Quantum gravity

Physics

Cosmic microwave background

Flatness (cosmology)

Entropy (arrow of time)

Diagrammatic reasoning

Astronomy

Horizon

Philosophy

Cosmology

Theoretical physics

Linguistics

Quantum cosmology

Quantum mechanics

Cosmic background radiation

Anisotropy

Cosmological model

Classical mechanics

Quantum

Classical and Quantum Gravity

We introduce the 'wedge diagram', an intuitive way to illustrate how cosmological models with a classical (non-singular) bounce generically resolve fundamental problems in cosmology. These include the well-known horizon, flatness, and inhomogeneity problems; the small tensor-to-scalar ratio observed in the cosmic microwave background; the low entropy at the beginning of a hot, expanding phase; and the avoidance of quantum runaway. The same diagrammatic approach can be used to compare with other cosmological scenarios.

Bouncing cosmology made simple