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The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way Galaxy. [1][2][3] The equation was formulated in 1961 by Frank Drake, not for purposes of quantifying the number of civilizations, but as a way to stimulate scientific dialogue at the first ...
Jupiter was the first of the Sun's planets to form, and its inward migration during the primordial phase of the Solar System affected much of the formation history of the other planets. Hydrogen constitutes 90% of Jupiter's volume, followed by helium, which forms 25% of its mass and 10% of its volume. The ongoing contraction of Jupiter's ...
The thoracic fraction is the fraction that enters the thorax and is deposited within the lung's airways. The respirable fraction is what is deposited in the gas exchange regions (alveoli). [156] The smallest particles, nanoparticles, which are less than 180 nanometers in size, may be even more damaging to the cardiovascular system.
539 Ma – present. The Phanerozoic Eon (Greek: period of well-displayed life) marks the appearance in the fossil record of abundant, shell-forming and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, with major mass extinctions at division points.
At the Cerro Paranal Observatory, a laser beam is used to create an artificial star to tune the Very Large Telescope (VLT). The search for exoplanets on which extraterrestrial civilizations could be found is one of the many missions of the VLT. The Kardashev scale (Russian: Шкала́ Кардашёва, romanized: Shkalá Kardashova) is a ...
Half-life (symbol t½) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive. The term is also used more generally to characterize any type of exponential (or, rarely ...
In complex analysis, Gauss's continued fraction is a particular class of continued fractions derived from hypergeometric functions. It was one of the first analytic continued fractions known to mathematics, and it can be used to represent several important elementary functions , as well as some of the more complicated transcendental functions .
136 Ps (4.32 Ga): The length of the legendary unit Kalpa in Hindu mythology, or one day (but not including the following night) of the life of Brahma. 143 Ps (4.5 Ga): The age of the Earth by our best estimates. Also the approximate half-life of the uranium isotope 238 U. 315 Ps (10 Ga): The approximate lifetime of a main-sequence star similar ...