For planets, comets and asteroids a different definition of absolute magnitude is used which is more meaningful for nonstellar objects.

For these, asha was the course of everything observable, the motion of the planets and astral bodies, the progression of the seasons, the pattern of daily nomadic herdsman life, governed by regular metronomic events such as sunrise and sunset.

For centuries, many philosophers and scientists supposed that extrasolar planets existed, but there was no way of knowing how common they were or how similar they might be to the planets of the Solar System.

For instance, in the 55 Cancri system the first planet – 55 Cancri b – was discovered in 1996 ; two additional farther planets were simultaneously discovered in 2002 with the nearest to the star being named 55 Cancri c and the other 55 Cancri d ; a fourth planet was claimed ( its existence was later disputed ) in 2004 and named 55 Cancri e despite lying closer to the star than 55 Cancri b ; and the most recently discovered planet, in 2007, was named 55 Cancri f despite lying between 55 Cancri c and 55 Cancri d. As of April 2012 the highest letter in use is " j ", for the unconfirmed planet HD 10180 j ( HD 10180 h is the confirmed planet with the highest letter ).

For example, the planets that orbit the pulsar PSR 1257 are often referred to with capital rather than lowercase letters.

For astrodynamics reasons, cheap spacecraft travel to other planets is only practical within certain time windows.

For the planets, the cubes of their distances from the Sun are proportional to the squares of their orbital periods.

For example, the motion of planets around the sun may be described in a particular type of spacetime, or the motion of light around a rotating star may be described in another type of spacetime.

For the outer planets, each planet is predicted to be roughly twice as far from the Sun as the previous object.

For example, the Astronomical Almanac uses TT for its tables of positions ( ephemerides ) of the Sun, Moon and planets as seen from the Earth.

For example, to test Newton's Law of Gravitation in our solar system, one needs information about the masses and positions of the Sun and all the planets.

For example, in 1933 H. G. Wells postulated in The Shape of Things to Come a Second World War in which Nazi Germany and Poland are evenly matched militarily, fighting an indecisive war over ten years ; and Poul Anderson's early 1950s Psychotechnic League depicted a world undergoing a devastating nuclear war in 1958, yet by the early 21st century managing not only to rebuild the ruins on Earth but also engage in extensive space colonization of the Moon and several planets.

For planets with atmospheres of any substance, however, there is an alternative: an autonomous flying robot, or " aerobot ".

For example, both Kepler's laws of the motion of the planets and Galileo's theories of motion worked out for terrestrial objects are reducible to Newtonian theories of mechanics, because all the explanatory power of the former are contained within the latter.

For typical terrestrial planets with a mass of 0. 5 – 1 Earth masses, such an impact typically results in a single moon containing 4 % of the host planet's mass.

For planets from specific fictional milieux, use the following lists and categories:

For superior planets the planet would typically move through in the night sky slower than the stars.

For the Moon, Ptolemy began with Hipparchus ' epicycle-on-deferent, then added a device that historians of astronomy refer to as a " crank mechanism ": He succeeded in creating models for the other planets, where Hipparchus had failed, by introducing a third device called the equant.

For example, the orbits of some repeating comets, and meteoroids leaving them, are in resonant orbits with Jupiter or one of the other large planets – so many revolutions of one will equal another number of revolutions of the other.

For scientific uses, a modern planetary ephemeris comprises software that generates positions of the planets and often of their satellites, or of asteroids or comets at virtually any time desired by the user.

For bodies with atmospheres, the landing occurs after atmospheric entry ( or less precisely for other planets, atmospheric reentry ) and the lander is first a re-entry vehicle.

For most planets, the Newtonian model's predictions are accurate ; for Mercury, it is slightly inaccurate and the model of general relativity must be used instead.

For example, orbital elements, especially osculating elements for minor planets, are routinely given with reference to two dates: first, relative to a recent epoch for all of the elements: but some of the data are dependent on a chosen coordinate system, and then it is usual to specify the coordinate system of a standard epoch which often is not the same as the epoch of the data.

For the family is the simplest example of just such a unit, composed of people, which gives us both some immunity from, and a way of dealing with, other people.

For there is also the `` face of reality '' in the form of the individual's perceptions of his own abilities and interests, of the objective possibilities open to him, of the familial and other social pressures to which he is exposed.

For instance, college-educated people consistently show up in study after study as more often than others supporters of the Bill of Rights and other democratic rights and liberties.

For by now the original cause of the quarrel, Philip's seizure of Gascony, was only one strand in the spider web of French interests that overlay all western Europe and that had been so well and closely spun that the lightest movement could set it trembling from one end to the other.

`` For six years my father had had to do too much commanding and convincing, '' writes the narrator, `` not to understand that man begins with ' the other ' ''.

For centuries the North Atlantic nations dominated the world and as long as they did they could afford the luxury of fighting each other.

For instance -- what about all those people Harold Rhodes went toward unhesitatingly, as if this were the one moment they would ever have together, their one chance of knowing each other??

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For the States which maintain two separate agencies -- one for the vocational rehabilitation of the blind, and one for the rehabilitation of persons other than the blind -- the Act specifies that their minimum ( base ) allotment shall be divided between the two agencies in the same proportion as it was divided in fiscal year 1954.

For instance, a site adjoining other publicly owned lands, such as a national forest or a public road, may be desirable, whereas a site next to an industrial plant might not.

For specialized types of displays, such as large three-dimensional units reproducing a product, package, human or animal figures, etc., reinforced plastics and rotationally molded vinyl plastisols are other materials frequently used.

For large letters, e.g. thermoformed of acrylic or butyrate, there are other techniques.

For an experiment to qualify as a binomial experiment, it must have four properties: ( 1 ) there must be a fixed number of trials, ( 2 ) each trial must result in a `` success '' or a `` failure '' ( a binomial trial ), ( 3 ) all trials must have identical probabilities of success, ( 4 ) the trials must be independent of each other.

For no particular reason, other than that the writer felt it might -- just might -- encourage both mates to be in attendance.

For a number of years Kentucky, Louisiana and several other states have been building state-sponsored vocational education schools that serve nearby school districts in several counties.

For the purposes of this discussion, the problem of relative prices is encompassed in these two variables, since GNP includes other prices.

`` For these and other reasons '', says Dr. Brodie, `` orthodontics can prolong the life of teeth ''.

For A good many seasons I've been looking at the naughty stuff on television, so the other night I thought I ought to see how immorality is doing on the other side of the fence in movies.

For we have said, in effect, that of the two alternatives to his position variously represented by the other participants in the demythologizing discussion, only one is really an alternative.

For some reason, this ellipsis in the conversation spread until it swallowed up every other topic.

For their purposes, oxygen and other gases were not drawn from the surrounding atmosphere through the medium of lungs but sustained artificially by solution in their shells.

* For a normal distribution, the arithmetic mean is equal to both the median and the mode, other measures of central tendency.

For easy viewing, the middle 2 beads on each wire ( the 5th and 6th bead ) usually are of a different colour from the other eight beads.

For these, other possible explanations have also been proposed.