Newton and the Standard Model

[modest]

QEdit: spinoff from thread elsewhere.

 

 

IMHO, a sign of a good model is that you don’t have to keep adding complexity to it to explain increasingly precise observations. I agree with Erasmus that the Standard Model exhibits this sign.

 

 

Agreed, but adding fictitious forces is also a bad sign. The end result may be between a complex truth or a fake simplicity. That's where we stand now, no?

 

-modest

[CraigD]

IMHO, a sign of a good model is that you don’t have to keep adding complexity to it to explain increasingly precise observations. I agree with Erasmus that the Standard Model exhibits this sign.

Agreed, but adding fictitious forces is also a bid sign. The end result may be between a complex truth or a fake simplicity. That's where we stand now, no?

I’m not sure which forces you mean, modest. :naughty:

 

The Standard Model has only 5 fundamental bosons, two of which (the W and Z) are considered carriers of a single force (the weak nuclear), while 1 (the as yet unconfirmed Higgs) is not typically associated with a force, but rather with the common “opposing force” of inertia. A 6th boson, the graviton, is not an accepted Standard Model particle, for which reason the Standard Model does not explain gravity.

 

I must confess that, with my limited technical understanding of particle physics, I find the graviton attractive, and the Higgs unsatisfying and difficult to grasp – I don’t, on an intuitive level, “get” the flaws with the former, or the compelling virtues of the latter. I’ve been hoping for several years to gain an appreciation of the Higgs mechanism before it’s confirmed, or in time to be able to offer worthwhile commentary on its failure to be discovered with the expected energies and techniques.

[modest]

I’m not sure which forces you mean, modest. :naughty:

 

The Standard Model has only 5 fundamental bosons, two of which (the W and Z) are considered carriers of a single force (the weak nuclear), while 1 (the as yet unconfirmed Higgs) is not typically associated with a force, but rather with the common “opposing force” of inertia. A 6th boson, the graviton, is not an accepted Standard Model particle, for which reason the Standard Model does not explain gravity.

 

huh?

 

The standard model does not have fictitious forces. A fictitious force is added to an inadequate law to make it applicable. Like adding the centrifugal force to Newtonian physics. I was saying that quantum mechanics may be complex, but at least it has this going for it.

[Qfwfq]

A fictitious force is added to an inadequate law to make it applicable. Like adding the centrifugal force to Newtonian physics.

The centrifugal force is just one example of what Newton called "inertial forces", I would scarcely say that it was "added to Newtonian physics". BTW it is more common to call inertial forces "apparent" than "fictitious".

[modest]

The centrifugal force is just one example of what Newton called "inertial forces", I would scarcely say that it was "added to Newtonian physics". BTW it is more common to call inertial forces "apparent" than "fictitious".

 

Yes,

Inertial force = fictitious force = apparent force = pseudo force

 

My point is that the standard model does not have these apparently fictitious forces. This is a very fundamental difference between the two that no one often mentions when comparing them. Otherwise we could use gravity in quantum mechanics as an apparent force without a foundation.

[Qfwfq]

Field theory is based on Lagrangian formulation, in which there is, in a sense, hardly a need for the notion of force. The word is still used in parlance as a term meaning interaction, pretty much a synonym, rather than to indicate a derivative of momentum.

 

The problem with gravity is in quantizing it, and when people say that the standard model "doesn't include" gravity, the meaning is not that the two can't be used together in describing phenomena in which both are relevant.

[CraigD]

The standard model does not have fictitious forces.

…

I was saying that quantum mechanics may be complex, but at least it has this going for it.

I agree. I was simply confused by your previous post, which I thought might be suggesting that the Standard Model does have such forces, and sought clarification. You’ve given it, thank you, clearing up my confusion. B)

 

A fictitious force is added to an inadequate law to make it applicable. Like adding the centrifugal force to Newtonian physics.

Classical mechanics’s use of pseudo-forces is, I think, fundamental, and stated explicitly in its third law of motion

For every force acting on an object, the object will exert an equal, yet opposite, force on its cause.

The real centripetal force : pseudo centrifugal force pair are just a special case of this for circular motion.

 

In the formalism of the gravity-less Standard Model (which I, for the most part, can only discuss, not actually formally do), the third law appears to be embedded in the rules governing the “exchange” of bosons by fermions. For example, two charged bodies/particles in circular motion about their barycenter (eg: an electron and positron) exchange a “swarm” of virtual photons of magnetic force, each photon carrying a vector quantity of energy to each fermion, resulting in an outcome agreeing (statistically) with classical mechanics. There is no “inertia particle of equal yet opposite force” in the model for this example, just a complicated, counterintuitive exchange of photons.

 

I find the Standard Model very satisfying. It has, to me, a “bookkeeping” quality, even if I’m not quite capable of keeping them, nor, for large, complicated interactions, is anybody. As the saying goes, the best reality simulator is reality. B)

[Qfwfq]

The third law is "embedded in" momentum conservation.

[modest]

Qfwfq,

CraigD,

 

I am absolutely in agreement with what you both are saying. I should have formed my thoughts more clearly to avoid this confusion.

 

People are frequently saying that QM governs the small and NM governs the large. I have no problem with this. There is also another major difference that is not frequently discussed. As it relates to this discussion here it is:

 

In a more classical physics gravity is a correction to be applied to Newton’s laws. It is not inherent or implicit to Newtonian physics. It is rather explicit. Gravity in Newtonian Mechanics is a fictitious force applied because it must be. There is no theory behind it or cause. I’m not saying this is wrong or bad - it is just lacking.

 

In the standard model gravity also has no understood cause. People see this as a weakness (well, some people who I’ve seen posting here). But, gravity is no more lacking in QM as in NM. The real difference lies where Newton’s system needs no explanation to add a fictitious force - the standard model absolutely does. This is a credit to the standard model that some people don’t see. Without the graviton or the Higgs boson (or some other similar mechanism) gravity and the electroweak aren’t going to work the way we know they should. This sets the standard model completely apart from the classical laws.

 

That's what I was thinking anyway.

 

-modest

[Qfwfq]

Aside from the fact that I disagree with:

In a more classical physics gravity is a correction to be applied to Newton’s laws. It is not inherent or implicit to Newtonian physics. It is rather explicit.

I also see that you are now shifting the meaning of fictitious force when you say:

Gravity in Newtonian Mechanics is a fictitious force applied because it must be. There is no theory behind it or cause. I’m not saying this is wrong or bad - it is just lacking.

This is more a matter of epistemology. However:

 

In the standard model gravity also has no understood cause.

I would simply say that the standard model doesn't describe gravity at all. In a like manner, QED doesn't describe strong interactions and QCD doesn't describe electromagnetic ones. Your point is therefore not even a substantial epistemological objection. It is a well known thing, once put in the appropriate terms.

 

Now, it also depends on what you mean by "understood cause" and what it would mean if said about the other interactions, and that has a lot do do with the matter of quantizing gravity.

[modest]

I would simply say that the standard model doesn't describe gravity at all. In a like manner, QED doesn't describe strong interactions and QCD doesn't describe electromagnetic ones. Your point is therefore not even a substantial epistemological objection. It is a well known thing, once put in the appropriate terms.

I hope it is well known.

 

but in anycase, could someone offer me an explanation to the rationality of relying on two different sets of physics to explain the same particles, only on different scales?

 

You don't have apparent forces in the standard model of particle physics. This is not an objection or an attack on either - just a difference between the two. There are many other differences pointed out by others. There are good reasons why you cannot have apparent forces in QM and there are good reasons why there are apparent forces in NM.

 

Put another way:

 

If the action of a body in a non-inertial reference frame violates Newton's laws a fictitious force can be added (to the calculation) to give an apparent force. And, it is worth noting (to someone who does not know) you cannot do this in quantum mechanics. You cannot define apparent forces in the standard model because the whole meaning of force is different.

 

If this is an irrelevant point then I apologize, but I do not think I am in any way wrong and I'm not trying to be misleading.

 

-modest

[Qfwfq]

You don't have apparent forces in the standard model of particle physics. This is not an objection or an attack on either - just a difference between the two.

It isn't really a difference between classical and quantum mechanics:

...it is worth noting (to someone who does not know) you cannot do this in quantum mechanics.

Yes you can, if you consider the quantum description in coordinates which aren't inertial. This simply isn't usually done, in most cases coordinates are chosen in the most suitable way. Of course, if one were to consider a case in which gravity is important, it might be handier to consider it as a (term in the) potential than to choose locally inertial coordinates...:)

 

You cannot define apparent forces in the standard model because the whole meaning of force is different.

As I have already said, the standard model is an instance of field theory, so the whole notion of force isn't useful. Now, it is possible to recover the notion of a potential, as the overall effect of the plethora of virtual particle exchanges, at which point the matter become much like in basic QM.

 

In any case, this type of thing is not of much interest and researchers find no problem with it. In courses, it isn't pointed out because it isn't essential; the brightest students can see this for themselves and if the less bright ones ask the professor, usually it'll just be patiently clarified.

 

If this is an irrelevant point then I apologize, but I do not think I am in any way wrong and I'm not trying to be misleading.

Fine. :) Folks here are ready to discuss the matter and show you what you are missing, I just thought it wasn't right to continue it in the original thread. I hope astrocuriousstudent hasn't already given up on finding help.

[modest]

 

As I have already said, the standard model is an instance of field theory, so the whole notion of force isn't useful. Now, it is possible to recover the notion of a potential, as the overall effect of the plethora of virtual particle exchanges, at which point the matter become much like in basic QM.

In any case, this type of thing is not of much interest and researchers find no problem with it.

 

“the whole notion of force isn't useful”

The notion of force is the point of the standard model. Interaction between particles through force-mediating particles is the backbone.

 

“not of much interest”

A physicist working with high-energy lasers or electromagnets might find the real-world effect of the force carriers ‘interesting’.

 

You don't have apparent forces in the standard model of particle physics. This is not an objection or an attack on either - just a difference between the two.

It isn't really a difference between classical and quantum mechanics:

 

The three fundamental forces in the standard model have cause and effect and foundation implicit to them. These assets are a part of the model. However, if the force of gravity is to be described in the standard model as a quantum mechanical analog to Newtonian gravity using fictitious potentials as you describe then gravity does not inherit these qualities that the other forces have. Gravity is still an effect without a cause. Both theories equally lack the ability to describe a force behind gravitation.

[Qfwfq]

You are failing to read my posts properly and completely and you misconstrue things that you do read. I don't see the point of arguing with you about it; if you are convinced of what you say, fine, but don't peddle it as fact. If you want to debate the matter, don't reply to my points by missing them and don't oscillate between different semantics of 'apparent' or 'fictitious'. I don't have to sort out your misunderstanding if you only misunderstand my attempts to clarify.

[Pyrotex]

...Agreed, but adding fictitious forces is also a bad sign. The end result may be between a complex truth or a fake simplicity. That's where we stand now, no?...

Well, no. That is not where we stand.

 

I fail to see how you conclude that 'centripetal' or 'centrifugal' forces are "fake" or "fictitious". If we put you in a cylinder with radius > 2 meters and spin it fast enough, those so-called "fake" forces will KILL YOU.

 

The 'centripetal' force is not "tacked on" or "added" to NM. It is implicit within NM. Third Law. It can be seen clearly by noting that circular motion is not "inertial". Circular motion requires that the vector of motion be changing continually. A changing vector is one definition of "accelleration". This means the body in circular motion is under accelleration continually. The origin of mechanical force via accelleration is an integral part of NM. :(

 

Again, from a different view. Assume a body attached to a horizontal wheel. Say a wooden horse on a merry-go-round, a common ride at amusement parks. At time T=1, the horse is going due East. At time T=2, the horse is going due South. The vector of motion of the horse has changed 90 degrees in the span of 1 unit of time. How could this be? Only because the wooden horse underwent an accelleration caused by its attachment to the spinning wheel. How can we understand the source of this accelleration? We equate the accelleration with a force that continually accellerates the body toward the center of the wheel.

 

If you are sitting on the horse, you will feel pulled in a direction away from the center of the wheel. This is the "reaction" you feel as a result of you and the horse being accellerated toward the center of the wheel. Action==reaction. :)

 

So. What part of this do you not understand? (if any) :)

[Pyrotex]

“the whole notion of force isn't useful”

The notion of force is the point of the standard model. Interaction between particles through force-mediating particles is the backbone. ...

I'm sorry Modest, but your understanding of elementary classical physics is either non-existent, or you are dissembling.

 

The notion of "force" is incredibly useful and powerful. It is as fundemental as the notions of "energy" and "accelleration". These were keystone concepts in Newton's Principia Mathematica, and all subsequent classical physics.

 

If you wish to change scales to the atomic and sub-atomic realm and talk about the exchange of particles, then do so. But the one does not contradict or change the other. "Force" at the sub-atomic scale is a different phenomenon than "force" at the human experience scale. Both these notions fulfill similar roles and have aspects in common, so they have the same name.

 

Modest, I think it's time you show some IQ if you want to be taken seriously around here. :)

[Qfwfq]

Actually Pyro his manner of quoting me has confused you too. The words he put in double quote are from the quote of my post, but it was somewhat like saying that Jesus Christ said "there is no God" according to the Bible. True, one may find those words in two of the Gospels, as being said by him.

 

Just goes to show, no point arguing when it isn't easy to keep track of who said what, and what they actually meant by it...