Editing Proton (section)

=== 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<sup>35</sup>&nbsp;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&nbsp;fm, negative (attractive) at greater distances, and very weak beyond about 2&nbsp;fm. These numbers were derived by a combination of a theoretical model and experimental 
[[Compton scattering]] of high-energy electrons.<ref name="Burkert2018" /><ref>{{Cite web |url=https://www.quantamagazine.org/swirling-forces-crushing-pressures-measured-in-the-proton-20240314/ |title=Wood C. Swirling Forces, Crushing Pressures Measured in the Proton. ''Quanta Magazine'' March 14, 2024 |date=14 March 2024 |access-date=April 1, 2024 |archive-date=April 1, 2024 |archive-url=https://web.archive.org/web/20240401060328/https://www.quantamagazine.org/swirling-forces-crushing-pressures-measured-in-the-proton-20240314/ |url-status=live }}</ref><ref>{{cite journal | last1=Burkert | first1=V. D. | last2=Elouadrhiri | first2=L. | last3=Girod | first3=F. X. | last4=Lorcé | first4=C. | last5=Schweitzer | first5=P. | last6=Shanahan | first6=P. E. |display-authors=1| title=Colloquium : Gravitational form factors of the proton | journal=Reviews of Modern Physics | volume=95 | issue=4 | date=2023-12-22 | issn=0034-6861 | doi=10.1103/RevModPhys.95.041002 | page=041002|arxiv=2303.08347| bibcode=2023RvMP...95d1002B }}</ref> However, these results have been challenged as also being consistent with zero pressure<ref>{{Cite journal |last=Kumerički |first=Krešimir |date=June 2019 |title=Measurability of pressure inside the proton |url=https://www.nature.com/articles/s41586-019-1211-6 |journal=Nature |language=en |volume=570 |issue=7759 |pages=E1–E2 |doi=10.1038/s41586-019-1211-6 |pmid=31168113 |bibcode=2019Natur.570E...1K |issn=0028-0836 |access-date=2024-03-27 |archive-date=2024-03-27 |archive-url=https://web.archive.org/web/20240327172609/https://www.nature.com/articles/s41586-019-1211-6 |url-status=live }}</ref> and as effectively providing the pressure profile shape by selection of the model.<ref>{{Cite journal |last1=Dutrieux |first1=H. |last2=Lorcé |first2=C. |last3=Moutarde |first3=H. |last4=Sznajder |first4=P. |last5=Trawiński |first5=A. |last6=Wagner |first6=J. |date=April 2021 |title=Phenomenological assessment of proton mechanical properties from deeply virtual Compton scattering |url=https://link.springer.com/10.1140/epjc/s10052-021-09069-w |journal=The European Physical Journal C |language=en |volume=81 |issue=4 |page=300 |doi=10.1140/epjc/s10052-021-09069-w |issn=1434-6044|arxiv=2101.03855 |bibcode=2021EPJC...81..300D }}</ref>