section_path: Charge radius/Pressure inside the proton
section_name: Pressure inside the proton
paragraph_text: Pressure inside the proton
  
  Since the proton is composed of quarks confined by gluons, an equivalent pressure that acts on the quarks can be defined. The size of that pressure and other details about it are controversial.
  
  In 2018 this pressure was reported to be on the order 10 Pa, which is greater than the pressure inside a neutron star. It was said to be maximum at the centre, positive (repulsive) to a radial distance of about 0.6 fm, negative (attractive) at greater distances, and very weak beyond about 2 fm. These numbers were derived by a combination of a theoretical model and experimental Compton scattering of high-energy electrons. However, these results have been challenged as also being consistent with zero pressure and as effectively providing the pressure profile shape by selection of the model.