# Proton Radius: Is it a Sphere or Shell?

• neurocomp2003
In summary, the radius of a proton is approximately 10^-15 meters. This radius can be thought of as a bounding volume or energy barrier for the quarks that make up the proton. However, this is just an approximate limit and as you get closer, the strong nuclear force becomes more significant. The charge radius of a proton is about 0.8 femtometers and the wave function is approximately spherical. When getting even closer, about 0.1 fermi, the strong force drops again and becomes repulsive. This can be seen in the iron-core-rebound responsible for certain types of supernovae. There have been studies on the possible shapes of a proton, with a less-technical report available for further reading.
neurocomp2003
a proton is given a radius...i think its ~10e-15
since a proton is uud is this "radius" like [1]a electron orbital density cloud that is said to be in atoms...that is to say that its a bounding volume(ie in computer geometry) or [2]an energy barrier on the uud of this radius size? Or [3]there is a shell that surrounds the uud?

I think it is just an approximate limit beyond which the strong nuclear force becomes significant. In other words, get closer than about 1 femtometre and you're into the range at which the quarks bind together. Beyond that, the strength of the strong force drops off rapidly.

There's another really interesting aspect:get closer than 0.1 fermi and the strong force drops again...

Daniel.

The quarks in a proton have the same type of wave function as the electrons iin an atom. There is no definite boundary like the surface of the Earth.
The "charge radius" of the proton is defined as the square root of the expectation value <\rho r_2>=<\sum q_i r_i^2>, summed over the 3 quarks.
This rms charge radius is about 0.8 fm. The wave function is approximately spherical, corresponding to L=0 for the orbitals.

dextercioby said:
There's another really interesting aspect:get closer than 0.1 fermi and the strong force drops again...

Daniel.
...and becomes repulsive, no? Like in the iron-core-rebound which is responsible for some types of supernovae?

## 1. What is the proton radius?

The proton radius is the physical distance from the center of a proton to its outer edge. It is considered to be one of the fundamental properties of a proton.

## 2. Is the proton radius a sphere or a shell?

The answer to this question is still a topic of debate and research in the scientific community. Some theories suggest that the proton has a spherical shape, while others propose that it may have a shell-like structure.

## 3. How is the proton radius measured?

The proton radius is typically measured using scattering experiments, where particles such as electrons are directed towards protons and their interactions are observed. Other methods, such as spectroscopy, have also been used to determine the proton radius.

## 4. Has the proton radius been accurately determined?

The accuracy of the proton radius measurement has been a subject of controversy in recent years. Previous measurements using certain methods have yielded different results, leading to ongoing research and discussions in the scientific community.

## 5. What is the significance of knowing the proton radius?

Understanding the proton radius is crucial for our understanding of the structure of atoms and the fundamental forces that govern them. It also has implications in areas such as nuclear physics, astrophysics, and cosmology.

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