Where does relic collide?

In biogeography and evolutionary biology a relict (also spelled relic) is a species, population, or trait that has survived from an earlier era while its relatives or its former range have largely disappeared. Forbes's 1846 memoir on the fauna and flora of the British Isles identified organisms left behind by past climatic epochs, the idea now called a relict distribution, and Habel and Assmann's 2010 Relict Species synthesized how such survivors are identified and conserved. Here the referent is a living survivor of a vanished biological world, dated by fossils and molecular divergence, not a venerated remnant of a saint or a leftover from the early universe.[1][2]

Unit

One surviving species, population, or trait persisting from an earlier era

Recovery means

Not applicable

Measured by

Identified by the fossil record, a restricted or disjunct range, and molecular divergence from living relatives

In cosmology a relic is matter or radiation left over from the hot early universe and still present today, such as the background radiation or a surviving population of particles. Alpher and Herman's 1948 Evolution of the Universe predicted the leftover radiation from the early expansion, later called the relic radiation, and Lee and Weinberg's 1977 Cosmological Lower Bound on Heavy-Neutrino Masses extended the idea to relic particles by computing how many survive as the universe cools. Here the referent is a physical remnant of the universe's first moments, measured as a temperature or a present-day abundance, and it has nothing in common with a saint's remains or a surviving species beyond the shared word.[3][4]

Unit

A leftover component of the early universe, a radiation field or a particle population

Recovery means

Not applicable

Measured by

Quantified as a background temperature or as a present-day number or mass density of surviving particles