Venus spins in the opposite direction that it orbits the Sun, which no other planet does. This may be because it came flying past our Sun and was caught by the gravitational field.
If this was the case, it could have happened anytime. However, it's spinning tremendously fast, and also it could well have been the thing which caused the strange happenings on our own planet as it flew by, recorded in the Bible: fired-up things in the sky (chariots of fire), weird tides in the oceans (parting of the Red Sea), unbalanced biology (the plagues of frogs and stuff).
Also, someone has noded the fact that Venus' pattern of craters is utterly dodgy.......
The Babylonians were the first to chart Venus, and looking at their records Venus appears very suddenly about 4-5000 years ago.
Just a theory.
Interesting theory.
A disadvantage would be Venus's circular orbit. You'd expect something coming in like that to be more elliptical, taking a lot longer than the time suggested to settle into its current orbit, which is the most circular of any planet in our system - less that 1% elliptic.
It is arguable that Uranus is also retrograde, depending which way up you define it.
Also, Venus has a well-formed high-pressure atmosphere; again, I'd expect that to take longer to form.
I'm no expert, but the sudden intrusion of something that large into the Solar System would probably have slightly more effect on us than a couple of frogs and a completely localized and very temporary parting of a specific part of the sea. I would expect significantly more than even the Biblical flood. I'd also suggest that if you are going to believe the Bible stories as written but look for "natural" causes, that'll take more faith than believing in God in the first place. I mean, how lucky would that have made Moses and the Israelites?!
Moses: "Well, it looks as though God doesn't exist, but a huge new planet ripped through the sky just as those pesky Egyptians were closing in on us, parted the sea allowing is to run through unharmed but then collapsed on the Egyptian army. Obviously, no-one will believe that, so we're sticking with the God story."
Sigh - I'd better respond to pjd, although this is off-topic here. Firstly, if Yam Suf were just a reedy marsh, why did the entire Egyptian army perish chasing a ragged bunch of ex-slaves? Secondly, the chariot and horses of fire separated aging Elijah from replacement Elisha, then Elijah was taken up to heaven in a whirlwind (2 Kings 2:11). Seems hard to believe that a meteor strike could take one man away but leave his companion unhurt and suitable for many years more work... As for the non-frog plagues, explaining away the whole lot as a package gets difficult. Agree with disruption point; not sure about a major meteor strike changing spin direction without smashing up the planet.
So here's a minor historical quibble. All ancient civilizations knew the planets Venus, Mars, Jupiter and Saturn. You'd also know them quite well if you lived without modern "light pollution" (under a dark sky), as you'd clearly see them every night. We're expected to believe that 4500 years ago a new planet showed up, and nobody bothered to make a note? I mean, they wrote about some utter triviality like frogs raining from the sky or a plague of locusts (material oddities, to be sure) and missed the appearance of another planet in the celestial spheres (a sure sign of Divine displeasure in most cultures)?
Of course, Velikovsky is here to stay. After all, Math is hard. At least that's what the media keep pushing.
Sorry to rain on your parade pedrolio, but there are a couple of counter arguments. It has since been updated in response to e-troon. /me gets out "The Big Book of Explaining Things Properly".
The parting of the red sea In the orginal hebrew version of this story, Moses led the Jews across the reed sea. The change happened when the text was translated into english many years ago. e-troon - the Egyptian army was following the Jews with horse and chariots. A marsh is basically just a large lake with plants growing right up to the surface, when the summer kicks in, the marsh can dry up, perhaps just on the surface, sometimes leaving a causeway across with a wall of water to the left and to the right. (sorry, slighty paraphrased). It is possible to sink through when you are too heavy ie. horses and chariots.
Chariots of Fire In biblical times, there was little in the way of light pollution. (There isn't that much around egypt now anyway) If there was a meteor shower eg. the leonid shower, you have your chariots of fire. I suppose I asked for that one. I don't know that much about this story and was just putting together an explanation for lights in the sky. /me leaves it at that.
The plague of frogs See e-troons answer. Rioting frogs should be the least of your worries if the solar system suddenly gains a new family member!
Last but not least, arriving only 5000 years ago. The arrival of another planet in the solar system would most likely disrupt the obits of all nearby planets including Earth. From this we would expect to see destabilised orbits shown by changes in the pattern of seasons and therefore weather. Given that we have records of what weather has been doing for much more the 5000 years from natural evidence (eg. tree rings, ice coring etc.), we would have detected such a large change a long time ago!
An explanation for Venus. Included here for posterity. I now now view it as bullshit Well, IANAP, but it is possible that the funny craters and the spin of Venus can be accounted for by a large meteor strike. I suppose it doesn't have to be a strike, a meteor passing close enough could have an effect without actually touching the planet. This could also produce scarring if parts break off. I won't say more than "it's possible", because this isn't my field of expertise.
What's more, although the rotation of Venus is unusual as compared to the other planets, the orbit of Venus is typical. As e-troon mentioned, Venus' orbit has a very low eccentricity; it is also inclined only 3 degrees from the ecliptic (that is, its orbital plane is nearly lined up with that of the earth and the other planets). The probability of this situation arising from a chance capture is basically nil.
As for the craters of Venus, there is an extensive discussion of them at: http://www.eoascientific.com/prototype/newcampus/space/11/venus/venus2.html#general The executive summary is that there doesn't seem to be anything about them that can't be explained by known processes.
The problem with this theory, in a nutshell, is that it focuses on one or two odd features of Venus while ignoring all the features that are perfectly ordinary. You could do that with any of the planets; all of them have something strange about them if you look hard enough. If you consider all of the evidence, there is no reason to believe there is anything exceptional about Venus.
No one I've asked has been able to tell me why this happens (hypothetical answers I've been given have had to do with the pressure on Venus, subterranean floes, etc. Use your imagination), but apparently it does.
Update: no comply says check out my WU in the venus node, the wipe out you talk of is, as i know it, a result of intense tectonics which allow the molten interior to esacpe through fissures
There you have it.
As for Venus' retrograde motion: Again, no one can be positively sure why, but the "accepted" hypothesis is that something big -- very big -- hit Venus early on in its life, thus causing it to rotate backwards. This makes sense, as well, because even if something catastrophic had happened to Venus billions of years ago, it's had time to right itself. So there. QED, I think.
Just two things.
Firstly what rpl says is right. An object can't just get trapped by the gravitational field of the sun. Finally it must end up with a net negative energy, and for this to happen it need to lose a lot more than the initial kinetic energy it had at infinity. Since an orbit closer to the sun means lower energy, you would probably expect an intruder to have an orbit with a very large semi-major axis.
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