Comment by westurner

Traditional belief: photons do not interact with photons, photons are massless according to the mass energy relation.

New findings: Photons interact as phonons in matter.

"Quantum entangled photons react to Earth's spin" (2024) https://news.ycombinator.com/item?id=40720147 :

> Actually, photons do interact with photons; as phonons in matter: "Quantum vortices of strongly interacting photons" (2024) https://www.science.org/doi/10.1126/science.adh5315 https://news.ycombinator.com/item?id=40600762

"New theory links quantum geometry to electron-phonon coupling" (2024) https://news.ycombinator.com/item?id=40663966 https://phys.org/news/2024-06-theory-links-quantum-geometry-... :

> A new study published in Nature Physics introduces a theory of electron-phonon coupling that is affected by the quantum geometry of the electronic wavefunctions