Why Gravity is Significant in Proton & Neutron Nuclei

[Andrew Mason]

This is not correct. A hydrogen atom (which has NO neutron) is a lot more stable than any of its isotopes. Thus, the pairing of a proton and a neutron does NOT produce a "very stable" configuration. The stability of a nuclear configuration is a lot more complex than that.

So is this incorrect?: http://hyperphysics.phy-astr.gsu.edu/hbase/particles/deuteron.html

The problem here is that there is a lack of understanding of quantum field theory. Keep in mind that QFT has been successfully used to obtain an accurate description of the band structure of the semiconductors that you are using in your modern electronics. So the validity of its methodology is well-known, even when you do not realize you are using it. The materials that you are using are littered with descriptions involving virtual phonons, magnons, spinons, polarons, etc.

So the fundamental issue now is to clearly understand QFT. Unfortunately, I think it is impossible to teach QFT online! :)

Next on my reading list is "An Introduction to Quantum Field Theory"

Andrew Mason

 

[quantumdude]

Could the binding energy not simply be stored in the form of matter rather than a force x distance concept of potential energy? The pairing of a proton and a neutron is a very stable configuration from an energy perspective. But when enough energy is added so that the particles are lifted out of that deep energy well, the result is a conversion of some of that matter back into energy.

Did you not see that the binding energy due to gravitation differs from the observed binding energy by about 38 orders of magnitude? Can you not perform a calculation to determine how much mass you would need to make up the difference? Just try it, and you'll see that it doesn't work.

Do we really have to be wedded to a concept of a 'force' within the nucleus? I say this knowing full well that there is probably something quite basic that I am missing so please be gentle on me.

I didn't say anything about forces. I spoke of binding energy.

Or perhaps hockey players grabbing a puck ... but I appreciate your analogy. As I understand your analogy, the skaters would only get closer together if the other was still holding onto the ball.

Nope. That's why I put them on ice skates. Even if the ball was dropped and rolled away, the skaters would move together, once the exchange had taken place.

Otherwise, if it is just the momentum of the ball that moves the 'grabber' toward the 'grabbee', the two don't get very close - not unless the ball is much more massive than the player.

Nope again. Look at the law of conservation of momentum. If the exchange is violent enough, the momentum transfer can be as high as you like.

So that begs the question: what is the skater/quark holding onto the ball/gluon with? Would you not have to assume some additional 'sticky' force there between the ball/gluon and the skater/quark?

The particles aren't holding onto the quanta with anything. Charged objects are sources of quanta. But as a side note, it is true in the case of the strong force that the quanta are also charged. But that is not necessary for the quanta to mediate the interaction, as demonstrated in the EM case.

 

[ZapperZ]

So is this incorrect?: http://hyperphysics.phy-astr.gsu.edu/hbase/particles/deuteron.html

You need to read what I said more carefully. I said

"This is not correct. A hydrogen atom (which has NO neutron) is a lot more stable than any of its isotopes."

"A lot more stable" does not mean one is stable and the other isn't. The fact that you can find more "H" or "H2" rather than "D" or "D2" imlies that H is more favorable to be formed than D.

So you are learning QFT? Have you also studied Second Quantization, which is practically the language of QFT?

Zz.

 

[Andrew Mason]

You need to read what I said more carefully. I said
"This is not correct. A hydrogen atom (which has NO neutron) is a lot more stable than any of its isotopes."

And I had said that a proton neutron pair is very stable. That is what I understood you to say was incorrect. I never said it was more stable than a proton. Probably nothing in the universe is as stable as a proton.

"A lot more stable" does not mean one is stable and the other isn't. The fact that you can find more "H" or "H2" rather than "D" or "D2" imlies that H is more favorable to be formed than D.

Or it simply implies that the D nucleus decays more rapidly than ^1_1H. Perhaps we started with only neutrons in the universe and that resulted in more ^2_1H than ^1_1H.

So you are learning QFT? Have you also studied Second Quantization, which is practically the language of QFT?

Not yet. I am brushing up on my undergraduate quantum physics text first and then we'll see how far I get. Thanks for the encouragement.

Andrew Mason

 

[Orion1]

Grainy Gravitation...

Did you not see that the binding energy due to gravitation differs from the observed binding energy by about 38 orders of magnitude? Can you not perform a calculation to determine how much mass you would need to make up the difference? Just try it, and you'll see that it doesn't work.

\propto_g = \frac{Gm_p^2}{\hbar c}

m_p - proton mass

\propto_g = 5.904*10^{-39}

Andrew, how much mass is required to increase the gravitational fine structure constant to 1 (\propto_g = 1)?

Probably nothing in the universe is as stable as a proton.

Some GUT theories predict the proton as 'unstable'.

Actually, the electron is the most 'stable' particle known, however this is tangential because electrons cannot carry colour.

Andrew, I recommend studying Quantum Electrodynamics prior to Quantum Field Theory.

[/color]

 

[ZapperZ]

Or it simply implies that the D nucleus decays more rapidly than ^1_1H. Perhaps we started with only neutrons in the universe and that resulted in more ^2_1H than ^1_1H.

And if you know this already, then this ring a bell that CLEARLY should have told you that a proton-neutron set up isn't as stable as a proton. Please note that originally, you are indicated that this set up is stable, as if it is the preferred ground state of a nuclei. I merely point out that it isn't when compared to a just a single proton as in the H atom. This means that the rest of your guesswork on the nucleon model falls apart. The nucleon structure isn't as naive as this. THAT is what I am trying to convey.

Zz.

 

[Andrew Mason]

Did you not see that the binding energy due to gravitation differs from the observed binding energy by about 38 orders of magnitude? Can you not perform a calculation to determine how much mass you would need to make up the difference? Just try it, and you'll see that it doesn't work.

There is no question that the observed binding energies in the nucleus are dozens of orders of magnitude greater than the gravitational binding energy of nuclear particles calculated using classical gravitational laws.

I didn't say anything about forces. I spoke of binding energy.

That's good. I am reluctant to equate the two concepts when speaking about the nucleus. I would like to leave open the possibility that the nuclear force might be viewed as something else - perhaps some kind of inertia in the process by which mass can be 'unraveled' into energy.

Nope. That's why I put them on ice skates.

Hockey players wear skates.

Even if the ball was dropped and rolled away, the skaters would move together, once the exchange had taken place.

I don't follow that. The momentum imparted by a particle is always in the direction of its motion. If the ball was pulled from the other skater and thrown back over the 'grabber's' head, they would move together because the grabbing skater would gain momentum in an equal and opposite direction to the ball. But the ball would depart the scene so it can't be repeated.

I can see how repeated back and forth motion of the same ball via alternating grabs by each skater would move them gradually closer together. The problem, however, is that the 'pull' from each grab is greatest the farther apart they are (so long as the grabber is within 'arms length' of the ball) and gets smaller the closer they get.

Nope again. Look at the law of conservation of momentum. If the exchange is violent enough, the momentum transfer can be as high as you like.

But that momentum lasts only until the ball stops with the grabber. The faster the exchange, the shorter the grabber's motion lasts. Bottom line is that the centre of mass of the grabber and ball cannot change on each grab.

The particles aren't holding onto the quanta with anything. Charged objects are sources of quanta. But as a side note, it is true in the case of the strong force that the quanta are also charged. But that is not necessary for the quanta to mediate the interaction, as demonstrated in the EM case.

I can conceive of virtual particles being exchanged between quarks within a nucleus a lot easier than I can conceive of virtual photons being exchanged over huge distances in an electric/magnetic field. Is it just my lack of imagination? How is it that the force varies as 1/r^2?

Andrew Mason

 

[Andrew Mason]

And if you know this already, then this ring a bell that CLEARLY should have told you that a proton-neutron set up isn't as stable as a proton. Please note that originally, you are indicated that this set up is stable, as if it is the preferred ground state of a nuclei.

That was not what I said nor what I was suggesting. I was using the pairing of a neutron and proton because, while it has a significant binding energy (which makes the configuration endure for long periods of time - hence stable), when it degenerates into separate particles there is a loss of mass. I was suggesting that we might think of the high binding energy of a neutron/proton pair as a 'resistance' to the 'unravelling' of matter rather than as a 'force' times 'distance'.

Andrew Mason

 

[quantumdude]

There is no question that the observed binding energies in the nucleus are dozens of orders of magnitude greater than the gravitational binding energy of nuclear particles calculated using classical gravitational laws.

OK, then what is it that prompts you to ask whether gravity can be responsible for nuclear binding? Clearly, nuclear stability cannot be accounted for by gravity as we know it. So you must be thinking of gravity as we don't know it.

Where does this idea come from?

How is it necessitated by any observational evidence?

Andrew: Or perhaps hockey players grabbing a puck ... but I appreciate your analogy. As I understand your analogy, the skaters would only get closer together if the other was still holding onto the ball.[/color]

Tom: Nope. That's why I put them on ice skates.

Andrew: Hockey players wear skates.

My remark was directed at the blue[/color] part.

Because the "particles" are on ice skates, they continue their motion, even if the ball is dropped after the exchange.

Tom: Even if the ball was dropped and rolled away, the skaters would move together, once the exchange had taken place.

Andrew: I don't follow that. The momentum imparted by a particle is always in the direction of its motion. If the ball was pulled from the other skater and thrown back over the 'grabber's' head, they would move together because the grabbing skater would gain momentum in an equal and opposite direction to the ball. But the ball would depart the scene so it can't be repeated.

But they are on ice skates[/color], so the momentum that was imparted by the exchange does not change, even if no subsequent exchanges take place. And I didn't say anything about throwing the ball after the exchange, I said that even if the ball was dropped, the two would still be attracted. Of course, the exchange cannot be repeated as you note, but that is beside the point. You said that the two skaters would not move towards each other unless one skater was holding the ball, and that is incorrect.

I can see how repeated back and forth motion of the same ball via alternating grabs by each skater would move them gradually closer together. The problem, however, is that the 'pull' from each grab is greatest the farther apart they are (so long as the grabber is within 'arms length' of the ball) and gets smaller the closer they get.

But that momentum lasts only until the ball stops with the grabber. The faster the exchange, the shorter the grabber's motion lasts. Bottom line is that the centre of mass of the grabber and ball cannot change on each grab.

No. The exchange only has to happen once, and the attraction would persist.

Once again, with emphasis: That's why I put them on ice skates.

The two skaters do not stop dead in their tracks once the ball is no longer being exchanged.

I can conceive of virtual particles being exchanged between quarks within a nucleus a lot easier than I can conceive of virtual photons being exchanged over huge distances in an electric/magnetic field. Is it just my lack of imagination?

Yes.

How is it that the force varies as 1/r^2?

The inverse square law is derivable from QFT. In Zee's book, QFT in a Nutshell, he derives it in the first chapter.

However, you need to seek out some education in physics at the basic level first. You said that your next stop is Intro to QFT. That's an admirable sentiment, but you are just not ready for it. That much is apparent from the way you are struggling with the momentum issue with the ice skaters. You should revisit classical mechanics first, and then classical EM theory, then quantum mechanics.

And then try QFT on for size.

 

[marlon]

Andrew,

I suggest you follow the advice of Tom on the QFT-thing here, otherwise it is going to be very hard and even quasi impossible for you to grasp the basic notions of QFT. You not only need to understand the algorithms and "calculus" used in QFT, you also need to see how and why QFT and the fields in particular are introduced. There is a very profound history and reason for this and not knowing this is like studying General Relativity without knowing the concepts of Newtonian physics. It just won't work.

QFT is very hard to learn, yet it is the most interesting and useful model of physics that we have up till now. In my opinion even the LQG and String-theories are Spielerei (this means : "toys") compared to the "maturity" that QFT has reached. Learning this too fast will have the risk of dropping out very soon because you just won't get the point...

just some advice, don't take this the wrong way...
marlon

 

[Andrew Mason]

OK, then what is it that prompts you to ask whether gravity can be responsible for nuclear binding? Clearly, nuclear stability cannot be accounted for by gravity as we know it. So you must be thinking of gravity as we don't know it.
Where does this idea come from?

I am not saying that gravity accounts for nuclear stability. Obviously the force of gravity is not sufficient to account for the binding energy of a proton and neutron (ie. the energy required to unbind them). I am suggesting that the explanation for this energy barrier might not require the existence of a mysterious nuclear force at all. If that is the case, then gravity might be the only force in the nucleus.

An analogy would be to very dense and heavy ball bearings (pretend they are made from neutron star matter) sitting on a level frictionless surface at the bottom of a deep Earth well. Their own gravity would attract them to each other and keep them together but is not the force that keeps them in the well. I am suggesting that there may be some energy barrier that keeps the nucleons from leaving the region of the nucleus, but that it is not a force x distance energy barrier (that is where the analogy ends, of course, because the energy barrier that keeps the ball bearings in the well is Earth gravity x height of the well).

How is it necessitated by any observational evidence?

It isn't necessitated. The question is whether observational evidence can have an alternate explanation. In case you haven't noticed, I don't like the strong nuclear force.

My remark was directed at the blue[/color] part.

I knew that. I was being facetious. I also play hockey.

Because the "particles" are on ice skates, they continue their motion, even if the ball is dropped after the exchange.

But if the ball drops, it is not moving toward the skater (the grabber). That means the skater has stopped the ball. Since the momentum of the ball in the direction of the skater has to equal to the momentum of the skater in the direction of the ball in the original frame of reference (ie. before the grab), the skater stops moving. The forward momentum of the skater has to equal the backward momentum of the ball. When the ball stops, the skater stops.

But they are on ice skates[/color], so the momentum that was imparted by the exchange does not change, even if no subsequent exchanges take place.

Do you not agree that in the original rest frame, the position of the center of mass of the skater and the ball cannot change? So either the ball keeps moving past the skater's back (ie he throws it behind him) and the skater keeps moving forward toward the other skater, or the ball and the skater stop.

And I didn't say anything about throwing the ball after the exchange, I said that even if the ball was dropped, the two would still be attracted. Of course, the exchange cannot be repeated as you note, but that is beside the point. You said that the two skaters would not move towards each other unless one skater was holding the ball, and that is incorrect.

That is what I originally said because, as I explained, I didn't think you were relying on transfer of momentum because unless the ball was very heavy the skater would not move very far toward the other skater.

In my subsequent post I said that the skater would move toward the other skater a little bit and then stop. I said: "I can see how repeated back and forth motion of the same ball via alternating grabs by each skater would move them gradually closer together." And I went on to take issue with your suggestion (perhaps I misunderstood) that once the skater began moving as he pulled the ball towards himself, he would continue moving toward the other. I said that he would only continue until the ball reached him and stopped. I still stand by that. I said "But that momentum lasts only until the ball stops with the grabber"

No. The exchange only has to happen once, and the attraction would persist.

I guess I don't know what you mean by 'attraction'. You cannot mean 'motion' because once the ball has stopped, the skater has to stop. (Or are you suggesting that the skaters are skating as well? {that was a joke})

Once again, with emphasis: That's why I put them on ice skates.

The two skaters do not stop dead in their tracks once the ball is no longer being exchanged.

Whatever happens on that frictionless ice surface, the center of mass of the 2 skater and ball system cannot move. I think we have to agree on that.

If one skater grabs the ball and brings it toward him and the ball stops, that skater must stop. If the other skater then grabs that ball and brings it to a stop against his chest, that skater moves a small distance toward the other and then stops.

If the skater who pulls the ball towards him never stops the ball (because the other skater grabs it back before it reaches his chest) and this is kept repeating, the two skaters will continue to move together. But I didn't think that was what you were saying because I thought you said the motion of the first skater to grab the ball would continue even if the ball was dropped (ie. after the first grab).

However, you need to seek out some education in physics at the basic level first. You said that your next stop is Intro to QFT. That's an admirable sentiment, but you are just not ready for it. That much is apparent from the way you are struggling with the momentum issue with the ice skaters.

I am not struggling with momentum at all. I am struggling with your example. I assure you I have no problem with basic physics. I studied physics from 1972-1976. That was a long time ago. I have't heard that the principle of conservation of momentum had changed since then.

You should revisit classical mechanics first, and then classical EM theory, then quantum mechanics.

And then try QFT on for size.

I don't need to revisit classical mechanics. I am rereading my 4th year quantum mechanics text and my 2nd year EM text. I appreciate that you are trying to be helpful, but I think that we are just misunderstanding each other's posts here.

Andrew Mason

 

[Andrew Mason]

just some advice, don't take this the wrong way...
marlon

I do appreciate the advice. I know that the contributors to this board have the best of intentions and I am very grateful for the opportunity to discuss these things. It has spurred my interest in revisiting the difficult areas of physics that 30 years ago drove me into law. Law makes a wonderful career, mind you, but it isn't physics.

Andrew Mason

 

[humanino]

I am not saying that gravity accounts for nuclear stability. Obviously the force of gravity is not sufficient to account for the binding energy of a proton and neutron (ie. the energy required to unbind them). I am suggesting that the explanation for this energy barrier might not require the existence of a mysterious nuclear force at all. If that is the case, then gravity might be the only force in the nucleus.

The question is whether observational evidence can have an alternate explanation.

The answer seems no, because the strong interaction applications are so numerous, and all in agreement with a very very simple, minimal assumption. Any other explanation would be more complicated. Occam razor.

I don't like the strong nuclear force.

I have contempt for lawyers. But I have no idea what being a lawyer could be so I am polite enough not to tell them, especially when I need their help.

we are just misunderstanding each other's posts here.

I doubt that we misunderstand yours.

 

[humanino]

But if the ball drops, it is not moving toward the skater (the grabber). That means the skater has stopped the ball. Since the momentum of the ball in the direction of the skater has to equal to the momentum of the skater in the direction of the ball in the original frame of reference (ie. before the grab), the skater stops moving. The forward momentum of the skater has to equal the backward momentum of the ball. When the ball stops, the skater stops.

This skater analogy has limits, it can not work so well at those scales, and will eventually run into difficulties. It was merely : the exchange can lead to either attraction or repulsion. But digging into it, I am not certain you will gain understanding in the nuclear interaction.

In my opinion, one should accept at some point, the historical developpement : if you are dealing with the proton/neutron structure, the first step is to understand the models which are not derived from fundamental laws. They are "intuited" with
1 classical analogies (as the skater, just closer to the problem)
2 quantum constraints
The reason one has to study those model : they work very well, for an approximative description. At the beginning, we had only innaccurate data, and those models were sufficient. And then, if you want to rigourously derive them, it is impossible. In order to gain understanding in the nuclei, you need to understand the meaning and the values of the parameters of the models.

Do you not agree that in the original rest frame, the position of the center of mass of the skater and the ball cannot change? So either the ball keeps moving past the skater's back (ie he throws it behind him) and the skater keeps moving forward toward the other skater, or the ball and the skater stop.

You are running in the difficulties. This is not a ball exchanged. In fact, there are two parts : a scalar and a vector part. Those are intrisically mixed. They lead to a subtle balance between repuslion and attraction.

I am not struggling with momentum at all. I am struggling with your example. I assure you I have no problem with basic physics. I studied physics from 1972-1976. That was a long time ago. I have't heard that the principle of conservation of momentum had changed since then.

See : this is mean. You know you are playing with an analogy. Do you only want to hear ? : at some point, any analogy fails. It only allows to communicate without equations, in order to emphasize a property. You extract the substance of a calculus, and then you think of an analogous phenomena, and you say "ok, remind in this simple case, it is the same ! " But you go "yes but also, if the ball is not inflated enough ... " This is not serious this skater thing. You are going nowhere with that.

Chiral Symmetry: Pion-Nucleon Interactions in Constituent Quark Models
http://smithers.physnet2.uni-hamburg.de/NN/NNnonlin.html

 

[Andrew Mason]

This skater analogy has limits, it can not work so well at those scales, and will eventually run into difficulties. It was merely : the exchange can lead to either attraction or repulsion. But digging into it, I am not certain you will gain understanding in the nuclear interaction.

I will go further than that and say that I am certain I won't.

See : this is mean. You know you are playing with an analogy. Do you only want to hear ? : at some point, any analogy fails. It only allows to communicate without equations, in order to emphasize a property. You extract the substance of a calculus, and then you think of an analogous phenomena, and you say "ok, remind in this simple case, it is the same ! " But you go "yes but also, if the ball is not inflated enough ... " This is not serious this skater thing. You are going nowhere with that.

I certainly did not intend to be mean and I apologize if it sounded like I was. But the analogy was yours. Conservation of momentum is not a minor detail. In order to have an exchange of gluons creating an enormous attractive force through momentum transfer, one would require some kind of imaginary negative momentum. I am not the only one who has had problems with the concept.

But don't give up on me just yet. I may surprise you with what I really do understand.

Andrew Mason

 

[Orion1]

Yukawa Aqua...

The lightest meson is the pion (quark anti-quark combination) which is NOT an elementary particle yet it DOES mediate a "part" of the strong force. I am referring to the socalled residual strong force that holds atomic nuclei together...

Can Deuterium Binding Energy be described as existing inside a Yukawa Potential Well?

Deuterium Binding Energy:
E_b = ((m_p + m_n) - m_D) E_n

Yukawa Potential Well:
U_y = f^2 \frac{e^{-\frac{r_D}{r_0}}}{r_D}

E_b = U_y

((m_p + m_n) - m_D) E_n = f^2 \frac{e^{- \frac{r_D}{r_0}}}{r_D}

f_D^2 = ((m_p + m_n) - m_D) E_n r_D e^{\frac{r_D}{r_0}}

\boxed{f_D = \sqrt{((m_p + m_n) - m_D) E_n r_D e^{\frac{r_D}{r_0}}}}

Key:
E_n = 931.5 \; Mev*amu^{-1} - mass-energy equivalence
m_p - Proton mass
m_n - Neutron mass
m_D - Deuterium mass
r_D - Deuterium nuclear radius
r_0 - Yukawa nuclear range

 

[humanino]

But don't give up on me just yet. I may surprise you with what I really do understand.

I trust you Andrew, you must certainly understand very well parts of physics apart from nuclear theory.

Conservation of momentum is not a minor detail. In order to have an exchange of gluons creating an enormous attractive force through momentum transfer, one would require some kind of imaginary negative momentum. I am not the only one who has had problems with the concept.

This is a very good question indeed, and I have not been able to figure out a satisfactory answer yet. I will work on it, and probably benefit much from the other posts here.

But your argument is not only meant against QCD : two opposite electric charges attract by exchanging photons.

 

[Andrew Mason]

The answer seems no, because the strong interaction applications are so numerous, and all in agreement with a very very simple, minimal assumption. Any other explanation would be more complicated. Occam razor.

I'll have to take your word for it at the moment because I really don't understand it in the depth required to have an informed opinion. At this stage I am simply asking questions.

But let me just say that Occam's Razor is a bit of a cop out. Occam's Razor just a generalization, not a principle of science. It does not apply, for example, to the machinery of the cell - the simplest explanation is hardly ever the way it really works. It doesn't apply to General Relativity compared to Newton. Newton was an advocate of it as a principle but as subsequent developments have shown, things were not always as simple as he thought. It applies best in situations where there is more than one possible explanation and one has to determine the most probable one. If it walks like a horse, talks like a horse and smells like a horse then it is probably a horse, not a zebra - (unless, perhaps, you are in the African savannah).

I have contempt for lawyers. But I have no idea what being a lawyer could be so I am polite enough not to tell them, especially when I need their help.

Nelson Mandela is a lawyer. Mahatma Gandhi was a lawyer. Franklin D. Roosevelt and Abraham Lincoln were lawyers. You have contempt for them? Unfortunately, we are bound by our professional oath to defend people and causes that many people dislike. So we learn to develop a thick skin - a very useful thing to have in this forum, I have found.

Andrew Mason

 

[anti_crank]

I'll have to take your word for it at the moment because I really don't understand it in the depth required to have an informed opinion. At this stage I am simply asking questions.

You are welcome to ask questions. However, the other question is what to do with the answers you've gotten. This thread has many of the trademarks of the old TD forum; however, the scientific discussion has managed to stay above crackpot material for the time being.

We've given you plenty of reasons, complete with calculations, why gravity is irrelevant in the nucleus and why the strong force is needed. The strong force has been tested in many other ways. It successfully predicts meson structure and lifetimes. The existence of gluons has received huge support from three-jet events. On the theoretical side, the color quantum number is required for anomaly cancellation in the GWS model . Hence without colored quarks, the weak force theory would break down, and a large number of particle physics experiments would be open problems. The italicized terms are terms you might try to do Google searches on, since I don't have the time to explain those things.

Now you suggest that gravity and/or the EM force might behave differently on nuclear scales. Experimental evidence refutes this. For example, if Maxwell's equations were to break down at that scale, EM waves of wavelengths close to the size of nuclei (1fm) should behave differently than other EM waves. This corresponds to an energy of about 1.2 GeV, and experimental data is available that confirms QED to much greater energies (smaller scales).

As for gravity, this may sound like a catch-22 to you. We believe gravity is so weak on nuclear scales that its effects are impossible to measure. We attribute everything we observe to EM/strong/weak interactions. You might say we mistakenly attribute the new gravitational effects to the fictional strong force. But you must keep in mind that when accurate data is available, those models can be tested to great accuracy, and so far they passed every test. Therefore if you want to overthrow the strong force, it is not enough to make broad suggestions about gravity holding the nucleaus together. Rather, you must provide a mathematical description of gravity that reproduces all those effects, then proceed to solve the other problems that the absence of strong nuclear forces would create.

At this point, you might argue that you don't have the training, the knowledge or the skills to make such a model. In that case, and with all due respect, please leave the physics to the physicists. I like to think that no physicist would tell you how to do your job, and I ask for the same professional courtesy from you. We do not have contempt for lawyers; I suspect humanimo was simply offended by your statement that you "don't like" the strong force. More on that later.

But let me just say that Occam's Razor is a bit of a cop out. Occam's Razor just a generalization, not a principle of science. It does not apply, for example, to the machinery of the cell - the simplest explanation is hardly ever the way it really works. It doesn't apply to General Relativity compared to Newton. Newton was an advocate of it as a principle but as subsequent developments have shown, things were not always as simple as he thought.

This was a completely different matter. The theories made different predictions, and experiments falsified Newton and supported Einstein.

It applies best in situations where there is more than one possible explanation and one has to determine the most probable one.

Is that not exactly what we would have here? Assuming that you somehow manage to construct a model of gravity/EM that does what you want, it will undoubtedly be very complicated. Why should that be the most probable then? The current theories, with the strong force included, are simpler than anything thus constructed. Of all the branches of science, particle physics is especially driven towards greater simplicity, and this drive is what makes for most of today's effort in this field.

In case you haven't noticed, I don't like the strong nuclear force.

This is an extremely unscientific attitude. We expect this from creationists who don't like the vast majorities of present theories, classical-physics mindsets who feel their worlds coming apart at the mere thought of relativity or quantum mechanics, and other crackpots who are fixated on one idea and cannot let go of it. In science, personal opinions are a luxury. Furthermore, personal opinions without some valid scientific or mathematical backing are not even science. This is not a good path you're heading down; consider this an attempt to pull you away from the edge.

 

[Andrew Mason]

Now you suggest that gravity and/or the EM force might behave differently on nuclear scales. Experimental evidence refutes this. For example, if Maxwell's equations were to break down at that scale, EM waves of wavelengths close to the size of nuclei (1fm) should behave differently than other EM waves. This corresponds to an energy of about 1.2 GeV, and experimental data is available that confirms QED to much greater energies (smaller scales).

I am not suggesting that EM theory breaks down for EM waves with wavelengths smaller than 10^{-15} m.. I was just questioning whether we really have evidence that the coulomb force between protons continues as their 'separation' distance becomes smaller than 10^{-15} m.. That may have more to do with the structure of the proton than EM theory. EM theory assumes point charges and does not explain what creates the coulomb force.

As for gravity, this may sound like a catch-22 to you. We believe gravity is so weak on nuclear scales that its effects are impossible to measure. We attribute everything we observe to EM/strong/weak interactions. You might say we mistakenly attribute the new gravitational effects to the fictional strong force.

Hang on. I am not talking about new gravitational effects. I am not suggesting that some new gravity would account for the huge binding energy of nucleons. I am just questioning whether we have to use traditional concepts of force x distance to account for that binding energy.

At this point, you might argue that you don't have the training, the knowledge or the skills to make such a model. In that case, and with all due respect, please leave the physics to the physicists. I like to think that no physicist would tell you how to do your job, and I ask for the same professional courtesy from you.

Scientific experts try to tell me how to do my job all the time. The problem is that they are frequently wrong and it takes a lawyer (and usually another expert) to make a judge understand that their explanations are wrong.

The current theories, with the strong force included, are simpler than anything thus constructed. Of all the branches of science, particle physics is especially driven towards greater simplicity, and this drive is what makes for most of today's effort in this field.

My interest, and I think it has always been the goal of science, is in trying to understand nature in terms of more fundamental concepts. Biology explains macroscopic life forms in terms of more fundamental units of life: the cell. Molecular biology seeks to explain complex behaviour of cells in terms of fundamental processes (protein synthesis being governed by the machinery of RNA/DNA transcription and translation). Physical chemistry explains the composition of matter in terms of combinations of a finite number of kinds of atoms and the electromagnetic forces between atoms. Physics explains all atoms as combinations of nucleons and electrons.

Nuclear physics tries to explain protons and neutrons in terms of more fundamental particles: quarks. Neutons and protons consist of two different combinatons of three quarks held together by an exchange of virtual particles. At this point we have trouble maintaining a conceptual framework because we have to rely on elaborate mathematical models to describe and predict what is happening. As we probe deeper into the nucleus the models become more elaborate rather than simpler. I am suggesting that perhaps there is a more fundamental principle or some simpler explanation that will tie it all together. I don't think I am alone.

This is an extremely unscientific attitude. We expect this from creationists who don't like the vast majorities of present theories, classical-physics mindsets who feel their worlds coming apart at the mere thought of relativity or quantum mechanics, and other crackpots who are fixated on one idea and cannot let go of it. In science, personal opinions are a luxury. Furthermore, personal opinions without some valid scientific or mathematical backing are not even science.

I do agree with you there. I never said the fact that I didn't 'like' an explanation was a reason to reject the explanation. I just meant it was reason for me to keep trying to see if there is not another more fundamental explanation that fits the evidence.

Andrew Mason

 

[quantumdude]

I am not saying that gravity accounts for nuclear stability.

If there is no strong force to provide the stability, then something else must do the job. It's as simple as that.

Obviously the force of gravity is not sufficient to account for the binding energy of a proton and neutron (ie. the energy required to unbind them). I am suggesting that the explanation for this energy barrier might not require the existence of a mysterious nuclear force at all. If that is the case, then gravity might be the only force in the nucleus.

There's nothing mysterious about the strong interaction. It's only mysterious to people who have not studied it.

An analogy would be to very dense and heavy ball bearings (pretend they are made from neutron star matter) sitting on a level frictionless surface at the bottom of a deep Earth well. Their own gravity would attract them to each other and keep them together but is not the force that keeps them in the well. I am suggesting that there may be some energy barrier that keeps the nucleons from leaving the region of the nucleus, but that it is not a force x distance energy barrier (that is where the analogy ends, of course, because the energy barrier that keeps the ball bearings in the well is Earth gravity x height of the well).

This is just silly. The energy well has to correspond to some potential. Don't you see that you're replacing the (well-understood) strong+weak+EM interaction with gravity and a mysterious[/color] energy well? Where does this well come from? God?

It isn't necessitated. The question is whether observational evidence can have an alternate explanation. In case you haven't noticed, I don't like the strong nuclear force.

You don't understand the nuclear force. This can be remedied with some study.

But if the ball drops, it is not moving toward the skater (the grabber). That means the skater has stopped the ball. Since the momentum of the ball in the direction of the skater has to equal to the momentum of the skater in the direction of the ball in the original frame of reference (ie. before the grab), the skater stops moving.

No. The if the ball is dropped after the exchange, then the skaters continue moving towards each other. There has to be another exchange to stop the skaters.

The forward momentum of the skater has to equal the backward momentum of the ball. When the ball stops, the skater stops.

Will you please work out the calculation? It's quite simple. You have a skater carrying a ball, and they are both moving at speed v. If the skater drops the ball, the skater does not stop. In fact, the skater moves faster, because of the reduced mass.

Do you not agree that in the original rest frame, the position of the center of mass of the skater and the ball cannot change?

Yes.

So either the ball keeps moving past the skater's back (ie he throws it behind him) and the skater keeps moving forward toward the other skater, or the ball and the skater stop.

No.

Please do a calucation, and you'll see that it does not work like this.

That is what I originally said because, as I explained, I didn't think you were relying on transfer of momentum because unless the ball was very heavy the skater would not move very far toward the other skater.

Please look up the definition of momentum. The ball need not be very heavy, if it is moving fast. I already explained this.

In my subsequent post I said that the skater would move toward the other skater a little bit and then stop. I said: "I can see how repeated back and forth motion of the same ball via alternating grabs by each skater would move them gradually closer together." And I went on to take issue with your suggestion (perhaps I misunderstood) that once the skater began moving as he pulled the ball towards himself, he would continue moving toward the other. I said that he would only continue until the ball reached him and stopped. I still stand by that. I said "But that momentum lasts only until the ball stops with the grabber"

And that is wrong.

I guess I don't know what you mean by 'attraction'. You cannot mean 'motion' because once the ball has stopped, the skater has to stop. (Or are you suggesting that the skaters are skating as well? {that was a joke})

Whatever happens on that frictionless ice surface, the center of mass of the 2 skater and ball system cannot move. I think we have to agree on that.

By "attraction" I mean that the skaters continue to move towards each other. While it is true that the center of mass of the entire system must not change its momentum, it is not true that the individual constituents of that system must stop moving. And no, the skaters need not have been skating prior to the exchange.

If the skater who pulls the ball towards him never stops the ball (because the other skater grabs it back before it reaches his chest) and this is kept repeating, the two skaters will continue to move together. But I didn't think that was what you were saying because I thought you said the motion of the first skater to grab the ball would continue even if the ball was dropped (ie. after the first grab).

That is precisely what I was saying.

I am not struggling with momentum at all. I am struggling with your example. I assure you I have no problem with basic physics. I studied physics from 1972-1976. That was a long time ago. I have't heard that the principle of conservation of momentum had changed since then.

You are indeed struggling with the idea of momentum.

First, you believe that only a very massive ball can impart an appreciable momentum transfer. But that is wrong because p=mv, so a lightweight but fast moving ball can also impart such an impulse.

Second, you believe that a system with total momentum of zero implies that the momentum of all the constituents must also be zero. But that is also wrong. Once a momentum transfer takes place (as in, say, the exchange of a ball from one skater to another), the center of mass of the system is motionless despite the fact that each skater continues moving[/color]. If a momentum q is imparted to skater 1, and a momentum -q is imparted to skater 2, then the total momentum is conserved and the skaters continue on their merry way, towards each other.

I don't know how to make it any clearer than that.

I don't need to revisit classical mechanics. I am rereading my 4th year quantum mechanics text and my 2nd year EM text. I appreciate that you are trying to be helpful, but I think that we are just misunderstanding each other's posts here.

No, you're understanding my posts just fine. It's just that you need to brush up on basic physics. I'm sorry that you disagree, but it's true.

 

[anti_crank]

I am not suggesting that EM theory breaks down for EM waves with wavelengths smaller than 10^{-15} m.. I was just questioning whether we really have evidence that the coulomb force between protons continues as their 'separation' distance becomes smaller than 10^{-15} m.. That may have more to do with the structure of the proton than EM theory. EM theory assumes point charges and does not explain what creates the coulomb force.

My point was that if you change Coulomb's law to act differently on those scales, you have to change Maxwell's equations as well, and so you change the properties of EM waves on those ranges. This consequence cannot be avoided.

If you're suggesting perhaps that protons have a charge distribution that may end up reducing the repulsive force, you may be partially correct. However, since the net charge on both protons remains positive, the net force will necessarily be repulsive, will equal the point-charge repulsion formula to a first order approximation.

Hang on. I am not talking about new gravitational effects. I am not suggesting that some new gravity would account for the huge binding energy of nucleons. I am just questioning whether we have to use traditional concepts of force x distance to account for that binding energy.

The traditional concepts of force x distance are not the right tools for this job. You need quantum mechanics for any analysis of nuclear structure. Let me add here that all alpha decays can be modeled using perturbation theory where the alpha nucleus must tunnel through the Coulomb barrier. This does a very good job of predicting alpha decays; hence the Coulomb force is unchanged for all heavy nuclei undergoing alpha decay. To see how it acts on the scale of smaller nuclei, you can go to scattering experiments. These allow us to probe the structure of protons and even resolve individual quarks. If the EM force behaved differently, those experiments would have to be reinterpreted. The tapestry of science is too tightly woven to hope that you can unravel one thread without having to make massive changes.

Scientific experts try to tell me how to do my job all the time. The problem is that they are frequently wrong and it takes a lawyer (and usually another expert) to make a judge understand that their explanations are wrong.

I find this quite surprising. What field of law do you practice?

My interest, and I think it has always been the goal of science, is in trying to understand nature in terms of more fundamental concepts... Nuclear physics tries to explain protons and neutrons in terms of more fundamental particles: quarks. Neutons and protons consist of two different combinatons of three quarks held together by an exchange of virtual particles. At this point we have trouble maintaining a conceptual framework because we have to rely on elaborate mathematical models to describe and predict what is happening. As we probe deeper into the nucleus the models become more elaborate rather than simpler. I am suggesting that perhaps there is a more fundamental principle or some simpler explanation that will tie it all together. I don't think I am alone.

I'm afraid I fail to see your point. Why exactly are we having trouble maintaining a conceptual framework? The mathematical models may be elaborate, but they do an excellent job of describing Nature. Right now the Standard Model reduces all of physics to some twenty-odd constants, and there are countless plans to reduce their numbers further by making a unified theory. Have you looked at such theories, like SU(5) or supersymmetry? In any event, there is no doubt that the strong force is here to stay, and will have to be included in any such searches. Since we have all done our best to give you reasons for the strong force's existence, the ball is in your court now: what evidence would be strong enough to convince you of its existence?

PS. I just realized that neutron stars might be a good place to see both gravity and strong nuclear forces at work. While I believe that the theories do a good job of predicting the properties of neutron stars (otherwise I'd know about it), I am not an astrophysicist, so I will have to defer this point.

 

[Nereid]

PS. I just realized that neutron stars might be a good place to see both gravity and strong nuclear forces at work. While I believe that the theories do a good job of predicting the properties of neutron stars (otherwise I'd know about it), I am not an astrophysicist, so I will have to defer this point.

I had a very nice post prepared, ready to post, then my browser crashed Will Bill give me a refund do you think?

We have modeled neutron stars, compared the results with observations, and the fit is very good. Unfortunately (or not!), we don’t have one in our neighbourhood, so we haven’t been able to perform controlled proton scattering experiments yet Indeed, the extent to which astronomy provides tests of a great deal of physics can sometimes be difficult to accept … I mean, a faint smudge of light in an image that’s full of other smudges is a gravitational lens, just as Uncle Al predicted?

Some highlights from models, which are based on General Relativity, the Standard Model (particle physics variety), as well as more pedestrian atomic physics, etc:
- there are well observed objects which have masses, densities, temperatures, surface compositions etc that match the models well (and few, if any, which don’t); pulsars are well-known examples
- from stellar evolution theory, we expect neutron stars to form under certain circumstances (e.g. ‘core collapse’ supernovae), and that’s just what we find; the Crab nebula is a good example
- the behaviour of neutron stars when mass is added – e.g. accretion from the other star of a close binary – is reasonably well studied, and observations match predictions closely; http://universe.gsfc.nasa.gov/press/images/rossi2000/
- research is under way into how waves in neutron stars can provide details of the internal structure of these gigantic nuclei, in a way similar to how seismology gives an idea of the internal structure of the Earth, and helioseismology the Sun
- indeed, studying neutron star may help us answer questions in high energy physics that aren’t possible to address here on Earth

 

[Andrew Mason]

If there is no strong force to provide the stability, then something else must do the job. It's as simple as that.

I agree.

There's nothing mysterious about the strong interaction. It's only mysterious to people who have not studied it.

All of physics is mysterious. We just reduce phenomena to fewer phenomena that we don't understand. That is the essence of all science. One should be cautious about saying these things are resolved. Planck's professor is a good example (he tried to dissuade Planck from taking up physics because all the great questions had been resolved - pre 1900).

How is energy converted to mass? How is it that our entire universe of matter and energy emerged from a point dozens of orders of magnitude smaller than a proton? Everything is mysterious at some level.

This is just silly. The energy well has to correspond to some potential. Don't you see that you're replacing the (well-understood) strong+weak+EM interaction with gravity and a mysterious[/color] energy well?

I am not replacing anything. I don't have a theory and I am not proposing one. I am just asking questions and suggesting that the nuclear force may not be a correct explanation of reality.

We measure the nuclear force indirectly. We measure energies. The fact is that the separation of a proton and neutron requires the creation of matter. That obviously requires energy. But perhaps the energy is not required to pull against an attractive force for the separation distance. Perhaps it is required to add mass to the separate proton and neutron. I am suggesting that the process of creating matter might be thought of as inhibiting separation.

We don't understand how matter is created. It obviously requires energy. Does it require that a force be applied to the proton for a particular distance? That is what I am asking. So far, no one seems to have come up with a good reason why it has to.

Where does this well come from? God?

Probably the same place that the universe came from. Are you suggesting that God can be ruled out?

Andrew Mason

 

[Andrew Mason]

No. The if the ball is dropped after the exchange, then the skaters continue moving towards each other. There has to be another exchange to stop the skaters.

Ok. Let's get this straight. There are two skaters at rest in the frame of reference of the ice, S1 and S2. S2 is holding a ball which is also at rest. S1 grabs the ball from S2 and pulls it toward himself accelerating the ball to a speed v_b. This results in momentum p_b = m_b v_b of the ball and necessarily imparts an equal and opposite momentum to S1 toward S2. S1 moves toward S2 at a speed v_{S1} = p_b/m_{S1}. I think we are agreed to this point.

Then S1 stops the ball at his chest and drops it (if he doesn't stop it, the ball would keep going past him). You seem to be saying that v_{S1} remains the same. I am saying that violates conservation of momentum. The reason is that in order to stop the ball, S1 has to absorb the ball's momentum p_b. Since that is equal and opposite to S1's momentum, this means that S1 stops.

But we don't even have to do that. We know that the momentum of the system is always 0 in the ice's frame of reference. If S2 is not moving and the ball is not moving, S1 can't be moving.

Will you please work out the calculation? It's quite simple. You have a skater carrying a ball, and they are both moving at speed v.

Why? How? This is not possible. They cannot possibly be moving at the same speed unless that speed is 0. See above.

If the skater drops the ball, the skater does not stop.

He does if he stops the ball and then drops it. I assume you mean by dropping the ball that the ball is stopped in the rest frame of the ice and does not go sailing off behind S1.

In fact, the skater moves faster, because of the reduced mass.

Not in this universe. And you think I need help with basic physics?

Please do a calucation, and you'll see that it does not work like this.

Calculations aren't required. It is just simple conservation of momentum. See above.

Please look up the definition of momentum. The ball need not be very heavy, if it is moving fast. I already explained this.

I don't need to look up the definition of momentum. Your comment that the skater speeds up if he reduces his mass is astounding really.

By "attraction" I mean that the skaters continue to move towards each other. While it is true that the center of mass of the entire system must not change its momentum, it is not true that the individual constituents of that system must stop moving. And no, the skaters need not have been skating prior to the exchange.

Well in your example if S2 and the Ball are not moving then S1 cannot be moving without violating conservation of momentum.

You are indeed struggling with the idea of momentum.

I am struggling with your concept of momentum. It is not Newton's.

First, you believe that only a very massive ball can impart an appreciable momentum transfer.

I never said that. I said that unless the ball was heavy, the skater would not move very far when the skater pulled it towards him. It has nothing to do with the speed at which he pulls it. It has to do with the location of the center of mass. That point can't change. If the ball is not heavy, the center of mass is very close to the skater. If the ball is very heavy, it is close to the ball, so the skater will move farther.

But that is wrong because p=mv, so a lightweight but fast moving ball can also impart such an impulse.

I have never said anything to suggest that I disagreed with that.

Second, you believe that a system with total momentum of zero implies that the momentum of all the constituents must also be zero. But that is also wrong.

I never said that. I said the center of mass can't move. The constituents can move all they want. But that point can't change.
You are really twisting what I have said here.

Once a momentum transfer takes place (as in, say, the exchange of a ball from one skater to another), the center of mass of the system is motionless despite the fact that each skater continues moving[/color]. If a momentum q is imparted to skater 1, and a momentum -q is imparted to skater 2, then the total momentum is conserved and the skaters continue on their merry way, towards each other.

You haven't got Skater 2 moving at all by Skater1 pulling the ball towards himself.

No, you're understanding my posts just fine. It's just that you need to brush up on basic physics. I'm sorry that you disagree, but it's true.

This is high school physics, Newton's laws. Your statement that the loss of mass by simply dropping the ball will cause S1 to speed up is patently absurd. I am sure you will realize that when you reread your post.

Andrew Mason

 

[Andrew Mason]

I find this quite surprising.

Ok, it may be a bit of an exaggeration.
One of the most frequent sources of error (e.g wrongful convictions) is incorrect expert evidence. Experts were found to say that hair and fibre could make a highly probable 'match', that bullets could be matched by their metallugical composition, that babies with heart problems can't have high digoxin levels naturally. A nurse was charged (and later discharged, fortunately) with murdering babies on the basis of bad science. Guy Paul Morin was wrongly convicted of murder on the basis of hair and fibre 'matches' (DNA later exhonerated him). Clayton Johnson was convicted because of experts who said his wife was murdered (later exhonerated by other experts and a whole body of other evidence). Hundreds, possibly thousands of cases based on the now discredited 'science' of bullet matching are now under review in the US.

A good example of 'expert' folly is in the acoustic experts who testified on the JFK assassination before the House Select Committee on Assassinations in 1978 and concluded that there were 4 shots. The fact that no one said that they were sure they heard 4 shots and 90% said there were exactly 3 (most of whom recalled the same pattern of shots 1...2...3) was completely ignored. The National Academy of Sciences later showed the errors. See: http://www.dufourlaw.com/jfk/shot_pattern_evidence.pdf

Even nobel physicist Luis Alvarez wrote an article in Physics Today advocating his new theory of jiggle effect (definitely an unproven technique which, in this case leads to conclusions that are inconsistent with the evidence). He did get some things right, mind you.

What field of law do you practice?

mainly litigation. see: http://www.dufourlaw.com/dufwho.htm#AM
For a good example of how an expert messed up a trial I was involved in and later corrected by the court of appeal, see: http://www.lawsociety.sk.ca/judgments/2003/Ca2003/2003skca40.pdf

Since we have all done our best to give you reasons for the strong force's existence, the ball is in your court now: what evidence would be strong enough to convince you of its existence?

Correct me if I am missing something, but the existence of the strong force is inferred from the binding energies that are observed for nuclear particles. Is there any other evidence of the strong force?

PS. I just realized that neutron stars might be a good place to see both gravity and strong nuclear forces at work. While I believe that the theories do a good job of predicting the properties of neutron stars (otherwise I'd know about it), I am not an astrophysicist, so I will have to defer this point.

I think you are right. If neutron star is as dense as the nucleus, then the nucleons in the neutron star are going to be within range of the strong nuclear force, if it exists. Now if we could only get a piece of a neutron star and see if it spontaneously flies apart...

There may be a way of testing the existence of the nuclear force if we could observe a star going through a gravitational collapse. As the density reached nuclear densities, there should be a significant release of energy as the nuclear force takes hold. That may be the theory behind the super nova explosion, I am not sure.
Andrew Mason

 

[quantumdude]

All of physics is mysterious. We just reduce phenomena to fewer phenomena that we don't understand.

OK fine, I'll amend my statement: The strong force is no more mysterious than any other interaction.

I am not replacing anything. I don't have a theory and I am not proposing one. I am just asking questions and suggesting that the nuclear force may not be a correct explanation of reality.

But that begs the question: Why does the Standard Model agree so well with experiment?

Probably the same place that the universe came from. Are you suggesting that God can be ruled out?

I'm saying that there is no need to introduce it. Likewise, there is no reason to introduce an energy well whose source is unknown.

 

[quantumdude]

This is high school physics, Newton's laws. Your statement that the loss of mass by simply dropping the ball will cause S1 to speed up is patently absurd. I am sure you will realize that when you reread your post.

I reread my posts, and now I see that I did not write what I intended to say. That's my fault, and I'm sorry for the confusion.

I meant for the exchange to be "sticky". That is, one skater actually rips the ball from the other's grasp, so that a fricitonal force develops between the skaters' hands and the ball. So, a force acts on each skater for a brief time interval. That sets both skaters into motion, and they will continue in that state of motion until acted on by a force.

Sorry, I've written this analogy so many times, in so many posts, that I got sloppy.

 

[Andrew Mason]

But that begs the question: Why does the Standard Model agree so well with experiment?

Probably because it was designed to explain experimental data. The Standard model made sense of a vast array of experimental data and reduced great complexity to something simpler. But even those who built the Standard Model don't really believe that it is the ultimate theory.

Murray Gell-Mann writes in his 1994 book "The Quark and the Jaguar" that the Standard Model is an ad hoc theory rather than a theory built on fundamental principles (like General Relativity, Newton's Laws, Maxwell's EM equations). It describes many interactions but does not relate them to each other. It requires arbitrary constants that are experimentally determined and not derivable from principle. And it does not include gravity. Despite all this, it is remarkably successful in explaining and predicting experimental data. It works. But that doesn't mean it is the last word as a theory.

I'm saying that there is no need to introduce it. Likewise, there is no reason to introduce an energy well whose source is unknown.

Until we know everything there is to know I wouldn't want to speculate on God's role in all of this.

I didn't introduce an energy well whose source is unknown. Empirically it has been shown to exist. Its source is unknown. I am just trying to understand what it represents. So far I see two possibilities: It could represent a strong force over a very short distance. Or it could represent something else.

Andrew Mason

 

[ZapperZ]

Probably because it was designed to explain experimental data. The Standard model made sense of a vast array of experimental data and reduced great complexity to something simpler. But even those who built the Standard Model don't really believe that it is the ultimate theory.

Murray Gell-Mann writes in his 1994 book "The Quark and the Jaguar" that the Standard Model is an ad hoc theory rather than a theory built on fundamental principles (like General Relativity, Newton's Laws, Maxwell's EM equations). It describes many interactions but does not relate them to each other. It requires arbitrary constants that are experimentally determined and not derivable from principle. And it does not include gravity. Despite all this, it is remarkably successful in explaining and predicting experimental data. It works. But that doesn't mean it is the last word as a theory.

Apparently, this thing will simply not go away...

Again, your information is a bit dated like your Feynman text. While the Standard Model came into being as a phenomenological model (as most anything that is new), it has outgrown that status! It has made several predictions that have been verified to be true. There are sound theoretical description that can verify many of its components. You would have known this had you studied something like Perkin's High Energy Physics text. So saying that the Standard Model is nothing more than an "ad hoc" theory in its CURRENT form is like saying the Maxwell equation is nothing more than a collection of experimental observation. Theories and descriptions evolve! 1994 may have been a good year, but man, that is ancient history in many areas of physics.

There are plenty of indications that the Standard Model isn't complete. No high energy physicist in their right mind would even claim that. However, these indications do not come from what you have in mind, nor based on what you have suggested.

May I also suggest that you do not try to counter a physics argument with quotations? Not only are quotations often taken out of context (Einstein's "knowledge-imagination" is a prime example), but also they mean nothing in a physics discussion of CONTENT. Open any physics journals and you will not see a rebuttal or a comment on a physics paper done simply via quotations.

I'm curious. Are you still hanging on to this question: "Can anyone explain to me why gravity would not be a significant force on the 'surface' of a proton or neutron?" In other words, are you still under the false impression that GRAVITY can produce a significant force in nuclear binding?

Zz.

 

[marlon]

A very nice question to you Andrew...from our most friendly science advisor, who is always in "the very best of moods"...


marlon

 

[Andrew Mason]

I'm curious. Are you still hanging on to this question: "Can anyone explain to me why gravity would not be a significant force on the 'surface' of a proton or neutron?" In other words, are you still under the false impression that GRAVITY can produce a significant force in nuclear binding?

I never said that gravity explained nuclear binding. I just pointed out that gravity on the 'surface' of a nucleon would be sufficient to keep nucleons together - ie. a little separation would cause the nucleons to return together quickly. The nuclear binding energy (of, say, a deuteron) is a different matter. It can't be explained by gravity as we know it, and I never suggested it was.

The atoms of H_2 can escape their EM binding energy 'well' without adding mass to the protons or electrons that comprise those atoms. The nucleons in a nuclear binding energy 'well' can only escape by adding mass to those nucleons. I am suggesting that the nuclear binding energy (or mass creation energy) can be thought of as a kind of barrier to exit rather than a force that keeps the nucleons together. If that is the case, then gravity could be the only force inside that barrier.

Andrew Mason

 

[quantumdude]

Probably because it was designed to explain experimental data.

OK, now we're getting somewhere. Now all I have to do is get you to accept that fitting the data is a good reason to accept[/color] a theory, rather than to reject[/color] it.

The Standard model made sense of a vast array of experimental data and reduced great complexity to something simpler. But even those who built the Standard Model don't really believe that it is the ultimate theory.

Of course they don't, and I don't believe that it's the ultimate theory either. But you can be assured that the next step in the process will not involve turning our backs on the Standard Model. In fact, it will most certainly be a requirement of the next theory that it include the Standard Model as a special case.

Murray Gell-Mann writes in his 1994 book "The Quark and the Jaguar" that the Standard Model is an ad hoc theory rather than a theory built on fundamental principles (like General Relativity, Newton's Laws, Maxwell's EM equations). It describes many interactions but does not relate them to each other. It requires arbitrary constants that are experimentally determined and not derivable from principle. And it does not include gravity. Despite all this, it is remarkably successful in explaining and predicting experimental data. It works. But that doesn't mean it is the last word as a theory.

Agreed.

Until we know everything there is to know I wouldn't want to speculate on God's role in all of this.

And there is no need to. Furthermore, there is no need to speculate on the role of a mysterious energy well that comes from nowhere and corresponds to nothing we know of. Do you agree?

I didn't introduce an energy well whose source is unknown. Empirically it has been shown to exist. Its source is unknown. I am just trying to understand what it represents. So far I see two possibilities: It could represent a strong force over a very short distance. Or it could represent something else.

Here's where I see this going.

You think that the strong force doesn't exist and that the EM force mysteriously turns off--for no apparent reason--at subnucleonic distances. In place of that you think that gravity + a potential well is responsible. But the gravitational interaction that is necessary to account for experimental data could not possibly be the same one that we know of classically. Therefore, we are looking at a gravitational interaction that is nothing like Newton's or Einstein's conception of it. We are looking at an interaction that behaves altogether differently from Newton's or Einstein's gravity at a very short distance, that holds the nucleus together, and that accounts for the observed hadron spectra.

I contend that you are simply attaching the label "gravity" to what is more commonly known as "the strong interaction".

 

[ZapperZ]

I never said that gravity explained nuclear binding. I just pointed out that gravity on the 'surface' of a nucleon would be sufficient to keep nucleons together - ie. a little separation would cause the nucleons to return together quickly.

But you can only say this if you complete turn OFF the coulomb force. What makes you think it is valid for you to extrapolate gravity up to that scale, and yet you keep complaining that EM fields should not work there? If you accept that gravity works the same way all the way to nuclear scale, then you should be fair and also invoke EM fields too! Then coulombic forces would have severely overwhelm the puny gravitational forces by comparison! Several people have already given you the order of magnitude difference between the two! And don't tell me that we have no experimental data that EM forces should work at that scale, because that argument can be used against your gravity also, which would then make your whole point moot.

The atoms of H_2 can escape their EM binding energy 'well' without adding mass to the protons or electrons that comprise those atoms. The nucleons in a nuclear binding energy 'well' can only escape by adding mass to those nucleons. I am suggesting that the nuclear binding energy (or mass creation energy) can be thought of as a kind of barrier to exit rather than a force that keeps the nucleons together. If that is the case, then gravity could be the only force inside that barrier.

I have no idea what you just said here or why it is even relevant. Atoms of H2 can "escape" from a "binding energy well"? Hello? I was talking about NUCLEAR binding, not MOLECULAR binding. H2 is a MOLECULE, and thus, each H atom have a molecular binding with the other H atom. This is NOT a nuclear binding energy. Please don't change or confuse the subject.

Zz.

 

[Andrew Mason]

But you can only say this if you complete turn OFF the coulomb force. What makes you think it is valid for you to extrapolate gravity up to that scale, and yet you keep complaining that EM fields should not work there? If you accept that gravity works the same way all the way to nuclear scale, then you should be fair and also invoke EM fields too!

Gravity appears to be different than the other forces. Nothing in EM or the Standard Model accounts for gravity. Only General Relativity does that. The principle of equivalence says that gravity and inertia can be considered equivalent, so gravity can be looked at as a pseudo-force or a curvature in space time. There is no evidence that space-time has quantum-like discreteness, unlike EM phenomena and the nucleus. So there is no reason to believe that gravity is any different at small distances. EM theory assumes point charges but we know that the proton is not a point charge.

According to the Standard Model, coulomb force is associated with the + and - 2/3 spin of quarks. The model does not explain how the coulomb force results from that and does not predict the nature of force that is created (perhaps my understanding of this is incorrect, in which case I would welcome correction). We don't really know where it begins. We only know that it is associated with quarks and exists in some region outside the proton, perhaps down to the quark level, perhaps not. Gravity, on the other hand, has no such limit because it is not so much a physical property of matter as it is a property of the space-time environment.

Then coulombic forces would have severely overwhelm the puny gravitational forces by comparison! Several people have already given you the order of magnitude difference between the two! And don't tell me that we have no experimental data that EM forces should work at that scale, because that argument can be used against your gravity also, which would then make your whole point moot.

I have explained why gravity would not turn off inside the nucleus. What evidence do we have that EM forces actually exist between protons in a He nucleus?

I have no idea what you just said here or why it is even relevant. Atoms of H2 can "escape" from a "binding energy well"? Hello? I was talking about NUCLEAR binding, not MOLECULAR binding.

Of course H atoms bind with EM molecular binding forces. I said "EM binding energy well" to distinguish it from nuclear binding energy.

My point was that there appears to be a fundamental difference between the two. Molecules can be separated without adding mass to the nuclei or electrons that compose those molecules. Nuculeons cannot be separated without adding mass to the nucleons.

H2 is a MOLECULE, and thus, each H atom have a molecular binding with the other H atom. This is NOT a nuclear binding energy. Please don't change or confuse the subject.

I was not trying to change the subject. I was just pointing out that separation of atoms in a molecule (which derives from a 1/r^2 force and therefore a -1/r energy potential) is very different from the separation of nuclear particles. I point out that one difference is that overcoming the nuclear potential results in adding mass to the separated parts (nucleons) while overcoming the EM potential does not add mass to the separated parts. While the energy required to separate atoms is the due to the need to apply a force over a distance, the energy required to separate nuclei is needed to create mass. Perhaps instead of looking at the nuclear binding energy as a continuous force between nucleons, we could look at it as a 'barrier' to separation. The analogy would be to a can of beans. The can prevents them from escaping. But it does not create a continuous force between the beans.

I am merely suggesting that if we looked at the nuclear potential in these terms, we would not need to invent a force that is enormous within a tiny distance (1 f.) and is effectively 0 outside that distance, and becomes repulsive at very short distances so as not to squish the nucleons.

Andrew Mason

 

[quantumdude]

There is no evidence that space-time has quantum-like discreteness, unlike EM phenomena and the nucleus. So there is no reason to believe that gravity is any different at small distances.

Yes, there is reason to think that quantum gravity is the correct path. You note general relativity, but fail to note that GR and QFT contradict each other. They can't both be right, and there is little doubt that a correct description of gravity will lead to a quantized theory.

According to the Standard Model, coulomb force is associated with the + and - 2/3 spin of quarks.

The electric charges are +1/3 and -2/3. All quarks have the same spin: 1/2.

The model does not explain how the coulomb force results from that and does not predict the nature of force that is created (perhaps my understanding of this is incorrect, in which case I would welcome correction).

As I noted in an earlier post, Coulomb's law is derivable from QFT. It is reducible to electric charges in motion. What the Standard Model does not explain is the existence of charges. But then again, neither does any other theory.

We don't really know where it begins. We only know that it is associated with quarks and exists in some region outside the proton, perhaps down to the quark level, perhaps not. Gravity, on the other hand, has no such limit because it is not so much a physical property of matter as it is a property of the space-time environment.

I have explained why gravity would not turn off inside the nucleus. What evidence do we have that EM forces actually exist between protons in a He nucleus?

We have yet to see a compelling reason to think that the EM interaction should switch off at any distance. And we have plenty of evidence in favor of the other side, in that all predictions of the Standard Model have been verified.

My point was that there appears to be a fundamental difference between the two. Molecules can be separated without adding mass to the nuclei or electrons that compose those molecules. Nuculeons cannot be separated without adding mass to the nucleons.

That's not true of molecules. There is a slight increase in mass.

I am merely suggesting that if we looked at the nuclear potential in these terms, we would not need to invent a force that is enormous within a tiny distance (1 f.) and is effectively 0 outside that distance, and becomes repulsive at very short distances so as not to squish the nucleons.

So instead, we invent a sourceless potential well to keep the nucleons together because gravity is not strong enough to keep them in, is that it?

I'm sorry, but this idea of yours hasn't a leg to stand on. The simple fact of the matter is that we would have to continue using the Standard Model, because there's not a single quantitative prediction here. And besides, you'd have to tailor the energy well just so that it fit the observed spectrum of hadrons. Whereas with the Standard Model, we have the following few ingredients:

1. Canonical quantization.
2. Special relativity.
3. A gauge group.

From just these 3 things, all the predictions follow.

 

[ZapperZ]

Your reply here is laced with ignorance and mistakes, and you seem to somehow have the ability to state all of the statements below as IF you have a complete knowledge of what you are stating. Nowhere in the immediate quote below was even a question or any sense of uncertainty of what you are stating:

Gravity appears to be different than the other forces. Nothing in EM or the Standard Model accounts for gravity. Only General Relativity does that. The principle of equivalence says that gravity and inertia can be considered equivalent, so gravity can be looked at as a pseudo-force or a curvature in space time. There is no evidence that space-time has quantum-like discreteness, unlike EM phenomena and the nucleus. So there is no reason to believe that gravity is any different at small distances. EM theory assumes point charges but we know that the proton is not a point charge.

According to the Standard Model, coulomb force is associated with the + and - 2/3 spin of quarks. The model does not explain how the coulomb force results from that and does not predict the nature of force that is created (perhaps my understanding of this is incorrect, in which case I would welcome correction). We don't really know where it begins. We only know that it is associated with quarks and exists in some region outside the proton, perhaps down to the quark level, perhaps not. Gravity, on the other hand, has no such limit because it is not so much a physical property of matter as it is a property of the space-time environment.

For someone who keeps insisting that all theories are subject to being challenged and being changed, you are quite arrogant in what you think gravitational theory should be and what it should not be. While GR has a number of verifications, in terms of degree of certainty, it has a LESS degree of certainty that classical E&M and QED. Now read that again - GR, which you are putting ALL your faith in, has a lower degree of certainty than classical E&M and QED. Furthermore, and pardon me for saying that, but I do not believe you even have a clue the complex theory of GR, much less are able to judge its validity.

Secondly, + and - 2/3 spin of quarks?!

Thirdly, you have this unhealth obsession with so-called "point charge". If you have studied physics at any considerable level, you would have noticed that the classical electrostatic description has an equivalent form to the classical gravitational description. There is a gauss's law equivalent for gravitational field, for example. Every single description for an electrostatic field, there is an identical equivalent for a gravitational field (except for the absence of an repulsive force). Thus, gravitational force ALSO considers the mass being acted upon as point mass sources! Someone should have clearly pointed this out in your original "derivation" of gravitational force. Don't believe me, go double check what you did... you put ALL of the mass of the proton to be at the radius of another proton. Ignoring the obvious fact that you have two protons overlapping each other already, you yourself are doing the very thing you are criticizing, lumping the mass of an object into a point mass.

So get over this "point charge" problem already.

I have explained why gravity would not turn off inside the nucleus. What evidence do we have that EM forces actually exist between protons in a He nucleus?

What evidence that it doesn't? We have no description or evidence that EM forces can just simply disappear. It is YOUR responsibility to prove that your "new imagination" has a valid impetus to be considered other than just something you thought of out of ignorance.

Of course H atoms bind with EM molecular binding forces. I said "EM binding energy well" to distinguish it from nuclear binding energy.

My point was that there appears to be a fundamental difference between the two. Molecules can be separated without adding mass to the nuclei or electrons that compose those molecules. Nuculeons cannot be separated without adding mass to the nucleons.

I was not trying to change the subject. I was just pointing out that separation of atoms in a molecule (which derives from a 1/r^2 force and therefore a -1/r energy potential) is very different from the separation of nuclear particles. I point out that one difference is that overcoming the nuclear potential results in adding mass to the separated parts (nucleons) while overcoming the EM potential does not add mass to the separated parts. While the energy required to separate atoms is the due to the need to apply a force over a distance, the energy required to separate nuclei is needed to create mass. Perhaps instead of looking at the nuclear binding energy as a continuous force between nucleons, we could look at it as a 'barrier' to separation. The analogy would be to a can of beans. The can prevents them from escaping. But it does not create a continuous force between the beans.

I am merely suggesting that if we looked at the nuclear potential in these terms, we would not need to invent a force that is enormous within a tiny distance (1 f.) and is effectively 0 outside that distance, and becomes repulsive at very short distances so as not to squish the nucleons.

Andrew Mason

This last set of paragraphs are a complete mystery to me. What EXACTLY is this about? Adding mass and not adding mass?? Applying force over a distance? Huh??! I have to add mass to separate nucleons? Tell me where I am adding mass in an alpha decay? And if you are somehow thinking that separated daughter nucleons ALWAYS have a higher total mass than the original parent nucleus, I have a fission reactor I want you to meet.

You are not suggesting anything. You are trying to ignore a huge part of physics that you have no clue on (QCD), and trying to replace it with your faulty physics knowledge. In the process, you are doing the exact same thing you are finding faults in with EM and QED. But what is even more appaling is that you are STILL insisting there is some validity in your faulty idea inspite of (i) your admission of lack of any serious knowledge in the matter you are talking about and (ii) the REPEATED explanation of those who are more knowledgeable than you on why your idea is wrong.

In the end, I find it ironic that you would spend time quoting Gell-Mann for something that suits your needs, and yet you blatantly reject his most significant contribution - the quarks and how they interact. I hate to think that this is how you practice your profession.

Zz.

 

[anti_crank]

I find it unbelievable that this thread is still going, and it raises serious doubts in my mind as to whether any progress is being accomplished. For the last time, I will summarize the main points:

-EM waves obey Maxwell's equations at all known ranges, including well past nuclear range. Hence it is contradictory to assume that classical forces from electrodynamics break down at such scales while the Maxwell equations stand since they come from the same mathematics.
-Scattering experiments confirm that the EM force works as expected. In fact, accelerators would not work if classical EM would break down at those scales/energies. In practice, we routinely accelerate particles to high energies (the LHC at CERN can accelerate protons to 100GeV) without any surprises.
-We know from scattering experiments that nucleons (protons/neutrons) have constituents, whose fractional charges can be measured and agree with the quark model
-The strong force model explains the observed spectrum of mesons and baryons beautifully. Heavy quark systems can be solved with the Schroedinger equation and an approximate, single-gluon exchange radial potential. The spectrum of allowed states for such systems matches observations very well.
-A force exists between nucleons and their constituents that allows certain decays which cannot be otherwise explained. The lifetimes are too small for the decays to be either electromagnetic or weak. We know this because lifetimes are inversely proportional to couplings. Gravity - unless strengthened immensly - is nowhere near the right coupling strength to allow such things.
-Gravity is negligible on the nuclear range, unless radical changes are made to it. Such changes are not warranted by any known results, and would make it a downright ugly theory. Try finding the ground state, using either Schroedinger eqn or Bohr quantization rules if Schr. is too hard, for a system of two heavy quarks bound by the gravitational potential. What's the expected radius - anywhere near the size of nuclei?
-Gluons are one prediction of QCD. Their existence, as well as some properties, can be inferred from three-jet events in accelerators and deep nuclear scattering experiments. The latter indicate that over 50% of a proton's momentum is carried by neutral (non-charged) constituents.
-Regarding neutron stars: see Nereid's post.

At this point, let me make an analogy that should make things clear. This problem has already been in the court of science, a court comprised of all scientists, past and present, who have dealt with this problem. Judgement has been passed by a large majority in favor of the strong nuclear force as presently known to provide the best explanation for the structure of nucleons. Since you've not provided any reasons for appeal that carry any merit upon in depth examination, the request for an appeal is denied. It's very possible for forensic experts to be wrong, and it simply goes to show the need to have multiple and independent experts analyse the problem and voice their opinion. Science is not dogmatic or authoritarian as is often believed by the general public, but relies on concrete evidence from experiments. This test was passed by the strong force, and it makes much less difference whether the experiments came before or after the theory than whether the experiments match the theory at all.

 

[quantumdude]

I'd like to thank everyone for their contributions, and ask that we move on.