Red Out

When most people hear the term “red out” they think of a sports team with red as the primary colour on their jerseys.  Some of the older folk might think about communism.  

The term “red out” has 3 separate meanings.  The first meaning is a medical reference that relates to the homogeneous red-orange colour seen by GI endoscopy that allows only the passage of light across the blood vessel-rich mucosa.

The second meaning for “red out” is another medical condition where centripetal acceleration drives blood to the head, causing a reddening of the visual field and bringing on a significant severe headache.  A red out usually happens when a person is subjected to a negative force of gravity, as in stunt flying or a sudden dive in a plane.  The mental confusion that develops at high accelerations may lead to near-unconsciousness (brown out) or unconsciousness (black out).  The term was first used by the military in 1942.

And the term “Cosmic Red Out” — or the third meaning for the term “red out” — can be found in an article by Michael S. Turner of the University of Chicago in the September 2009 issue of Scientific American.  Turner applies the term to the proposed situation in which acceleration continues and where the Milky Way/Andromeda/et al fusion galaxy eventually finds itself alone in the observable universe.  The term ‘red out’ is designed to refer to the ever increasing cosmic redshift of extra-galactic bodies.