Sign up for Brilliant (for free) and get 30 days of full access to all of their courses, go to https://brilliant.org/MinutePhysics - The first 200 people get 20% off a premium subscription! A lot of people took pictures of the recent solar eclipse in North America and got photos where there’s a ghostly image of the eclipse floating in the sky nowhere near where the sun is! REFERENCES: Lens flare prediction based on measurements with real-time visualization https://doi.org/10.1007/s00371-018-1552-4 Physically-Based Real-Time Lens Flare Rendering http://doi.acm.org/10.1145/1964921.1965003 From the Series of Articles on Lens Names: Tessar, by H. H. Nasse. Carl Zeiss Camera Lens Division March 2011 https://www.cambridgeincolour.com/tutorials/lens-flare.htm https://www.toolfarm.com/tutorial/in-depth-lens-flares-for-video/ https://petapixel.com/what-is-lens-flare/ https://www.maxon.net/en/red-giant/vfx-suite/real-lens-flares ****************************** Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics Link to Patreon Supporters: http://www.minutephysics.com/supporters/ MinutePhysics is on twitter - @minutephysics And facebook - http://facebook.com/minutephysics Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute! Created by Henry Reich ... https://www.youtube.com/watch?v=z_WRaTsGbVE

Thanks to CuriosityStream for their support. Go to http://www.curiositystream.com/minutephysics to watch Particle Fever and get Nebula! Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics Link to Patreon Supporters: http://www.minutephysics.com/supporters/ 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) https://en.wikipedia.org/wiki/Korteweg%E2%80%93deVriesequation http://mathworld.wolfram.com/Korteweg-deVriesEquation.html Paper: Absorption of Very High Energy Gamma Rays in the Milky Way https://arxiv.org/pdf/1608.01587.pdf Paper: Observing light-by-light scattering at the Large Hadron Collider (LHC) https://arxiv.org/pdf/1305.7142.pdf Mass-Energy Scale http://labs.minutelabs.io/Mass-Energy-Scale/ Optical Depth https://en.wikipedia.org/wiki/Opticaldepth The electromagnetic spectrum and photon energies http://labman.phys.utk.edu/phys222core/modules/m6/The%20EM%20spectrum.html Gravitational Lensing http://andybohn.com/research/lensing.html Ask an Astrophysicist on gamma ray scattering and energies in cosmology http://teacherlink.ed.usu.edu/tlnasa/reference/imaginedvd/files/imagine/docs/askastro/answers/970412e.html Measuring Vacuum Polarisation with High Power Lasers https://arxiv.org/pdf/1510.08456.pdf Detecting vacuum birefringence with X-ray free electron lasers and high-power optical lasers https://indico.desy.de/indico/event/12654/session/2/contribution/8/material/slides/0.pdf Vacuum birefringence in the head-on collision of XFEL and optical high-intensity laser pulses https://arxiv.org/pdf/1807.03302.pdf ATLAS makes first direct detection of Light-by-light scattering at the LHC https://atlas.cern/updates/press-statement/atlas-sees-first-direct-evidence-light-light-scattering-high-energy Two Photon Physics http://www.hep.ucl.ac.uk/opal/gammagamma/gg-tutorial.html https://en.wikipedia.org/wiki/Two-photonphysics Thesis: The Opacity of the Universe for high and very high energy γ-rays http://inspirehep.net/record/1254304/files/desy-thesis-13-033.pdf MinutePhysics is on twitter - @minutephysics And facebook - http://facebook.com/minutephysics And Google+ (does anyone use this any more?) - http://bit.ly/qzEwc6 Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute! Created by Henry Reich ... https://www.youtube.com/watch?v=Fv1JJ227CQk