Some believe Venus came into our solar system within the last 4 to 5000 years. Here's the arguement:

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.

Velikovsky's "cosmology" (I use the term loosely) bears more hallmarks of a conspiracy theory than of a scientific theory. Its physics are ridiculous, but that's never bothered a pseudoscience.

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, slightly 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 orbits 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.

Not to burst anyone's bubble, but this theory makes no sense astrophysically. First, an object entering the solar system from outside will enter with a velocity similar to the velocity dispersion in the solar neighborhood, say about 20 km/s. In order to be captured into a solar orbit the interloper must lose all that excess energy through two-body interactions with the other planets. It's not easy to design a scenario where this happens, let alone get it to happen by chance. Download an n-body simulator and try it.

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:
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.

IAAAP I Am An Astro-Physicist. (or at least i will be in two years).

regardless i want to say a few things, and comment on others posts.

pedrolio states: "However, it's spinning tremendously fast"

This is not true. Venus is spinning backward realitive to all other planets in the solar system but it is doing so at a rate of once every 230ish days, very very slowly. This is easily explained in nebular formation theory. Small pockets of a propilid may spin in any direction as long as the net angular momentum is non zero in any given direction. Venus was in or near such a pocket.

pedrolio also states: "Also, someone has noded the fact that Venus' pattern of craters is utterly dodgy......."

I'm not really sure what he means by dodgy but venus' cratering pattern is not very well known in the first place. The planet is shrouded in thick clouds. We never visualy see the surface. We do have radio images but these can't pick up small features. Add in the plethora of active volcanoes and the constant acid rain and a crater on venus wouldn't stick around very long at all. The surface of the planet is quite young and free of much of its infantile cratering.

pjd states: "The arrival of another planet in the solar system would most likely disrupt the obits of all nearby planets including Earth."

You would think a planet like venus just appearing in our solar system would change orbits but in reality it would have very little effect at all. I just did a quick calculation and i found that the acceleration of earth toward venus due to its presence is .000000001 m/s^2 I am willing to say for argument's sake i am off by plus or minus 100%. And this is when the planets are at inferior conjunction and are closest together. So yeah the orbit of earth would change. Would anyone but and astro-physicist even notice? no. We didn't even have measurements this accurate until less than 100 years ago.

Now as for what i have to say. Venus is BRIGHT. If you know where to look you can see it is broad day light. People would have noticed its appearance. Secondly a body of this size would have had to have been moving very slow to be caught in a circular orbit. Something moving that slowly has very little momentum, which means it would easily been bumped off course by other bodies in the solar system. An area which i have researched is nebular formation theory with compute simulations. I ran a sim a few times and notice that a slow moving body need to be undisturbed and in perfect alignment to get into a stable circular orbit. In our solar system this just couldn't happen.

In conclusion this idea just doesn't work

One more thing, pjd says "a meteor passing close enough could have an effect without actually touching the planet" For this to happen the meteor would have to be HUGE, and pass very very very close. Remember Fg= MMG/R^2. The Universal Law Of Gravitation
I hate to break it to you, but Venus' crater pattern is dodgy for a reason. The surface of Venus is very hot (approximately 470ÂșC) -- so hot, in fact, that parts of it are molten. Now, you'd be hard pressed to find a crater on a molten surface, but it is possible -- we've seen them on Venus. Venus' surface has one interesting quirk, though, which accounts for the aforementioned lack of craters. Every so often (I think it's 100,000,000 years or so, but I'm not sure. Ask a professional.), Venus' surface wipes itself clean. Craters? Gone. Islets of molten rock that managed to cool enough to solidify on the surface? Gone.

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 needs 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.

Secondly, this point about tides and the parting of the sea. Tides are a 1/R^3 force. This is why the tidal effect of the sun is much smaller than that of the moon. Thus a planet like Venus really has very negligible effect on the tides of Earth.

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