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Rare Earth Hypothesis
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, and subsequently human intelligence, required an improbable combination of astrophysical and geological events and circumstances. According to the hypothesis, complex extraterrestrial life is an improbable phenomenon and likely to be rare throughout the universe as a whole. The term "Rare Earth" originates from '' Rare Earth: Why Complex Life Is Uncommon in the Universe'' (2000), a book by Peter Ward, a geologist and paleontologist, and Donald E. Brownlee, an astronomer and astrobiologist, both faculty members at the University of Washington. In the 1970s and 1980s, Carl Sagan and Frank Drake, among others, argued that Earth is a typical rocky planet in a typical planetary system, located in a non-exceptional region of a common barred spiral galaxy. From the principle of m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Blue Marble (remastered)
''The Blue Marble'' is a photograph of Earth taken on December 7, 1972, by either Ronald Evans (astronaut), Ron Evans or Harrison Schmitt aboard the Apollo 17 spacecraft on its way to the Moon. Viewed from around from Earth's surface, a cropped and rotated version has become one of the most reproduced images in history. In the original NASA image, named AS17-148-22727 and centered at about with the South Pole facing upwards, ''The Blue Marble'' shows Earth from the Mediterranean Sea to Antarctica. This was the first time the Apollo trajectory made it possible to photograph the south polar ice cap, despite the Southern Hemisphere being heavily cloud cover, covered in clouds. In addition to the Arabian Peninsula and Madagascar, almost the entire coastline of Africa and most of the Indian Ocean are clearly visible, 1972 North Indian Ocean cyclone season#Very Severe Cyclonic Storm Sixteen (16B), a cyclone in the Indian Ocean is also visible, the South Asian mainland and Australi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frank Drake
Frank Donald Drake (May 28, 1930 – September 2, 2022) was an American astrophysicist and astrobiologist. He began his career as a radio astronomer, studying the planets of the Solar System and later pulsars. Drake expanded his interests to the search for extraterrestrial intelligence (SETI), beginning with Project Ozma in 1960, an attempt at extraterrestrial communication. He developed the Drake equation, Physics Today 14 (4), 40–46 (1961). which attempts to quantify the number of intelligent lifeforms that could potentially be discovered. Working with Carl Sagan, Drake helped to design the Pioneer plaque, the first physical message flown beyond the Solar System, and was part of the team that developed the Voyager Golden Record. Drake designed and implemented the Arecibo message in 1974, an extraterrestrial radio transmission of astronomical and biological information about Earth. He is the father of Advanced SETI. Drake worked at the National Radio Astronomy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetosphere
In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo theory, dynamo. In the space environment close to a planetary body with a dipole magnetic field such as Earth, the field lines resemble a simple magnetic dipole. Farther out, field lines can be significantly distorted by the flow of electrically conducting plasma (physics), plasma, as emitted from the Sun (i.e., the solar wind) or a nearby star. Planets having active magnetospheres, like the Earth, are capable of mitigating or blocking the effects of solar radiation or cosmic radiation. Interactions of particles and atmospheres with magnetospheres are studied under the specialized scientific subjects of plasma physics, space physics, and aeronomy. History Study of Earth's magnetosphere began in 1600, when William Gilbert (astronomer), W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Satellite
A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are colloquially referred to as moons, a derivation from the Moon of Earth. In the Solar System, there are six planetary satellite systems containing 418 known natural satellites altogether. Seven objects commonly considered dwarf planets by astronomers are also known to have natural satellites: , Pluto, Haumea, , Makemake, , and Eris. As of January 2022, there are 447 other minor planets known to have natural satellites. A planet usually has at least around 10,000 times the mass of any natural satellites that orbit it, with a correspondingly much larger diameter. The Earth–Moon system is a unique exception in the Solar System; at 3,474 kilometres (2,158 miles) across, the Moon is 0.273 times the diameter of Earth and about of its mass. The next largest ratios are the N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circumstellar Habitable Zone
In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.J. F. Kasting, D. P. Whitmire, R. T. Reynolds, Icarus 101, 108 (1993). The bounds of the HZ are based on Earth's position in the Solar System and the amount of radiant energy it receives from the Sun. Due to the importance of liquid water to Earth's biosphere, the nature of the HZ and the objects within it may be instrumental in determining the scope and distribution of planets capable of supporting Earth-like extraterrestrial life and intelligence. As such, it is considered by many to be a major factor of planetary habitability, and the most likely place to find extraterrestrial liquid water and biosignatures elsewhere in the universe. The habitable zone is also called the Goldilocks zone, a metaphor, allusion and antonomasia of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galactic Habitable Zone
In astrobiology and planetary astrophysics, the galactic habitable zone is the region of a galaxy in which life is most likely to develop. The concept of a galactic habitable zone analyzes various factors, such as metallicity (the presence of elements heavier than hydrogen and helium) 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. In the case of the Milky Way, its galactic habitable zone is commonly believed to be an annulus with an outer radius of about and an inner radius close to the Galactic Center (with both radii lacking hard boundaries). Galactic habitable-zone theory has been criticized due to an inabi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Universe
The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from sub-atomic particles to entire Galaxy filament, galactic filaments. Since the early 20th century, the field of cosmology establishes that space and time emerged together at the Big Bang ago and that the Expansion of the universe, universe has been expanding since then. The observable universe, portion of the universe that can be seen by humans is approximately 93 billion light-years in diameter at present, but the total size of the universe is not known. Some of the earliest Timeline of cosmological theories, cosmological models of the universe were developed by ancient Greek philosophy, ancient Greek and Indian philosophy, Indian philosophers and were geocentric model, geocentric, placing Earth at the center. Over the centuries, more prec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SETI
Seti or SETI may refer to: Astrobiology * SETI, the search for extraterrestrial intelligence. ** SETI Institute, an astronomical research organization *** SETIcon, a former convention organized by the SETI Institute ** Berkeley SETI Research Center, an astronomical research organization *** SETI@home, a distributed computing project ** Active SETI, the attempt to send messages to intelligent aliens Egyptology * Seti (commander), grandfather of Seti I * Seti (Viceroy of Kush) * Seti I (died 1279 BC), pharaoh * Seti II (died 1197 BC), pharaoh * Seti-Merenptah, a son of Seti II * Seti, son of Amun-her-khepeshef * Sethi, one of List of children of Ramesses II#, the sons of Ramesses II Music * SETI (band), an ambient music band from New York City * SETI (The Kovenant album), ''SETI'' (The Kovenant album), an album by metal band The Kovenant Places * Seti River, a tributary of the Karnali River in Nepal * Seti Gandaki River or Seti River, a tributary of the Trishuli River in Nepal * S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extraterrestrial Life
Extraterrestrial life, or alien life (colloquially, aliens), is life that originates from another world rather than on Earth. No extraterrestrial life has yet been scientifically conclusively detected. Such life might range from simple forms such as prokaryotes to Extraterrestrial intelligence, intelligent beings, possibly bringing forth civilizations that might be Kardashev scale, far more, or far less, advanced than humans. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life is known as astrobiology. Speculation about the possibility of inhabited worlds beyond Earth dates back to antiquity. Early Christianity, Christian writers discussed the idea of a "plurality of worlds" as proposed by earlier thinkers such as Democritus; Augustine of Hippo, Augustine references Epicurus's idea of innumerable worlds "throughout the boundless immensity of space" in ''The City of God''. Pre-modern writers typicall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Copernican Principle
In physical cosmology, the Copernican principle states that humans are not privileged observers of the universe, that observations from the Earth are representative of observations from the average position in the universe. Named for Copernican heliocentrism, it is a working assumption that arises from a modified cosmological extension of Copernicus' argument of a moving Earth. Origin and implications Hermann Bondi named the principle after Copernicus in the mid-20th century, although the principle itself dates back to the 16th–17th century paradigm shift away from the Ptolemaic system, which placed Earth at the center of the universe. Copernicus proposed that the motion of the planets could be explained by reference to an assumption that the Sun is centrally located and stationary in contrast to the geocentrism. He argued that the apparent retrograde motion of the planets is an illusion caused by Earth's movement around the Sun, which the Copernican model placed at t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Principle Of Mediocrity
A principle may relate to a fundamental truth or proposition that serves as the foundation for a system of beliefs or behavior or a chain of reasoning. They provide a guide for behavior or evaluation. A principle can make values explicit, so they are expressed in the form of rules and standards. Principles unpack the values underlying them more concretely so that the values can be more easily operationalized in policy statements and actions. In law, higher order, overarching principles establish rules to be followed, modified by sentencing guidelines relating to context and proportionality. In science and nature, a principle may define the essential characteristics of the system, or reflect the system's designed purpose. The effective operation would be impossible if any one of the principles was to be ignored. A system may be explicitly based on and implemented from a document of principles as was done in IBM's 360/370 ''Principles of Operation''. It is important to differen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
