1500 Locust Street
1500 Locust Street
The Moon
The Moon is Earth's only natural satellite. Its diameter is about one-quarter of Earth's (comparable to the width of Australia),[17] making it the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet.[f] It is larger than all known dwarf planets in the Solar System.[18] The Moon is a planetary-mass object with a differentiated rocky body, making it a satellite planet under the geophysical definitions of the term. It lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is about one-sixth of Earth's at 0.1654 g—Jupiter's moon Io is the only satellite in the Solar System known to have a higher surface gravity and density.
The Moon orbits Earth at an average distance of 384,400 km (238,900 mi), or about 30 times Earth's diameter. Its gravitational influence is the main driver of Earth's tides and very slowly lengthens Earth's day. The Moon's orbit around Earth has a sidereal period of 27.3 days. During each synodic period of 29.5 days, the amount of visible surface illuminated by the Sun varies from none up to 100%, resulting in lunar phases that form the basis for the months of a lunar calendar. The Moon is tidally locked to Earth, which means that the length of a full rotation of the Moon on its own axis causes its same side (the near side) to always face Earth, and the somewhat longer lunar day is the same as the synodic period. Due to cyclical shifts in perspective (libration), 59% of the lunar surface is visible from Earth.
The most widely accepted origin explanation posits that the Moon formed 4.51 billion years ago, not long after Earth's formation, out of the debris from a giant impact between Earth and a hypothesized Mars-sized body called Theia. It receded to a wider orbit because of tidal interaction with the Earth. The near side of the Moon is marked by dark volcanic maria ("seas"), which fill the spaces between bright ancient crustal highlands and prominent impact craters. Most of the large impact basins and mare surfaces were in place by the end of the Imbrian period, some three billion years ago. Although the reflectance of the lunar surface is low (comparable to that of asphalt), its large angular diameter makes the full moon the brightest celestial object in the night sky. The Moon's apparent size is nearly the same as that of the Sun, allowing it to cover the Sun almost completely during a total solar eclipse.
The Moon is the only celestial body
visited by humans.
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet,[f] with a diameter about one-quarter that of Earth (comparable to the width of Australia).[16] The Moon is a planetary-mass object with a differentiated rocky body, making it a satellite planet under the geophysical definitions of the term and larger than all known dwarf planets of the Solar System.[17] It lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is about one-sixth of Earth's at 0.1654 g, with Jupiter's moon Io being the only satellite in the Solar System known to have a higher surface gravity and density.
Eagle is the common name for many large birds of prey of the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. Most of the 68 species of eagles are from Eurasia and Africa.[1] Outside this area, just 14 species can be found—2 in North America, 9 in Central and South America, and 3 in Australia.
Eagles are not a natural group but denote essentially any kind of bird of prey large enough to hunt sizeable (about 50 cm long or more overall) vertebrates.
Setaria is a widespread genus of plants in the grass family.[5][6] The name is derived from the Latin word seta, meaning "bristle" or "hair", which refers to the bristly spikelets.[7]
The genus includes over 100 species distributed in many tropical and temperate regions around the world,[8] and members are commonly known as foxtail or bristle grasses.[2][9][10][11][12][13]
The grass is topped by a cylindrical long-haired head, which tend to droop when ripe. The seeds are less than 6 millimetres (1⁄4 inch) in length.[14]
Numerous species were once considered members of Setaria but have since been reassigned to the following genera: Brachiaria, Dissochondrus, Echinochloa, Holcolemma, Ixophorus, Oplismenus, Panicum, Paspalidium, Pennisetum, Pseudoraphis, Setariopsis, and Urochloa
Uses
The grains can be eaten raw, though are hard and can be bitter; boiling can reduce both of these properties.[14]
Several species have been domesticated and used as staple crops throughout history: foxtail millet (S. italica), korali (S. pumila) in India, and, before the full domestication of maize, Setaria macrostachya in Mexico.[18] Several species are still cultivated today as food or as animal fodder, such as foxtail millet and korali (S. pumila), while others are considered invasive weeds.[19] S. viridis is currently being developed as a genetic model system for bioenergy grasses.
Other species that have been cultivated as crops include S. palmifolia (highland pitpit) of Papua New Guinea, where it is cultivated as a green vegetable; S. parviflora (knot-root foxtail), historically cultivated in Mesoamerica; and S. sphacelata (African bristle grass) of Sudan, a "lost millet" of Nubia.[20]
