inner tragedy, he is given information and he elaborates a theory which includes what he got and, above all, how much it is distant from it and why (i.e. errors, that's why they are so important), but there is a huge problem: he does not know the set of events on which the laws he works out will apply, that's the thrill of Physics, as Nietzsche said: "Human, too human" (but he could not understand more).

 

[reilly]

Physics : It's what the physicists do !

Why is this in QM ? I'm moving it to GP.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

I quite agree. In fact, I've heard this from many professional physicists -- sure, it's a bit cheeky, but it is undisputably correct. (So is: physics is the most terrifying subject in pantheon of topics offered to school and universiy sudents -- except, perhaps, for organic chemistry, and for me, Number theory)

Physics goes way back prior to Galileo and Newton -- Aristotle wrote about physics. in fact many have written about physics -- physicists from Aristotle to Green, Hawking and Penrose, Oppenheimer, Bohr and Einstein, Wheeler and Wigner and Whitten, and .. They seldom agree, except in broad outline that physics is devoted to understanding how the world and the universe work -- and physicists do a lot of picking and choosing , within that broad mandate, of what they will study.

Just look at a few freshman physics texts, for the most part they all cover the same topics, but past that they an be all over the map. Physicists are a varied bunch, they study a huge number of areas, hundreds I'm sure, if not thousands; some are highly mathematical, some are not, some are fast, some are slow and deliberate in their work, some are philosophical, some not... What they do is physics -- so, in a very real sense, what they do defines physics. (Why not define a subject, often dealing with operational definitions, by means of an operational definition?)

You might as well ask: what is the law, what is medicine...

Regards,
Reilly Atkinson

 

[NeutronStar]

And I understand that the fact that physics is a science is immediately obvious, it is still a definitive aspect.

I certainly agree with you on this point.

NeutronStar, I don't want to spar with you on such a futile subject, but a case can be made for studying mathematics scientifically.

I'm not interested in sparring on this topic either. I also agree with you that a case can be made for studying. My point is that current modern mathematics does not take that approach and therefore formally it cannot be said to be a science.

 

[Maxos]

Physics goes way back prior to Galileo and Newton -- Aristotle wrote about physics.

No.

That is incorrect.

We cannot take the word Physics and then say: "Anyone who used this word or something similar is a Physicist".
Aristotle did not know the notion of Quantifying, and nobody did, before Galileo, he did not know method (Only some "engineer" like Archimedes knew it, at some extent), he did not know modern Mathematics!

Galileo, Descartes and Newton invented Physics, full stop.

 

[Juan R.]

Today, my lecturer asked us to define physics. No one give a very obvious and correct answer to the lecturer. Can anyone here give me the best defination of the meaning of physics?? Thanks

Of course, it is imposible to define a science in a complete form but following definitions may be useful.

Physics is that part of science devoted to study of basic laws of universe. This implies study of basic behavior of spacetime, interactions, and, of course, energy. Physics say directly nothing of the behavior of 5-(1,3-butadiinil)-1,5,8-nonatrien-3-ino.

In fact, physicists even do not know that is

However is a part of universe and follows basic laws, laws of physics. But of course also follows laws of chemistry. It follows both togheter.

Chemistry is, basically, the study of "matter" and their interactions. Chemistry focuses on chemical matter: nucleus (nuclear chemistry), atoms, molecules, solutions, solids (solid chemistry), cosmological matter (cosmochemistry), etc.

There is a great superposition between physics and chemistry. But physicists are generally more interested in general laws, for example, general laws for atoms (in an abstract form) whereas chemists are more interested in concrete forms of matter, e.g. interested in exclusive laws applicable to Fe, H, or C.

Chemists are also interested in general laws (physics laws) because apply to chemical systems of their interest. There are many examples of laws of physics discovered by chemists or with a pure chemical basis. Since conservation of energy was named several times here. Let me to say that law of conservation of energy was discovered by chemists. In his first version (Hess law) was known decades before Mayer own work.

Mayer was a physician (with knowledge of chemistry from chemist Gmelin) who generalized chemical Hess law of chemical reactions in bodies to all the universe (1840). He did atempts to publish on a famous physics journal but failed. In following years, physicists broadly rejected the idea of conservation of energy and attacked to him seriously in a public form. Mayer attempted to suicide but family rescue him. Only in 1850, physicists began to take the law seriously. However, chemists accept law perfectly and was published by first time on 1842 on the journal of chemistry of Liebig and Whöler Annalen der Chemie.


Biology is basically the study of living matter. Recently physicists also are very interested in living matter. There exists superposition between chemistry and biology also.

"Special" sciences: sociology, chemistry, biology, etc. are not reduced to physics. That is, they are not applied physics like many physicists incorrectly believe (physicists who newer study those science in detail; one or two basic courses of chemistry in physics universty is to unknow chemistry). The popular physicists claim that all of chemistry has been reduced to applied physics is completely wrong and is based in a general misunderstanding of ontological nature of our universe.

As a final note, i would to say that popular idea chemistry has been reduced is maintained with few sucess since Newtonian epoque. Already then physicists claimed that all of chemistry was explained with the inverse square law (attraction and repulsion between chemical bodies). Of course they failed and did again in at least 6 new times. Also Diract and his recent quote of all of chemistry has been reduced (Gell-Mann has recognized in the Quark and the Jaguar that Dirac exagerated).

Last Weinberg claim that chemistry has been reduced is again false, even introducing last electroweak interaction for explaining chemical isomerism, chemistry is not applied physics. This is difficult to understand for physicists because proofs and concepts are very involved (for example in complex systems theory one cannot work with simple math of particle physics and one needs of modern analysis of RHS, and new systems of logic), but there is dozens of well-known examples of that in chemical literature.

Physics is also understood like that part of canonical science

www.canonicalscience.com

when complexities are ignored (that is when reductionist method work). For example quantum mechanics arises when canonical processes vanish (e.g. for zero Omega transport coefficient). String equation arises from crane ("canonical brane") equations, etc.

 

[reilly]

History

No.

That is incorrect.

We cannot take the word Physics and then say: "Anyone who used this word or something similar is a Physicist".
Aristotle did not know the notion of Quantifying, and nobody did, before Galileo, he did not know method (Only some "engineer" like Archimedes knew it, at some extent), he did not know modern Mathematics!

Galileo, Descartes and Newton invented Physics, full stop.

>>>>>>>>>>>>>>>>>>>>>>.

First, I'm far from the only one to have made the statement to which you object. See, for example, the excellent series, The World of Physics, Vol 1-3,(J.H.Weaver, ed.) which have articles by many of the worlds leading physicsts and scientists, including Aristotle-- Vol1, p291, excerpts from his Natural Science and Its Principles. Further, you will find in this series quite a few knowledgeable physicists who are hip to Aristotle's role as a physicist in the development of physics. Scientists today owe much to Aristotle. He shed light on many things -- he asked the right questions. That he could not answer them in terms of our modern sensibilities, simply reflects how much we've learned much since his time.

Regards,
Reilly Atkinson

 

[Maxos]

No, it is false.

And I have already explained why.

You haven't considered my objections.

You look like "Simplicio" from Galileo's "Dialogue", you quote and don't say.

 

[memarf1]

The ACTUAL definition

Physics: The Study of things that can be Measured.

Thats how simple it is.

So, for all you guys debating who physicists were and/or are... Anyone that specializes in studying things that can be measured can call themselves a physicist.

 

[Maxos]

Gute Nacht!

What does "measure" mean?

Don't you agree on the fact that measuring is based on the notion of quantifying, that was introduced by Galileo?

Your definition seems to depend on mine.

 

[Juan R.]

Physics: The Study of things that can be Measured.

Thats how simple it is.

So, for all you guys debating who physicists were and/or are... Anyone that specializes in studying things that can be measured can call themselves a physicist.

Of course this is completely wrong.

Even asuming that you mean "measured" in a pure physical sense, you continue to be completely wrong.

In fact, you are mixing physics with physical science.

See for example, the clasificatory scheme for scientific disciplines used by Proceedings of the National Academy of Sciences of the United States of America (the famous PNAS).

Chemistry, Computer sciences, geophysics, mathematics, and of course physics belonging to the physical sciences category. Which is a branch of Natural sciences supercategory.

 

[Maxos]

Yes, but in my opinion, Maths is """""only""""" language.

 

[Juan R.]

Yes, but in my opinion, Maths is """""only""""" language.

Other call to math a proper science. Some mathematicians talk about existence of experiments on math.

 

[Maxos]

Mathematicians should be used to demonstrating instead of "talking".

 

[memarf1]

Of course this is completely wrong.

Even asuming that you mean "measured" in a pure physical sense, you continue to be completely wrong.

In fact, you are mixing physics with physical science.

See for example, the clasificatory scheme for scientific disciplines used by Proceedings of the National Academy of Sciences of the United States of America (the famous PNAS).

Chemistry, Computer sciences, geophysics, mathematics, and of course physics belonging to the physical sciences category. Which is a branch of Natural sciences supercategory.

Its really commendable that you can split hairs and completely miss the point. Have you ever had a physics class? Just so you know, I have had many, and at least in Physics A, B and Modern Physics, as well as Mechanics and Mathematical physics, this exact question is posed. What is the definition of Physics. The teacher in every case, defines physics as the study of things that can be measured.

Now, for the other guy that responded to my answer using galileo. I do not wanat to get into this debate with you, and really do not want to put that much thought into it.

For the math guy, Yes, Math is a science, as I have also had ample philosophy classes and in them some questions have been posed. Among them, what is a science, Every time Physics is the most pure science then biology, and then usually math. Many under the top 3 and then On the bottom is almost always Psychology.

 

[Juan R.]

Its really commendable that you can split hairs and completely miss the point. Have you ever had a physics class? Just so you know, I have had many, and at least in Physics A, B and Modern Physics, as well as Mechanics and Mathematical physics, this exact question is posed. What is the definition of Physics. The teacher in every case, defines physics as the study of things that can be measured.

Are you suggesting that PNAS does not know that is science or physics? Yeah!

I'm sorry, I forget that a "general course" on physics given by your teacher is primary literature (of course only in your insane mind).

It is a standard classsificatory scheme of epistemology and ontology of science that physics belongs to the physical sciences category or sciences of "measuring".

Chemistry, Computer sciences, geophysics, mathematics, and of course physics belonging to the physical sciences category. Which is a branch of Natural sciences supercategory. This the official clasifficatory scheme of PNAS.

I have some time, i will find for you some list of disciplines index (UNESCO, etc.) for you

****************************

But find DW standard index

#
# 100 Philosophy and Psychology
# 200 Religion
# 300 Social Science
# 400 Language
# 500 Natural Science and Mathematics
# 600 Technology (Applied Sciences)
# 700 Arts
# 800 Literature
# 900 Geography and History

---------------

#
# 520 Astronomy
# 530 Physics
# 540 Chemistry
# 550 Earth Sciences
# 560 Paleontology
# 570 Life Sciences
# 580 Botanical Sciences
# 590 Zoological Sciences

Physics is of course not THE science of measuring. Other sciences also measure. In a laboratory of chemistry one is measuring lot of things.

I provide a simple and available (online) reference now.

Acording to Wikipedia the "physical sciences" include:

* Astronomy, the study of the universe beyond the atmosphere of the Earth.
* Chemistry, the science dealing with the composition of substances, their interactions with energy and each other.
* Many of the Earth sciences, including:
o Geography, the broad study of physical, ecological and political variations across the Earth's surface.
o Geology, the study of the planetary structure of Earth and the physical processes which shape it.
o Hydrology, the study of the movement and distribution of water across the Earth's surface.
o Meteorology, the study of weather patterns and other atmospheric phenomena.
* Physics, the quantitative science dealing with matter and energy.

It is really difficult to think that chemistry or geology are not about "measuring".

What do physicist (of A, B, or mathematical physics ) measure the composition of Fe+ on a sample of river water guy?