Chapter 04 · A Theory of Everything
A Theory of Everything
Can all forces and particles be unified?
A unified theory has been the goal of fundamental physics since Einstein. String theory dominated for decades as the primary unification candidate. But several recent proposals reframe the question entirely: maybe unification is about replacing what sits underneath both quantum theory and general relativity, not about extending either. Read these alongside more conventional approaches.
Families (3)
- FrontierAsymptotic SafetyA quantum theory of gravity in its own right, no strings or supersymmetry needed. Gravity is asymptotically safe at the Planck scale: couplings approach a non-trivial fixed point, the theory stays predictive, and the same framework predicts the Higgs mass conditionally.5 variants
- FrontierString TheoryParticles as vibrating strings in 10 or 11 dimensions, with five mathematically consistent superstring theories unified by an 11D parent. Dominant unification candidate for four decades; the empirical contact problem and the landscape problem remain open.5 variants · Bridges to Ch. 1 String Landscape
- SpeculativeBeneath the Standard ModelFamiliar physics emerges from a deeper substrate; quantum theory and gravity are not the foundation.2 variants
Bridged from other chapters
These variants live in their own chapters but also answer this chapter's question.