English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We show that the rest mass of a system consisting of two photons is arelativistic invariant having the same magnitude in all inertial referenceframes in relative motion. A scenario which starts with two photons wheretheirs frequencies are equal to each other the magnitude of the rest mass ofthe system depends on the angle made by the momentums of the two photons. Thebehavior of the photons when detected from two inertial reference frames isillustrated using a relativistic diagram which displays in true values thephysical quantities (scalar and vector) introduced in order to characterize thedynamical properties of the photon. We consider that the obtained resultsshould be taken in the discussions, some time fierce, between those who ban theconcept of relativistic mass and those who consider that its use is harmless.

The rest mass of a system of two photons in different inertial reference frames: 0+0=0 and 0+0>0