In the first episode of the Cosmos series, Carl Sagan, a famous cosmologist and popularizer, brings the entire history of the Universe together in a one-year calendar, a calendar summarizing the entire history of the Universe in one year.
The departure is given by the Big Bang, on January 1st at 0 hour, and our present is represented by December 31st at midnight. The real duration of this condensed year is 13.8 billion years since it is the age of the Universe. Each day on the calendar represents 37.8 million years, each hour 1.6 million years, each minute 26 millennia and each second 438 years.
The cosmos is therefore born on January 1st. And, very quickly, probably on the night of January 2 to 3, the first stars appear. The first galaxies are forming from January 10, but it takes a long time – until around May 12 – for ours, the Milky Way, to take its spiral shape with arms, even though some of its constituents have been around for a long time. Many events take place in the following weeks, but the main next step is the hatching of our Solar System on September 2nd in a somewhat remote corner of the Milky Way. The Earth is obviously part of it, and it is on our planet, which is formed on September 14, that the cosmic calendar is concentrated for the last four months of the year.
Life appeared quite quickly, on September 9, in the form of single-celled organisms. The first multi-cellular beings appeared at the beginning of November, but it is in the second half of December that the tree of life will branch out at full speed. The prologue of the so-called Cambrian explosion is played on December 14. On this day, the first animals, sponges, are reported. On December 17, arthropods landed, including the famous trilobites, joined on the 18th by fish, on the 20th by terrestrial plants, on the 21st by insects, on the 22nd by amphibians and on the 23rd by reptiles.
Dinosaurs are born on Christmas
In our cosmic calendar, Christmas Day, December 25th, marks the birth of the dinosaurs that will dominate the Earth for a few days. On the 26th, the first mammals finally appear, one day before the birds and two before the flowers. At dawn on December 30, a large asteroid hit our planet, causing the disappearance of the dinosaurs except for the birds. On the same day, as if to symbolize a change of era, the first primates make their appearance in the class of mammals.
We have almost reached the end of our calendar, in the early hours of December 31, the last day of this year in which the entire history of the Universe has been condensed. From the matter created on January 1, an abundance of worlds has sprung up, myriads of galaxies, stars and planets. It is this matter that is the guiding thread of history. In our eyes, however, there is one absent: man, who has still not appeared on the great cosmic theater. All his evolution will be played out on this last day of the year.
The distant ancestor of the great apes (of which we are a part) appears shortly after 2 p.m. on this December 31st. In the evening, around 8 p.m., the human lineage separates from that of the chimpanzees. A little before 11 p.m., Homo erectus walks on the surface of the Earth. Homo sapiens, the modern man, finally invites himself on the world stage at 11:48 p.m. and we have few traces of his activity until the last minute of the year. At 23h59mn20s, he adorns the Lascaux cave. In the seconds that follow, he invents agriculture. At 23h59mn47s, he begins to write and to melt metals. Two seconds later, he builds the Great Pyramids of Giza.
The last ten seconds
Here we are in the last ten seconds of the calendar, ten seconds that cover the essence of what man calls History and which, brought back over a whole year, give the measure of our tiny place in the Universe. Ten seconds before the end of this year, Sargon founds the Akkadian Empire in Mesopotamia and stones begin to rise on the site of Stonehenge, at the same time discovering the alphabet and the wheel. At 23h59mn51s, it is the beginning of the New Empire in Egypt. A second later, Judaism was born, the first great monotheistic religion. Athens and Rome are founded in the following second. Another shift of the second hand and Alexander the Great conquers the world. At 23h59mn55s, Christianity appears, and the Roman Empire is at its apogee. A second later, it falls, and Mohammed is born, lives and dies. Then Charlemagne is crowned Emperor, and the Crusades begin. It is 23h59mn58s and the Hundred Years War rages, Constantinople is taken, and Christopher Columbus discovers America. During the last second of this cosmic year, peoples revolt against their kings, two world wars take place, man is technologically advanced enough to go to the Moon, change the climate of his planet … and trace the history of the cosmos.
In this calendar, the 70-80 years that a human life lasts represent a sixth of a second… Astronomy, by not giving us any privileged place in the Universe and by giving us the idea of our infinitesimal measure, in space and time, has the power to make us modest.
Year 2 the future of the Earth and the Solar System
1Ma = 1 million years, 1Ga = 1 billion years
On January 1st, at 00h00mn23s Chernobyl is no longer contaminated. At 16:30mn Africa cuts in two, the eastern part breaks off. January 2 (50Ma), the Mediterranean Sea closes because of the collision between Europe and Africa. January 3 (100Ma), Saturn loses its rings. January 17 (700Ma), the atmospheric CO2 level is too low, all complex life dies. February 8 (1Ga), the oceans evaporate. March 1 (2 Ga), all life on Earth has disappeared. March 18 (3Ga), beginning of the collision between the Andromeda galaxy and the Milky Way. April 9 (4Ga), the Sun becomes a red giant. April 16 (4Ga) the surface of the Earth is at 1330°C. June 28 (7Ga) the Sun destroys the Earth. August 12 (8Ga) the Sun becomes a white dwarf. December 31 (12Ga) the solar system disappeared.
The future of the Universe
1Ta = 1000 billion years
Year 8, April 1st (100Ga), galaxies disappear behind the horizon line.
Year 7247, December 13 (100Ta), end of star formation.
Year 72479, July 11th (1000Ta), the temperature of the Sun fell to -268°C.
