3.16.2010
Moon
The Moon is Earth's only natural satellite and the fifth largest satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is 384,000 kilometres , about thirty times the diameter of the Earth. The common centre of mass of the system is located at about 1,700 kilometres —a quarter the Earth's radius—beneath the surface of the Earth. The Moon makes a complete orbit around the Earth every 27.3 days, and the periodic variations in the geometry of the Earth, Moon and Sun system are responsible for the phases of the Moon, which repeat every 29.5 days .The Moon's diameter is 3,474 kilometres. Thus, the Moon's surface area is less than a tenth of the Earth, and its volume is about 2 percent that of Earth. The pull of gravity at its surface is about 17 percent of that at the Earth's surface. The Moon is the only celestial body on which human beings have made a manned landing. Soviet Union's Luna programme was the first to reach the Moon with unmanned spacecraft, the United States' NASA Apollo program achieved the only manned missions to date, beginning with the first manned lunar mission by Apollo 8 in 1968, and six manned lunar landings between 1969 and 1972–the first being Apollo 11 in 1969. Human exploration of the Moon temporarily ceased with the conclusion of the Apollo program. The U.S. had committed to return to the Moon by 2018 however that commitment has been put into jeopardy by the proposed 2011 budget, which will cancel Constellation, NASA's project to send humans back to the moon by 2020. On November 13, 2009, NASA announced the discovery of proof that water exists on the Moon, based on data obtained from its LCROSS lunar impact mission. The Moon is in synchronous rotation, which means it rotates about its axis in about the same time it takes to orbit the Earth. This results in it nearly always keeping the same face turned towards the Earth. The Moon used to rotate at a faster rate, but early in its history, its rotation slowed and became locked in this orientation as a result of frictional effects associated with tidal deformations caused by the Earth. The surface of Earth's Moon is marked by impact craters which form when asteroids and comets collide with the lunar surface. There are about half a million craters with diameters greater than 1 km on the Moon. The continuous bombardment of the Moon by comets and meteoroids has most likely added small amounts of water to the lunar surface. If so, sunlight would split much of this water into its constituent elements of hydrogen and oxygen, both of which would ordinarily escape into space over time because of the Moon's weak gravity. The Moon is a differentiated body, being composed of a geochemically distinct crust, mantle, and core. This structure is hypothesized to have resulted from the fractional crystallization of a magma ocean shortly after its formation, at about 4.4 billion years ago. In terms of elements, the crust is composed primarily of oxygen (41% to 46% by mass), silicon (21%), magnesium (6%), iron (13%), calcium (8%), and aluminium (7%). Based on geophysical techniques, its thickness is estimated to be on average about 50 km. Eclipses can only occur when the Sun, Earth, and Moon are all in a straight line. Solar eclipses occur near a new Moon, when the Moon is between the Sun and Earth. In contrast, lunar eclipses occur near a full Moon, when the Earth is between the Sun and Moon. The angular diameters of the Moon and the Sun as seen from Earth overlap in their variation, so that both total and annular solar eclipses are possible. In a total eclipse, the Moon completely covers the disc of the Sun and the solar corona becomes visible to the naked eye. Since the distance between the Moon and the Earth is very slightly increasing over time, the angular diameter of the Moon is decreasing. This means that hundreds of millions of years ago the Moon would always completely cover the Sun on solar eclipses, and no annular eclipses were possible. Likewise, about 600 million years from now (if the angular diameter of the Sun does not change), the Moon will no longer cover the Sun completely, and only annular eclipses will occur.
2.27.2010
Planets

A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, history, science, mythology, and religion. The planets were originally seen by many early cultures as divine, or as emissaries of the gods. As scientific knowledge advanced, human perception of the planets changed, incorporating a number of disparate objects. In 2006, the International Astronomical Union officially adopted a resolution defining planets within the Solar System. This definition has been both praised and criticized, and remains disputed by some scientists. The planets were thought by Ptolemy to orbit the Earth in deferent and epicycle motions. Though the idea that the planets orbited the Sun had been suggested many times, it was not until the 17th century that this view was supported by evidence from the first telescopic astronomical observations, performed by Galileo Galilei. By careful analysis of the observation data, Johannes Kepler found the planets' orbits to be not circular, but elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, and some share such features as ice-caps and seasons. Since the dawn of the Space Age, close observation by probes has found that Earth and the other planets share characteristics such as volcanism, hurricanes, tectonics, and even hydrology. Since 1992, through the discovery of hundreds of planets around other stars, called extrasolar planets, scientists are beginning to understand that planets throughout the Milky Way Galaxy share characteristics in common with our own. As of February 2010, there are 429 known extrasolar planets, ranging from the size of gas giants to that of terrestrial planets. Planets are generally divided into two main types: large, low-density gas giants, and smaller, rocky terrestrials. Under IAU definitions, there are eight planets in the Solar System. In order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four gas giants, Jupiter, Saturn, Uranus, and Neptune. Apart from the planets, the Solar System also contains at least five dwarf planets and hundreds of thousands of small solar system bodies. With the exception of Mercury and Venus, all planets are orbited by one or more natural satellites. It is not known with certainty how planets are formed. The prevailing theory is that they are formed during the collapse of a nebula into a thin disk of gas and dust. A protostar forms at the core, surrounded by a rotating protoplanetary disk. Through accretion (a process of collision) dust particles in the disk steadily accumulate mass to form ever-larger bodies. Local concentrations of mass known as planetesimals form, and these accelerate the accretion process by drawing in additional material by their gravitational attraction. These concentrations become ever denser until they collapse inward under gravity to form protoplanets. After a planet reaches a diameter larger than the Earth's moon, it begins to accumulate an extended atmosphere, greatly increasing the capture rate of the planetesimals by means of atmospheric drag.Terrestrials are Planets that are similar to Earth, with bodies largely composed of rock: Mercury, Venus, Earth and Mars. At 0.055 Earth masses, Mercury is the smallest terrestrial planet in the Solar System, while Earth is the largest terrestrial planet. Gas giants are Planets with a composition largely made up of gaseous material and are significantly more massive than terrestrials: Jupiter, Saturn, Uranus, Neptune. Jupiter, at 318 Earth masses, is the largest planet in the Solar System, while Saturn is one third as big, at 95 Earth masses. Ice giants, comprising Uranus and Neptune, are a sub-class of gas giants, distinguished from gas giants by their significantly lower mass (only 14 and 17 Earth masses), and by depletion in hydrogen and helium in their atmospheres together with a significantly higher proportion of rock and ice. Before the August 2006 decision, several objects were proposed by astronomers, including at one stage by the IAU, as planets. However in 2006 several of these objects were reclassified as dwarf planets, objects distinct from planets. Currently five dwarf planets in the Solar System are recognized by the IAU: Ceres, Pluto, Haumea, Makemake and Eris. Several other objects in both the Asteroid belt and the Kuiper belt are under consideration, with as many as 50 that could eventually qualify. There may be as many as 200 that could be discovered once the Kuiper belt has been fully explored. Dwarf planets share many of the same characteristics as planets, although notable differences remain namely that they are not dominant in their orbits. By definition, all dwarf planets are members of larger populations. Ceres is the largest body in the asteroid belt, while Pluto, Haumea, and Makemake are members of the Kuiper belt and Eris is a member of the scattered disc. Scientists such as Mike Brown believe that there may soon be over forty trans-Neptunian objects that qualify as dwarf planets under the IAU's recent definition
2.16.2010
Earth
Earth. A place that we call home. A place for many species that live and share spaces. Our planet is Earth and is our home and our space. Where started all this? why? We are the only planet with life in this dark misterious space?With this blog I express my opinion about the Universe, I will post here important discoveries about the Universe, like planets, Stars, black holes, teories, laws of Physic that some scientists made about the space and time, videos and questions that we all know but maybe no one will aswer us.
Our planet, Earth is very precious because is our space and behind of our planet exist the unknown that we try discovery. Like a house we feel confortable because we are safe from the danger that is unknow. I hope you like this blog , forgive me about my English that sometimes can fail and welcome to the "Universe Space and Time"!
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