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1741. Graphs and ellipses
... Graphs Ellipses . 11a. Ellipses . ... As already noted, the cartesian system labels any point in a plane (e. g. on a flat sheet of paper) by a pair of numbers (x,y), its distance from two perpendicular axes. ... is an ellipse . ... One point and the distance R defines a circle, two points and the distance R 1 + R 2 define an ellipse. ... Hint: Make a sketch of the ellipse and the axes which define it, mark one of the points at which it crosses the x-axis, and examine R 1 and R 2 of that point]. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/stargaze/Sellipse.htm -- 21.1 Кб -- 22.12.2007
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1742. (S-7a) The Black Hole at the Center of our Galaxy
... S-6.The X-ray Sun . S-7.The Sun's Energy . S-7A. The Black Hole at . our Galactic Center . ... Our Sun is part of a huge wheel-shaped collection of stars. ... However, unless that object happens to be headed directly at the black hole (a relatively small target) it will just swing around and fly away again, like a comet making a pass at the Sun. ... Far from being a voracious devourer of stars and of interstellar gas, "our own" black hole is rather benign. ... What holds galaxies together? ...
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Ссылки http://www.cosmos.ru/mirrors/stern/stargaze/Sblkhole.htm -- 12.2 Кб -- 22.12.2007
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1743. Elements of Algebra
... M-2 Origin of Algebra . ... 1) Isolate x in each equation and find its value, following the . rule that "when equal operations are performed on both . ... Write down a new equation for each step. ... For operations applied to both sides: (+2) add 2 . ... Solve once by (a) expressing y of one equation in terms of x, then . ... You may furthermore add one equation to the other, or subtract it: because the quantities you add or subtract to both sides are equal, what is left is also a valid equality. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/stargaze/Salgeb1A.htm -- 12.8 Кб -- 22.12.2007
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1744. Kepler's Three Laws of Planetary Motion
... Kepler Laws . ... Planets move around the Sun in ellipses , with the Sun at one focus . ... Kepler's laws describe the motion of planets around the Sun. ... The orbit of the Earth around the Sun. ... and third, he, proved that if the above two held, Kepler's laws could be derived mathematically..... but with one small change : planets orbited not around the Sun, but around a common center of gravity. ... The Earth's orbit, and most planetary orbits, are very close to circles. ... Kepler's 3rd Law . ...
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Ссылки http://www.cosmos.ru/mirrors/stern/stargaze/Kep3laws.htm -- 35.5 Кб -- 22.12.2007
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1745. Magnetism before Gilbert "
... Review Article . ... De Magnete . ... A Gilbert Expt. ... Compasses were also built into portable sundials, whose pointers had to face north to give the correct time. ... If a compass needle was balanced evenly on its pivot before being magnetized, then afterwards its north end would be pulled downwards, and a tip had to be snipped off to restore balance. ... Norman used a compass needle balanced on a horizontal axis, able to swing in a vertical plane lined up in the north-south direction. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/upto1600.htm -- 8.6 Кб -- 22.12.2007
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1746. The Sun's Magnetic Cycle
... The Magnetic Sun . ... Galileo had guessed they were clouds floating in the Sun's atmosphere, obscuring some of its light. ... It turned out that the Sun has a polar field somewhat like the Earth's, but that it reverses its polarity during each 11-year cycle. ... Sunspot fields were evidently produced by electric currents, and it was well known that such currents could be generated by a " dynamo process ," by the motion of an electric conductor (e.g. the flow of solar plasma) through a magnetic...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/sunspots.htm -- 9.4 Кб -- 22.12.2007
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1747. Magnetic Reversals and Moving Continents
... The Magnetic Sun . ... Earth's Core . ... Magnetic Reversals . Moving Continents . ... Most dry land has a modest elevation above sea level, while most of the ocean floor is about 3 kilometers (or 2 miles) lower down. ... Its magnetization is in the direction of the local magnetic force at the time when it cools down. ... Ocean floor magnetization (USGS figure) . ... Every half million years, on the average, the Earth's magnetic polarity reverses, and so does the magnetization of the ocean floor. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/reversal.htm -- 14.9 Кб -- 22.12.2007
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1748. Planetary Magnetism
... The planets differ greatly in size and properties, and their fields differ too. ... In 1959, after the Earth's radiation belt had been discovered, Frank Drake observed Jupiter and concluded from the relative intensities in a range of wavelengths that the signal was probably emitted by electrons trapped in a strong magnetic field. Then in 1973 the space probe Pioneer 10 passed by Jupiter and found there, sure enough, an enormous planetary magnetic field and a very intense radiation belt. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/planetmg.htm -- 13.1 Кб -- 22.12.2007
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1749. The Magnetosphere
... What are those " magnetic storms " which occasionally disturb the Earth's magnetic field? ... Earth's Core . ... The glow followed magnetic field lines (lines of force) and converged near the magnetic poles of the terrella. ... This suggested that somehow, during storms, a large electric current circled the Earth above its equator. ... In space such currents most easily flow along magnetic field lines, because the particles that carry them (mainly electrons) tend to stay attached to such lines. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/magspher.htm -- 14.2 Кб -- 22.12.2007
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1750. Magnetometers
... A typical electromagnet, such as is used in a relay or machinery, has an iron core around which the current-carrying coil is wound. The coil's magnetic field is greatly strengthened by the iron, because the iron atoms (or arrays of such atoms arranged in crystals) are magnetic. ... When current flows in the coil, however, its magnetic field lines up the magnetic axes of atoms in the core, and they add their magnetism to the one created by the electric current alone, making it much stronger. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/magmeter.htm -- 13.3 Кб -- 22.12.2007
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1751. London in 1600 "
an error occurred while processing this directive] . ... De Magnete . ... A Gilbert Expt. ... London in 1600 . ... London Bridge London in 1600 was a rapidly growing city of 75000 residents, with perhaps twice as many in the suburbs outside its walls. ... Another focus was London Bridge, a stone structure of many small arches spanning the river Thames. ... He put on his plays in the Globe theatre , a ring-shaped structure built in 1599 on the banks of the Thames from the remains of an earlier theatre. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/lond1600.htm -- 7.6 Кб -- 22.12.2007
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1752. One of Gilbert's Experiments
... Given two magnets, Gilbert knew that magnetic poles can attract or repel, depending on polarity. ... That is, the end of an iron bar stuck to an S pole of a magnet (south-seeking pole) temporarily becomes an N-pole. ... Gilbert confirmed his guess of temporary ("induced") magnetism by an original experiment (see drawing). ... Under the influence of the terrella, each became a temporary magnet with the same polarities, and the temporary poles of each bar repelled those of the other one. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/inducemg.htm -- 9.9 Кб -- 22.12.2007
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1753. Origin of The Earth's Magnetism
... The Magnetic Sun . ... Earth's Core . ... It is an uncanny fact that the Earth's magnetic axis is close to its rotation axis--that the magnetic poles, where the magnetic force points straight down, are quite close to the geographical ones. ... The Earth's magnetism is no exception, and its energy seemes to come from fluid motions in the Earth's core, from circulating flows that help get rid of heat produced there. ... Scientists are still not sure about what provides the heat in the Earth's core. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/dynamos2.htm -- 13.7 Кб -- 22.12.2007
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1754. Review of "De Magnete"
... by William Gilbert, ix+246 pp, 7/6 (37.5 p) in London; . ... Published by Peter Short, London, 1600. [an error occurred while processing this directive] . ... But the notion of a scientific textbook was unfamiliar when De Magnete first appeared in 1600. ... The first book starts with an historical survey, then reviews the basic magnetic properties of a lodestone (poles, attraction and repulsion, magnetisation of iron) and ends with the famous chapter on the Earth itself being a great magnet. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/demagrev.htm -- 14.7 Кб -- 22.12.2007
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1755. About Gilbert's Work
... De Magnete . ... More on "De Magnete" . ... A Gilbert Expt. ... Before Gilbert . ... different parts of Gilbert's terrella Of his own experiments, the most important was conducted with a magnetized " terrella " ("little Earth"), a spherical magnet serving as a model for the Earth. ... In addition to studying magnets. ... The last of the 6 "books" into which Gilbert's work is divided deals with the motion of Earth in space and its possible connection to magnetism. ... Magnetism from Gilbert to 1820 ....
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/demagadd.htm -- 8.3 Кб -- 22.12.2007
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1756. Teaching about Magnetism Teaching about Magnetism
... For Teachers . ... Earlier today I was asked to tell you about the magnetosphere , about the complicated interaction involving the Earth's magnetism, the solar wind and magnetic phenomena on the Sun's surface, like sunspots. ... In the minds of most Americans magnetism is forever associated with specially treated iron , with patterns of iron filings and with the way the compass needle lines up with the north-south direction. ... Slide 1) . ... Not too close , or the two magnetic needles interact. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/MagTeach.htm -- 19.6 Кб -- 22.12.2007
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1757. Introduction to "Stargazers" (for Teachers)
... Space index . ... That CD contained "From Stargazers to Starships" where this file now resides--a course and resource on astronomy, physics, space and related mathematics. It also contained non-mathematical courses on the magnetism of Earth and of space around it, and more. The file you are reading focuses on ways in which a teacher (or an independent student) might use all that material. ... Earth Sciences teachers may use #S-1 to S-1b on weather and climate, as well as sections on space. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/stargaze/edufiles.htm -- 22.2 Кб -- 22.12.2007
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1758. Chronology of early astronomy,mechanics and spaceflight
... Dates in red are from the basic timeline of events related to "From Stargazers to Starships". ... and astronomy, see the AIP Center for the History of Physics . ... of the Earth, Sun and Planets, see here . ... 3000 BC--beginning of the bronze age, named for the first useful metal alloy. ... 1200 BC (approx)---Trojan war. ... 1903, 17 December---First successful flight by the Wright brothers at Kitty Hawk, North Carolina. ... 1932---Sulfa drugs, first new anti-bacterial weapon. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/stargaze/Stimelin.htm -- 45.1 Кб -- 22.12.2007
[ Сохраненная копия ] Ссылки http://www.cosmos.ru/mirrors/stern/stargaze/Stimeln2.htm -- 45.1 Кб -- 22.12.2007
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[ Сохраненная копия ] Ссылки http://www.cosmos.ru/mirrors/stern/stargaze/Stimeln2.htm -- 45.1 Кб -- 22.12.2007
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1759. "Get a Straight Answer"
... Asymmetry of the Moon's orbit. ... What if the Earth's axis were tilted 90? to the ecliptic? ... Gravity at the Earth's Center . ... So--if the gravitational force of the sun is powerful enough to hold the Earth in orbit, then how could the Earth's gravitational force be powerful enough to hold me down, counter-acting the gravitational force of the sun? ... 2) Being on the orbiting Earth, your body already responds to the Sun's gravity, by sharing the Earth's velocity of 30 km/s around the Sun. ...
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Ссылки http://www.cosmos.ru/mirrors/stern/stargaze/StarFAQs.htm -- 55.1 Кб -- 22.12.2007
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1760. FAQ: "The Great Magnet, the Earth"
... Listed below are questions submitted by e-mail to the author of "The Great Magnet, the Earth." ... Only some of the questions that arrive are listed, either because they keep coming up again and again--on the reversal of the Earth's magnetic field, for instance-- or because the answers add extra details, which might interest other users. ... Pole shifts? ... Measuring Earth's magnetic field . ... So, my question is: Why isn't the Earth's magnetic north pole a "true" magnetic north pole? ...
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Ссылки http://www.cosmos.ru/mirrors/stern/earthmag/magnQ&A1.htm -- 62.8 Кб -- 22.12.2007
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