Can light block itself? The strange reality of photon interactions.
In short: While we usually think of photons as passing through one another like ghosts, they can actually collide. This video explores the complex physics behind how light interacts with itself and what it means for our understanding of the universe.
Photons typically do not interact directly because they lack a charge. However, they can undergo "light-by-light scattering" through several mechanisms: mediation by passing leptons, gravitational lensing, or vacuum fluctuation pair production—where photons briefly transform into virtual particles like electron-positron pairs.
These interactions are visualized using "box diagrams" in Feynman diagrams. Scientists have observed these effects using high-power lasers to measure vacuum polarization and birefringence, as well as at the Large Hadron Collider (LHC), where the ATLAS experiment made the first direct detection of light-by-light scattering.
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- Summary by Intellect · source: Do Photons Cast Shadows?
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