In 1950 AD, the eminent physicist Enrico Fermi asked a poignant question:
Fermi is better known for his work on Chicago Pile-1, the first nuclear reactor, as well as his contributions to quantum theory, nuclear and particle physics, and statistical mechanics. He has been called the “architect of the nuclear age,” and is one of the men referred to as the “father of the atomic bomb,” due to his work on the Manhattan Project which developed the atom bomb during World War 2. His question was in regard to our understanding of the galaxy and our place within it. Given the age of the galaxy and the vast number of stars, unless the Earth is very atypical, extraterrestrial life should be common. If a multitude of advanced extraterrestrial civilizations exists in the Milky Way, why haven’t they come to the Earth? Why don’t we find their spaceships and probes? Where is everybody?
Our lone wandering system cannot be considered a prime colonial target for any other civilization, as it dashes past other stars in galactic terms. A logical prime colonial target for colonization outside of one’s own Stellar Group would be a star cluster like Pleiades. The Pleiades Star Cluster contains over 1000 stars that are expected to stay in close proximity for the next 250 million years. The difference would be like comparing the Eurasian continent to Easter Island. Nevertheless, our world does have life on it, and has had life for at least 3.7 billion years.(2)Yoko Ohtomo et al. (2013-12-08) “Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks” Nature Geoscience. If nothing else, basic curiosity should have brought someone into the system.
The appearance of life on Earth continues to be a mystery, as it seems to have appeared very early in the existence of the planet, with some studies dating its appearance to as early as 4.25 billion years ago.(3)Rachel Courtland (2008-07-02) “Did newborn Earth harbour life?” New Scientist Terrestrial life is composed of cells containing long polymers of deoxyribonucleic acid (DNA) which encode a protein replicating system allowing the cells to replicate via division.(4)Bruce Alberts et al. (2002) Molecular Biology of the Cell, Fourth Edition DNA encodes the protein replicating systems of animals, plants, protists, archaea and bacteria. The nature of DNA was originally discovered by Francis Crick and James Watson in 1953 AD, and by the 1960s Crick was concerned with the origins of the genetic code. As Crick late wrote in his 1981 book entitled Life Itself, Its Origin and Nature:
In the 1950s through 1970s many molecular biologists were puzzled by the problem of the origin of a protein replicating system as complex as the one found in organisms on Earth. In 1966 the eminent Soviet-Ukrainian astrophysicists Iosif Shklovsky and American cosmologist Carl Sagan jointly proposed that life on Earth may have been seeded through directed panspermia by other civilizations.(6)Iosif Shklovskii and Carl Sagan (1966) Intelligent life in the universe This concept was expanded by Francis Crick and noted chemist Leslie Orgel in their paper entitled Directed Panspermia in 1973. (7)Francis Crick and Leslie Orgel (1973) “Directed panspermia” Icarus, Volume 19 Pages 341 Crick and Orgel speculated about the possibility that the production of living systems from molecules may have been a very rare event in the universe, but once it had developed it could be spread by intelligent life forms using space travel technology, a process Shklovsky and Sagan had previously labeled Directed Panspermia.
Panspermia itself is an ancient Greek concept, that life had arrived on the Earth from the sky, when meteors had fallen carrying life. It was one of several theories proposed in the ancient Greek civilization to explain the existence of life. The idea was not a new idea at the time, precursors are found in Greek and neighboring Hurrian mythology. In Greek Mythology when the Titan Cronus over-threw the rule of the personification of the sky Uranus, he cut off Uranus’ testicles which fell into the Earth’s oceans as fiery meteors. According to the early Greek scholar Hesiod’s Theogony, Aphrodite, the major Greek fertility goddess, was born from the sea-foam (aphros) caused by the testicles impacting the ocean.
In the Hurrian mythology, there was a similar belief that the god Kumarbi bit off his father Anu’s testicles during a struggle. As in the case of Uranus, Anu was a personification of the universe itself. Anu declared that Kumarbi would be come pregnant, and so Kumarbi spit out the testicles, and where they landed on the Earth two new gods came into existence, the Tigris River in modern Iraq, and Tašmišu the rain god. Kumarbi was still pregnant and so cut the child Teshub the storm-god from his abdomen.(9)Gwendolyn Leick (1998) Dictionary of Ancient Near Eastern Mythology Page 106 All three of these water-gods Tigris (River), Tašmišu (Rain), and Teshub (Storm) were also the source of life in the dry lands of the Hurrian civilization.
In the ancient Greek concept of Panspermia, meteors that crashed to the earth and sea carried the seeds of life throughout the universe. Wherever they landed, life emerged if the environment was suitable. The idea continues to be widely accepted as possible among astronomers, however until we explore other worlds and star systems this will remain a theory. Shklovsky, Sagan, Crick, and Orgel’s hypothesis of Directed Panspermia does offer an alternate explanation of how life arrived on the Earth so soon after the planet’s formation. This was the point of the Directed Panspermia hypothesis; Crick, Orgel, and many other molecular biologists were very pessimistic about the concept that Abiogenesis could have taken place on the Earth in the first 1.5 billion years of the Earth’s existence, as was documented at the time. Abiogenesis is the scientific name for the emergence of life from non-living matter. Now with the window reduced to approximately 400 million years, of generally hellish conditions as the planet still had a partially molten surface, experiencing frequent collisions with other Solar System bodies, and consent massive volcanic explosions, how much less plausible is Terrestrial Abiogenesis?
References [ + ]
|1.||⇑||Carl Sagan (2002) Cosmos, Random House|
|2.||⇑||Yoko Ohtomo et al. (2013-12-08) “Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks” Nature Geoscience.|
|3.||⇑||Rachel Courtland (2008-07-02) “Did newborn Earth harbour life?” New Scientist|
|4.||⇑||Bruce Alberts et al. (2002) Molecular Biology of the Cell, Fourth Edition|
|5.||⇑||Francis Crick (1981) Life Itself, Its Origin and Nature. Simon & Schuster|
|6.||⇑||Iosif Shklovskii and Carl Sagan (1966) Intelligent life in the universe|
|7.||⇑||Francis Crick and Leslie Orgel (1973) “Directed panspermia” Icarus, Volume 19 Pages 341|
|8.||⇑||Hesiod (circa 700 BC) Theogony|
|9.||⇑||Gwendolyn Leick (1998) Dictionary of Ancient Near Eastern Mythology Page 106|