why does all planets rotate on their axis with const. angular velocity & on what this angular vel. depends?
108530
Not all the planets do rotate on their axes with constant angular velocity (see reference) and even two rotate in the opposite direction to earth (counter clockwise when viewed from the celestial north pole); venus and uranus (called retrograde motion). \n\nThe rough alignment of all the angular momentum vectors in the solar system, including orbital and rotational angular momenta of all the planets, moons and the sun is presumably a left over relic from the angular momentum when the system was formed from a rotating gaseous collection of material.
731964
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.
888499
If you're speaking of the motion of Earth on it's axis or it's rotation about the sun, the answer is the scientific principle of Inertia, read now!\n\nThe principle of inertia is one of the fundamental laws of classical physics which are used to describe the motion of matter and how it is affected by applied forces.Inertia is the property of an object to resist changes in velocity unless acted upon by an outside force.Inertia is dependent upon the mass and shape of the object. The concept of inertia is today most commonly defined using Sir Isaac Newton's First Law of Motion, which states:\n\nEvery body perseveres in its state of being at rest or of moving uniformly straight ahead, except insofar as it is compelled to change its state by forces impressed. [Cohen & Whitman 1999 translation]\n\nThe description of inertia presented by Newton's law is still considered the standard for classical physics. However, it has also been refined and expanded over time to reflect developments in understanding of relativity and quantum physics which have led to somewhat different (and more mathematical) interpretations in some of those fields.\n\nNow read more at the links below:
739091
because the earth rotates on an axis
91267
You are referring to a concept in planetary astronomy call inclination of orbit.  The "disc" that the Earth revolves around the Sun on is called the ecliptic plane.\n\nTechnically speaking every other planet has some orbtial inclination or tilt of their disc.  But it is very small so the eight major planets are said to orbit in roughly the same plane (ecliptic).  \n\nPluto is different.  Its orbital inclination angle is about 18 degrees with respect to the ecliptic.  That's big compared to the other planets. \n\nNow the question is why are the eight major planets in the same plane?  Why is Pluto not?\n\nWhen the solar system formed it was originally a giant sphere of gas and dust and over time was gravitationally attracted into a compacted sphere.  When this happens systems need to conserve angular momentum.  This results in the sphere becoming flattened.  This flattened sphere now looks like a disc.  The disc is roughly the ecliptic plane. An analogy to this scenario is pizza dough being spun by a chef into a disc. \n\nPluto, it is believed, was probably originally part of this disc but later had an intereaction with another object which since changed its orbit.
63676
These are good questions. I do not think anyone knows exactly, but I have heard the conjecture often that Pluto is an escaped moon or a captured planet from somewhere else, and was not present at the formation of the Solar System. Also it is possible that Pluto's strange orbit is the result of some collision. \n\nThe rotational angular momentum of Uranus is quite different from the other planets. It's rotational axis is tilted significantly from the orthogonal to the ecliptic (plane of orbits of most planets), and it is said to rotate in the "opposite" sense to earth and the sun and some of the other planets. However, since the tilt of Uranus' rotational axis is roughly 97.92 degrees, I do not know how strongly I would want to assert that it rotates in the opposite or retrograde sense to most of the other bodies in the solar system. Again, this could be caused by a collision. In one of the attached references, it is claimed that this could be caused by a tidal effect, but it is hard for me to understand how. \n\nIt turns out that both Pluto and Venus also rotate in a retrograde sense, so it is not that uncommon, although theories of the origin of the solar system imply that one would not expect a lot of deviations of angular momentum from the major direction of angular momentum in the system. In the case of our system, especially given the orbits of the planets with small inclinations to the ecliptic, and the very large angular momenta of the Sun, Jupiter and Saturn, this is basically correct. \n\nNeptune is probably called the blue planet because it is blue, although of course Uranus and Earth are blue as well (for different reasons). Neptune's blue is at least partly caused by the presence of methane in its atmosphere.
876446
The sun rotates on its own axis that what causes the gavational pull to keep the planets moving around it.
279727
By rotating on it's axis I think you mean how long it takes to spin around, not orbit the sun.  Ths number varies from comet to comet, and it is rather hard to measure.  That said the ones that we have measured tend to have rotational periods of between 3 and 15 hours.
168503
Finally, the gravitational pull between the Earth and Sun causes the Earth to travel around, or "orbit", the Sun at a velocity of 29.8 km/sec. At the same time, the Earth also turns on its axis causing the daily cycle of day and night. This "rotational velocity" is approximately .47 km/sec. That means that at the same time we're hurdling through space at nearly 67,000 mph, we're also spinning around in circles at over 1000 mph! Whew! Almost makes you dizzy, doesn't it?
457404
All the planets in our solar system rotate in the same direction with the exception of Venus which rotates *very* slowly in the opposite direction.  It was theorised that it once suffered a glancing blow from a very large object that reversed its spin.\n\nHmm - by rotate I mean on their own axis - not around the sun, in which case all planets go the same direction.
347854
It's pretty arbitrary isn't it? Look down on the North pole and the earth is turning clockwise, look down on the South Pole and it's the other way around.\n\nA more interesting question is: why are (almost) all planets orbiting and rotating in the same direction?\n\nThe solar system, earth included, is supposed to have formed from a dust cloud that contracted due to gravity. This cloud rotated in a certain way. As spin has to be conserved, all bodies in the solar system rotate in the same way.
553599
The angular momentum is conserved, and linear is not.\n\nGravity is a central force (meaning one that only depends on the radial distance between objects) and central forces conserve angular momentum.  \n\nA way to think of it is this:  angular momentum is something like mass x radius x linear velocity.  Watch an orbit simulation and you'll notice that as earth gets closer to the sun (radius decreases) it's speed increases.  Also as the earth gets farther from the sun, it slows down.  The two trade off (i.e. increase radius, decrease linear velocity, and vice versa) in a way that their product stays constant.  \n\nThe linear momentum is not constant for the same reason.  Linear momentum is mass x velocity, and from the above it's easy to see that velocity is not constant (there is one wrinkle:  if the orbit is circular then the magnitude of the velocity is constant, but its direction is not; so the velocity, a vector quantity that has magnitude and direction, is changing).\n\n\nI hope that helps.
448217
It goes back to when the solar system was formed.  The sun (and the planets, for that matter) were formed when a gigantic cloud of gas and dust collapsed.  When that cloud collapsed, it had something called 'angular momentum', which really just means that it was spinning a little bit.  When a large, slowly spinning thing collapses to something smaller, the rate of rotation speeds up (think about an ice skater that pulls her arms in...she spins up!).  Anyway, so now we have all this gas and dust in a disk that's orbiting the new Sun.  The dust eventually forms into planets.  As the dust collapses into new planets, the same thing happens, and the planets start spinning themselves.  So basically, the earth and moon and whatnot spin because of angular momentum.  I hope this made sense/helped!
111203
I think the current theory is that it comes from the origin of the solar system as a spinning mass of material. This material had a certain angular momentum, which was retained as the material coalesced into the sun and the planets and moons and other bodies. So there are only a few planets and moons whose orbital and rotational angular momentum vectors are not aligned with each other (like Neptune, and Venus, Triton and a few of the smaller, more distant moons of Jupiter and Saturn).
433264
Objects orbit one another because they have a curved trajectory that results from the vector addition of their momentum (in the direction of travel, tangential to the orbit) and the gravitational attraction to the other object (normal to the orbit).\n\nThis vector is constantly changing in direction (but not to any significant degree in magnitude) because of the object's motion, but it always keeps the satellite's acceleration pointed towards the object is it orbiting, resulting in smooth, roughly circular motion.
180154
because of the differing sizes of each planet the time it takes each planet to rotate differs. we also have to factor in the speed at which each planet is rotating.
843079
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.