Talk:Physics

Physics is the study of nature in the broadest sense. Physicists attempt to find the most general rules that govern all of nature. Physics generally breaks down in to the study of the properties of matter, fields, space, time, and energy and how they interact. To describe these phenomena, physicists generally us the most precise language available to them, mathematics.

Or something of that general sort. Perhaps even a mention that physics really is the study of everything in nature (i.e., mention that chemistry is a subset of physics that is governed by the molecular-atomic description of matter, and that biology is a subset of chemistry). Just musing. --BlackGriffen

Ok, I like your definition [...]

I'm not sure all biologist would agree with your reductionist view of biology as a subset of chemistry as a subset of physics, so I don't want to go there. Biologists pose and answer questions that are different from questions of physics. For instance, even if you knew all laws of physics, you still wouldn't know why we have our eyes in the head and not on our asses. --AxelBoldt

[...] I suggest to move Quantum electrodynamics and Statistical Mechanics to central theories. --css

I think something should be included on ancient greek physics. Not all was Aristotle. From the top of my head Archimedes found out interesting things that are still applied.

If I may return to the proposed definition ... I think it's a huge improvement. The current physics and chemistry definitions seem as if they were contrived solely to appear complementary. The distinction between physics and chemistry isn't that one emphasizes energy and the other matter, but rather that chemistry tends to focus on the interactions of chemical elements and compounds, whereas physics has a much broader (but more fundamental) scope ranging from quanta to cosmology. --Scrutchfield

And what do "quanta" and "cosmology" have in common? Energy. To simply categorize physics as "the study of everything" is imperceptive. When modeling sand falling into a pile (or nuts sorting in a jar) a physicist doesn't really care about the identity of the particles at hand, just certain "bulk" properties that relate to its energetics. The chemist tries to understand how the material composition in turn generates those energetic qualities, but then usually isn't capable of formulating the dynamic description of what happens when it's shaken (or spilled). A physicst usually could care less about why niobium is better for a collider than copper, just that it is. And chemists don't just care about chemical elements and compounds, there is a whole field of chemistry dedicated to monitoring interactions of nuclei with nucleons (nuclear chemistry) -- still matter. As a point of culture, chemists tend to focus on the diversity of matter and how that affects interactions with energy-- and physicists focus on the unity of energy, and how that affects matter. Physical chemists very nicely bridge this -- they put quite a bit of energetics while still caring deeply about the identity of that which is being studied. While the duality may sound a bit contrived, there is definitely some truth to the statements, and while not perfect, it's more meaningful than what's there now.

And what do "quanta" and "cosmology" have in common? Momentum. To simply categorize physics as "the study of everything" is imperceptive. When modeling sand falling into a pile (or nuts sorting in a jar) a physicist doesn't really care about the identity of the particles at hand, just certain "bulk" properties that relate to its momenta. (Or replace momentum by mass, spin, or any of the other fundamental properties of objects, and you start to see the problem. There is nothing special about energy.) -- CYD

Momentum is intimately related to energy, anyways -- it's the velocity-integral of energy. Maybe here is something which will help out the distinction (as a simplified) example of the difference of cultures: One thing which astrophysicists study is the color of stars. This has everything to do with the blackbody radiation, which has to do with the temperature of the star, and really has not much to do with the composition of the stars. There are scientists who study the spectral lines which emanate from stars. This property depends very intimately on the matter composition of those stars. These scientists are known as astrochemists (Tak Oka@chicago is an example). Maybe I phrased that first sentence wrongly, but to distill physics to the "study of everything" can be seen as rendering it meaningless or maybe is a sign of arrogance on the part of physicists. The point is this: physicists care deeply about energy and the identity of the matter is usually irrelevant (insert "assume cow is a sphere" joke here). Chemists care deeply about the identity of the matter, and energetics are used only as a tool to descriptively understand what makes matter tick.

Maybe I should say it this way: momentum, spin, or any of the 'fundamental properties of objects' are manifestations of energy (or vice versa). Mass, in our current model, is the only one that you suggested that really isn't (I guess it's "sort of a mystery" as to why gravitational and inertial mass are the same). Energy is a convenient label because it's sort of 'in opposition' to matter. There is something special about matter which makes it diverse and interesting to chemists, an attitude which the canoncial physicist doesn't share (and of course there are people in between like physical chemists). When you say that physics is 'the study of everything', that implies that the biologist is a physicist and a chemist is a physicist, but I doubt either of them would agree, nor would a physicist feel that a biologist or a chemist is one of them. I'm not trying to drive a wedge between the disciplines, because there is still room for people who approach their subject of study in a hybrid way, but there are significant cultural differences which need to be addressed in the definition. I personally find it interesting that "conservation of mass" which frequently gets attributed as a "law of physics", when historically speaking, a chemist (Antoine Lavoisier) came up with it first.

Actually, there are plenty of people who identify themselves as astrophysicists, that spend most of their time poring over spectral lines; that's how you find a star's redshift, among other things. As for signs of arrogance, making a blanket statement that physicists don't care about the identity of the matter they are looking at sure sounds like a great example of it. Incidentally, about two centuries passed after the formulation of mechanics before people started paying attention to the quantity we now call "energy"; I hope you're not trying to imply that Isaac Newton wasn't doing physics. There are countless other examples of physics research in which "energy" plays a minimal or zero role (for instance, cosmologists hardly ever talk about energy, because it is not "globally" well defined in general relativity.) But maybe you think of them as "hybrid" physicists?

As for "momentum, spin, or any of the 'fundamental properties of objects' are manifestations of energy (or vice versa)", the less said the better.

You'll probably reply that what you mean isn't really energy in the technical sense, but something else that makes a thing interesting to a physicist (call it "oompf" or whatever.) But then your thesis degenerates into a kind of hand-wavy philosophizing that may be an interesting topic of discussion of sci.physics, but doesn't belong on Wikipedia. -- CYD

Fair enough. However, there is something distinctly different about the cultures of chemistry and physics. When physicists deal with matter, they tend to deal with its bulk properties (elasticity, conductance, granularity, charge density, ionization potential, et cetera). You describe astrophysicists poring over spectral lines -- but, in your own words, the emphasis is on finding the redshift. There's nothing arrogant about noting the differences between cultures, there's no judgement involved there. Chemists use physicist's tools and physicists use chemist's tools. Nowhere am I implying that Newton wasn't doing physics -- in fact, he is the quintessential physicist -- Newton described the motion of planets and the effects of gravity in the most general and bulk of terms -- to him it didn't matter if it was a cow or a cannonball.

Maybe the problem is this: At one point, physics was "the study of everything" (and before that it was actually what we would call "medicine") -- this definition is rather outdated and imprecise. It needs to be revised.

All life is physiology, all physiology is biology, all biology is chemistry, all chemistry is physics, and all physics is math..... Gelsamel 03:17, 1 Dec 2004 (UTC)

Hmm, I see that the history section in Physics has been copied pretty much wholesale into that article. That's fine, but I think we should also keep the section in Physics, because in addition to giving a history it also describes the subtopics of physics which I think is important for the article. As for History of Physics, if it is supposed to justify its own article, more historical material should be added to distinguish it, e.g. precise dates and a greater level of detail. Then at the end of Physics we add a line like "for a more detailed history of physics, see History of Physics" (currently pointless, as there isn't more detail yet.) --CYD

How about renaming "proposed theories" to, say, "current research topics"? Then we can include current experimental efforts as well. I don't think a new section should be added to the end of the article just for this, putting it with the other lists should be fine. -- CYD

Then we'd have to get rid of Grand Unified Theory and Theory of Everything. There's no correspondence between the two categories so it wouldn't be a renaming but a replacing.

I'm not sure about that. GUTs and TOEs are part of current research efforts, aren't they? Alternatively, we could add descriptions of current research efforts to the end of the article, after the History of Physics section (actual descriptions, not just a list bullet points.) Or, we could have another article, say Current research topics in physics and link to it. --CYD

What does TOE mean? Principally, it means M-theory. F-theory is related to M. Loop quantum gravity was never meant to be and never will be a TOE (and I agree with the opinion that it's not even scientific). Friedman(?) is looking at something that may or may not even be interesting. So basically TOE = M.

I got the impression that research in GUTs is dead. Especially after '95 or so when everyone joined M-theory, or should I say, when the strings community absorbed the supergravity community. I'm sure that people are doing various calculations with GUTs and hoping for evidence one way or another but nobody seems to look for, nor expects, any conceptual breakthroughs.

We can have anything you like, I'm not picky. But when the topic of hot research was introduced I came up with a big blank, which led me to think "hmmm, good question!" It took me quite a bit of brain raking to come up with 'search for SUSY' and 'search for Higgs boson'. I'd add dark matter (maybe!), gravitational waves and gamma ray bursts to the list, but I really don't know that much. -- ark

Explaning high Tc superconductivity; explaining sonoluminescence; search for WIMPs; search for axions; explaining neutrino oscillations (and thus the solar neutrino problem); explaining the muon g-2 factor; explaining energetic cosmic rays; the large extra dimensions hypothesis; etc. Baez has a longer list at http://math.ucr.edu/home/baez/physics/General/open_questions.html -- CYD

Large extra dimensions hypothesis? I've never heard of that! What is it?

An alternative to SUSY that's being seriously considered. You can find plenty of related sites with a Google search, but the original paper is here: http://arxiv.org/abs/hep-ph/9803315 -- CYD

How about "Proposed theories and research directions"? And then we add Supersymmetry, Higgs boson etc. AxelBoldt, Monday, June 3, 2002

I just replaced the translation of "phusis" as "matter" back to "nature", given the following two sites: http://www.studylight.org/lex/grk/view.cgi?number=5449 and http://www.dictionary.com/search?q=physics . AxelBoldt, Wednesday, May 29, 2002

When a current is run through a wire, this current creates a magnetic field. (Please note that current is flows from the positive to the negative, while electrons actually flow from the negative to the positive. Although this makes current imaginary and backwards, it is still used here.) If this current carrying wire is placed in another magnetic field, the two fields will interact, and there will be a force on the wire. This force is perpendicular both to the flow of the current and the direction of the other magnetic field.

In order to make this relationship between current direction, magnetic field direction, and force on current easier to understand, our high school physics teacher taught us a hand symbol affectionately known as the physics gang sign. First of all, this sign is always done with the RIGHT HAND. If done with the left, the directions will be incorrect. To make the gang sign:

1. Extend the right hand and stick up the thumb. 2. Point the index finger straight ahead, as if pointing the kid's version of a gun at someone. 3. Extend the middle finger to the left, so it is perpendicular to the index finger.

The result is that each finger is perpendicular to the other two. If this is the case, you have made the sign correctly. If not, repeat steps 1-3. Middle finger represents Magnetic Field, the Index finger represents current (represented by I.), and the thumb therefore represents the force. Armed with this knowledge, you will be equipped to answer questions about electricity and magnetism interaction, and when you see your fellow physics students in the halls, you can flash the physics gang sign confident in the knowledge that you are the only ones who know how to use it.

Physics Exercises

I just created a new Wikibook here: http://wikibooks.org/wiki/Physics:_Exercises_with_Solutions. If anybody is good at or enjoys making up physics problems in any branch that would be a big help.

What's there seems good. Perhaps the solutions could be more thorough?

Brianjd 05:56, 2004 Jun 16 (UTC)

Theories

There are two theories on the physics page that are not on the theoretical physics page: Time Cube and Variable Speed of Light. I have not read much on physics so I dunno how accurate the lists are in general. But they seem to be inconsistent enough to warrant changing.

Brianjd 05:59, 2004 Jun 16 (UTC)

Another category is experimental physics

Well, as an experimental physicist, I protest :-) The page mentiones 2 categories, theoretical and applied phyisics. I think they are apples and pears. The correct division is theoretical vs experimental, and fundamental vs applied. There are 4 combinations, so 4 categories. I am an experimental fundamentalist :-) (particle physics). I think I'll correct the page soon. Pál 01:04, 10 Jul 2004 (UTC)

Thank you. I was wary about my division and nomenclature. Rmalloy 16:55, 11 Jul 2004 (UTC)

Proposed better definition for physics

As it appears "the study of energy and its interactions with matter" (symmetric to the definition of chemistry -- "the study of matter and its interactions with energy"). This is, generally, speaking, what physicists do:

Celestial Mechanics (doesn't matter what planets and moons are made of, it still works). Quantum physics (doesn't matter what the particle is, it obeys these rules) Thermodynamics Fluid Dynamics Electrodynamics

The only exception is possibly Nuclear Physics, which concerns itself deeply with the identity of the nucleons involved (but then some people would consider that to be Nuclear Chemistry) and the categorization of Elementary particles...

Can someone remove the rambling portion about how Physicists think they are fundamental. I don't think that it really adds anything, or, at least, maybe, be moved to a section on the "culture" of physics.

Went ahead and streamlined this page.

There were some really rambling sections, which had very little to do with physics and more to do with rivalries between physicists and other scientists, or vague philosophical supposition of how physics is more important than the other sciences.

I removed those and summed it up in a 'hinting' fashion in the introductory paragaph. I hope these aggressive changes aren't too unpalatable.

I think that you got rid of too much important information. Providing different points of view is extremely important, and there's nothing wrong with too much information, as long as it's right. Perhaps a vote on keeping it the way it is now or reverting it? --SonicAD 13:26, 17 Aug 2004 (UTC)

Not true. Too much information can drown the reader in information, bore them, or just generally turn them away from the page. This is the "Physics" page, it should be very general, and in particular, it needs to be well organized. Look at how the Chemistry and Biology pages look (if you want, before I made some minor changes to them) and check out the history of the Physics page, and see how much of a sorry state it was in, in comparison. Instead of rambling on about it, provide links to other wiki pages which present alternative viewpoints, as well as 'generally accepted' viewpoints.

It's true that streamlining was necessary. But you deleted a whole bunch of useful information. Quoting from the page on Wikipedia's editing policy:

"With large proposed deletions or replacements, it may be best to suggest changes in a discussion, lest the original author is discouraged from posting again. One person's improvement is another's desecration, and nobody likes to see their work destroyed without warning."

The best idea would probably have been to have discussed the changes here first before making them. Doesn't quite matter right now, though. (Just remember that for the future) Best option right now, of course, is to allow for discussion. I, myself, do think that, especially in the first section, streamlining was needed, but not a few whole paragraphs worth of deletion --SonicAD 23:27, 17 Aug 2004 (UTC)

Fair enough. As a compromise measure i will replace some of the paragraphs and stick them elsewhere in the article. At the very least, they didn't belong at the top.

Calculus based VS. Algebra-based Physics

What exactly is the difference between calculus-based and algebra-based physics? Are they two different ways of approaching the same field, or is there a deeper meaning? I'm interested in taking an undergraduate degree in physics; therefore, before I take classes I'd like to familiarize myself with it on a general level. Thank you. --Cormac Canales 22:09, 26 Sep 2004 (UTC)

Well, IMO, the difference is that you can do derivations from more fundamental physical principles and solve more complex problems with knowledge from Calculus-based Physics courses, whereas with Algebra-based physics it's going to be more like "Here's the equation you use to get the solution." In any case, Algebra-based Physics courses will not go far beyond classical mechanics, very simple thermodynamics problems, a little special relativity, very simple electromagnetism, and some modern physics (probably a little more I'm missing...) There is absolutely no fundamental distinction aside from the fact that any treatment of Physics without Calculus will be extremely elementary. It's the difference between Little League and Major League.--Conwiktion 06:38, 2 Oct 2004 (UTC)

I've only taken a physics course where calculus was not applied (basic high school level physics), but I knew a little calculus at the time and it made some things much simpler. Now that I know calculus and have done some more physics in my spare time it seems frankly silly to approach physics without calculus. Using calculus makes the physics seem more unified, and less - like Conwiktion points out - like a bunch of equations. --Tothebarricades 09:07, Jun 16, 2005 (UTC)

Ok... Time Cube link

Ok, I just wanted to call people's attentions to the fact that someone added link to the Time Cube article. Given that it is not a purely "physical" theory (in that it is not in the tradition of physics, and is based in a great part on pure metaphysics), I personally think that it should be removed. However, I would be greatly interested in what others thought on this (that's primarily the reason why I'm saying this ;) ).--Conwiktion 02:31, 6 Oct 2004 (UTC)

I vote to remove it, but I can't claim this is an unbiased opinion; I think the Time Cube theory was written by a Kook. --Mtruch 22:36, 10 Oct 2004 (UTC)

Theories, Truth, Proof, and the Scientific Method

I don't like the phrase "Experimental physicists perform experiments designed to be able to decide which of the proposed theories is true." as it implies that theories can be proven correct. Experiments only prove a theory false; positive results merely add support or strength to a theory, but never proof. Eventually a theory may become so well supported people think of it as proven, but that is dogma, not real proof. Mtruch 22:17, 10 Oct 2004 (UTC)

I agree with you. Would it be better to say something along the lines "Experimental physicists perform experiments designed to find evidence for or against a theoretical model" or "Experimental physicists perform experiments designed to test the predictions of a theoretical model"? Neither of these statements really have the same meaning of your correction, but they at least are not misleading like the article is currently, and they are easy to grasp by a lay audience. We don't want to give people like a 5th grader doing a school project the impression that (all) experimentalists are out to squash the careers of theorists by trying deliberately to disprove their theories :P--Conwiktion 04:49, 12 Oct 2004 (UTC)

This is a ridiculously idealized picture of what experimentalists do. Experimentalists often work to find out how something works, in the absence of any theory. In fact it's often been the case that theory follows experiment! -- CYD

Right, and the text in the article reflects this as well- I typed in a couple sentences that state that new theories are most often born of experimental results that contradict current theory. Should we re-arrange the text to make it clearer? I think that the idea that new theories are motivated by experimental results is implied in the (still highly idealized) idea that experimentalists perform experiments to test the predictions of a theory. If the theory does not have prediction power, then another theory must take its place. Aside from which, this article should be directed towards a lay audience- a proffesional or quasi-proffesional audience should have a clear enough picture of the roles that theorists and experimentalists play anyways.

(Also, it appears that a pro-experimentalist has editted this section of the article, making it perilously close to being NPOV, in my opinion. Shall we correct this, or is the text as it stands OK?)--Conwiktion 14:25, 12 Oct 2004 (UTC)

Both points are important. As an experimentalist, I know that often theory follows experiment, and many experiments probe where no theories exist. The interaction between theorist and experimentalist is complex, with either side playing 'leader' whenever they see fit to head in that direction. That does not contradict with the fact that as a science, physics' theories cannot be proven. Too many lay people I talk to talk about proven physics theories, or dismiss theories because they heard it was not (or has not yet) been proven. Theories get stronger with more supporting evidence (especially if they made a new prediction that experiments later support), or weaker (or fail) when experiments provide contradicting evidence, but never proven.

You can argue that I'm being pedantic, but the power of physics (actually, of the scientific method) comes from the inability to prove something; that a theory is only as good as the scientific experiments that support it, and long after people believe it's true, it can be squashed by a single experiment. (Of course, many theories that have been found false are still very accurate in certain regiemes, and therefore still have their place, i.e. classical mechanics). Mtruch 15:20, 12 Oct 2004 (UTC)

Yes, you are being pedantic. There is a distinction between Scientific Proof and Mathematical Proof. Scientific proof involves the concept of Occam's Razor. Sure you can really never prove anything right or wrong 100%, in science. You always have a model that is "good enough, for now" or "as good as we can seem to get it". The notion of "proof" does it imply that it must be 100% -- otherwise we would never need the phrase "proving beyond the shadow of a doubt".

Why aren't women good at physics?

You can call it stereotyping, you can call it sexist, you can call it whatever but physics history has shown that men has alway been better than women at this subject due to the extreme amount of dorkism men possess. Harvard/MIT has roughly 100 students annually graduating with a degree in physics and about less than 10 of those are women. It simply can't be coincidence. I continue to ask why in this present day and age, where both sexes are essentially equal, women can't do physics? Has there been any scientific research on this topic? Any links would be appreciated.

You answer yourself there. It is stereotyping, sexism and many more things. I direct you to read a bit of history of the human race. You will find that women were, are and most likely will be for sometime discriminated in education and in all other areas of society. Fact. --LexCorp 20:21, 19 Feb 2005 (UTC)

Incidentally, there's an article in a recent Scientific American issue about just this topic, and it's very interesting. It's a very touchy issue, but if we can accept that there are some fundamental differences in the brains of males and females, as research suggests, certain things can follow. Here is the article. (http://www.sciam.com/article.cfm?articleID=000363E3-1806-1264-980683414B7F0000) --Tothebarricades 09:01, Jun 16, 2005 (UTC)

How much force could an egg withstand?

Does anyone know how much force (in Newtons) a raw egg could withstand? Green789 15:32, 19 Feb 2005 (UTC)

At least 600N. Lecture Demonstration 14:28, 9 Mar 2005 (UTC)

This would definately depend on how the force is applied. Squashing an egg vertically and horizontally is bound to be different. Also you could wind a string around the egg and increase the tension. If you really want to know you'll have to do some experiments.MarSch 14:55, 18 Mar 2005 (UTC)

Energy conservation

is a consequence of time translation symmetry. I believe there are some models of GR that don't have this. Thus energy can simply disappear.MarSch 14:55, 18 Mar 2005 (UTC)

Learning Physics

I think there should be something on the main Physics page about Learning Physics, both as advice to the reader and to remind us all to attempt pedagogical coherence. Here's a draft:

We "learn" a topic in Physics many times, in many ways. There are many aspects of Mechanics that our bodies understand perfectly, long before we learn names for things like angular momentum; for these, it is just a matter of learning a language -- a set of names for things and conventions for discussing their relationships. Electricity and Magnetism are quite different; we have almost no instinctive understanding of the subject and have to learn the words and their referents at the same time. This is often the "watershed" at which those comfortable with abstractions go on in Physics and those who rely on physical Common Sense balk at the strangeness of Physics.

In primary and secondary school, most people get the impression that Physics is an exercise in algebra: all you need to do is pick the right formula, plug the right numbers in and "turn the crank". These unlucky souls are usually shocked when they meet up with University Physics for the first time and discover that the formulas are merely "shorthand" for something they are meant to understand.

The aspiring Physicist learns and re-learns each topic in Physics over and over, each time discovering the shallowness and inadequacy of her previous understanding. This is a delightful and rewarding experience that even those who do not aspire to become Physicists can enjoy.

To accomodate this experience, it is important to identify the "level" at which any particular treatment is presented. There is no point in introducing Electricity and Magnetism using vector calculus for readers who have not yet studied calculus of any kind, even though it is a beautiful and elegant way to describe the subject. And there is no point in talking about "F = m a" to someone who has just completed a course in Lagrangian Mechanics. The reader needs to have a way of estimating whether the material is at his level, or mistaken impressions will result.

OK, this is a little rambly; your turn. -- Jess

I think as an encyclopedia Electricity and Magnetism should be very general like "there exists something called charge and like charges attract etc..", but should then refer the reader to the different theories about electromagnetism, like "special relativity explains the necessity of magnetism in the presence of electrism(?)..". I will now take a look and see whether this is the caseMarSch 16:39, 25 Mar 2005 (UTC)

Orgones and Times cubes

Dear all,

As my first edit (I'm not even registered yet) I took out some references to "orgone theory" and "timecube theory" in the Fringe Theories section. Since there are many physicists, such as myself, contributing to this page (and I have little time) I won't even try to explain why these theories do not qualify as science. Just wanted to warn everyone that these links have been re-added (they are in the main article right now) by IP 136.186.1.117, with no reason stated.

I will not revert the changes, since I consider myself an outsider. But someone with a little more time should take care of this.

Cheers

(Just took 5 minutes more checking the other contributions of IP 136.186.1.117. Seems that the Greenwich Mean Time article was also heavily edited... with timecube theory.)

14.55, 26th of April 2005 (GMT)

Very good obvservation. These are not physics theories at all. They aren't even scientific. Time cube is even up for deletion. Will remove these links. -MarSch 13:15, 27 Apr 2005 (UTC)

History

I thought the history section was a mess. A lot of physicists were never mentioned by their full name, some were mentioned twice for the same reason (Schwinger, Tomonoga and Feynman) and there was no clear order to the discussion of the 20th century. I've tried to spend a few minutes improving it. One thing I find frustrating about it is that there is a lot of emphasis given to theoretical particle physics at the expense of the experimental side and other branches of physics. It would be great if someone could make it a little more balanced. --Joke137 16:28, 7 May 2005 (UTC)

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