Talk:Force/Archive 5

Defining Force

Two statements:

Definition In physics, force is what causes a mass to accelerate experienced as a push or a pull.

Nuclear forces the weak nuclear force is responsible for the decay of certain nucleons into leptons and other types of hadrons.

I know that these are conventionally unexceptional statements but they have always bothered me both with their apparent mutual inconsistency (accelerate - no - decay) and with the fact that nothing as such is being defined (what IS a force?).

George Berkeley, Newton's contemporary, admirer and critic complained that in making forces central to his analysis of the regularities of motion, Newton had merely replaced one mystery, the will of the spirit, with a multitude of mysteries. (Sorry, can't locate the reference.)

But consider this:

Electromagnetic forces With the development of quantum field theory and general relativity, it was realized that "force" is a redundant concept arising from conservation of momentum (4-momentum in relativity and momentum of virtual particles in Quantum Electrodynamics). The conservation of momentum, from Noether's theorem, can be directly derived from the symmetry of space and so is usually considered more fundamental than the concept of a force. Thus the currently known fundamental forces are considered more accurately to be "fundamental interactions".

Fundamental forces All the forces in the Universe are all based on four fundamental forces.

Am I correct in concluding from these that

• acceleration is caused by the net absorption or emission of gauge bosons bringing in or carrying away momentum from the mass

• forces are mathematical concepts intended solely to assist in analysing the trajectories of accelerated masses

• radioactive decay is, at present levels of knowledge, an uncaused random event in the course of which momentum is redistributed between the decay products through the absorption and emission of gauge bosons

• the mathematical concept which best assists in analysing the trajectories of products of the decay of certain nucleons into leptons and other types of hadrons is termed the weak nuclear force.

If this is correct, I'm sure that the light would click on for a great many people if something to this effect was added, perhaps at the end of the article but referenced as a caveat right at the start. GWHodgson212.67.102.183 (talk) 16:50, 24 March 2008 (UTC)

Thanks for your comments, GWHodgson! You are basically correct in your explanation of the situation. I'll add a bit more to see if that helps matters: The weak nuclear force is, in point of fact, what allows leptons and hadrons to interact. It's both a force of repulsion and attraction just like the electromagnetic force or the color force. Most of the time we see weak nuclear force acting repulsively (which is what radioactive decay is associated with) because it is much more likely to get a single particle to split than it is to get two weakly interacting particles to combine. However, in very high density environments such as those found during the formation of neutron stars, the attractive nature of the weak-nuclear force can cause some amazing effects. So let's workshop here how we can best get this subject across to the lay reader. ScienceApologist (talk) 18:33, 24 March 2008 (UTC)

Okay, so I thought a lot about this issue and thought that having a description of Feynman diagrams may help elucidate the matter. Please tell me what you think of the new section. ScienceApologist (talk) 15:07, 25 March 2008 (UTC)

Yes, I do find the inclusion of the section on Feynman diagrams helpful. The following might complete the job.

I suggest the the first sentence of the article be reworded as:

In physics, force is the perceptible cause of the acceleration of a mass (change in the rate or direction of its motion) and is experienced as a push or a pull.

and, to tie in the concepts, replace the first mention of momentum in the second paragraph with "momentum (quantity of motion)".

I'm speaking as a layman so the use of the imprecise term "motion" might be objectionable in a technical article, but I find it aids understanding. The suggested qualifications remind the unwary that accelerate doesn't just mean go faster and sets up the concept that momentum is something that can be carried.

The second part of the third paragraph usefully puts force into context but I suggest it be reworded slightly as follows:

Following the development of quantum mechanics, it is now understood that momentum is a fundamental property of particles and that, according to the standard model of particle physics, changes in momentum are the consequence of the net emission or absorption by particles of momentum-carrying gauge bosons. Effects which are at the macro level experienced as a "force" are the consequence of the aggregate effect of these boson-mediated fundamental interactions. In modern physics, only four fundamental interactions are known; in order of decreasing strength, they are: strong, electromagnetic, weak, and gravitational.[1] High-energy particle physics observations in 1970s and 1980s confirmed that the weak and electromagnetic forces are expressions of a unified electroweak interaction. No gauge boson has yet been demonstrated for mediating the gravitational interaction and what is perceived as the "force" of gravity is more accurately attributable to the the effect of distortions by massive bodies of the curvature of spacetime as explicated in Einstein's Theory of General Relativity.

This wording expresses what I would like to be the case, ie that forces are artefacts of perception (which would have resolved Bishop Berkeley's complaint - he thought everything was an artefact of perception). I think this is a valid inference from reading the article in full but, if this is not the accepted view (and the articles on Force Carriers and Gauge Boson both seem to view forces as things which can be carried), then I would have to accept that an encyclopedia entry shouldn't stray too far into the realms of speculation.GWHodgsonSkeptical-H (talk) 11:06, 26 March 2008 (UTC)

Each in turn

1. Suggested: In physics, force is the perceptible cause of the acceleration of a mass (change in the rate or direction of its motion) and is experienced as a push or a pull. instead of In physics, force is what causes a mass to accelerate experienced as a push or a pull.

   The addition of "and" is good. However, a force need not be "perceived" to exist. The definition of "acceleration" is indeed confusing to the lay person, but I think that the wikilink on acceleration covers it. We need to be careful to not go overboard in description in the lead.

2. Provide definition: "momentum (quantity of motion)"

   Hmm, this isn't exactly an accurate definition of momentum since momentum is, in fact, both mass and motion. Again, the wikilink I think should suffice, but maybe we can reword things without providing definitions to make it clearer. I want this to be intelligible, but I'm afraid that including these points might be confusing for many and an annoyance to even more.

3. Following the development of quantum mechanics, it is now understood that momentum is a fundamental property of particles and that, according to the standard model of particle physics, changes in momentum are the consequence of the net emission or absorption by particles of momentum-carrying gauge bosons. Effects which are at the macro level experienced as a "force" are the consequence of the aggregate effect of these boson-mediated fundamental interactions. In modern physics, only four fundamental interactions are known; in order of decreasing strength, they are: strong, electromagnetic, weak, and gravitational.[1] High-energy particle physics observations in 1970s and 1980s confirmed that the weak and electromagnetic forces are expressions of a unified electroweak interaction. No gauge boson has yet been demonstrated for mediating the gravitational interaction and what is perceived as the "force" of gravity is more accurately attributable to the the effect of distortions by massive bodies of the curvature of spacetime as explicated in Einstein's Theory of General Relativity.

   There is a slight issue here with the sentence: "Effects which are at the macro level experienced as a "force" are the consequence of the aggregate effect of these boson-mediated fundamental interactions." This sentence misses the fact that forces also exist on the micro level. A single boson-mediated fundamental interaction often has a "force" associated with it. For example, an electron accelerates because it emits a photon: this is due to the electromagnetic force acting on the electron. One micro-interaction: still a force since a mass accelerated. Also, the last sentence is debatable: the graviton exists if gravitational waves exist, and the Hulse-Taylor pulsar is strong evidence that gravitational waves exist. Let's just keep the regimes completely separate for the lead, but maybe we can explore this a bit more in our section on gravity. (A link to gravitons is probably appropriate, no?)

I will implement the wording I think is good, but let's keep discussing the problematic wording.

ScienceApologist (talk) 20:49, 26 March 2008 (UTC)

Response to each

1a. A force need not be "perceived" to exist.

Ahh - exist! Yes, I was hoping to sneak in the notion that forces don’t exist as real entities, but working through your point on photon emission (3a. below) has disabused me of that (for the time being - but I see the new reference to string theory in the current version of the article may, in time, vindicate me).

1b. the wikilink on acceleration covers it.

I feel that encyclopedia articles, as opposed to dictionary definitions, are intended for the benefit of the non-expert, so some laxity in terminological rigour, some redundancy in definion, can be tolerated so long as the essence of the subject is conveyed clearly, accurately and usefully. How much, of course, is a matter for editorial judgement. However, excessive rigour can be counter-productive because the student simply is not going to follow up every link and reference to tease out the subtleties and nuances of the terms used (in my case, not least, because on my antiquated setup it takes my browser an age to download and assemble each Wikipedia page).

2. momentum (quantity of motion)

The phrase is there in the momentum article, albeit as an archaic term used before the concept of momentum had been fully worked out. The idea of quantity, as opposed to magnitude, took care of the mass dimension.

I was trying to link in the concepts of force -> acceleration -> momentum -> boson using motion as the hook, but why not do it directly and

• insert at the start of para 2: "Acceleration is simply a change in momentum."
• Alternatively, might it be preferable to ditch acceleration in the definition in favour of change of momentum (pace all the F=ma elementary science teachers out there)?

3a. an electron accelerates because it emits a photon: this is due to the electromagnetic force acting on the electron.

There is another way to tackle this: does the electron accelerate because it emits a photon, in which case, what causes it to emit, or does it emit the photon because it accelerates, if so, why does it accelerate? And do the same considerations apply in the case of absorption?

If we have a). force -> electron -> emission/absorption -> acceleration, then it is the emission or absorption which causes the acceleration while the force provokes the emission or "sets up" the electron to be responsive to absorption. But if it is b). force -> electron -> acceleration -> emission/absorption, then it is force that causes the electron to accelerate and emission or absorption is a book-keeping adjustment, a balancing entry, by the system to conserve momentum.

With a)., a mere capacity to accelerate in response to absorption doesn’t convey the sense of active agency that we expect from force and it would seem that, for acceleration by absorption, the agency of force is redundant, in which case we have instances of acceleration without force. With b)., force is a necessary cause for all cases of acceleration, but then we must ask - who’s keeping the books?

• Assuming b). is rejected, is it possible to include a quantum description of acceleration by gauge boson absorption such that the active agency of a force is required?

3b. the last sentence is debatable: the graviton exists if gravitational waves exist

I wasn’t questioning the possibility of a quantum explanation for gravity, I was, in a way, trying to make even clearer the significance of the reconciliation problem that physics is struggling with. One of the several "aha!" moments I had, reading this article, was your apparently deliberate omision of a mention of this postulated particle, explaining instead gravitational effects such as ballistic trajectory in terms of spacetime. This was the first time I had really felt the weight of the divide between the quantum and relativistic approaches to gravity. My impression up till now was that relativity was defective in the way that Newtonian mechanics was defective, of relevance only for engineers grappling with stellar distances and inconceivable speeds but good for its time until the particle physicists could come up with the truth. I had no idea that relativity could teach me things about the flight of a baseball. That, I think, needs to be preserved, so:

• I wouln’t want to see too much made of the search for the graviton if this were to have the effect of impugning the explanatory power of the General Theory.

3c. Let's just keep the regimes completely separate for the lead

I suggested the rewording because at present we go from the particle level, where forces are gauge boson mediated, to the rest, where, apparently, it’s all spacetime. There’s the level of everyday non-gravitational forces which needs to be accommodated.

• I suggest removing the sentence beginning "On large scales" in para 3 and adding instead to the end of the paragraph (i.e. once gravity has been formally introduced): "The gravitational interaction, perceived as a force, is more accurately attributable to the curvature of spacetime as explicated in Einstein's Theory of General Relativity."

Skeptical-H (talk) 17:40, 28 March 2008 (UTC)

Further interactions

1a. Tabled, for the time being.

1b. we might include a quick description of accelerations somewhere other than the lead. Basically acceleration is a change of velocity. Velocity subsumes both speed and direction. Ergo acceleration is a change in speed and/or direction.

2.The issue is very subtle, if I'm to understand your questions correctly. We are trying to determine, it seems, whether it is acceleration or momentum that is more natural to use as a description of what is involved with forces. It comes down to whether you think mass should be involved in discussions of motion (dynamics) or whether it shouldn't (kinematics). It is generally thought that kinematics is a cleaner introduction to mechanics than dynamics: most people are not prepared to subsume the mysteries of mass into the conceptual rigor required to offer descriptions of motion through space and time. While momentum is a more rigorous approach to force definitions: it defies conceptual simplicity. F=ma, for better or worse, is the second most famous equation in physics and it isn't, in point-of-fact, totally wrong. I think we need to use acceleration and momentum in the order in which they appear, but we can provide conceptual definitions of these terms in an early section.

3a. Forces exist because of the absorption and emission of gauge bosons. In other words, we really have emission/absorption --> force --> acceleration. Force, in such a conceptual framework proceeds from the emission and absorption of particles which in turn is associated with accelerations. One could remove the force altogether. However, I do not see emission/absorption --> acceleration --> force as making much sense. The force is the thing that does the accelerating: and while it is equivalent mathematically to say that an acceleration must have an accompanying force, the acceleration in these situations is a response that occurs due to the conservation of momentum which is directly associated with forces, no acceleration.

3b. Relativity and quantum mechanics both need to be accommodated in a unified theory and it is not clear which one will suffer the most modification in the end.

3c. Your suggested sentence and rewording seems reasonable.

ScienceApologist (talk) 17:46, 29 March 2008 (UTC)

All is now clear

Maybe it's because I've spent the last few days grappling with this subject, and read the article several times, but I don't have problems with acceleration and momentum now.

My confusion was centred on decay, dealt with earlier, and the nature of the force/boson mediation. Your 3a. reply finally cleared things up. I suggest the following be inserted after the end of the first sentence of the Feynman diagrams section: Gauge bosons have momentum. When a particle emits (creates) or absorbs (annihilates) a gauge boson a force is generated which accelerates the particle in response to the momentum of the boson, thereby conserving momentum as a whole. This force is the fundamental force associated with the particle/boson interaction.

Skeptical-H (talk) 21:53, 30 March 2008 (UTC)

done. ScienceApologist (talk) 14:45, 1 April 2008 (UTC)

Comments from a lay reader

I've been reading this article aloud with my roommate, who is a physics major. He thinks the page makes sense if you have taken physics, but not necessarily otherwise. I would have to agree. There are many confusing sections. I know that some, such as "Feynman diagrams", might be out of reach for the lay reader, but there are same basic sections such "Newtonian mechanics", which can be improved. My roommate explained everything to me as we were reading and I kept saying, "Why didn't they just say that?" I am convinced this material can be explained to those of us who want to understand! Here is my list of suggestions and confusions (interspersed are copy editing suggestions):

Questions

• Could we advise readers to read the vector article before reading this one or perhaps offer a one-paragraph introduction to vectors? Vectors seem to be very important to this article.

  Sure! How would we do this? ScienceApologist (talk) 12:17, 13 April 2008 (UTC)

  Which suggestion? Awadewit (talk) 03:28, 14 April 2008 (UTC)

  How do we make a one-paragraph introduction to vectors without it seeming artificial? 69.86.169.166 (talk) 12:52, 14 April 2008 (UTC)

  Could you integrate a simpler description of vectors into the first few paragraphs of the "Description" section, which already discusses the topic of vectors? Awadewit (talk) 16:37, 16 April 2008 (UTC)

  I tried. Please tell me if I did a good job or not. ScienceApologist (talk) 23:40, 21 April 2008 (UTC)

  Excellent! Just add one more sentence: Associating forces with vectors avoids such problems because [add reason]. Most people need such reasoning filled in for them (even though it is in the paragraph). Seriously. Awadewit (talk) 03:29, 22 April 2008 (UTC)

Lead

• According to Newton's Second Law, the combination of all forces acting on a body (known as the net force or resultant force) is equal to the acceleration multiplied by the mass of the object. - The lead should be the simplest part of the article. As such, is it absolutely necessary to include phrases such as "according to Newton's Second Law" and "known as net force or resultant force"? I would try to focus the essentials - the basics - only.

   Done

• Since momentum is a vector physical quantity that has both magnitude and direction, forces must also be vectors. - Sadly, vectors are not something I learned about in high school mathematics - is there any way to make this easier to understand? Any way to avoid clicking?

  Hmm. The idea that force is a vector is so fundamental to the descriptions of forces provided by basically everybody, I think we cannot really avoid discussing it, but maybe we can phrase it in a way that is easier to understand. I'll mull it over. ScienceApologist (talk) 12:17, 13 April 2008 (UTC)

  I believe this issue may be resolved with the current wording. Please check. ScienceApologist (talk) 23:40, 21 April 2008 (UTC)

  I consider this resolved with the addition of the vector paragraph. We have now avoided the clicking problem. Awadewit (talk) 03:29, 22 April 2008 (UTC)

• Rotational effects are determined by the torques (the rotational equivalent of forces), while deformation and pressure are determined by the stresses that the forces create with respect to certain areas of the object. - Save multiple definitions for the article - find the simplest wording for the lead (even if it means saving "torque" for the body of the article!).

  Initially, this was included in the lead to allow us to explain the situations that forces create. Newton's second law is a basic introduction, but torquing, stressing, deforming, and pressuring are all things that people talk about and are all due directly to forces. I think some people use these terms in a colloquial sense without ever thinking about their relation to forces. What do you think? ScienceApologist (talk) 12:17, 13 April 2008 (UTC)

  They use these terms all of the time? Perhaps other people. Perhaps a simplified version of the sentence - maybe just focusing on torque? Awadewit (talk) 03:28, 14 April 2008 (UTC)

  Sure, people use the term "stress", "pressure", "deform" all the time. They often don't even realize that what they are talking about is so closely related to the physical concept of forces and, indeed, has its etymology from classical physics. 69.86.169.166 (talk) 12:52, 14 April 2008 (UTC)

  Forces acting on three-dimensional objects may also cause them to rotate, deform, or result in a change in pressure. Torque determines rotational effects: the rotational equivalent of forces. Stress forces created within the object determine deformation and pressure. - This is written more simply now, but I'm still not sure all of these things need to be mentioned - if the idea is to say that colloquial ideas like pressure use the idea of force, why not just say that? Also, the writing is very choppy. Awadewit (talk) 16:37, 16 April 2008 (UTC)

  I'm in agreement with you, but I'm not sure what direction to take this in. I'm going to have to think a bit more about it. ScienceApologist (talk) 23:40, 21 April 2008 (UTC)

Pre-Newtonian

• From antiquity, the concept of force was recognized as integral to the functioning of each of the simple machines. - "From antiquity" or "In antiquity, the concept of force has been recognized..."?

  It's still recognized as such. Maybe "Since" is better? ScienceApologist (talk) 12:17, 13 April 2008 (UTC)

  It would have to be: "Since antiquity, the concept of force has been recognized..." Awadewit (talk) 03:28, 14 April 2008 (UTC)

   Done

• The mechanical advantage given by a simple machine allowed for less force to be used in exchange for that force acting over a larger distance. - "larger" or "greater"?

  Technically either/both, but "greater" might make more sense for the lay reader. ScienceApologist (talk) 12:20, 13 April 2008 (UTC)

  I thought "greater" was used for numbers. Awadewit (talk) 03:28, 14 April 2008 (UTC)

  Well, in physics the "number" and the property are often confused. I see your point, though.  Done 69.86.169.166 (talk) 12:52, 14 April 2008 (UTC)

  A distance can also be longer. Ward20 (talk) 08:12, 14 April 2008 (UTC)

• Philosophical development of the concept of a force proceeded through the work of Aristotle. - This sentence could be more precise - how did it proceed?

  I'll take a crack. ScienceApologist (talk) 12:20, 13 April 2008 (UTC)

• Aristotle believed that it was the natural state of massive objects on Earth, such as the elements water and earth, to be motionless on the ground and that they tended towards that state if left alone. - I would replace all instances of "massive" in the article with "objects that have mass". "Massive" to me means "enormous".

   Done

• This theory, based on the everyday experience of how objects move, such as the constant application of a force needed to keep a cart moving, had conceptual trouble accounting for the behavior of projectiles, such as the flight of arrows. - This sentence is missing the "because" explanation. I understand what it is driving at, but I've taught freshman composition courses long enough to know that it needs the other half for many students.

  Will do. ScienceApologist (talk) 12:23, 13 April 2008 (UTC)

Newtonian mechanics

• Isaac Newton is recognized as the first person to argue explicitly that a constant force causes a constant rate of change (time derivative) of momentum. In essence, he gave the first, and the only, mathematical definition of force—as the time-derivative of momentum: F = dp / dt. - These sentences are repetitive.

   Done

• In Principia Mathematica, Newton set out three laws of motion which have direct relevance to the way forces are described in physics. - "direct relevance"? What does that mean? I interpreted that mean that they aren't the exact formulas used or something. This caveat needs to be better explained or eliminated if it is not crucial.

   Done

• Newton's first law of motion states that objects continue to move in a state of constant velocity unless acted upon by an unbalanced external force. - "unbalanced"? This was quite confusing. I got a demonstrating using two cups from my roommate. I thought it meant that the force was unbalanced on one "side" - I was very wrong and very silly, apparently. The unbalanced bit either needs to be explained or cut. My roommate was of the opinion that it is probably not crucial in a first order explanation - it is a special case.

  I removed the offending unbalanced bit and kept in "net force". Will this work? 69.86.169.166 (talk) 12:52, 14 April 2008 (UTC)

  It makes sense to me. Awadewit (talk) 16:37, 16 April 2008 (UTC)

• Newton developed this law as an extension of the work of Galileo that connected the condition of constant velocity, whether it be zero or nonzero, to the concept of a lack of net force (see a more detailed description of this below). - Why do we have describe objects at rest as having "zero velocity"? This is confusing. How much is gained here, in the second sentence explaining Newton's first law?

  There is a very deep connection between realizing that rest and constant velocity are the same situation and the idea that no net force acts on inertial objects. In any case, I tried to rephrase. Tell me what you think. 69.86.169.166 (talk) 12:52, 14 April 2008 (UTC)

  Since rest is physically indistinguishable from non-zero constant velocity, Newton's first law directly connects inertia with the concept of relative velocities. Specifically, in systems where objects are moving with different velocities, it is impossible to determine which object is "in motion" and which object is "at rest"; it is equivalent to switch between what is called in physics "inertial frames of reference". - Is there any way to make the notion of "relative velocities" clearer? Would an example help here? Awadewit (talk) 16:37, 16 April 2008 (UTC)

  The problem is that examples are cumbersome since they involve no less than three different frames of reference to make the point. Nevertheless, I have taken a crack at it. Please tell me what you think. ScienceApologist (talk) 23:40, 21 April 2008 (UTC)

  I think this helps enormously. Awadewit (talk) 03:29, 22 April 2008 (UTC)

• The use of Newton's second law in either of these forms as a definition of force has been disparaged in some of the more rigorous textbooks,[3][13] because this removes all empirical content from the law. In fact, the in this equation represents the net (vector sum) force; in equilibrium this is zero by definition, but (balanced) forces are present nevertheless. Instead, Newton's second law only asserts the proportionality of acceleration and mass to force, each of which can be defined without explicit reference to forces. Accelerations can be defined through kinematic measurements while mass can be determined through, for example, counting atoms. However, while kinematics are well-described through reference frame analysis in advanced physics, there are still deep questions that remain as to what is the proper definition of mass. General relativity offers an equivalence between space-time and mass, but lacking a coherent theory of quantum gravity, it is unclear as to how or whether this connection is relevant on microscales. With rather more justification, Newton's second law can be taken as a quantitative definition of mass by writing the law as an equality, the relative units of force and mass are fixed. - This entire paragraph needs to be rewritten or removed. Basically what I came away with (which was apparently completely wrong), was that Newton was wrong.

  This paragraph has been a real problem for a while. There are two issues: Newtonian definitions of force are not necessarily empirically precise (sayeth Walter Noll) and forces themselves become redundant rather than fundamental concepts when looking at advanced physics. I'll mull it over and see if I can come up with a better way of stating all this. 69.86.169.166 (talk) 12:52, 14 April 2008 (UTC)

• Given the empirical success of Newton's law, it is sometimes used to measure the strength of forces (for instance, using astronomical orbits to determine gravitational forces). Nevertheless, the force and the quantities used to measure it remain distinct concepts. - Perhaps this last bit could be explained better and more examples given? I have found that students learn best from example. It is actually quite hard to learn from the abstract principle.

  I tried to make the astronomical orbits example clearer. Do you need more? ScienceApologist (talk) 19:12, 14 April 2008 (UTC)

  For some reason, I can't find this again. Awadewit (talk) 16:37, 16 April 2008 (UTC)

• This means that systems cannot create internal forces that are unbalanced. However, if objects 1 and 2 are considered to be in separate systems, then the two systems will each experience an unbalanced force and accelerate with respect to each other according to Newton's second law. - I think this could be explained better. I didn't really understand it until I received yet another cup demonstration. Again, I think concrete examples might help the pitiful lay reader such as myself.

  I'll try my best. This is actually a very important concept and we should try to get it right. ScienceApologist (talk) 19:12, 14 April 2008 (UTC)

  This did not help - I really think concrete examples would help here. Most readers are unable to think in the highly abstract terms demanded by the article, especially about an unfamiliar topic. Awadewit (talk) 16:37, 16 April 2008 (UTC)

• Generalizing this to a system of an arbitrary number of particles is straightforward. - I read "straightforward" as meaning easy and scoffed at the article, because, of course, I was struggling to read through something I didn't understand well. Apparently, though, it is trying to say that it is easy to extrapolate to other, more complicated systems - is there a better way to say this?

  Sorry. "Straightforward" is a common word in mathematics and physics but is not so common in other places. It means, roughly, "tedious to derive and based on rules already discussed". What about using the word "possible" instead of "straightforward"? ScienceApologist (talk) 19:23, 14 April 2008 (UTC)

  "possible" sounds good. Awadewit (talk) 16:37, 16 April 2008 (UTC)

Descriptions

• Since I know nothing about vectors, paragraphs 2-4 at the beginning of the "Descriptions" section were near-impenetrable to me. I think this might be a good place for one paragraph on what a vector is. I also think this section could be simplified. Once again, after my roommate explained the free-body diagrams, it all became clear.

  Remanded to the Questions section above. ScienceApologist (talk) 19:32, 14 April 2008 (UTC)

• Organizational issue: It would have been nice to have the "Normal force" and "Friction" sections before the "Equilibria" sections. Would that make sense? Currently, the "Normal force" section repeats what is in the "Statical equilibrium" section.

  I am aware of this issue. This stems from the peculiar situation of trying to give examples of situations where equilibria occur before examples of forces have been given. Should organization proceed as examples then descriptions or descriptions then examples? I also don't think that the normal force is quite an exact repetition of the static equilibrium section. We should dialog a bit more about this. ScienceApologist (talk) 19:32, 14 April 2008 (UTC)

  Examples and then descriptions - concrete followed by the abstract. Although not the most sophisticated or accurate way to learn, this is the most common way to learn. :) Awadewit (talk) 16:58, 16 April 2008 (UTC)

• The "Feynman diagrams" section is not explained well - I don't know if this can be rectified. I have a book that does explain them well for the layperson - Deep Down Things - I'll check and see if it says anything about force.

  Please let us know. I tried my very best to write this section as well as I possibly can. ScienceApologist (talk) 19:32, 14 April 2008 (UTC)

  If you have a chance to look at this book, I think the chapters titled "The Marriage of Relativity & Quantum Theory" and "Physics by Pure Thoughts: Gauge Theory" might help. This is the clearest book on particle physics for the layperson that I have seen (and I have a lot of them!). I was shocked how much I could understand reading this book - it attempted to explain much more than other popular science books on the topic and managed to do so extraordinarily well. Awadewit (talk) 16:58, 16 April 2008 (UTC)

• Can we do anything about the "Special relativity" section? I know many readers who will run away because it is all equations. I don't really understand myself. Would anything from the introduction to special relativity page help?

  I didn't write this section, but I understand it. Maybe a brief introduction could help. I'll have to mull this one over. ScienceApologist (talk) 19:32, 14 April 2008 (UTC)

MOS (since it is up for FAC)

• Be sure that the first example of a word is link.

  I've tried to do this, but if you catch anything please fix it! ScienceApologist (talk) 19:32, 14 April 2008 (UTC)

• Try linking more terms, such as "scalar", "free-fall".

  I believe they are linked, just not every time (only the first time). ScienceApologist (talk) 19:32, 14 April 2008 (UTC)

  I believe in linking when the reader might want to click. :) What do you think? Awadewit (talk) 16:58, 16 April 2008 (UTC)

  Sure. Be my guest. I've been reprimanded before for overlinking, so I'll defer to your judgment. ScienceApologist (talk) 23:52, 21 April 2008 (UTC)

• Be sure footnotes come after punctuation marks.

   Done

• Be sure there is consistency in century references (I saw some "17th century" and some "seventeenth century", for example).

   Done

I'll finish up my notes later! I hope this helps. Awadewit (talk) 04:00, 11 April 2008 (UTC)

It does, more than I can say. ScienceApologist (talk) 19:32, 14 April 2008 (UTC)

Electromagnetic forces

• Unifying all these observations into one succinct statement became known as Coulomb's Law - This is oddly phrased.

   Done

• Subsequent mathematicians and physicists found the construct of the electric field to be useful for determining the electrostatic force on an electric charge at any point in space. Based on Coulomb's Law, knowing the characteristics of the electric field in a given space is equivalent to knowing what the electrostatic force applied on a "test charge" is. - This needs to be explained - I don't know what an electric field or a test charge is - should I have to click on both? (I'm tired of clicking, by the way!)

  I don't think that there's any way around making these statements. For one, the "test charge" is fundamental to the definition of a magnetic field, but we can try to make the wording more descriptive. ScienceApologist (talk) 21:33, 14 April 2008 (UTC)

  Could we describe them even more? Awadewit (talk) 17:23, 16 April 2008 (UTC)

• Meanwhile, knowledge was developed of the Lorentz force of magnetism, the force that exists between two electric currents. - "knowledge was developed"? - an odd phrase

   Done

• However, attempting to reconcile electromagnetic theory with two observations, the photoelectric effect, and the nonexistence of the ultraviolet catastrophe, proved troublesome. - nonexistence or existence of the catastrophe? also, I would explain the catastrophe

  nonexistence actually. The ultraviolet catastrophe was a theoretical prediction that was not observed. I'll mull over how to explain it succinctly. ScienceApologist (talk) 21:56, 14 April 2008 (UTC)

• It is a common misconception to ascribe the stiffness and rigidity of solid matter to the repulsion of like charges under the influence of the electromagnetic force. - Oh, yes, I do this all of the time! Common to whom? Is this really necessary?

  Well, it is common among middle school science teachers, for example. ScienceApologist (talk) 21:56, 14 April 2008 (UTC)

  Trying to stave off the problems in science education, i see. Well, who am I to argue with that? Is there any way to phrase it better, however?

Nuclear forces

• The strong force is today understood to represent the interactions between quarks and gluons as detailed by the theory of quantum chromodynamics (QCD)[39]. The strong force is the fundamental force mediated by gluons, acting upon quarks, antiquarks, and the gluons themselves. The strong interaction is the most powerful of the four fundamental forces. - It may be impossible, but could we give readers a hints of what these particles are?

  You mean like, "quarks are the constituents of protons and neutrons, antiquarks are the constituents of antiprotons and antineutrons while gluons are the things that hold the quarks together"? I'm not sure if this will help or not. If it does, let me know and I'll include it. 69.86.169.166 (talk) 05:32, 15 April 2008 (UTC)

  I think it does help. Those other particles are slightly more familiar, especially protons and neutrons. For example, my parents know what protons and neutrons are, but they don't know what the rest are. Awadewit (talk) 17:23, 16 April 2008 (UTC)

• The strong force only acts directly upon elementary particles. However, a residual of the force is observed between hadrons (the best known example being the force that acts between nucleons in atomic nuclei) as the nuclear force. Here the strong force acts indirectly, transmitted as gluons which form part of the virtual pi and rho mesons which classically transmit the nuclear force (see this topic for more). The failure of many searches for free quarks has shown that the elementary particles affected are not directly observable. This phenomenon is called colour confinement. - No idea what is happening here and I even have some vague notion what these particles are supposed to be.

  This is a summary of how the strong nuclear force works. Basically, the gluons "glue" together the 3 quarks per hadron (proton/neutron) However, protons and neutrons are glued together in nuclei of atoms through left-over waveparticles from the gluon that form other bosoms (rho and pi mesons) that are the things that actually transmit forces between nuclei. Quarks individually never appear because gluons make sure that they are always found tied to other quarks. That's my rough translation. Can you suggest anyway to combine these translations together? 69.86.169.166 (talk) 05:32, 15 April 2008 (UTC)

  Trying: "Although the strong force only acts directly upon elementary particles, a residue is observed between hadrons. In hadrons, the strong force acts indirectly, where it is transmitted as gluons. The failure to find free quarks, the particles that make up hadrons, demonstrates that the affected elementary particles are not directly observable, a phenomenon referred to as "colour confinement". [This is important because?] So, how badly did I do? Awadewit (talk) 17:23, 16 April 2008 (UTC)

Non-fundamental forces

• A bit more explanation in the "Continuum mechanics" section might be nice.

   Done

  This is better. I sense this is an area where knowledge of tensors would be helpful? Awadewit (talk) 17:23, 16 April 2008 (UTC)

• Tension forces can be idealized using ideal strings which are massless, frictionless, unbreakable, and unstretchable. - What about "imagined" instead of "idealized"? (Not as precise, I know.)

  The problem with imagined is that it implies that tension forces aren't real (they are). Maybe better to say "modeled"? 69.86.169.166 (talk) 05:34, 15 April 2008 (UTC)

  "Modeled" sounds excellent. Awadewit (talk) 17:23, 16 April 2008 (UTC)

• I'm not sure I understand the difference between "tension" and "elasticity". They sound very similar.

  Tension involves no stretching. Elasticity involves stretching. 69.86.169.166 (talk) 05:34, 15 April 2008 (UTC)

  Springs don't stretch? (Sorry I'm so dense - I often ask very silly questions in my attempts to understand this stuff.) Awadewit (talk) 17:23, 16 April 2008 (UTC)

• This provides a definition for the moment of inertia which is the rotational equivalent for mass. In more advanced treatments of mechanics, the moment of inertia acts as a tensor that, when properly analyzed, fully determines the characteristics of rotations including precession and nutation. - Too advanced for me? :)

  If you thought vectors were difficult, imagine the sort of thing that acts on a vector to yield a totally different vector. Now imagine that this sort of thing has physical significance (relating two seemingly independent physical vectors). That's a tensor. It's so matehmatically complicated that most times it isn't formally introduced until 2nd year physics at the university level. Should we indulge ourselves with an introduction to tensors, or should we allow some mystery in our prose?ScienceApologist (talk) 06:19, 15 April 2008 (UTC)

  Actually, that was an excellent explanation. I'm sure the mathematics isn't that complicated! My roommate tells me nothing is that difficult in physics and math - one just has to think about it for a while. He's usually right about that. Vectors, for example, aren't difficult - I just didn't know anything about them until very recently. :) Why don't you add that little explanation into the article? Physics without the math is nothing, I am told. Awadewit (talk) 17:23, 16 April 2008 (UTC)

• The "Non-conservative forces" section lost me.

  Oh no! This is one of the sections of which I am most proud. Did you follow the beginning at least? Where did we lose you? ScienceApologist (talk) 06:19, 15 April 2008 (UTC)

  For certain physical scenarios (what kinds of physical scenarios?), it is impossible to model forces as being due to gradient of potentials. (I forgot, what is the "gradient of potentials"?) This is often due to macrophysical considerations (What are "macrophysical considerations" - larger than physical?) which yield forces as arising from a macroscopic statistical average of microstates. (What are microstates?) For example, friction is caused by the gradients of numerous electrostatic potentials between the atoms, but manifests as a force model which is independent of any macroscale position vector. (Still lost on gradients; not clear on causation/manifestation distinction) Nonconservative forces other than friction include other contact forces, tension, compression, and drag. However, for any sufficiently detailed description, all these forces are the results of conservative ones since each of these macroscopic forces are the net results of the gradients of microscopic potentials.(So, you add up the tiny forces and you get the "one big force" - this can't be right - I'm missing something) The connection between macroscopic non-conservative forces and microscopic conservative forces is described by detailed treatment with statistical mechanics. In macroscopic closed systems, nonconservative forces act to change the internal energies of the system, and are often associated with the transfer of heat. According to the Second Law of Thermodynamics,(What was that again, that I learned fifteen years ago, I'm asking myself) nonconservative forces necessarily result in energy transformations within closed systems from ordered to more random conditions as entropy increases.

  Here are my thoughts as I read. :) Awadewit (talk) 17:37, 16 April 2008 (UTC)

That's it! Awadewit (talk) 03:20, 14 April 2008 (UTC)