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Astrobiology is a scientific field within the life and environmental sciences that studies the origins, early evolution, distribution, and future of life in the universe by investigating its deterministic conditions and contingent events. As a discipline, astrobiology is founded on the premise that life may exist beyond Earth.
The biosphere, also known as the ecosphere, is the worldwide sum of all ecosystems. It can also be termed the zone of life on Earth. The biosphere is virtually a closed system with regard to matter, with minimal inputs and outputs. Regarding energy, it is an open system, with photosynthesis capturing solar energy at a rate of around 100 terawatts. By the most general biophysiological definition, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, cryosphere, hydrosphere, and atmosphere. The biosphere is postulated to have evolved, beginning with a process of biopoiesis or biogenesis, at least some 3.5 billion years ago.
The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way Galaxy.
Extraterrestrial life, alien life, or colloquially simply aliens is life which does not originate from Earth. No extraterrestrial life has yet been conclusively detected. Such life might range from simple forms such as prokaryotes to intelligent beings, possibly bringing forth civilizations that might be far more advanced than humanity. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life is known as astrobiology.
An extinction event is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the background extinction rate and the rate of speciation. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from disagreement as to what constitutes a "major" extinction event, and the data chosen to measure past diversity.
The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. As a 2015 article put it, "If life is so easy, someone from somewhere must have come calling by now."
Paleontology, also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch. It includes the study of fossils to classify organisms and study their interactions with each other and their environments. Paleontological observations have been documented as far back as the 5th century BC. The science became established in the 18th century as a result of Georges Cuvier's work on comparative anatomy, and developed rapidly in the 19th century. The term has been used since 1822 formed from Greek παλαιός, ὄν, and λόγος.
The Gaia hypothesis, also known as the Gaia theory, Gaia paradigm, or the Gaia principle, proposes that living organisms interact with their inorganic surroundings on Earth to form a synergistic and self-regulating, complex system that helps to maintain and perpetuate the conditions for life on the planet.
In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the origin of life and the evolution of biological complexity such as sexually reproducing, multicellular organisms on Earth required an improbable combination of astrophysical and geological events and circumstances.
The Great Filter is the idea that in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. The Great Filter is one possible resolution of the Fermi paradox.
The history of Earth concerns the development of planet Earth from its formation to the present day. Nearly all branches of natural science have contributed to understanding of the main events of Earth's past, characterized by constant geological change and biological evolution.
James Fraser Kasting is an American geoscientist and Distinguished Professor of Geosciences at Penn State University. Kasting is active in NASA's search for habitable extrasolar planets. He is considered a world leader in the field of planetary habitability, assessing habitable zones around stars. He was elected a member of the National Academy of Sciences in 2018. Kasting also serves on the Advisory Council of METI.
The history of life on Earth traces the processes by which living and fossil organisms evolved, from the earliest emergence of life to present day. Earth formed about 4.5 billion years ago and evidence suggests that life emerged prior to 3.7 Ga. Although there is some evidence of life as early as 4.1 to 4.28 Ga, it remains controversial due to the possible non-biological formation of the purported fossils.
Donald Eugene Brownlee is a professor of astronomy at the University of Washington at Seattle and the principal investigator for NASA's Stardust mission. In 2000, along with his co-author Peter Ward, he co-originated the term Rare Earth, in reference to the possible scarcity of life elsewhere in the universe. His primary research interests include astrobiology, comets, and cosmic dust. He was born in Las Vegas, Nevada.
The Medea hypothesis is a term coined by paleontologist Peter Ward for a hypothesis that contests the Gaian hypothesis and proposes that multicellular life, understood as a superorganism, may be self-destructive or suicidal. The metaphor refers to the mythological Medea, who kills her own children.
The biological and geological future of Earth can be extrapolated based on the estimated effects of several long-term influences. These include the chemistry at Earth's surface, the cooling rate of the planet's interior, the gravitational interactions with other objects in the Solar System, and a steady increase in the Sun's luminosity. An uncertain factor is the pervasive influence of technology introduced by humans, such as climate engineering, which could cause significant changes to the planet. For example, the current Holocene extinction is being caused by technology, and the effects may last for up to five million years. In turn, technology may result in the extinction of humanity, leaving the planet to gradually return to a slower evolutionary pace resulting solely from long-term natural processes.
In astrobiology and planetary astrophysics, the galactic habitable zone is the region of a galaxy in which life might most likely develop. The concept of a galactic habitable zone analyzes various factors, such as metallicity and the rate and density of major catastrophes such as supernovae, and uses these to calculate which regions of a galaxy are more likely to form terrestrial planets, initially develop simple life, and provide a suitable environment for this life to evolve and advance. According to research published in August 2015, very large galaxies may favor the birth and development of habitable planets more than smaller galaxies such as the Milky Way. In the case of the Milky Way, its galactic habitable zone is commonly believed to be an annulus with an outer radius of about 10 kiloparsecs (33,000 ly) and an inner radius close to the Galactic Center.
Rare Earth: Why Complex Life Is Uncommon in the Universe is a 2000 popular science book about xenobiology by Peter Ward, a geologist and evolutionary biologist, and Donald E. Brownlee, a cosmologist and astrobiologist. The book is the origin of the term 'Rare Earth Hypothesis' which denotes the central claim of the book: that complex life is rare in the universe.
Michael R. Rampino is a Geologist and Professor of Biology and Environmental Studies at New York University, known for his scientific contributions on causes of mass extinctions of life. Along with colleagues, he's developed theories about periodic mass extinctions being strongly related to the earth's position in relation to the galaxy. "The solar system and its planets experience cataclysms every time they pass "up" or "down" through the plane of the disk-shaped galaxy." These ~30 million year cyclical breaks are an important factor in evolutionary theory, along with other longer 60-million- and 140-million-year cycles potentially caused by mantle plumes within the planet, opining "The Earth seems to have a pulse," He is also a research consultant at NASA's Goddard Institute for Space Studies (GISS) in New York City.
The Life and Death of Planet Earth is a popular science book by paleontologist Peter Ward and astronomer Donald E. Brownlee. Released in 2003, the book picks up where Rare Earth leaves off, this time talking about why the Earth's ability to support complex and, especially, intelligent life is not just rare in space, but also in time.
References
- 1 2 3 Matt Williams (29 July 2020). "Beyond "Fermi's Paradox" IV: What is the Rare Earth Hypothesis?". Universe Today . Retrieved 6 June 2021.
Origins: The term "Rare Earth" takes its name from the book Rare Earth: Why Complex Life Is Uncommon in the Universe (2000), by Peter Ward and Donald E. Brownlee ... As the authors describe it, the Rare Earth argument comes down to two central hypotheses ... making Earth a very special place
- 1 2 3 Dietrich, William (2005-12-09). "Prophet, Populist, Poet of Science". Pacific Northwest Magazine. Retrieved 26 October 2010.
After initially doubting that a comet killed the dinosaurs and allowing that an impact might have ended the Permian age, he reconsidered both stands — coming up with a non-comet ending to the Permian and then producing some of the clearest fossil-record evidence (the extinction of a marine creature called an ammonite) to prove the dinosaur calamity actually happened.
- ↑ "Peter Ward" (PDF). Save the Nautilus. Retrieved 3 August 2023.
- ↑ "Advisers, Microbe Mind Forum". Archived from the original on 2014-02-28.
- 1 2 Bennett, Drake (January 11, 2009). "Dark green. A scientist argues that the natural world isn't benevolent and sustaining: it's bent on self-destruction". Boston Globe . Retrieved October 21, 2012.
- ↑ Motluk, Alison (2002-01-29). ""Future Evolution" by Peter Ward". Salon . Archived from the original on 2010-03-29. Retrieved 2010-10-20.
- ↑ "Anthropology Update/ Future Evolution". Talk of the Nation . National Public Radio. 2002-03-22. Retrieved 2010-10-19.
- ↑ Ward, Peter Douglas (2007). Under a Green Sky: Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us About Our Future. New York: Smithsonian Books/Collins. OCLC 224875122.
- Christopher Cokinos (July–August 2007). "Under a Green Sky". Orion (Review). Archived from the original on 2007-10-23.
- ↑ Peter Ward speaker profile. TED . Retrieved 2009-02-27.
- ↑ D'Arconte (February 10, 2009). "Is Mother Nature nuts?". The Sun Chronicle . Retrieved 2009-02-27.
- ↑ "Guests: Peter Ward". Coast to Coast AM. Retrieved 1 June 2021.
Sources
- The Science of Doom: Peter Ward takes on the great unknowns, Pacific Northwest magazine (Seattle Times), December 11, 2005, p. 12ff
