BOSTON — Each cosmological decade represents a 10-fold increase in years. When the universe was 10 years old, it ended its first cosmological decade. At 100, the universe marked its second cosmological decade. At 10 billion years, it cleared its 10th cosmological decade.
The Primordial Era - the big bang to the fifth cosmological decade
This covers the universe's first 100,000 years, from the big bang and the formation of light elements such as hydrogen, helium, and lithium to the birth of the first stars and galaxies.
The Stelliferous Era - the sixth
to 14th cosmological decades
You are here. Most of the energy in the expanding universe comes from nuclear fusion in the hearts of stars, and the universe is replete with galaxies. As this era ends, galaxies run out of hydrogen gas, star formation virtually ceases, and the longest-lived stars, red dwarfs, slowly fade.
The Degenerate Era - the 15th
to 39th cosmological decades
Ordinary matter is locked up in stellar remnants - white dwarfs, neutron stars, and black holes. The universe is colder, darker, and more diffuse. It also contains widely scattered planets and brown dwarfs - star wannabes that failed to acquire enough mass and density to ignite during earlier eras. Over time, dark matter, which dominated galaxies in earlier eras, is annihilated in the cores of white dwarfs. This becomes the universe's main source of energy. Eventually, the supply of dark matter is exhausted, while proton and neutron decay finish off everything but black holes.
The Black Hole Era - the 40th
to 100th cosmological decades
Black holes, objects with gravity so strong that even light can't escape, are the only remaining recognizable astronomical objects. Even they evaporate eventually through a process known as Hawking radiation, which becomes the universe's major energy source. The era ends when the last of the largest black holes evaporates.
The Dark Era - the 101st
cosmological decade and beyond
The still expanding universe is populated only with electrons, positrons, neutrinos, and photons of enormous wavelengths. Yet out of this seemingly moribund expanse of space-time, the authors posit that new universes can emerge.
(c) Copyright 1999. The Christian Science Publishing Society