Planetary Properties

Venus is the second planet from the Sun, with a nearly circular orbit having an average radius of 0.7 A.U. This gives it an orbital period of 225 days. Like Mercury, but unlike the other planets, Venus has no moons. The physical properties of Venus are summarized in this table and the orbital properties in this table.
Slow Retrograde Rotation
Venus is peculiar in that its rotation, first measured by Doppler shift of radar waves from Earth in the early 1960s, is retrograde (in the opposite sense of the Earth) and because it is very slow: a day on Venus corresponds to 243 Earth days. If one could see the Sun at the surface (the thick clouds make this impossible), a solar day would last 117 Earth days on Venus. Here is a simulation illustrating the rotation of Venus relative to the position of the Sun.

Why Retrograde Rotation?
At present, we have no conclusive explanation for the rotation of Venus. The most plausible theories invoke the collision of two large masses to form Venus in just such a way to cancel most of the rotation for the two masses, or the collision of Venus with a large planetesimal early in its formation that canceled the rotation. While this is consistent with our general understanding of planetesimal collisions in shaping the Solar System, we have no direct evidence to support these conjectures.
The Cloud Layer

Venus is always covered by a thick layer of clouds that make it impossible to see the surface for light in the visible part of the spectrum. These clouds help Venus reflect 77 percent of incoming solar radiation (that is, its albedo is 0.77) and the amount of sunlight making it to the surface is 10 percent of that found for Earth. Light at radar wavelengths penetrates the cloud deck and allows us to study the surface. A comparison of the motion of the surface with that of the upper clouds indicates that while the surface takes about eight months to rotate, the clouds rotate all the way around the planet in about four days. This indicates that there are very high velocity winds in the upper part of the Venusian atmosphere.

Earlier Misconceptions of Venus

In earlier times, there was considerable speculation concerning the possibility of life on Venus, sometimes with rather elaborate characteristics. In 1686 a French "man of letters," Bernard de Fontenelle, wrote that

I can tell from here . . . what the inhabitants of Venus are like; they resemble the Moors of Granada; a small black people, burned by the sun, full of wit and fire, always in love, writing verse, fond of music, arranging festivals, dances, and tournaments every day. (Quoted in National Geographic, June 1975)
Now apart from the fact that this description is rather unremarkable because it probably sounds like everyday student life around a great university like yours, it turns out that Monsieur de Fontenelle was quite incorrect about Venus and its conjectured inhabitants.