Why Does Starlight Cross Billions of Light-Years Without Fading Away?

A flashlight fades in a few meters. So how does starlight cross billions of light-years and still reach your eyes? We look at what light is (zero mass, and no time at all), why space is silent but not dark, the inverse square law, how empty space really is, and the three things that do touch light on the way: redshift, dust and gravitational lensing. Then how Subaru, Hubble and Webb catch the faintest light, all the way back to the cosmic microwave background. The pictures are real photos and images from NASA, ESA, ESO and Wikimedia Commons. #space #science #astronomy Images and videos: The cosmic microwave background (Planck): ESA and the Planck Collaboration, CC BY 4.0 — https://commons.wikimedia.org/wiki/File:Co... The Sun (SDO): NASA/SDO (AIA), Public domain — https://commons.wikimedia.org/wiki/File:Th... The Andromeda Galaxy: Adam Evans, CC BY 2.0 — https://commons.wikimedia.org/wiki/File:An... Albert Einstein: public domain, Public domain — https://commons.wikimedia.org/wiki/File:Al... Neptune (Voyager 2): NASA, Public domain — https://commons.wikimedia.org/wiki/File:Ne... The Milky Way (ESO): ESO/S. Brunier, CC BY 4.0 — https://commons.wikimedia.org/wiki/File:ES... Edwin Hubble: Johan Hagemeyer, Public domain — https://commons.wikimedia.org/wiki/File:St... The James Webb Space Telescope (artist's impression): ESA, CC BY 4.0 — https://commons.wikimedia.org/wiki/File:Th... Webb's First Deep Field: NASA, ESA, CSA, and STScI, Public domain — https://commons.wikimedia.org/wiki/File:We... Sunset over the ocean: Lilac55, CC BY-SA 4.0 — https://commons.wikimedia.org/wiki/File:A_... The 1919 solar eclipse: Frank Watson Dyson / Arthur Eddington / Charles Rundle Davidson, Public domain — https://commons.wikimedia.org/wiki/File:19... Galaxy cluster Abell 2218 (Hubble): NASA, ESA, A. Fruchter and the ERO Team (STScI, ST-ECF), Public domain — https://commons.wikimedia.org/wiki/File:Th... The Subaru Telescope: International Gemini Observatory/NOIRLab/NSF/AURA/Subaru Observatory, CC BY 4.0 — https://commons.wikimedia.org/wiki/File:Su... Hubble Ultra Deep Field: NASA and the European Space Agency. Edited by Noodle snacks, Public domain — https://commons.wikimedia.org/wiki/File:Hu... The Holmdel Horn Antenna: Erik Dunham, CC BY-SA 3.0 — https://commons.wikimedia.org/wiki/File:Ho... The Moon: Luc Viatour, CC BY-SA 3.0 — https://commons.wikimedia.org/wiki/File:Fu... The Earth from Apollo 17: NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans, Public domain — https://commons.wikimedia.org/wiki/File:Th... BGM: Suno AI