The Cosmic Calendar is a method to visualize the chronology of the universe, scaling its currently understood age of 13.8 billion years to a single year in order to help intuit it for pedagogical purposes in science education or popular science.
In this visualization, the Big Bang took place at the beginning of January 1 at midnight, and the current moment maps onto the end of December 31 just before midnight. [1] At this scale, there are 437.5 years per cosmic second, 1.575 million years per cosmic hour, and 37.8 million years per cosmic day.
The concept was popularized by Carl Sagan in his 1977 book The Dragons of Eden and on his 1980 television series Cosmos . [2] Sagan goes on to extend the comparison in terms of surface area, explaining that if the Cosmic Calendar were scaled to the size of a football field, then "all of human history would occupy an area the size of [his] hand". [3]
A similar analogy used to visualize the geologic time scale and the history of life on Earth is the Geologic Calendar.
Date | Gya (billion years ago) | Event |
---|---|---|
1 Jan | 13.8 | Big Bang, as seen through cosmic background radiation, which would have been last emitted 14 minutes after midnight |
19 Jan | 13.1 | Oldest known Gamma Ray Burst |
26 Jan | 12.85 | First galaxies form [4] |
16 Mar | 11 | Milky Way Galaxy formed |
13 May | 8.8 | Milky Way Galaxy disk formed |
2 Sep | 4.57 | Formation of the Solar System |
6 Sep | 4.4 | Oldest rocks known on Earth |
Date in year calculated from formula
T(days) = 365 days * ( 1- T_Gya/13.797 )
Date | Gya (billion years ago) | Event |
---|---|---|
14 Sep | 4.1 | First known remains of biotic life (discovered in 4.1 billion-year-old rocks in Western Australia). [5] [6] |
21 Sep | 3.8 | First Life (Prokaryotes) [7] [8] [9] |
30 Sep | 3.4 | Photosynthesis |
29 Oct | 2.4 | Oxygenation of atmosphere |
9 Nov | 2 | Complex cells (Eukaryotes) |
5 Dec | 0.8 | First multicellular life [10] |
7 Dec | 0.67 | Simple animals |
14 Dec | 0.55 | Arthropods (ancestors of insects, arachnids) |
17 Dec | 0.5 | Fish and Proto-amphibians |
20 Dec | 0.45 | Land plants; Ordovician–Silurian extinction events |
21 Dec | 0.4 | Insects and seeds |
22 Dec | 0.36 | Amphibians; Late Devonian extinction |
23 Dec | 0.3 | Reptiles |
24 Dec | 0.25 | Permian–Triassic extinction event; 57% of all biological families and 83% of all genera die |
25 Dec | 0.23 | Dinosaurs |
26 Dec | 0.2 | Mammals; Triassic–Jurassic extinction event |
27 Dec | 0.15 | Birds (avian dinosaurs) |
28 Dec | 0.13 | Flowers |
30 Dec, 06:24 | 0.065 | Cretaceous–Paleogene extinction event, non-avian dinosaurs die out [11] |
Date / time | Mya (million years ago) | Event |
---|---|---|
30 Dec | 65 | Primates |
31 Dec, 06:05 | 15 | Apes |
31 Dec, 14:24 | 12.3 | Hominids |
31 Dec, 22:24 | 2.5 | Primitive humans and stone tools |
31 Dec, 23:44 | 0.4 | Domestication of fire |
31 Dec, 23:52 | 0.2 | Anatomically modern humans |
31 Dec, 23:55 | 0.11 | Beginning of most recent Glacial Period |
31 Dec, 23:58 | 0.035 | Sculpture and painting |
31 Dec, 23:59:32 | 0.012 | Agriculture |
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The cosmos is an alternative name for the universe or its nature or order. Usage of the word cosmos implies viewing the universe as a complex and orderly system or entity. The cosmos, and understandings of the reasons for its existence and significance, are studied in cosmology – a broad discipline covering scientific, religious or philosophical aspects of the cosmos and its nature. Religious and philosophical approaches may include the cosmos among spiritual entities or other matters deemed to exist outside the physical universe.
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An order of magnitude of time is usually a decimal prefix or decimal order-of-magnitude quantity together with a base unit of time, like a microsecond or a million years. In some cases, the order of magnitude may be implied, like a "second" or "year". In other cases, the quantity name implies the base unit, like "century". In most cases, the base unit is seconds or years.
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This more than 20-billion-year timeline of our universe shows the best estimates of major events from the universe's beginning to anticipated future events. Zero on the scale is the present day. A large step on the scale is one billion years; a small step, one hundred million years. The past is denoted by a minus sign: e.g., the oldest rock on Earth was formed about four billion years ago and this is marked at -4e+09 years, where 4e+09 represents 4 times 10 to the power of 9. The "Big Bang" event most likely happened 13.8 billion years ago; see age of the universe.
Cosmology is a branch of physics and metaphysics dealing with the nature of the universe, the cosmos. The term cosmology was first used in English in 1656 in Thomas Blount's Glossographia, and in 1731 taken up in Latin by German philosopher Christian Wolff, in Cosmologia Generalis. Religious or mythological cosmology is a body of beliefs based on mythological, religious, and esoteric literature and traditions of creation myths and eschatology. In the science of astronomy, cosmology is concerned with the study of the chronology of the universe.
Big History is an academic discipline which examines history from the Big Bang to the present. Big History resists specialization, and searches for universal patterns or trends. It examines long time frames using a multidisciplinary approach based on combining numerous disciplines from science and the humanities, and explores human existence in the context of this bigger picture. It integrates studies of the cosmos, Earth, life, and humanity using empirical evidence to explore cause-and-effect relations, and is taught at universities and primary and secondary schools often using web-based interactive presentations.
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