The orbits are always open behind, never being surrounded by bone.
The first, for a memoir on the construction of a clepsydra for measuring time exactly at sea, he gained at the age of twenty-four; the second, for one on the physical cause of the inclination of the planetary orbits, he divided with his father; and the third, for a communication on the tides, he shared with Euler, Colin Maclaurin and another competitor.
The squamosals form the posterior outer margin of the orbits and are frequently continued into two lateral downward processes across the temporal fossa.
It is also remarkable that all the great planets and many of the small ones have their orbits very nearly in the same plane, and nearly circular in form.
In this way we account most simply for the uniformity in the direction in which the planets revolve, and for the mutual proximity of the planes in which their orbits are contained.
Elliptic orbits, and a parabolic orbit considered as the special case when the eccentricity of the ellipse is 1, are almost the only ones the astronomer has to consider, and our attention will therefore be confined to them in the present article.
The modern method of determining orbits from three or four observations was first developed by C. F.
Nasal apertures very large, and extending high on the face between the orbits; nasal bones short, elevated, triangular and pointed in front.
No post-orbital processes or any separation between orbits and temporal fossae.
The orbits of earth and moon are elliptical, so that the earth is sometimes nearer, sometimes farther away from the sun, and the same is the case with the moon in relation to the earth.
It has been supposed that certain electrons revolve like satellites in orbits around the atoms with which they are associated, a view which receives strong support from the phenomena of the Zeeman effect, and on this assumption a theory has been worked out by P. Langevin, 2 which accounts for many, of the observed facts of magnetism.
As a consequence of the structure of the molecule, which is an aggregation of atoms, the planes of the orbits around the latter may be oriented in various positions, and the direction of revolution may be right-handed or left-handed with respect to the direction of any applied magnetic field.
For those orbits whose projection upon a plane perpendicular to the field is righthanded, the period of revolution will be accelerated by the field (since the electron current is negative), and the magnetic moment consequently increased; for those which are left-handed, the period will be retarded and the moment diminished.
The long-sought cause of the "great inequality" of Jupiter and Saturn was found in the near approach to commensurability of their mean motions; it was demonstrated in two elegant theorems, independently of any except the most general considerations as to mass, that the mutual action of the planets could never largely affect the eccentricities and inclinations of their orbits; and the singular peculiarities detected by him in the Jovian system were expressed in the so-called "laws of Laplace."
John Kepler inferred that the planets move in their orbits under some influence or force exerted by the sun; but the laws of motion were not then sufficiently developed, nor were Kepler's ideas of force sufficiently clear, to admit of a precise statement of the nature of the force.
From an investigation of all the observations upon Mercury and the other three interior planets, Simon Newcomb found it almost out of the question that any such mass of matter could exist without changing either the figure of the sun itself or the motion of the planes of the orbits of either Mercury or Venus.
The great variety in the apparent motions of meteors proves that they are not directed from the plane of the ecliptic; hence their orbits are not like the orbits of planets and short-period comets, which are little inclined, but like the orbits of parabolic comets, which often have great inclinations.
The main anatomical justification of this sub-family is given by the postfrontal bones, which, besides bordering the orbits posteriorly, are extended forwards so as to form the upper border of the orbits, separating the latter from the frontals.
ELLIPTICITY, in astronomy, deviation from a circular or spherical form; applied to the elliptic orbits of heavenly bodies, or the spheroidal form of such bodies.
He was several times a successful competitor for the prizes given by the Academy of Sciences of Paris; the subjects of his essays being: - the laws of motion (Discours sur les lois de la communication du mouvement, 1727), the elliptical orbits of the planets, and the inclinations of the planetary orbits (Essai d'une nouvelle physique celeste, 1735).
Orbits so nearly circular in form that the unaided eye would not notice the deviation from that form.
But as the orbits are not centred on the sun, which is in a focus of each, the displacement of the seeming circle would be readily seen in the case of Mercury and of Mars.
The same statements are true of the orbits of the satellites around their primaries.
The major planets all move around the sun in the same direction, from west to east, in orbits but little inclined to each other.
All the known minor planets have the same common direction, but their orbits generally have a greater eccentricity and mutual inclination.
The general rule is that the satellites also move round in the same direction, and in orbits of moderate inclination.
For the elements of the orbits, and the general character of the several planets see PLANET.
He studied medicine at GÃ¶ttingen, 1 7771 7 80, attending at the same time Kaestner's mathematical course; and in 1779, while watching by the sick-bed of a fellow-student, he devised a method of calculating cometary orbits which made an epoch in the treatment of the subject, and is still extensively used.
A table of eighty-seven calculated orbits was appended, enlarged by Encke in the second edition (1847) to 178, and by Galle in the third (1864) to 242.
His demonstration that the planes of all the planetary orbits pass through the centre of the sun, coupled with his clear recognition of the sun as the moving power of the system, entitles him to rank as the founder of physical astronomy.
Aberration Of Light This astronomical phenomenon may be defined as an apparent motion of the heavenly bodies; the stars describing annually orbits more or less elliptical, according to the latitude of the star; consequently at any moment the star appears to be displaced from its true position.
Pursuing the investigations of Laplace, he demonstrated with greater rigour the stability of the solar system, and calculated the limits within which the eccentricities and inclinations of the planetary orbits vary.
The skull is elongated, with an overhanging occiput, complete bony rims to the orbits, and the premaxillae separated from the arched and rather long nasals.
The skull generally resembles that of Camelus, the relatively larger brain-cavity and orbits and less developed cranial ridges being due to its smaller size.
Before leaving it for Queen's College, Oxford, in 1673, he had observed the change in the variation of the compass, and at the age of nineteen, he supplied a new and improved method of determining the elements of the planetary orbits (Phil.
When the orbits are eccentric, the tidal disturbance varying with the distance between the two components will probably cause changes in their absolute brilliancy; the variation due to change in the aspect of the system presented to us may thus be supplemented by a real intrinsic variation, both, however, being regulated by the orbital motion.
Albrecht has shown that, of the 10 members of the S Cephei class for which both the orbits and the light-variations are thoroughly known, the maximum light always occurs approximately at the time when the brighter component is approaching us most rapidly; this relation, which seems to be well established, is a most perplexing one.
In a number of cases measures of the relative positions of the two stars, continued for many years, have shown that they are revolving about a common centre; when this is so there can be no doubt that they form a binary system, and that the two components move in elliptic orbits about the common centre of mass, controlled by their mutual gravitation.
From the very few orbits that have as yet been determined one interesting result has been arrived at.
Most of the orbits are remarkably eccentric ellipses, the average eccentricity being about 0.5.
Tidal action also accounts for the progressively increasing eccentricities of the orbits, already referred to.
The mutual gravitation of a large number of stars crowded in a comparatively small space must be considerable, and the individual stars must move in irregular orbits under their mutual attractions.
Lvi.; the orbits of the principal binaries are discussed in T.
His great contribution to astronomy dates from 1866, when he showed that meteors or shooting stars traverse space in cometary orbits, and, in particular, that the orbits of the Perseids and Comet III., 1862, and of the Leonids and Comet I., 1866, were practically the same.
If in this we put r= I/u, and eliminate t by means of (15), we obtain the general differential equation of central orbits, viz.
The orbits may be divided into two classes according as h2>
We have seen that under the law of the inverse square all finit orbits are elliptical.
The question presents itself whether ther then is any other law of force, giving a finite velocity from infinity, under which all finite orbits are necessarily closed curves.
The n formulae of this type represent a normal mode of free vibration; the individual particles revolve as a rule in elliptic orbits which gradually contract according to the law indicated by the exponential factor.
If the friction be relatively small, all the normal modes are of this character, and unless two or more values of ~ are nearly equal the elliptic orbits are very elongated.
The results of these skilfully conducted observations were published in a memoir on The Uranian and Neptunian Systems. 3 From this research it appears that the orbits of all four satellites of Uranus are sensibly circular, and although no special search was made, he concludes that none of Sir William Herschel's supposed outer satellites can have any real existence.
As early as 1860 Newcomb communicated an important memoir to the American Academy, 4 On the Secular Variations and Mutual Relation of the Orbits of the Asteroids, in which he discussed the two principal hypotheses to account for the origin of these bodies - one, that they are the shattered fragments of a single planet (Olbers' hypothesis), the other, that they have been formed by the breaking up of a revolving ring of nebulous matter.
Discarding those of Uranus, in which the orbits of the satellites are highly inclined to the ecliptic, and in which manifestly some exceptional influences have been at work, we find that the satellites revolve around the primaries also in the same direction (Exceptions are Saturn ix.
- Among recent works on the determination of orbits, J.
Von Oppolzer's Lehrbuch zur Bahnbestimmung der Kometen and Planeten (2 vols.), which contains voluminous tables, formulae, and instructions for the computation of orbits in the many special cases that arise.