How much space inside a proton?

Question

AS per string-theory a proton contains 3 quarks right, so is there any estimate of how much of proton is empty and how much is occupied by quarks? some one told 1 part in 10^3 is occupied by quarks......how correct is this?

Answer 1

There are several subtleties in this question.

When discussing quantum level objects, it is rather difficult to talk about how much space they occupy. The reason is that they always have a wave nature and so are not localized. When we say that electrons and quarks are point particles, we mean that they act like such under the overall quantum picture of non-localized objects.

Next, when you say that protons are made of 3 quarks, this is a good first approximation, but is not strictly true. We usually think of protons as being made from two up quarks and one down quark. But it turns out that quarks can and do change types 'on the fly', so there is a substantial fraction of strange quark in a proton. There is also a significant contribution from the gluons that hold the quarks together inside the proton. Again, this has to do with the way quantum mechanical object behave. Protons are not simply three quarks which can be thought of as classical balls or even strings. They are much more dynamic that that.

Finally, in string theory, the length of the individual strings representing the quarks and other particles are on the order of Planck's length. This is *incredibly* small, so if you only use that in you computation of how much of a proton is empty, you will get much less that 1 in 10^3 occupied by quarks. Once again, the whole question is rather unusual in the quantum realm. More relevant is the 'cross section' of a proton to various reactions, but this 'size' can change a lot depending on the reaction considered.

Answer 2

I suspect the figure of 10^3 was in error.

You seem to be imagining that there is some imaginary 'shell' surrounding the quarks which we call "a proton." This is (obviously) not true. This means that we can't give a definitive volume of a proton (unless we take an average volume, given the size of the nucleus, but even then, the size of a nucleus is not known to much precision, except that it is of the order of 10^-15m)
FURTHERMORE, quarks are currently believed to be fundamental particles, much like electrons. They are also believed to be POINT particles. I.E. particles with no volume.
This means they occupy no space within the "imaginary proton boundary."
HOWEVER, quantum theory at such a minute level would lead us to believe that the position of a proton would be subject to a fairly large uncertainty. Indeed, if you treat the quarks as waves then you might reach the conclusion that they could occupy any position within the "imaginary proton boundary."

In short, the way that quarks interact to create a proton is still open to great debate, and current theories can only give superficial answers. If the person who told you it was 1 part in 10^3 was a respectable source (such as a leading physicist in sub-nuclear particle theory) then perhaps you should ask him for an explanation of how he came by the figure, otherwise i seriously doubt the validity of it.

Answer 3

No, string theory is not what tells us that a proton is made up of 2 up and 1 down quarks. String theory works at a much for fundamental level. It tries to explain what quarks are, and how each of the forces interact with fundamental particles, The theory that contains the quark model is QCD.

Before I answer your question about the proton you need to realize that when you start talking about particles such as protons, electrons, quarks, etc the idea of volume and distinct sizes breaks down. Quantum theories tell us that we can only measure the size of an object to a certain accuracy. When we start looking at fundamental particles this inaccuracy is on the order or larger than the physical size of the particle. In other words no matter how good we get at measuring the size of things, we will never be able to measure the size of the particles. This isn't the fault of our equipment, but its a law of physics. If physics tells us that we can't measure the size of something, then we must ask ourselves if the idea of volume or length really applies for these particles, and the answer is no. Now protons are large enough that we can measure their dimensions but quarks are not.

Answer 4

According to Quantron theory which is different from String theory; my Calculation indicates that Space structure occupies
52 percent of the Proton's Total Volume..
As far as quarks are concerned the posisition and volume of a quark structure has been Undetermined since they are Unable to identify the mass and function of these little broken pieces of the atom which they call quarks.
In Nuclear fisson the components of the Nucleous are split and has nothing to do with quarks. Therefore it means That the Quantron theory is more pausible because it breaks up the the elementary particles into smaller components.,
Hence The total rest mass structure of the Proton occupies only 48 per cent of its rest volume which is in the order of 10^-45 meter^3

Answer 5

Hi. That would depend on the density of quarks.

Answer 6

I believe there is no space in a proton, at least not like there is between an electron and a nucleus. A proton is tightly bound together.

Answer 7

It would be relative to the size of the measurer. A whole universe of tiny people could be in there.