Why Can Light Travel Billions of Years Without Running Out of Energy? | Brian Greene Explains

How can a beam of light cross the universe for billions of years and still reach us? In this video, physicist Brian Greene explains why light doesn’t “run out of fuel” the way a car, a rocket, or any moving object eventually does. We explore: Why light has no mass and why that changes everything How photons carry energy without needing to be pushed or powered Why light only loses energy through redshift, not through travel itself How the expansion of space stretches light’s wavelength over cosmic distances Why we can still see ancient light from the earliest galaxies Whether you’re curious about physics, astronomy, or the nature of the universe, this explanation will change the way you think about the light reaching your eyes from distant stars. If you enjoyed this video, like, comment, and subscribe for more science explained clearly. Hashtags: #briangreene #light #physics #astronomy #cosmology #universe #space #science #photons #redshift #spacetime #astrophysics #scienceexplained #quantumphysics Tags: Brian Greene, Brian Greene explains, why light never runs out of energy, how light travels billions of years, can light run out of energy, how does light travel through space, light travel across the universe, photons explained, what is a photon, light has no mass, speed of light, cosmological redshift, expanding universe, space expansion, ancient light, light from distant galaxies, how far can light travel, does light lose energy, physics explained, astronomy explained, cosmology, astrophysics, universe, space and time, theoretical physics, science explained, science documentary, Brian Greene physics, Brian Greene universe, Brian Greene light Disclaimer: This video is created for educational and informational purposes only. All rights to the original content, including the speaker’s likeness, voice, and ideas, belong to their respective owners. This channel is not affiliated with, endorsed by, or sponsored by Brian Greene or any associated organization. Clips and commentary are used under the principles of fair use for the purposes of education, commentary, and discussion. If you are the copyright owner and have any concerns about this content, please contact us and we will address the matter promptly.