Uploads from Physics Explained

Currently Playing: The Brightest Thing That Can Ever Exist

Huge thanks to Careerist for sponsoring the video. Launch your career in tech today: https://crst.co/5kksy Is there a fundamental limit to how bright the universe can get? From household light bulbs to supernovae, quasars, and colliding black holes, the universe produces staggering bursts of energy. In some of the most extreme events ever observed, the energy released per second briefly rivals that of entire galaxies. So can luminosity increase without bound, or do relativity and gravity impose a hard ceiling? In this video, we build a simple but powerful argument using Einstein’s theories. Special relativity limits how fast energy can escape a region of space, while general relativity limits how much energy can be packed into that region before gravitational collapse occurs. When these constraints are combined, a remarkable scale emerges: a maximum possible luminosity, set only by the speed of light and Newton’s gravitational constant. This scale, known as the Planck luminosity, is unimaginably large, exceeding the combined light of every star in the observable universe. Yet no confirmed observation has ever exceeded it. We explore why this bound appears to exist, why it is uniquely classical in three spatial dimensions, how it connects to the idea of a maximum force, and what it may be telling us about spacetime and quantum gravity. 📚 Resources & References • Corrado Massa — Does the Gravitational “Constant” Increase? Astrophysics and Space Science (1995) https://link.springer.com/article/10.1007/BF00627550 https://adsabs.harvard.edu/full/1995Ap%26SS.232..143M • LIGO Scientific & Virgo Collaborations — Observation of Gravitational Waves from a Binary Black Hole Merger (GW150914) Physical Review Letters (2016) https://arxiv.org/abs/1602.03837 • LIGO Scientific & Virgo Collaborations — The Basic Physics of the Binary Black Hole Merger GW150914 https://dcc.ligo.org/public/0126/P1600161/013/BBHBasicsANDPFullAuth.pdf • Aden Jowsey & Matt Visser — Reconsidering Maximum Luminosity International Journal of Modern Physics D (2021) https://arxiv.org/abs/2105.06650 • Vitor Cardoso, Taishi Ikeda, Christopher J. Moore & Chul-Moon Yoo — Remarks on the Maximum Luminosity Physical Review D (2018) https://doi.org/10.1103/PhysRevD.97.084013 https://arxiv.org/abs/1803.03271 • Wolfgang Wieland — Evidence for Planck Luminosity Bound in Quantum Gravity Classical and Quantum Gravity (2025) https://arxiv.org/abs/2402.12578 https://doi.org/10.1088/1361-6382/adb536 • John D. Barrow & G. W. Gibbons — Maximum Tension: With and Without a Cosmological Constant Monthly Notices of the Royal Astronomical Society (2015) https://arxiv.org/abs/1408.1820 • Craig J. Hogan — Energy Flow in the Universe NATO Science Series / Springer https://doi.org/10.1007/978-94-010-0540-1_13 https://arxiv.org/abs/astro-ph/9912110 • Charles W. Misner, Kip S. Thorne & John Archibald Wheeler — Gravitation W. H. Freeman (1973) • John D. Barrow & Frank J. Tipler — The Anthropic Cosmological Principle Oxford University Press https://global.oup.com/academic/product/the-anthropic-cosmological-principle-9780192821473 • Christoph Schiller — Motion Mountain, Vol. II: Relativity and Cosmology https://www.motionmountain.net/book.html • P. G. Tello et al. — Breaking Spacetime European Journal of Physics (2025) https://doi.org/10.1088/1361-6404/ae04b4 https://cds.cern.ch/record/2947203/files/document.pdf 🤝 Support the channel Patreon → https://www.patreon.com/physicsexplained (Your support helps fund research time, visuals, and high-quality explanations.) 🔗 Follow me Instagram → https://www.instagram.com/physics_explained_ig X (Twitter) → https://twitter.com/PhysicsExplain1