Astronomy in medieval Islam – Wikipedia, the free encyclopedia

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Islamic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age (8th15th centuries),[1] and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and later in the Far East and India. It closely parallels the genesis of other Islamic sciences in its assimilation of foreign material and the amalgamation of the disparate elements of that material to create a science with Islamic characteristics. These included Greek, Sassanid, and Indian works in particular, which were translated and built upon.[2] In turn, Islamic astronomy later had a significant influence on Byzantine[3] and European[4] astronomy (see Latin translations of the 12th century) as well as Chinese astronomy[5] and Malian astronomy.[6][7]

A significant number of stars in the sky, such as Aldebaran and Altair, and astronomical terms such as alidade, azimuth, and almucantar, are still referred to by their Arabic names.[8][9] A large corpus of literature from Islamic astronomy remains today, numbering approximately 10,000 manuscripts scattered throughout the world, many of which have not been read or catalogued. Even so, a reasonably accurate picture of Islamic activity in the field of astronomy can be reconstructed.[10]

Ahmad Dallal notes that, unlike the Babylonians, Greeks, and Indians, who had developed elaborate systems of mathematical astronomical study, the pre-Islamic Arabs relied entirely on empirical observations. These observations were based on the rising and setting of particular stars, and this area of astronomical study was known as anwa. Anwa continued to be developed after Islamization by the Arabs, where Islamic astronomers added mathematical methods to their empirical observations.[12] According to David King, after the rise of Islam, the religious obligation to determine the qibla and prayer times inspired more progress in astronomy for centuries.[13]

Donald Hill (1993) divided Islamic Astronomy into the four following distinct time periods in its history:

The period of assimilation and syncretisation of earlier Hellenistic, Indian, and Sassanid astronomy.

The first astronomical texts that were translated into Arabic were of Indian and Persian origin.[14] The most notable of the texts was Zij al-Sindhind,[n 1] an 8th-century Indian astronomical work that was translated by Muhammad ibn Ibrahim al-Fazari and Yaqub ibn Tariq after 770 CE under the supervision of an Indian astronomer who visited the court of caliph Al-Mansur in 770. Another text translated was the Zij al-Shah, a collection of astronomical tables (based on Indian parameters) compiled in Sasanid Persia over two centuries. Fragments of texts during this period indicate that Arabs adopted the sine function (inherited from India) in place of the chords of arc used in Greek trigonometry.[12]

This period of vigorous investigation, in which the superiority of the Ptolemaic system of astronomy was accepted and significant contributions made to it. However, Dallal notes that the use of parameters, sources and calculation methods from different scientific traditions made the Ptolemaic tradition "receptive right from the beginning to the possibility of observational refinement and mathematical restructuring".[15] Astronomical research was greatly supported by the Abbasid caliph al-Mamun through The House of Wisdom. Baghdad and Damascus became the centers of such activity. The caliphs not only supported this work financially, but endowed the work with formal prestige.

The first major Muslim work of astronomy was Zij al-Sindh by al-Khwarizmi in 830. The work contains tables for the movements of the sun, the moon and the five planets known at the time. The work is significant as it introduced Ptolemaic concepts into Islamic sciences. This work also marks the turning point in Islamic astronomy. Hitherto, Muslim astronomers had adopted a primarily research approach to the field, translating works of others and learning already discovered knowledge. Al-Khwarizmi's work marked the beginning of nontraditional methods of study and calculations.[16]

In 850, al-Farghani wrote Kitab fi Jawani (meaning "A compendium of the science of stars"). The book primarily gave a summary of Ptolemic cosmography. However, it also corrected Ptolemy based on findings of earlier Arab astronomers. Al-Farghani gave revised values for the obliquity of the ecliptic, the precessional movement of the apogees of the sun and the moon, and the circumference of the earth. The book was widely circulated through the Muslim world, and even translated into Latin.[17]

The period when a distinctive Islamic system of astronomy flourished. The period began as the Muslim astronomers began questioning the framework of the Ptolemaic system of astronomy. These criticisms, however, remained within the geocentric framework and followed Ptolemy's astronomical paradigm; one historian described their work as "a reformist project intended to consolidate Ptolemaic astronomy by bringing it into line with its own principles."[18]

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The Solar System – Astronomy For Kids – KidsAstronomy.com

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Our solar neighborhood is an exciting place. The Solar System is full of planets, moons, asteroids, comets, minor planets, and many other exciting objects. Learn about Io, the explosive moon that orbits the planet Jupiter, or explore the gigantic canyons and deserts on Mars.

The Solar System is made up of all the planets that orbit our Sun. In addition to planets, the Solar System also consists of moons, comets, asteroids, minor planets, and dust and gas.

Everything in the Solar System orbits or revolves around the Sun. The Sun contains around 98% of all the material in the Solar System. The larger an object is, the more gravity it has. Because the Sun is so large, its powerful gravity attracts all the other objects in the Solar System towards it. At the same time, these objects, which are moving very rapidly, try to fly away from the Sun, outward into the emptiness of outer space. The result of the planets trying to fly away, at the same time that the Sun is trying to pull them inward is that they become trapped half-way in between. Balanced between flying towards the Sun, and escaping into space, they spend eternity orbiting around their parent star.

This is an important question, and one that is difficult for scientists to understand. After all, the creation of our Solar System took place billions of years before there were any people around to witness it. Our own evolution is tied closely to the evolution of the Solar System. Thus, without understanding from where the Solar System came from, it is difficult to comprehend how mankind came to be.

Scientists believe that the Solar System evolved from a giant cloud of dust and gas. They believe that this dust and gas began to collapse under the weight of its own gravity. As it did so, the matter contained within this could begin moving in a giant circle, much like the water in a drain moves around the center of the drain in a circle.

At the center of this spinning cloud, a small star began to form. This star grew larger and larger as it collected more and more of the dust and gas that collapsed into it.

Further away from the center of this mass where the star was forming, there were smaller clumps of dust and gas that were also collapsing. The star in the center eventually ignited forming our Sun, while the smaller clumps became the planets, minor planets, moons, comets, and asteroids.

Once ignited, the Sun's powerful solar winds began to blow. These winds, which are made up of atomic particles being blown outward from the Sun, slowly pushed the remaining gas and dust out of the Solar System.

With no more gas or dust, the planets, minor planets, moons, comets, and asteroids stopped growing. You may have noticed that the four inner planets are much smaller than the four outer planets. Why is that?

Because the inner planets are much closer to the Sun, they are located where the solar winds are stronger. As a result, the dust and gas from the inner Solar System was blown away much more quickly than it was from the outer Solar System. This gave the planets of the inner Solar System less time to grow.

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Gravity Ghost

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Reviewed on PC

Gravity Ghost is one of the oddest and most relaxing space adventures Ive ever embarked upon. While its view of the cosmos is grounded in science you learn plenty about slingshot trajectories and astro-geometry its really brought to life by a vibrant sense of spirituality. Physics and mysticism combine in an experience thats both funny and sad, eccentric and poignant, soothing and frequently baffling. Even though the challenge remains slight throughout and it never really makes the most of its most promising mechanics, I found Gravity Ghost a delightful curiosity throughout.

Before heading through the space gate, where things get surreal very quickly, a little context is useful. You play as a young girl who has died in an unspecified incident and been reincarnated among the stars. The visuals have a charming roughness to them you can see individual, textured brushstrokes and when combined with the simple, cartoon character design and its joyful use of colour, it feels like playing a game illustrated by a child. Is this the dead girl coming to terms with what has happened to her? I think thats the intention, and I found it strangely moving. Yes, Gravity Ghost initially seems a bit silly, but crucially its never flippant; it never loses sight of its underlying narrative about how this girl died.

Her moving story is pieced together by journeying from planet to planet, solving simple but novel physics-based puzzles, and illuminating constellations. No matter where you are in the cosmos the challenge is always the same: you must collect a tiny star located somewhere in the level, usually orbiting another planet to unlock a door which leads to the next system. This is complicated by the intrusion of gravity, which makes leaping from planetoid to planetoid manageable, but less than straightforward.

Just like in Mario Galaxy, when youre close to a sizeable chunk of mass, youre drawn towards it and can land on its surface. But thats where the similarities end, as Gravity Ghost expects you to take more daring leaps into the black stuff. It's much less daunting than it sounds because of the lack of a "death" situation, and I felt encouraged to experiment with the invisible forces, determined by the layout of orbiting bodies in a given level, push and pull you around the screen. Youre not entirely at the mercy of gravity, however; you can resist and sometimes even break away from the gravity of a nearby planet, and drift freely in space until snared by another rock.

But even as I solved puzzle after puzzle, I never felt like I truly understood how best to exploit this invisible force and turn it to my advantage. Collecting space debris makes the girls hair grow which I assume is supposed to function as some kind of aid, giving form to the invisible forces at work and while it was useful to see the trajectory I had been on, I found it next to useless when plotting my next course.

Special abilities are soon introduced to give you more control while drifting through space, and they do make getting around a bit easier. By the end, youre able to hover briefly in the air, adopt a super-dense form, and dash left or right all of which allow you to deviate from a set orbit. The pacing of these abilities is well-judged, too, with each one being introduced once Id was comfortable with the last. Yet no matter how many abilities I gained, I never got rid of the feeling that I was wrestling with gravity. Maybe thats how its supposed to feel, like its this great force that can never be truly tamed, but it also felt like I was never really improving, either. Right until the end, I found trial-and-error and patience were just as valuable as my newfound abilities.

What's strange is that Gravity Ghosts lays groundwork for more complexity and different types of puzzles, yet never capitalizes on it. For instance, you can cycle through different unlockable outfits to transform planets into lush jungle worlds, balls of unset lava, or a number of things in between, each with their own gravitational properties.. Initially, I assumed it was going to be how you tame gravity, so I began experimenting, creating fire planets, which make you jump a little higher, and crystal planets, which are superdense and warp the fabric of space around them and slow you down. But I soon realised it didnt really matter. Barring a few exceptions, most levels can be solved without any terraforming whatsoever. Its a shame, since its presented as a substantial mechanic, and is used to uncover more about the girls past, but in terms of the individual level design it feels oddly inessential.

That said, it rarely hindered my enjoyment, since this is the kind of puzzle where the idea of challenge seems incidental; its much more concerned with wrapping a sad tale in a distinctive, weirdly pleasurable sensory experience. In short, Gravity Ghost wants you to enjoy the act of feeding lettuce to a giant space rabbit, rather than make that into a challenge.

And when it comes to mood, Gravity Ghost truly excels. The music is superb, with piano and synth working in tandem to create a score that is both stirring and emotive; the art is vibrant and stimulating, yet its soft and friendly style prevent it from ever feeling garish. The voice acting is downright bizarre, too, with the delivery ranging from what sounds like archive recordings to the kind of intense bounciness you would expect from Saturday-morning cartoons. It feels like an episode of Adventure Times rerouted through the final act of 2001: A Space Odyssey; one minute youre learning about optics from a giant owl while fixing a lighthouse next to a black hole, the next youre uncovering more of about its buried, earth-bound story about this girl and her tragic death. Its amusing and odd, but also stark and poignant.

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Gravity Ghost

X Prize Chairman Peter Diamandis on Investing in Artificial Intelligence – Video

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X Prize Chairman Peter Diamandis on Investing in Artificial Intelligence
Feb. 4 -- Peter Diamandis, chairman at X Prize Foundation, talks about the investment opportunities in funding research into artificial intelligence. He spea...

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X Prize Chairman Peter Diamandis on Investing in Artificial Intelligence - Video

Musk's warning ignites PR war over artificial intelligence

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Paul Sancya/AP Elon Musk, Tesla Chairman, Product Architect and CEO, speaks at the Automotive News World Congress in Detroit last month. Depending on whom you ask, advances in artificial intelligence are either humanity's biggest threat or our best shot at curing diseases.

On one side of the debate are billionaire entrepreneurs such as Elon Musk and Bill Gates and physicist Stephen Hawking, who say AI is a potential menace to humankind with super-intelligent machines that could run amok. Some of its biggest backers include billionaires Paul Allen and Jack Ma.

With criticism on the rise, supporters - led by researchers at Allen's AI institute and Stanford University - are seeking to give their field an image makeover.

Allen's group recently began touting an AI project aimed at improving medical care. Stanford is undertaking an AI study on ethics and safety set to run for 100 years. It's all part of a deliberate push in the AI community to address growing concerns about the technology as the field expands, with venture capital funding in the area rising 20-fold since 2010 and dozens of new startups popping up.

"Someone has impugned us in very strong language saying we are unleashing the demon, and so we're answering," said Oren Etzioni, chief executive officer of the Allen Institute for Artificial Intelligence. "The conversation in the public media has been very one-sided."

The more organized effort now marks the first sustained moves by scientists and entrepreneurs to engage the public and try to quell their fears.

Max Tegmark, a Massachusetts Institute of Technology physics professor and co-founder of the Future of Life Institute, is one researcher trying to carve out common ground. Tegmark began circulating an open letter in early January in Puerto Rico at the institute's first conference, which was attended by Musk, among others. The letter, whose signers now include Musk, Etzioni and many researchers and advocates on both sides, was made public on Jan. 12.

"There had been a ridiculous amount of scaremongering," said Tegmark, who sometimes goes by "Mad Max." "And understandably a lot of AI researchers feel threatened by this."

Talking about how to imbue intelligent agents with human ethics is "common sense," said Stuart Russell, a professor at University of California at Berkeley and co-author of the textbook Artificial Intelligence: A Modern Approach. Take the example of a household robot, he said - sort of like Rosie the maid from The Jetsons.

"It has to understand human values so it doesn't do stupid things," he said. "You don't want it to accidentally cook the cat for dinner."

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Musk's warning ignites PR war over artificial intelligence

SpaceTalks with Derek Nelson, Optical Navigation Engineer, KinetX Aerospace, Inc. – Video

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SpaceTalks with Derek Nelson, Optical Navigation Engineer, KinetX Aerospace, Inc.
Derek Nelson is an Optical Navigation Engineer for the Space Navigation and Flight Dynamics (SNAFD) Practice at KinetX Aerospace, Inc. KinetX is responsible for providing end-to-end interplanetar...

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SpaceTalks with Derek Nelson, Optical Navigation Engineer, KinetX Aerospace, Inc. - Video

Colorado remains at the top of national aerospace employment in 2014

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Mathew Smith, vice president of United Launch Alliance, introduces the ULA team. (Cyrus McCrimmon, The Denver Post)

Despite a decrease in overall aerospace industry employment nationwide, Colorado in 2014 retained its No. 1 ranking in the nation for private aerospace employment as a percentage of total employment, according to data from the Metro Denver Economic Development Corp.

The state also retained its No. 3 rank in total private-sector aerospace employment, behind Florida and California.

The 2014 Colorado Aerospace Industry Cluster Profile doesn't contain many "aha" moments. In fact, it reveals that statewide aerospace employment actually decreased by 0.2 percent.

However, the decline was minimal compared with the nation overall.

"We obviously always want to see employment growth, but the fact that Colorado has been able to remain constant while the rest of the U.S. is experiencing a 2.6 percent decline shows we are holding steady and strong," Colorado Space Coalition director Vicky Lea said Friday.

This strength comes from Colorado's robust aerospace ecosystem, which combines a highly educated workforce; a scientific base that includes research universities and federal laboratories; eight of the United States' major space contractors, such as Lockheed Martin, Ball Aerospace and United Launch Alliance; a large military space presence; and a robust network of space-related small businesses.

But while this all positions Colorado for success, there are measures that must be taken to continue the state's aerospace dominance among them, Lea said, a continued state focus on STEM education and a continued flow of money.

"We need to ensure NASA and the Department of Defense budget funding and programs and missions that Colorado companies are involved with continue to be funded," Lea said. "We also need to make sure we're not only importing talent but also growing our own aerospace engineers here."

Colorado also has an entrepreneurial spirit that is bolstered by the state's commitment to helping grow advanced technology and a combination of federal and state programs providing seed money for up-and-coming companies.

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Colorado remains at the top of national aerospace employment in 2014