Why does Venus revolve so slowly and backwards as well?

Question

As it does not have a moon what slowed it down?

Answer 1

Women. Who will ever understand them?

Answer 2

Nobody knows the answer to this problem.
It is because it is rotating so slowly that it is retrograde, IE it is slower than its orbiting around the sun.
Something must have happened in the past that altered the speed of the planet's rotation. It has a heavy atmosphere and tidal effects on this (the gravitation field of the sun?) could have slowed the rotation to some extent. The presence of the earth may have had some effect, and the fact that the approaches to the earth are almost the same as 5 Venusian days, suggests some kind of close linkage, though of course it could be chance.
However we do not know, and cannot see how these effects alone could have caused the slowing that exists. Almost certainly some other element is involved: close approach by or collision with a comet being the most likely. If the comet collided with Venus, we may never know, but if it was a near miss, the comet could return at some time in the future, assuming that it did not pass too close to the sun and be swept up by its gravitational field.

Answer 3

most probably, collisions with big blocks of matter at the time the solar system formed are partly to blame for the slow (and backwards) rotation of Venus.

But of course one big effect (for the slow rotation, not going backwards) is tidal effect from the sun. Mercury is closest to the sun and takes 58 days to rotate, Venus is fairly close and takes 243 days, Earth is further away and needs 1 day, Mars takes a little over 1 day, Jupiter takes less than 10 hours, etc). Tidal effect means that the planet gets squeezed towards the main body, so the rotational energy gets lost in internal frictions.

This is also why our Moon rotates in almost exactly the time it takes it to revolve around the Earth, which is an equilibrium point towards which all satellites tend.

Our own Earth used to rotate a good deal faster. in the Devonian period about 380 million years ago, the days were just 21.8 hours, and currently the days are growing by about 2 seconds every 100'000 years,

If you look up a table of planets, you'll notice that there are sizeable differences in the rotation, but also in the axis tilt (well, Venus has a very small axis tilt, just 2.6 degrees, which would suggest that whatever big collisions took away a lot of its rotational momentum, ended up having little effect on the axis tilt).

My view is that the axis tilt also comes from collisions, because in a model of solar system formation without collisions, you'd expect for all planets to end up with parallel axes or rotation, which is hardly the case (Earth 23.4 degrees, Mars 25.2, Saturn 26.7, Uranus 97.8, Neptune 28.3).


Back to Venus: orbital period 224.7 days, rotational period -243 days, so some very hefty collision a long time ago sent it spinning backwards, and since then tidal effects have slowed (or accelerated?) it to something close to equilibrium, and in a couple hundred million years it may rotate in 224.7 days.

Hope this helps

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Answer 4

If viewed from above the Sun's north pole, all of the planets are orbiting in an anticlockwise direction; but while most planets also rotate anticlockwise, Venus rotates clockwise in "retrograde" rotation. The question of how Venus came to have a slow, retrograde rotation was a major puzzle for scientists when the planet's rotation period was first measured. When it formed from the solar nebula, Venus would have had a much faster, prograde rotation, but calculations show that over billions of years, tidal effects on its dense atmosphere could have slowed down its initial rotation to the value seen today.

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Answer 5

i read at a geology book that the angular velocity of venus equal to the velocity of spining around the sun and thia causes we see only one side of it and perhaps this is because it seems so slowly.

Answer 6

I guess it was some really violent collision during its primodial stage that caused it flip over.

But it would be interesting to find out how such a violent collision could avoid shattering it

Answer 7

Calculations show that over billions of years, tidal effects on its dense atmosphere could have slowed down its initial rotation to thevalue seen today.

wikipedia.com

Answer 8

Perhaps its initial spin was opposite in direction to Earth's and much smaller.

Answer 9

Accretion theory: see link below

Answer 10

mayb its not WE R backwards! bet u didnt think of tht did ya