### Einstein-de Sitter model

**(Einstein-de Sitter universe)**
(universe tuned to the smallest expansion that continues forever)

The **Einstein-de Sitter model** of the universe
(i.e., **Einstein-de Sitter universe**)
posits a universe constrained by gravity according
to general relativity, and expanding
just enough that it will continue expanding to infinity,
and no more than that. (Analogous is a rocket launched
at exactly escape velocity and no more.)
It is a particular **Friedmann model** for a **flat**
matter-only universe, i.e., at the critical density.
Friedmann models (or **Friedmann universes**)
are models of the universe adhering to the **Friedmann equations**,
a solution to Einstein's general relativity equations.
The Einstein-de Sitter model is, in effect, an approximation of
modern models such as the Lambda-CDM model, and before evidence of
dark energy was discovered, observation supported the Einstein-de
Sitter model and it was used as a realistic model.

An earlier model, termed a **de Sitter universe**, represents a
theoretical universe simplified in that the effects of matter are
ignored. It showed expansion of the universe and was early among models
that did so.

(*physics,model,cosmology*)
**Further reading:**

http://en.wikipedia.org/wiki/Einstein-de_Sitter_universe

http://en.wikipedia.org/wiki/De_Sitter_universe

https://ned.ipac.caltech.edu/level5/Watson/Watson2_4_1.html

http://www.einsteins-theory-of-relativity-4engineers.com/einstein-de-sitter.html

**Referenced by pages:**

anti-de Sitter space (AdS)

Friedmann model

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