# Wikenigma - an Encyclopedia of Unknowns Wikenigma - an Encyclopedia of the Unknown

# Universe shape and size

The 'Observable Universe' is limited by the speed of light and the length of time that it has been in existence. It's possible that the 'Observable Universe' is the *real* size, or, because light has a finite speed, there may be more of the universe 'outside' the limit that we have so far been able to observe.

See : Expansion of the universeplugin-autotooltip__plain plugin-autotooltip_bigExpansion of the universe

unknowable

Current cosmological theory, backed up by many diverse observations, suggests that the universe is not only expanding, but that the speed of expansion is accelerating over time. Thus the limit of the observable universe is not only receding away from us (and from every other location in the universe) but the speed at which it recedes is increasing.

If the observable universe encompasses the entire universe, we may be able to determine the structure of the entire universe by observation. However, if the observable universe is smaller than the entire universe, our observations will be limited to only a part of the whole, and we may not be able to determine its global geometry through measurement. From experiments, it is possible to construct different mathematical models of the global geometry of the entire universe, all of which are consistent with current observational data; thusit is currently unknown whether the observable universe is identical to the global universe, or is instead many orders of magnitude smaller.

Source : Wikipedia

As noted above, as well as its size, the 'shape' of the universe is also unknown. Recent measurements indicate that it's probably 'flat' (i.e. with zero curvature).

The exact shape is still a matter of debate in physical cosmology, but experimental data from various independent sources (WMAP, BOOMERanG, and Planck for example) confirm that the universe is flat with only a 0.4% margin of error. Theorists have been trying to construct a formal mathematical model of the shape of the universe.

[source as above]

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