Geologic Time

From Annals of the Former World by John McPhee, an awesome perspective:

In like manner, geologists will sometimes use the calendar year as a unit to represent the time scale, and in such terms the Precambrian runs from New Year's Day until well after Halloween. Dinosaurs appear in the middle of December and are gone the day after Christmas. The last ice sheet melts on December 31st at one minute before midnight, and the Roman Empire lasts five seconds. With your arms spread wide again to represent all time on earth, look at one hand with its line of life. The Cambrian begins in the wrist, and the Permian Extinction is at the outer end of the palm. All of the Cenozoic is in a fingerprint, and in a single stroke with a medium-grained nail file you could eradicate human history. Geologists live with the geologic scale. Individually, they may or may not be alarmed by the rate of exploitation of the things they discover, but, like the environmentalists, they use these repetitive analogies to place the human record in perspective–to see the Age of Reflection, the last few thousand years, as a small bright sparkle at the end of time. They often liken humanity's presence on earth to a brief visitation from elsewhere in space, its luminous, explosive characteristics consisting not merely of the burst of population in the twentieth century but of the whole residence of people on earth–a single detonation, resembling nothing so much as a nuclear implosion with its successive neutron generations, whole generations following one another once every hundred-millionth of a second, temperatures building up into the millions of degrees and stripping atoms until bare nuclei are wandering in electron seas, pressures building up to a hundred million atmospheres, the core expanding at five million miles an hour, expanding in a way that is quite different from all else in the universe, unless there are others who also make bombs.

(cf Edge of the Universe (1999-06-08), Relativity Plus Astrophysics (2000-03-29), Cosmic Context (2000-11-10), Universal Knowns (2002-06-13) Essential Knowledge (2005-06-20), Seeing Nature (2005-07-19), Assembling California (2007-05-30), Our Job for the Rest of Our Life (2015-07-18), Play Big (2018-08-31), Operating System of the Universe (2019-10-17), Reading the Book of Nature (2021-09-10), Webb Space Telescope (2022-01-29), ...) - ^z - 2022-10-18