Why Quantum Gravity Doesn't Work

Try Opera Browser for free: https://opr.as/Opera-browser-physicsexplainedvideos Quantum mechanics and general relativity both describe nature with astonishing precision, but when we try to combine them using the same perturbative tools that work so well in quantum electrodynamics, the method breaks down. In QED, the small value of the fine-structure constant ensures that higher-order corrections remain tiny, allowing us to make incredibly accurate predictions. For gravity, however, the effective coupling grows with the square of energy. As we approach the Planck scale, loop corrections become unsuppressed, renormalisation fails, and smooth spacetime stops being a useful description. This does not mean physics itself collapses; it means our current mathematical framework reaches its limits. At low energies, quantum gravity works perfectly as an effective theory, giving small, well-defined corrections to Newton’s law. But at extremely high energies, perturbation theory loses predictive power, hinting that spacetime may be emergent from something deeper. 📚 Resources and References Lectures on Particle Physics — David Tong https://www.damtp.cam.ac.uk/user/tong/particle.html Quantum Gravity at the Planck Length — Joseph Polchinski (SLAC Summer Institute Lectures) https://arxiv.org/abs/hep-th/9812104 Particles, Feynman Diagrams and All That — Michael Daniel (IOP Physics Education) https://doi.org/10.1088/0031-9120/41/2/001 https://faculty.washington.edu/seattle/physics541/%202010-reading/diagrams-3.pdf Gravity as a Quantum Field Theory — Roberto Percacci (Symmetry) https://www.mdpi.com/2073-8994/15/2/449 Quantum General Relativity and Effective Field Theory — John F. Donoghue https://arxiv.org/abs/2211.09902 Introduction to Elementary Particles — David Griffiths (Wiley-VCH) https://www.wiley.com/en-us/Introduction+to+Elementary+Particles%2C+2nd+Revised+Edition-p-9783527406012 String Theory (Cambridge Part III Lecture Notes) — David Tong https://www.damtp.cam.ac.uk/user/tong/string.html How Do Feynman Diagrams Work? — James Robert Brown (Perspectives on Science) https://direct.mit.edu/posc/article/26/4/423/15455/How-Do-Feynman-Diagrams-Work Why Quantum Gravity is Hard — David Wakeham https://hapax.github.io/physics/hacks/qgrav/ Quantum Gravity — Carlo Rovelli (Cambridge University Press) https://www.cambridge.org/core/books/quantum-gravity/9EEB701AAB938F06DCF151AACE1A445D Introduction to the Effective Field Theory Description of Gravity — John F. Donoghue https://arxiv.org/abs/gr-qc/9512024 QED: The Strange Theory of Light and Matter — Richard Feynman (Princeton University Press sample) https://assets.press.princeton.edu/chapters/i2352.pdf The Basics of Quantum Electrodynamics — Donie O’Brien (Trinity College Dublin) https://www.maths.tcd.ie/~donie/includes/QEDintro.pdf Quantum Gravity in Everyday Life — C.P. Burgess (Living Reviews in Relativity) https://arxiv.org/abs/gr-qc/0311082 🤝 Support the channel Patreon → https://www.patreon.com/physicsexplained (Your support allows me to devote more time to high-quality research, visuals, and explanations.) 🔗 Follow me Instagram → https://www.instagram.com/physics_explained_ig X (Twitter) → https://twitter.com/PhysicsExplain1