Do Photons Cast Shadows?

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This video is about two-photon (gamma-gamma) physics, and how photons can interact with each other - either mediated by a passing lepton, or gravitationally via lensing, or via vacuum fluctuation pair production of vertical particles (electron-positron pair, for example). This is the so-called "box diagram" feynman diagram.
REFERENCES
Water waves interact with each other (weakly nonlinear shallow water waves)
Paper: Absorption of Very High Energy Gamma Rays in the Milky Way
Paper: Observing light-by-light scattering at the Large Hadron Collider (LHC)
Mass-Energy Scale
Optical Depth
The electromagnetic spectrum and photon energies
Gravitational Lensing
Ask an Astrophysicist on gamma ray scattering and energies in cosmology
Measuring Vacuum Polarisation with High Power Lasers
Detecting vacuum birefringence with X-ray free electron lasers and high-power optical lasers
Vacuum birefringence in the head-on collision of XFEL and optical high-intensity laser pulses
ATLAS makes first direct detection of Light-by-light scattering at the LHC
Two Photon Physics
Thesis: The Opacity of the Universe for high and very high energy γ-rays
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Created by Henry Reich