Why do Uranus and Venus have opposite spins even though rotation of planets is due to gravity of the sun?
543004
Technically, the general rotation direction of the Sun and most planets is a leftover from the original solar nebula from which the Solar System formed.  As the planets and Sun coalesced, they retained the rotation direction of the original nebula.\n\nDuring the coalescence phase, asteroid-size chunks collided and stuck together.  As more and more of these chunks collected, the planets grew in size.  However, these chunks not only brought mass to the mix, they also brought momentum.  Since most of the materials were probably all travelling in more or less the same direction, the general rotation direction of the growing planets remained the same.\n\nIn the case of Venus and Uranus, it is suspected that a major collision between the planet and another body literally tipped the planets over due to an off-center orientation of the collision.  Uranus tipped over on its side, probably due to its size relative to the other body.  Venus, being smaller, tipped so far over that its rotation was reversed.
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.
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!
577490
N0-Venus and Mercury are the only planets that don't, perhaps because being close to the sun reduces the ability to hold onto a moon.
182160
First of, there's no force causing planets to rotate. \n\n"Most of the rotation comes from the conservation of angular momentum. The formula is 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\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."
130418
There is really only three planets that exhibit retrograde motion; Venus, Uranus and Pluto. \n\nWhen viewed from the vantage point of the north celestial pole, the planets rotate on their axes in a counter clockwise direction, except for Venus, Uranus and Pluto, which rotate in a clockwise (i.e., retrograde) direction. \n \nIt is also interesting that the rotational axis of Uranus is roughly orthogonal to those of the other planets, almost in the plane of its orbit. \n\nInterestingly, all of the orbits of the planets are also in a counter clockwise direction, as the rotation of the sun.
902718
You are confusing the terms here.\n\nOnly planets outside the orbit of the Earth (superior) are ever at opposition.  Opposition is when the Sun, Earth and that planet line up in that order*.  Therefore, Mars, Jupiter, Saturn, Uranus and Neptune can all be at opposition.  Inferior planets though that orbit inside the Earth's orbit, (namely Venus and Mercury) can never be at opposition because their orbits will never take them past the Earth so that the Earth will be between them and the sun.\n\nInferior planets can, however be at conjunction.  This is when either the planet, sun and Earth line up in that order or the sun, the planet and the Earth line up in that order*.\n\nOpposition is an alright time to view a planet because it is fully illuminated.  If a light source is behind you and you look at something you see it is totally illuminated (assuming it's far enough away for your shadow to not interfere).  The conjunction that Mercury and Venus expirience is a very bad time to view the planets because either they are infront of the sun from our point of view and so we can't make the planet out in the blinding light, or it is behind the sun from our point of view anyway*.
238707
Venus, Uranus and Pluto\n\nI agree with the answer above about Uranus.
338419
First, all planets in our solar system are tilted, although Mercury isn't tilted much.  And yes, this is what causes seasons.\n\nWe can observe seasonal changes (growing and shrinking of polar ice caps and the dust storms they seem to induce) on Mars.  I believe Neptune also has very strange seasons that we don't know much about.\n\nOn a bigger, gaseous planet like Jupiter though, although it tilts we wont see much in the way of seasons because it's atmosphere is affected by many other things that make it turbulent as is.\n\nIn the case of Venus, it has such a wild greenhouse effect (and might be close to being perfectly upside down, I can't recall) that I don't think we will see much in the way of seasons there either.
373260
Smaller bodies are more readily affected than are larger bodies, and closer bodies are more readily affected than farther bodies.  Many of the moons in the solar system are locked to their planets in much the same way that our moon is locked with earth.  Pluto and its moon Charon are thought to both be locked to each other.  The constant pull of our moon is actually slowing the earth down slowly but surely with every tide.  It will take billions of years, and the sun will likely burn us to a cinder before we get locked in with the moon, but it is happening.  As for why the sun doesn't lock us in, well, the moon kind of saves us from that.  If we were spinning more slowly than the moon was rotating around us, it would try to pull us faster to reach equilibrium (though the earth would succeed in slowing its rotation down (and into an ever deteriorating orbit...probably why we don't see any examples of this in nature) more than it would succeed in speeding us up).  In fact, we are slowly imparting more speed to the moon with every rotation, and the moon is expanding its orbital radius in every rotation as a result.  Given enough time, it would escape.\n     If we had no moon to keep us "spun up", the sun would  probably have a little more effect on us.  Mercury, though not locked with the same face towards the sun, is rotating very very slowly, likely due to the same forces that we are talking about.  Venus is rotating even more slowly than Mercury...and in retrograde (some believe as a vestige of some primordial collision).  Again, given enough time the sun would probably succeed in locking both Venus and Mercury...but time is not on the sun's side.  It will likely reach it's red giant stage (vaporizing both Mercury and Venus as well as Earth) before it succeeds in "locking them in".
827722
The very slow rotation of Venus and the "backward" (retrograde) rotation might mean that it collided, in the past (probably toward the end of their formation), with an object of similar size.\n\nThe slow rotation may also have something to do with tidal lock with the Sun. Just an idea I am not sure.
627348
The Sun does indeed rotate. different part of sun rotates at different time. its like jupiter. \nA rigid body such as the Earth will clearly have a single rotation rate. But since the Sun is made of gas, different parts of it rotate at different speeds. Near the Sun's equator, it completes one rotation every 27 Earth days. But near the poles, it's about 31 Earth days. This is called "differential rotation".
378554
Yup, one of the better theories right now is that Venus formed the "normal" way, but then turned over during the course of the evolution of the solar system.  The obliquity (tilt angle of each planet) can be effected by the orbits of all the other planets.  If you work the calculations you will find that Venus could have a dramatic change in it's obliquity over the course of time.\n\nIf you assume that Venus formed with the same type of tilt shown by the other inner worlds you can quickly show that the effects of the other planets will drive the tilt of Venus into a chaotic zone, where the tilt will rapidly change in an almost unpredictable manner (almost).  One way out of this unstable zone is if Venus were to turn all the way over, upside down (obliquity exceeds 180 degrees).  By doing so it would make Venus appear to have a spin opposite from the rest of the planets.\n\nThere are some issues with this theory, one of them is that Venus, while it does spin "backwards" also spins very slowly.  This is also hard to explain, but people have tried to change the rotation rate of venus through impacts, or near impacts with large, planetesimal-sized objects.  It may possible to help drive venus' tilt over with this method also.
366583
This is because of their centre of gravity.\n\nAll of their constituent mass is  pulled with an even force into the centre of the object....thus the surface of the celestial body is equidistant from the centre...ie. almost spherical.\n\nMany are in fact oval due to the fact that they spin around. This moves some of the mass to the equator of the object....rightly due to centrifugal force.
562236
Its earth and venus...the reason behind it is due to their some what similar size, mass of planet, rotation and revolution time and gases in some cases. hope so u satisfied with my answer.
1056449
Yup, it's orbital period is the same as its rotational period due to tidal forces. \n\nAs it orbits the Earth it spins on it's axis, it takes the same amount of time to make one rotation as it does one orbit so it looks like it's not spinning at all from down here.
388209
For years it was thought that in the case of Venus that the Earth was the culprit. It is a curious fact that as Venus rotates three times on its axis in 729.27 days, the Earth goes twice around the Sun ( 728.50 days) This has suggested to many dynamicists that Earth and Venus are locked into a 3:2 tidal resonance. There are many bodies in the solar system that seem to be locked into various kinds of spin-orbit resonances, especially families of asteroids with the planet Jupiter. Mercury also seems to be gravitationally locked into some kind of resonance with the Sun since its day (58.646 days) and its year ( 87.969 days) are also in the proportion of 3:2. \n\nwhat happened in essence is that venus spins once a year which is about zero rotation in the normal planetary sense.  evidently the way the solar system formed it just sucked the spin out of venus.  that probably accounts for why it's a greenhouse.