I was on the internet yestderday and I found this...

It says that nobody knows why Venus spins backwards, but I've a theory as to why.

I was simply spinning around one of those cheap Tesco's muffin boxes (the ones with the 'hole' in the centre) by rotating my finger in the centre when I came up with the idea that the box represents Venus, and the movement of my finger represents the momentum/movement of its core, and so, I spun it the other way, and sure enough, the box's rotation reversed also.

But since (and this is according to google) the sun rotates, and thus began another theory of the sun's centre of gravity moving Venus in orbit, while Venus' core rotates it in the opposite direction to a normal planet.

Ideas?

The thing is, all things in the solar system SHOULD spin in the same direction - the fact that a few things spin in the opposite direction when almost everything else spins in the same direction indicates there's something strange about those objects. The question is not so much "why Venus spins backwards mechanically", but "what imparted momentum in the opposite direction of the rest of the solar system?"

The obvious answer would be a massive collision, but there's no evidence of such around Venus, unlike the Earth, which has the Moon (and Pluto, which has Charon).

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> " The obvious answer would be a massive collision, but there's no evidence of such around Venus, unlike the Earth, which has the Moon (and Pluto, which has Charon)."

The lack of a moon is expected for Venus:

With Tellus, the impact with Theia was prograde, thus imparting more angular momentum. An impact causing Venus to rotate backward would have to be retrograde. Material must move about 8 KM/S laterally for Low-Venera Orbit. The retrograde-nature of the collision probably would not leave enough angular momentum for material to enter orbit.

Besides, If Luna would orbit Venus at about 400 MM, it could either pop out of the Hill-Sphere or crash into Venus:

The Hill-Sphere of Tellus has a radius of about 1.5 GM. The Hill-Sphere of Venus has a radius of about 1 GM. Objects orbiting more than half-way out to the surface of the Hills-Sphere have unstable orbits. The have spikes of eccentricity; they can pop out of the Hill-Sphere or collide with their primaries. The orbital radius of Luna is dangerously close to the instability-portion of the Hill-Sphere of Venus.

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4556437

I've heard the same theory: Something massive had collided with Venus too. Perhaps Venus had a moon and its orbit deteriorated, or a huge asteroid hit it.

It's an interesting theory, but the amount of energy and mass needed to change the rotation of a planet would be... a lot. There's still a lot unknown about Venus; its thick and toxic atmosphere make it difficult to study.

I'm on about Venus' orbit, what did you think i meant?
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4556741

The orbit of Venus is prograde and very circular. Venus has nothing unusual on the orbital front.

We all believed that you meant its retrograde rotation. You could not have meant the orbit of Venus because nothing is unusual about the orbit.

* Rotation is an object spinning.
* Revolution is an object going around like a planet orbiting a star.

4556741

After rereading your original post, I get the impression that you believe that the rotation of the sun drags the planets along in their orbits. Although framerotation exists, is is vastly to small for this. The reason planets orbit the Sun is gravity. The probable reason the planets revolve the same direction the sun rotates, and with the exception of Venus, rotate in the same direction too is that the sun and planets formed from a rotating collapsing cloud; we all inherited the rotation of the cloud in our rotations and revolutions.

4557082 so gravity keeps the planet orbiting around the sun, and the momentum of Venus' core spinning in reverse means the palnet spins backwards?

4558819

Yes:

Venus revolves around the Sun in its orbit the same way as the other planets. It rotates on its axis the opposite way the other planets rotate. Venus rotates very slowly. 1 Possible way this could have happened is that Venus might have started rotating the same way as everything else, as one would expect from forming out of the same spinning collapsing cloud which formed the Sun and other planets, but an object might have had a glancing collision against Venus opposite its direction of rotation, this making Venus rotate slowly backwards. Venus still revolves around the Sun in its orbit the same way as all of the other planets.

4558872 Alright, thanks!