Beyond the standard Big Bang model

Beyond the standard Big Bang model there may be a more accurate approximation (or generalization) than that of the standard model. Observational cosmologists consider the standard Big Bang model to be a good approximation to the Universe,

• in spatial extent from the Earth outwards towards the observational sphere
• and in time backwards from the present towards some limiting "time=zero"

It might be the case that the spatial size of the Universe is smaller than this observational sphere and so the whole Universe is observable. See the shape of the universe in the standard big bang model. Although, if there are structures of the universe outside of the observational sphere, they cannot be directly observed but may be possible to deduce its structure indirectly. For example, parts of the universe may have influenced the cosmic microwave background before expanding out of direct view.

Similarly, it may be possible to deduce what happened "before the big bang" by looking at indirect evidence. Speculations about what happened before the big bang usually involve quantum gravity.

• Plasma cosmology
• the quasi Steady State model
• chaotic inflation
• brane cosmology models (including ekpyrotic scenarios in which the big bang is the result of a collision between branes)
• models including the Hartle-Hawking boundary condition in which the whole of space-time is finite

Some of these scenarios are either qualitatively or quantitatively (algebraically) compatible with one another. Some are concerned with local properties (sometimes assumed the same everywhere), others also deal with global properties. Each involves a different number of elements of theoretical physics and/or heuristic hypotheses.

See also

• Cosmology
• List of astronomical topics
• Non-standard cosmology

References