Cosmological principle

Unsolved problem in physics:

Is the universe homogeneous and isotropic at large enough scales, as claimed by the cosmological principle and assumed by all models that use the Friedmann–Lemaître–Robertson–Walker metric, including the current version of the ΛCDM model, or is the universe inhomogeneous or anisotropic?^[1]^[2]^[3]

(more unsolved problems in physics)

In modern physical cosmology, the cosmological principle is the notion that the spatial distribution of matter in the universe is uniformly isotropic and homogeneous when viewed on a large enough scale, since the forces are expected to act equally throughout the universe on a large scale, and should, therefore, produce no observable inequalities in the large-scale structuring over the course of evolution of the matter field that was initially laid down by the Big Bang.

^ Cite error: The named reference Snowmass21 was invoked but never defined (see the help page).
^ Cite error: The named reference Billings was invoked but never defined (see the help page).
^ Cite error: The named reference Migkas et al was invoked but never defined (see the help page).

[Snowmass21-1] Cite error: The named reference Snowmass21 was invoked but never defined (see the help page).

[Billings-2] Cite error: The named reference Billings was invoked but never defined (see the help page).

[Migkas_et_al-3] Cite error: The named reference Migkas et al was invoked but never defined (see the help page).

[1]

[2]

[3]