could somebody explain in very easy terms Johannes keplers 1st-3rd laws?
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Kepler has 3 laws of planetary motion. \n\n1. The first is about the shape of the orbit of a planet. The orbits of planets are not circles, but ellipses. \n\nTo draw a circle, attach a string to a nail, and then place a pencil at the other end of the string. Pull the string taut, and then trace a circle around the nail. The circle is a bunch of points that are all the same distance from the center point, the nail. \n\nTo draw an ellipse, we just make a slight change. We put two nails in, and loop a loop of string around them, and put a pencil in the loop, pulling the string taut again and away from the nails. You trace out an oval by moving the pencil, keeping the tension on the loop of string. The two nails are at places called FOCI of the ellipse (plural of focus and a generalization of the idea of center of the circle). The ellipse is the collection of points whose sum of distances from the two foci (the nails) is contant. \n\nKepler's first law tells us that the planets travel in ellipses, and the sun is at one of the foci of the ellipse. \n\n2. Kepler's 2nd law tells us something about the time it takes the planet to go around the ellipse. If you draw a line from the sun (one of the foci) to the planet, as the planet goes in the orbit, this line covers an area that is sort of triangle shaped, with a curved side, and a bit lopsided. This area that the line covers is called the area swept out by the planet as it goes on its orbit. So if one looks at any given period of time, like a day, anywhere in the orbit, the area swept out by the planet is the same. If you look at the area swept out in a week, any area swept out by the planet in a week is the same, no matter where the planet is in the orbit. \n\nSo kepler's 2nd law is, planets sweep out equal areas in equal times. \n\n3. Kepler's third law has some math in it, and has to do with how long it takes the planet to go on one cycle (all the way around the orbit: for the earth, this is a year) and how big the orbital ellipse is. It can be used to compare the orbits of two or more different planets as well. \n\n\nSuppose that the time it takes the planet to go around the orbit one complete cycle is T. Suppose that the distance all the way across the orbit at its widest point is D. \n\nThen the square of the time T divided by the cube of the distance D is a constant. \n\n(time for orbit)x(time for orbit)\n_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _     = constant\n\n(distance D)x(distance D)x(distance D)\n\nIn other words\n\nTxT/DxDxD = constant or \n\nT^2/D^3 = constant\n\n\nSo how does this compare two planets? \n\nSuppose the time for one cycle for planet 1 is T1, and the distance across for planet 1 is D1. \n\nAnd the time for one cycle for planet 2 is T2, and the distance across for planet 2 is D2\n\nThen (T1^2)/(D1^3)= (T2^2)/(D2^3)\n\nso the two orbits of the two planets are compared !
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he wrote the three laws of motion .\nJump to: navigation, search\n   Sir Isaac Newton \n\nSir Isaac Newton at 46 in Godfrey Kneller's 1689 portrait. \nBorn \n4 January [O.S. 25 December 1642] 1643\nWoolsthorpe-by-Colsterworth, Lincolnshire, England \nDied \n31 March [O.S. 20 March] 1727\nKensington, London \nSir Isaac Newton, President of the Royal Society, (4 January 1643 – 31 March 1727) [OS: 25 December 1642 – 20 March 1727] was an English mathematician, physicist, astronomer, alchemist, chemist, inventor, and natural philosopher who is generally regarded as one of the greatest scientists and mathematicians in history.\n\nNewton wrote the Philosophiae Naturalis Principia Mathematica in which he described universal gravitation and the three laws of motion, laying the groundwork for classical mechanics. By deriving Kepler's laws of planetary motion from this system, he was the first to show that the motion of objects on Earth and of celestial bodies are governed by the same set of natural laws. The unifying and deterministic power of his laws was integral to the scientific revolution and the advancement of heliocentrism.\n\nAmong other scientific discoveries, Newton realized that the spectrum of colours observed when white light passes through a prism is inherent in the white light and not added by the prism (as Roger Bacon had claimed in the thirteenth century), and notably argued that light is composed of particles. He also developed a law of cooling, describing the rate of cooling of objects when exposed to air. He enunciated the principles of conservation of momentum and angular momentum. Finally, he studied the speed of sound in air, and voiced a theory of the origin of stars. Despite this renown in mainstream science, Newton actually spent more time working on alchemy than physics, writing considerably more papers on the former than the latter24.\n\nNewton played a major role in the history of calculus, sharing credit with Gottfried Leibniz. He also made contributions to other areas of mathematics, for example the generalized binomial theorem. The mathematician and mathematical physicist Joseph Louis Lagrange (1736–1813), said that "Newton was the greatest genius that ever existed and the most fortunate, for we cannot find more than once a system of the world to establish." 20\n\nfor more info go to http://en.wikipedia.org/wiki/Isaac_Newton
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Silly...  The point your instructor is making is that barring any impeding object (air) in the horizontal(to the ground) velocity vector will remain the same (First Law of Motion).  Of course his use of never is inappropriate.  Any thrown object will eventually fall, go into orbit, or escape earth's gravity and fly into space.  At which point the object might encounter another impeding object...\nI recommend that you suggest to your instructor that he reword the question. (Forget trying to get the point).  Explain to him that Newton's First Law states "An object at rest tends to stay in rest and an object in motion tends to stay in motion in a straight line at constant speed unless acted upon by an outside force."...  Notice Newton himself refrains from the use of NEVER and uses the unless clause.  Explain to the instructor that you were using the UNLESS in the 1st Law.  That is to say he did not tell you to ignore gravity or any other impeding objects.  So, tell the instructor that you now understand what he was asking BUT s/he would be better off either taking out the NEVER (which Newton would not have used) with "until it hits the ground."\n\nAddition:\nGiven the Q as a true/false statement and understnading that the question is asking about Newton's First Law and knowing that even Newton says "nisi quatenus a viribus impressis cogitur statum illum mutare." which means "unless acted upon by an external and unbalanced force."  I would say FALSE! \n(The word "never" should not have been used).
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Kepler's Laws (of planetary motion) use Calculus (first quarter/semester if that is what you were wondering about).  You can get a good understanding of them by simplifying them with geometry, trig and logic though I believe.\n\nMost descriptions of the motion of bodies (like planets and comets) use calculus, trig(for angles), and some other basic geometry, as well as good ole logic.
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Kepler's Laws \nIllustration of elliptical orbit of a planet with the sun at the left focus. The semi-major and semi-minor axes are denoted by  and . The shaded triangular area element is needed for the discussion of Kepler's second law. Perihelion and aphelion are respectively the points on the orbit nearest and farthest from the sun. Note that at perihelion and aphelion the velocity is purely tangential, i. e., the velocity component along the radius vector is zero.  \nJohannes Kepler, using data compiled by Tycho Brahe, inferred three laws governing the motions of planets in the solar system: \nPlanets move in elliptical orbits with the sun at one focus. \nEqual areas are swept out in equal times by the line connecting the sun and the planet. \nThe square of the period of revolution of the planet around the sun is proportional to the cube of the semi-major axis of the ellipse. \nThese laws were instrumental in the development of modern mechanics and the universal law of gravitation by Isaac Newton. \nShowing that the first law is consistent with Newtonian mechanics is mathematically more difficult than we can undertake in this course. However, the second law turns out to be a simple consequence of the conservation of angular momentum. It shows an elliptical orbit with the area swept out as a planet moves from position 1 to position 2. We estimate this area as , where we have ignored the small unshaded part of the area to the right of the shaded triangle. The distance traveled by the planet in time  is , so the magnitude of the velocity is . However, in computing the angular momentum, we need the tangential component of the velocity, i. e., the component normal to the radius vector . This is simply . The angular momentum is , where  is the mass of the planet. Combining this with the formula for  results in \nSince gravitation is a central force, angular momentum is conserved, which means that  is constant. Thus, we have shown that conservation of angular momentum is equivalent to Kepler's second law. \nKepler's third law turns out to be a consequence of the universal law of gravitation. We can prove this for circular orbits. We know that a planet moving in a circular orbit around the sun is accelerating toward the sun with the centripetal acceleration , where  is the speed of the planet's motion in its orbit and  is the orbit's radius. This acceleration is caused by the gravitational force, so we can equate the force divided by the planetary mass to , resulting in where  is the mass of the sun. This may be solved for Eliminating  in favor of the period of revolution  results in ...This agrees with Kepler's third law since the semi-major axis of a circle is simply the radius .
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Kepler's 3rd law says T = (2*pi*R^1.5)/sqrt(G*M) where M is the mass of the central body (i.e., the sun, not Mars) ~ 2*10^30 kg. Then R = [sqrt(G*M)*T/(2*pi)]^(2/3). I get 2.7298*10^11 m.
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There is no force that causes the planets to rotate. Most of the rotation comes about from the conservation of angular momentum. Angular momentum is given by L=m*w*r2 where m is the mass, w is the angular velocity in radians per second, and r is the radius of the circular motion. Due to conservation of angular momentum, if the radius of the orbit decreases, then its angular velocity must increase (as the mass is constant).\n\nAll planetary and stellar systems are born from the collapse of dense interstellar clouds. The clouds may originally be very large (even thousands of light years across). Consider a portion of the cloud the collapses from a size of a light year or so to the size of the solar system. That is a huge change in the size of the system. So, the very slight rotation that the cloud has in the beginning is increased dramatically when the collapse takes place. In fact, this is one of the barriers in star formation: there is excess angular momentum and there has to be a way of losing angular momentum before you can form a star.\n\nAnyway, the bottom line is that stars like the Sun spin from the original angular momentum that was there in the solar nebula from which it formed. Not only that, all orbital motion of the planets (including the spin) is due to this orginal angular momentum.\n\nYou are saying that original angular momentum of the cloud causes orbital motions and rotations of the planets(mostly). But in the case of orbital motions we have gravitational force that gives us some restrictions of movement(Kepler laws,for example).\n\nWhat I am saying is that there will be no planets if there was no initial angular momentum in the primordial solar nebula. If a nebula with absolutely no rotation collapses, then there will only be a central non-rotating star and there will not be any planets. Planets form out of a protostellar disk, which itself forms only because of the initial angular momentum of the cloud. The dynamics of a rotating body is of course controlled by forces like gravity. Kepler's laws are a direct consequence of gravity. \n\nAll the planets in our solar system spin.
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1. Diferentiation\n\n2. Outgassing\n\n3. Spring (vernal) equinox\n\n4. This is just presession, the natual motion of a spinning body in a graviational field. not sure what "forces" you are looking for.\n\n5. It marks the equinoxes, the days of the year of even amounts of sun and dark, and we start several of our coordinate systems from the point of the spring equinox.
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Hmmm.  I can’t see the image in the link you suggest, but I’ll take a stab at answering…\n\nBasically, Copernicus used math to figure things out.  To draw a figure for himself or for publication, he might use a compass or a straightedge, but what motivated his change from a geocentric to a heliocentric system—i.e., from an Earth-centered to a Sun-centered system—was a combination of aesthetics and mathematics.  The reason people took him seriously is because of the latter:  he provided a mathematical basis for saying that the Sun, and not Earth, lay at the center of our planetary system.\n\nBut you ask a more interesting question…  How did he figure out that the Sun was slightly off center in the solar system?  Indeed, Copernicus didn’t really put the Sun at the center:  he put the center of Earth’s circular orbit at the center of the system.  The Sun didn’t exactly coincide with that spot.\n\nWhat’s important to note is that, although planets follow elliptical orbits, the orbits are actually quite close to being circular.  The main effect on astronomical observations is the apparent change in speed as the planet orbits the Sun:  when a planet is closer to the Sun, it orbits faster, and when it’s farther away, it moves more slowly in its orbit.  So the Sun being off-center affects the motion of the planets around it.  Although Copernicus didn’t think of things this way, he nonetheless had to accommodate the change in orbital speed, which was accomplished (in part) by moving the Sun off center.\n\nUnfortunately, things get a little messy at this point.  Copernicus’s primary motivation in rearranging the planets was to preserve an Aristotelian ideal of uniform circular motion.  To do this, he did away with the “equant,” an important part of the Ptolemaic system (that came several centuries after Aristotle), and it was the equant that actually described the speeding up and slowing down I referred to in the previous paragraph.  Instead, Copernicus inserted additional epicycles and it was those epicycles that further shifted the Sun away from the center of the system.\n\nSo…  The short answer to your question would be “math.”  Copernicus used math to determine that the Sun was slightly off-center in the solar system.  But he also chose not to place the Sun at the center for some reason he never specifically described, and he further removed the Sun from the center by adding the same kind of epicycles for which his predecessor Ptolemy was criticized.\n\nUm.  I hope that helps…?\n\n(An afterthought.  If you’re interested in astronomical tools the likes of which Copernicus would have used, take a look at the last link below.  A variety of astronomical tools—astrolabes, armillary spheres, torquetums, sun dials, quadrants, cross staffs, compasses, or water clocks—might make their appearance in an image from that time, so the page at Humboldt University might help identify those.)\n\n\nRyan Wyatt\nRose Center for Earth & Space\nNew York, New York
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Well to understand Elliptical Orbits and Kepler's Three Laws of Planetary Motion, the triangle formed by  the two focus of the ellipse and the body in orbit do come into play.
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By carefully and meticulously studying their orbits and taking note of their positions in the sky night after night for many many years. This work begun with the invention of the telescope but it wasn´t until Johannes Kepler got his hand on all that work, including the work of his mentor Tycho Brahe, that the elliptical nature of planetary motion was discovered. Until then planets were thought to be moving in perfect circles for many resons except scientific. The circle was a nice and harmonic shape. But Kepler, with all those measurments at his hands, couldn´t fit the circle into his charts and models. He thought for years about what other geometrical shapes could fit it and eventually thought to try the ellips. And it fit in (almost) perfectly. From that breakthrough he was able to come up with simple mathematical explanations for planetary motion, now dubbed Kepler´s laws. Isaac Newton later expanded on those laws and the result were Newtons laws. Kepler published his work in 1609 in a book called New Astronomy. (Some errors in Keplers laws could not be explained and corrected until Albert Einstein introduced his work on the space/time relation.)
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Kepler has three laws of planetary motion:\n\n1. The orbit of a planet about a star is an ellipse with the star at one focus.\n\n2. A line joining a planet and its star sweeps out equal areas during equal intervals of time.This is also known as the law of equal areas.\n\n3. The squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axis of the orbits. This one has an equation tied to it:\n\nT^2 = xa^3, where T = orbital period of a planet and a = semimajor axis of orbit
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Newton's First Law of Motion:\n 1. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.  \n\nNewton's Second Law of Motion:\n 2. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.  \n\nNewton's Third Law of Motion:\n 3. For every action there is an equal and opposite reaction.
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Period is proportional to R^3/2.\nThis is an answer I posted to bombay2pac2000 under Astronomy & Space 8 hours previously, and it applies here as well.\nKepler's 3rd law says: Orbital period T = 2*pi*R^1.5/SQRT(GM)\nwhere R is the radius (in the case of a circular orbit), G is the universal gravitational constant and M is the mass of the central body.  In orbit, centrifugal acceleration CA balances gravitational acceleration GA.  CA=w^2R (where w is omega, the orbital angular rate which = 2pi/T). So CA = (2pi/T)^2*R. From Newton we know GA = GM/R^2. Put 'em together, \nCA = GA\nR*(2pi)^2/T^2 = GM/R^2 \nT^2 = R^3*(2pi)^2/GM\nT = 2*pi*(R^3/2)/SQRT(GM)
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Newton's laws of motion together with his law of gravity give a relation among\n\n    * the period P of a planet's orbit.\n    * the distance a from the planet to the Sun.\n    * a constant G measured in laboratory experiments.\n    * the mass M of the Sun. \n\n(For our purposes, assume the orbits are circles. Also assume that the mass of a planet is tiny compared to the mass of the Sun.)\n\n\nUsing this relation with P and a for the Earth gives the mass of the Sun.\n\nM ~ 2 x 1030 kg.\n\nWe will use this relation later on to get the masses of other stars.\n\nIt can also be used to get the masses of galaxies!\n\nDavison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA soper@bovine.uoregon.edu
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Astronomers define a coordinate system on the sky that lets them identify the relative positions of stars, planets, the Sun and other celestial phenomena (the coordinates are called "right ascension" and "declination", but we don't need to worry about that here). Because of their great distance from the Earth, the positions of most stars are fixed on the grid. The positions of the planets and the Sun, however, are seen to "travel" through the coordinate grid in systematic (though sometimes complicated) patterns. The paths of the planets was carefully observed by Tycho Brahe in the late 1500s. Following Brahe's death in 1601, Johannes Kepler used the data to develop a set of laws that govern the way the planets move around the Sun (he proposed them in 1609). These laws, (creatively) called Kepler's Laws, still hold today.\n\nWith Kepler's laws in hand, one can easily interpret the motion of the Sun through the coordinate grid described above as the result of the tilt of the Earth by 23.5 degrees with respect to the plane in which the Earth orbits the Sun. Since Kepler was the one to correctly interpret the motion of the planets and the Sun through the sky, he is the one that I would attribute the title "Discoverer of the 23.5 degree tilt", in the early 1600s.
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Hey...I think it was Johaness Kepler...and his Kepler's Laws of Planetary Motion