How did the early sientist solve the problem of the planets moving backwards?
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Hi. The smart ones figured out the notion of 'parallax' and realized that the outer planets must revolve around the Sun.
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Isaac Newton's Laws of Motion were first published in his work Philosophiae Naturalis Principia Mathematica (1687). Newton used them to prove many results concerning the motion of physical objects. In the third volume (of the text), he showed how, combined with his law of universal gravitation, the laws of motion would explain Kepler's laws of planetary motion.
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Interesting question.  You can extend it - why does the Earth continue to turn on its axis?  And circle the sun?  Why does the sun circle the center of the galaxy?  Why do things keep going, year after year for billions and billions of years?\n\nNewton thought about this and came up with one of his famous laws:  Without an external force, a body in motion stays in motion, a body at rest stays at rest.\n\nThe second half is easy.  Put a rock on the floor and it will stay there forever until you pick it up.  It won't move without an external force.  So what if you shoot a bullet into the air.  We all know it falls back, but why?  Because the force of gravity acts on it.  Take away gravity and it will still stop.  Why?  Because the friction of air on the bullet's surface will slow it down and finally stop it.  Take away air, take away gravity, and the bullet will go on forever.\n\nSo to answer your question:  Simply put, the asteroids have no forces to stop them.  Gravity keeps them trapped around the sun, but they outside of the range where they fall in, so they simply continue to go around, just like the planets such as Earth.  The asteroids started in motion at the formation of the solar system 4.5 billion years ago, and except for random collisions that altered courses and accelerated (or decelerated) the rocks, no force has acted on them to slow them down.  A perfect example of Newton's law, even more amazing because Newton did not know of the existence of asteroids.
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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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Not sure who was the 'first' but the Egyptian Ptolemy left records that show he knew the Earth was a sphere.  He even calculated its circumference fairly accurately.\n\nWhere he was incorrect, of course, was proposing a geocentric view of the universe with the Earth in the middle and fairly complicated system of orbits to describe the movement of the various visible astronomical bodies.  It wouldn't be until Copernicus over a thousand years later, until this particular view was corrected.
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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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Planets would only describe circular orbits if they were moving with the correct speed for their distance from the sun. Any slight disturbance to their motion, such as asteroid impact, would cause their motion to become elliptical. For instance if they lost energy (and speed) as a result of a collision they would be pulled closer to the sun as the result of its gravity. This would cause them to speed up and start moving away from the sun until their speed decreased so much that they were pulled towards the sun again. This is the elliptical motion of planets.\nUnless the solar system were intelligently designed it would be impossible (probability = 0) for any planet to be moving in a /perfect/ circle.
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begin our explanation of how Newton changed our understanding of the Universe by enumerating his Three Laws of Motion. \n\nNewton's First Law of Motion:\nI. 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\nThis we recognize as essentially Galileo's concept of inertia, and this is often termed simply the "Law of Inertia". \n\nNewton's Second Law of Motion:\nII. 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\nThis is the most powerful of Newton's three Laws, because it allows quantitative calculations of dynamics: how do velocities change when forces are applied. Notice the fundamental difference between Newton's 2nd Law and the dynamics of Aristotle: according to Newton, a force causes only a change in velocity (an acceleration); it does not maintain the velocity as Aristotle held. \n\nThis is sometimes summarized by saying that under Newton, F = ma, but under Aristotle F = mv, where v is the velocity. Thus, according to Aristotle there is only a velocity if there is a force, but according to Newton an object with a certain velocity maintains that velocity unless a force acts on it to cause an acceleration (that is, a change in the velocity). As we have noted earlier in conjunction with the discussion of Galileo, Aristotle's view seems to be more in accord with common sense, but that is because of a failure to appreciate the role played by frictional forces. Once account is taken of all forces acting in a given situation it is the dynamics of Galileo and Newton, not of Aristotle, that are found to be in accord with the observations. \n\nNewton's Third Law of Motion:\nIII. For every action there is an equal and opposite reaction.  \n\nThis law is exemplified by what happens if we step off a boat onto the bank of a lake: as we move in the direction of the shore, the boat tends to move in the opposite direction (leaving us facedown in the water, if we aren't careful!).
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In ancient Greece it was already accepted. Probably much earlier in Egypt and or in the Persian area. Maybe even 20 000,30 000, 40 0000 + years earlier. But, since there was no paper or standardized language until recently in our history. It was not recorded.  From what I've read. Either,Aristarchus  in Greece already theorized that the Earth revolves around the Sun. You're asking when the Heliocentric hypothesis was accepted. It's still not accepted by some today. Copernicus never made this discovery himself. He just learned about it when he went to study in Italy. He found a text in a library. It was a book form Ancient Greek. Then, he just re wrote it to Latin. The Greeks got a lot of their knowledge from the Egyptians and vice versa.
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Sagittarius, not that it matters anyway... -_-\n\nIn short, had you been born at the same time on the same day of the year 2,000 years ago, you would have been born under a different sign.\n\n---\nBecause of the precession of the equinoxes, the equinox and solstice points have each moved westward about 30 degrees in the last 2,000 years.\n\nThus, the zodiacal constellations named in ancient times no longer correspond to the segments of the zodiac represented by their signs.\n\nPrecession of the equinox is caused by the fact that the axis of the earth's rotation (which causes day and night) and the axis of the earth's revolution around the sun (which marks the passage of each year) are not parallel.\n\nThey are 23 l/2 degrees away from lining up; that is, the earth's axis of rotation is tilted. This tilt also causes our seasons, a fact that Ptolemy did understand but that many people do not understand even today. Ptolemy understood that the rotation axis of the earth was slowly precessing, or moving in a circle, with an angular radius of 23 1/2 degrees with a period of around 26,000 years. He deduced this from comparisons of data taken by the ancient Sumerians 2,000 years before his time.
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Sun-centered theory developed by Copernicus in which he was convinced that the sun was the center of the universe and the Earth was in fact a planet.
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The truth is that any cutting-edge field is "constantly changing."  It is poorly understood by lay men that in science, one does not suddenly make a discovery that is perfect in its original form and is instantly accepted by everyone.  Quite the contrary--every field of inquiry involves a battle of ideas and wills, with new data refining some old ideas, or maybe eliminating old ideas.\n\nTake the path of the earth around the sun.  Copernicus introduced a heliocentric (sun-centered) paradigm, and Europe exploded into cultural wars against the implications of it.  But contrary to popular belief, Copernicus was wrong.  His model was faulty.  Few people realize that the older, earth-centered models with the cumbersome concentric spheres was actually much more accurate than that of Copernicus.  Much later, Kepler figured out the problem with Copernicus' model and fixed it.  Copernicus had assumed that the orbits were circular, and this was incorrect.  Kepler used Brahe's data and deduced that the orbits were actually eliptical.  And guess what?  Even Kepler wasn't exactly correct!  His model was great for most of the planets, but there was one exception--Mercury.  That little ball of molten rock didn't quite behave as it should by either theory.  It wasn't until Einstein came up with his general theory of relativity less than a hundred years ago that Mercury's orbit was seen to fit the model.\n\nAnd all the while, controversies raged.  Copernicus' theories were seen as heretical, and Galileo was imprisoned for life for supporting them.  Einstein was denounced by German Nationalists for his "Jew Physics"--and even to this day, there are those that oppose relativity in favor of Newtonian physics, though they are (like creationists) rare in academia.\n\nYou get a distorted view of science by looking only at this current trial of a widely supported and broadly accepted notion of evolution by natural selection.  The bulk of the controversy is political, not scientific; and the few changes that we see within the evolutionary camps are the markings not of a weakness in the theory of evolution, but of the strengths of the scientific method.
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Hey...I think it was Johaness Kepler...and his Kepler's Laws of Planetary Motion
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The Mysteries of Mars \n\nWhy did so many of the early cultures worship the Planet Mars?  They were terrified of this strange planet.  It was called the "God of War." Why?  (The term "martial arts" is still in our working vocabulary.) And there are other mysteries that seem to be associated with this strange planet.\n\nThe recent space age discovery of "orbital resonance"-the tendency of orbits to synchronize on a multiple of one another--has led to a fascinating conjecture that the orbits of the Earth and the Planet Mars were once on resonant orbits of 360 days and 720 days, respectively.  A computer analysis has suggested that this could yield orbital interactions that would include a near pass-by on a multiple of 54 years, and this would occur on either March 25 or October 25. Such near pass-bys would transfer energy, altering the orbits of each.\n\nIn near proximity, such pass-bys would be accompanied by meteors, severe land tides, earthquakes, etc., and this would help explain why all the ancient cultures were so terrified by the Planet Mars and why calendars tended to reflect either March or October.  A series of such pass-bys could also explain a number of the "catastrophes" of ancient history, including the famous "long day of Joshua" and several other Biblical episodes. \n\nStability appears to have been attained during the last near pass-by in 701 B.C., resulting in Earth's and Mars' present orbits of 365 1/4 days and 687 days, respectively.  Provocative, but where's the evidence?\n\nThis remarkable conjecture, that Mars made pass-bys near the Earth, would seem to be corroborated by Jonathan Swift (1667-1745) in his famous fantasy known as Gulliver's Travels.  In his third voyage, Gulliver visits the land of Laputa, where the astronomers brag that they know all about the two moons of Mars.  Their highly detailed description includes the size, the rotation, the revolutions, etc., of each of the two moons. \n\nWhat makes this particular allusion so provocative is that the two moons of Mars were not discovered by astronomers until 151 years after Swift's publication of Gulliver's Travels in 1726.  It was in 1877 that Asaph Hall, using a new telescope at the U.S. Naval Observatory, shocked the astronomical world by discovering the two moons of Mars. \n\nWhat makes the two moons so difficult to see is that they are only about 8 miles in diameter and have an albedo (reflectivity) of only 3%.  They are the darkest objects in the solar system: they are almost black.  The two moons are also unique in their rotations and one of them is the only object in the solar system that orbits in reverse.  For Swift to have "guessed" these correctly is absurd.  \n\nYet the telescopes of his day were inadequate to have actually seen these objects.  But then how could he have known what the astronomers of his day did not? Swift, in order to embroider his satirical fiction, undoubtedly drew upon ancient records he probably assumed were simply legends, not realizing that they were actually eye witness accounts of ancient sightings when Mars was close enough for the two moons of Mars to be viewed with the naked eye!\n\nOther Implications \n\nThe possibility that the Planet Mars interacted with the Planet Earth may have implications beyond simply ancient perturbations of our calendar and the subsequent veneration of October 31 as Halloween. It has been widely noted that the ancient Stonehenge monument in England and the Great Pyramid at Cairo have astronomical implications.  The geometric and mathematical mysteries of these fabled monuments have been the subject of much conjecture.  Cairo was founded on August 5, A.D. 969 by conquering Fatimid armies and named, "Al Kahira," after Mars.  Why?\n\nAnd there are other enigmas.\n\nThe Nebular Hypothesis \n\nMost of us have been taught that the planets of our solar system came out of the sun. It may come as
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The matter that made up the sun and planets existed at one time as a very large disk. As the matter clumped together, it was already on the same plane. That's the theory, anyway.
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"no vestige of a beginning, no prospect of an end.” - Hutton\n\nHutton was the FIRST to realize (or to be credited w/ realizing) that geologic cycles were going on w/in & on the earth.\n\nHe noticed all the geologic processes that went on from day to day, year to year, etc. & wondered how long they have been going on. He was the first to notice what we now call the rock cycle.\n\nHe stated that the earth was much older than the 6000 years that the Church believed to be true. He believed it had to be for all the length of time that it took processes to occur in the present.\n\nHe is most notable for his Principle of Uniformitarianism (which rose out of some of the observations listed above) which states that the geologic processes that have gone on in the past still go on today & at the same rates.
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Don't listen to Vh -- obviously the planets didn't start moving until Newton came around.\n\nAnd there was no electricity, ever, until Maxwell invented it.\n\nThe internet came with either Bob Dole or Al Gore, I always forget. :)