### isotropy

**(statistical isotropy)**
(uniformity in all directions)

**Isotropy** means uniformity in all directions.
This is an assumption made about space, i.e., the
universe which is one of the assumptions of the
cosmological principle, in turn an assumption of the
Big Bang theory.
The absence of isotropy is **anisotropy**.
Both terms are used regarding the cosmic microwave background to describe
the fact that it comes at us from all directions:
it is basically isotropic but has a small anisotropy
that is of much research interest.

**Isotopic radiation** is radiation from a body that
is emitted from it in all directions, i.e., like
electromagnetic radiation (EMR) from a star. When an especially bright
source is discovered, such as with a redshift
showing great distance but observable, an immediate
question is whether this is isotropic radiation
or is anisotropic, e.g., **beamed** in our direction.
If it is indeed isotropic, then its luminosity
(its power; in this case, its **isotropic radiant energy** output)
must be extreme and its high-luminosity mechanism
is of research interest.

(*mathematics,cosmology*)
**Further reading:**

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

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

**Referenced by pages:**

anisotropy

cosmological principle

Eddington approximation

Hellings and Downs curve

Index