Consequences of proton size being smaller than thought to be?

[olee]

Hi, i was wondering what the implication is of the fact that the proton is smaller than was thought to be.

there is an article about it http://www.chem.info/News/Feeds/2010/07/topics-plant-operations-the-proton-smaller-than-thought/"

thanks

 

[alxm]

Well, we don't know for sure yet if that result is correct. But if we assume it is, the chemical effect? I can only assume you mean chemically, since this is the chemistry sub-board.

The answer to that is: No chemical consequences. It's too small an effect. Basically you don't need to take nuclear size into account whatsoever as far as chemistry is concerned. Usually it's treated as if it were infinitesimally small, and finite-size corrections are many orders of magnitude smaller than chemical energies. It's so small it couldn't even be measured accurately at all for an ordinary hydrogen atom. This result came from replacing the electron in helium with a muon.

For the physicists it's more interesting because there's a discrepancy between theory and experiment.

 

[olee]

Well, we don't know for sure yet if that result is correct. But if we assume it is, the chemical effect? I can only assume you mean chemically, since this is the chemistry sub-board.

The answer to that is: No chemical consequences. It's too small an effect. Basically you don't need to take nuclear size into account whatsoever as far as chemistry is concerned. Usually it's treated as if it were infinitesimally small, and finite-size corrections are many orders of magnitude smaller than chemical energies. It's so small it couldn't even be measured accurately at all for an ordinary hydrogen atom. This result came from replacing the electron in helium with a muon.

For the physicists it's more interesting because there's a discrepancy between theory and experiment.

Thanks for the reply. The article says they used http://i38.tinypic.com/1zobuyq.png". Surely the proton size affects spectroscopy, does it not?
I'm interested in the fact that you mentioned that it's more interesting for physicists. I'm not debating, but I was wondering if you could explain why that is so.

I appreciate the reply.

 

[alxm]

The article says they used http://i38.tinypic.com/1zobuyq.png". Surely the proton size affects spectroscopy, does it not? I'm interested in the fact that you mentioned that it's more interesting for physicists. I'm not debating, but I was wondering if you could explain why that is so.

Right, meant to say hydrogen of course. Yes, it affects spectroscopy, but not enough that it can be measured, ordinarily. The measurement here is of the hydrogen Lamb shift, a very slight shift between the 2s and 2p levels of the atom. Which is an effect of quantum electrodynamics (vacuum polarization). Calculating it theoretically requires using the charge-radius of the proton. The muon is 200x heavier than the electron, so it's 200x closer to the nucleus and the effect of nuclear structure in its Lamb shift is correspondingly magnified. Here, they found a discrepancy - either the calculations which worked for hydrogen didn't work anymore, or the size of the proton was different.

This interesting for the physicists because the Lamb shift is an important test-case for QED. If the experimental results hold, then something is wrong with the QED calculations of the Lamb shift, and while I wouldn't go so far as to assume something's wrong with QED itself, it might mean there's some as-of-yet-unknown effect they haven't been taking into account.

Chemically it's not interesting because when you talk about an energy of chemical interest, such as the heat of formation of a molecule (even a simple one such as H2), then the experimental accuracy is lower (say, 7 decimals for H2, as opposed to the 10-12 decimals for the Lamb shift), and theory matches experiment without having to take QED effects into account.

 

[LudusRex]

for your question. The discovery that the proton is smaller than previously thought has significant implications for our understanding of the fundamental building blocks of matter and the laws of physics.

Firstly, it challenges our current models of the structure of the atom. The proton is one of the three main components of an atom, along with neutrons and electrons. The size of the proton is a key factor in determining the size and stability of an atom. With a smaller proton size, the overall size and stability of atoms may need to be reevaluated.

Furthermore, the size of the proton also affects our understanding of the strong nuclear force, which is responsible for holding the nucleus of an atom together. A smaller proton size could potentially change the strength of this force and have implications for nuclear reactions and energy production.

Moreover, this discovery could have implications for our understanding of the universe and the formation of stars and galaxies. Protons play a crucial role in the formation of stars through the process of nuclear fusion. A smaller proton size could potentially affect the rate and efficiency of this process and impact our understanding of the evolution of the universe.

In addition, the discovery of a smaller proton size could also have practical applications in fields such as nuclear energy and medicine. A better understanding of the size of protons could lead to more efficient and safer nuclear reactors, as well as improved techniques for medical imaging and radiation therapy.

Overall, the discovery of a smaller proton size has far-reaching consequences and will likely lead to further research and advancements in our understanding of the fundamental properties of matter. It is an exciting development in the field of physics and has the potential to revolutionize our understanding of the universe.