Hubble volume

It is expected that at least one string per Hubble volume is formed.

In regard to configurations such as the distribution of matter, almost all will differ from our Hubble volume.

In principle, it would be impossible to scientifically verify an identical Hubble volume.

A key requirement is that inflation must continue long enough to produce the present observable universe from a single, small inflationary Hubble volume.

More generally, the term "Hubble volume" can be applied to any region of space with a volume of order .

This follows directly from the cosmological principle, wherein it is assumed our Hubble volume is not special or unique.

Given infinite space, there would, in fact, be an infinite number of Hubble volumes identical to ours in the universe.

However, because there are infinitely many, far beyond the cosmological horizon, there will eventually be Hubble volumes with similar, and even identical, configurations.

The Hubble volume is sometimes defined as a volume of the universe with a comoving size of .

However, the term is also frequently (but mistakenly) used as a synonym for the observable universe; the latter is larger than the Hubble volume.

Accordingly, an infinite universe will contain an infinite number of Hubble volumes, all having the same physical laws and physical constants.

If space is infinite, or sufficiently large and uniform, identical instances of the history of Earth's entire Hubble volume occur every so often, simply by chance.

A generic prediction of chaotic inflation is an infinite ergodic universe, which, being infinite, must contain Hubble volumes realizing all initial conditions.

Some cosmologists even use the term Hubble volume to refer to the volume of the observable universe, although this has a radius approximately three times larger.

Tegmark argues that a level III multiverse does not contain more possibilities in the Hubble volume than a level I-II multiverse.

In effect, all the different "worlds" created by "splits" in a level III multiverse with the same physical constants can be found in some Hubble volume in a level I multiverse.

In cosmology, a Hubble volume, or Hubble sphere, is a spherical region of the Universe surrounding an observer beyond which objects recede from that observer at a rate greater than the speed of light due to the expansion of the Universe.

The section of spacetime that can be observed is the backward light cone (all points within the cosmic light horizon, given time to reach a given observer), while the related term Hubble volume can be used to describe either the past light cone or comoving space up to the surface of last scattering.