0352

 No, photons do not travel at "maximum entropy."

Photon Basics

Photons are massless quanta of light that always move at the speed of light in vacuum, *c*. They do not decay spontaneously and can travel indefinitely unless absorbed or scattered by matter. Their energy redshifts due to cosmic expansion, gradually lowering it over time. [physicsforums](https://www.physicsforums.com/threads/light-entropy-will-photon-energy-last-forever.707861/)

Entropy Clarification

Entropy measures disorder or information content in a system, not a speed or travel state. A single photon has an intrinsic entropy derived from quantum processes, often *s = hν/T* for light in thermal equilibrium, where *h* is Planck's constant, *ν* is frequency, and *T* is temperature. Photons themselves are low-entropy carriers; they increase total entropy only upon interactions like absorption, which disperses energy. [pmc.ncbi.nlm.nih](https://pmc.ncbi.nlm.nih.gov/articles/PMC9688985/)

In Expanding Space

Free-streaming photons maintain constant proper entropy per photon but contribute to the universe's entropy growth indirectly through expansion and rare scatterings. Even in heat death scenarios, photons persist, but their diluted, uniform distribution prevents useful work, aligning with maximum universal entropy without implying photons are "at" it. [physicsforums](https://www.physicsforums.com/threads/is-there-an-effective-life-time-of-the-universe-where-it-will-reach-max-entropy.619135/)

https://www.perplexity.ai/search/do-photons-keep-traveling-at-m-9c4Vo3TAQDOpTkyFlj3tyA#0