[mike777]

Read an article today about Protons. It seems they are made up of three Quarks. The mystery is that the Quark's properties of mass, spin and magnetic moment do not add up. For instance the Mass of the quarks are only 1.5% of the Proton. Virtual Quarks are suppose to make up the difference but experiments imply otherwise.

Just as the Proton seems to be missing stuff I may be missing a few facts here. Can any one help solve this mystery?

[DrTodd13]

First off, a proton consists of 3 quarks, two of which are typically of the same type. There are 6 quark types but only 2 of these are found in "stable" matter, the up quark and the down quark. As far as I knew, the spin and magnetic moment were accounted for but only the mass offered any real curiosity. The last thing I saw said that the additional energy was "binding" energy. I had not heard anyone seriously suggesting that virtual quarks somehow add to the mass of the proton.

[mike777]

Right 3 Quarks not kinds of quarks. Adding up the spins only gives you 20-30% of the Proton's spin. They call this a "spin crisis" Also it seems only one-third of the magnetic moment is explained by the 3 Quarks. Virtual quarks were suppose to make up the balance but seem not to.

Also "Strange Quarks" are flitting in and out of existence but they all fall short of adding up. Even adding in the Gluons(binding energy) does not help. They may contribute somewhere from zero to forty percent of spin resulting in a spin crises 2?

Hopefully I got these facts correct but even so it seems this is a mystery?

[helene_t]

How can you have 20-30% of the spin? I thought spin was a discrete property.

[mike777]

helene_t, on May 20 2006, 08:49 AM, said:

How can you have 20-30% of the spin? I thought spin was a discrete property.

If I understood the article correctly, you can break down the spin of the Proton into its component spin parts. The article says there is a spin crisis, the component spins do not add up. The quarks have different spin properties but they should add up.

The mass and magnetic momentum components also do not add up. That is the mystery. I was hoping there are some scientists out there who could explain.

[bid_em_up]

I dont know, but it all sounds kinda quarky to me.

[whereagles]

The mass that is missing is indeed binding energy.

The proton is actually quite hard to understand, even for nuclear physicists. For instance, the 3 quarks are confined within the proton and that isn't well understood. In fact, explaining confinement is a million-dollar question.

[mike777]

whereagles, on May 23 2006, 09:51 AM, said:

The mass that is missing is indeed binding energy.

The proton is actually quite hard to understand, even for nuclear physicists. For instance, the 3 quarks are confined within the proton and that isn't well understood. In fact, explaining confinement is a million-dollar question.

If it is energy than how can it be missing mass, it is energy? energy converted from mass maybe but still energy and not mass?

[helene_t]

Energy and mass are the same thing, Mike. When a 50-kg person climbs a 10-meter staircase, the Eart-person two-body system aquires 5000 joule of potential energy and therefore also aquires a mass gain of (5000 divided by the square of the light speed) kilograms. The same thing happens if you squeeze three mutual repelling quarks into each others neigbourhood.

[luke warm]

slightly off topic here, but i have a question concerning helene's formula which uses the square of light speed...

if this constant is/can be used in energy formulas, has the fact (i assume it's a fact) that the speed of light has been shown to be not quite so constant as we thought affected any of the formulas that use it?

[mr1303]

The speed of light is calculated from the following formula

α = e^2 / h bar c

where e is the charge on an electron, h bar is h/2 pi (where h is Planck's constant) and alpha is the fine structure constant, which is related to the strength of the electromagnetic force.

Somewhere in Oklo, there is a "natural" nuclear reactor, where Uranium 235 undergoes fission to form Samarium 149, which can capture neutrons to form Samrarium 150. The rate of this neutron capture is meant to be proportional to alpha.

Depending on who you ask, the rate has varied over the past 2 billion years. If it has, then alpha has varied, and so c has varied. If not, then alpha has not and so c has not.

Source: New scientist, June 2004.

In my opinion, since the fact that the speed of light is or isn't constant hasn't been accepted either way, the equations that use it shouldn't be considered to vary either.

[Gerben42]

All these theories about varying constants is nice but are there any observations to support this? I would think it'd be highly problematic to have a varying light speed.

[helene_t]

In what way "varying"? Light travels faster in vacuum than in chicken soup, but it's the speed of light in vacuum that counts when you compute mass/energy equivalents, even if the proton is bound in a chicken soup molecule.

(Oh sorry, obviously it means that it was different in the past).

But to answer Jimmy's question: yes, if the speed of light was different yesterday then I gained a different mass when I climbed my staircase yesterday.

This post has been edited by helene_t: 2006-May-24, 04:24

[slothy]

helene_t, on May 24 2006, 03:23 AM, said:

In what way "varying"? Light travels faster in vacuum than in chicken soup,

IF you ever tasted my ex-wife's chicken soup, nothing never mind light, not even gamma rays can travel through it

[helene_t]

Gerben42, on May 24 2006, 09:42 AM, said:

I would think it'd be highly problematic to have a varying light speed.

I would say so too. Suppose today it takes two seconds for a light beam to reach the moon, while yesterday it took one second. You could account for this in four ways:
1) The moon has moved further away
2) The speed of light has decreased
3) The grandfather-clock (more precisely, the gravity-based penudulum) has increased it's pace because of :
3a) The Earth has become heavier
3b ) The constant of gravity, G, has changed.

Without any other evidence, any of the four explanations is as good as any other, so you may chose the one you find estetically most appealing. My order of preference is:

3b ) Since I don't understand gravity anyway so I have no reason to prefer G to stay constant.

1) The problem with this is that it violates conservation of angular momentum, unless offset by some other adjustment. But I'm sure some tricks with wormholes or such can solve that issue.

3a) Seems to violate conservation of mass. You would have to postulate some invisible flux of matter into the Earth, and it would have to come frome somewhere.

2) You can't have conservation of mass and conservation of energy at the same time if the speed of light is allowed to change. So that would be my last choice.

[Al_U_Card]

How about the exchange of gluons between quarks? This not only keeps them "together" in the proton, the force they exchange gets stronger the farther apart they are! "And I think to myself......what a wonderful world"

[whereagles]

mike777, on May 23 2006, 05:18 PM, said:

whereagles, on May 23 2006, 09:51 AM, said:

The mass that is missing is indeed binding energy.

The proton is actually quite hard to understand, even for nuclear physicists. For instance, the 3 quarks are confined within the proton and that isn't well understood. In fact, explaining confinement is a million-dollar question.

If it is energy than how can it be missing mass, it is energy? energy converted from mass maybe but still energy and not mass?

E = mc^2

E = energy
m = mass
c^2 = velocity of light, squared

Ok, it's more complicated than that, but I think you see the point now.

[whereagles]

Gerben42, on May 24 2006, 07:42 AM, said:

All these theories about varying constants is nice but are there any observations to support this? I would think it'd be highly problematic to have a varying light speed.

Why problematic? Varying speed of light actually solves a couple of problems in cosmology. I agree it feels a bit strange, but it doesn't break any fundamental law of physics. It's just food for thought.

As for observations: no, there aren't any. The variation is normally taken in the very early universe, like in the first 3 minutes. After that the speed of light became what we see today.

[whereagles]

helene_t, on May 24 2006, 12:06 PM, said:

You can't have conservation of mass and conservation of energy at the same time if the speed of light is allowed to change.

Not sure if applying a straightforward E = mc^2 is enough to validate your reasoning. I'd have to check the original papers on the subject, but I don't think a variable c is going to spoil anything.

[Al_U_Card]

The energy in ergs (dyne cm/ sec 2) is equal to the mass in grams times the (speed of light in cm/sec ) squared.

Variable values of c are postulated for all kinds of phenomena such as the hyper inflation of the early universe as well as explaining how we came to have an excess of matter which resulted in the observable universe.