On Saturday, October 25, 2014 8:48:59 PM UTC+1, palsing wrote:
On Saturday, October 25, 2014 11:54:44 AM UTC-7, Quadibloc wrote:

... In eight years, there are five conjunctions between Venus and the Sun from
Earth's viewpoint, so the Earth catches up with Venus in its orbit five times.

Thus, from Earth, Venus is seen to go through its phases five times, while a
stationary observer would see it go through its phases thirteen times (5 + 8).

John Savard

Yes, and this graphic...

http://www.lunarplanner.com/Images/V...et%20Paths.gif

... represents the path of Venus among the fixed stars over each of those 5 passages, the differences between them having to do with the position of Venus WRT the ecliptic, that is, if Venus is above the Sun or below the Sun or nearly even with the Sun as it arrives at inferior conjunction.

Alas, poor Gerald has no chance to understand, since he cannot visualize perspectives, even if his life depended on it... which, fortunately for Gerald, it doesn't...

What is encouraging is that people can put the increase in size of Venus and changes in phases as it approaches the Earth's orbit in context of its motion around the Sun so they should have no problem with the view of the Earth from Mars when its phases and increase in size will eventually be imaged..

http://www.farhorizons.nl/planets/Ve...007%20oost.jpg

There is no need to throw good information after bad so that Owen at JPL has the responsibility of setting his colleagues straight on how the motion of the Earth around the Sun and against the background stars would look like from the surface of Mars using the known principles based on the motion of Venus as seen from the Earth.

The input of the Earth's orbital motion into observations of the motion of the inner planets from the Earth's surface requires nimble reasoning as it requires a number of important modifications which chained older astronomers to observations which ultimately are counter-productive. The most notable modification is switching the reference for the Sun apparent motion through the background field of stars to the productive apparent motion of the background stars behind the central Sun thereby creating the background for appreciating the grandstand motion of the inner planets around the Sun.

Here is the less productive view of the Sun's motion through the Zodiac by Huygens and its nonsensical extension via Newton

" Here take notice, that the Sun or the Earth passes the 12 Zodiacal signs,or makes an entire revolution in the ecliptic in 365 days, 5 hours 49 min. or there about, and that those days, reckon'd from noon to noon, are of different lenghts; as is known to all that are vers'd in Astronomy" Huygens

"That the fixed stars being at rest, the periodic times of the five primary planets, and (whether of the sun about the earth, or) of the earth about the sun, are in the sesquiplicate proportion of their mean distances from the sun." Newton

Yes it is a tangle and yes most of it can be dealt with in a reasoned way so everyone can get a clear insight into where they stand without having to cut each other to pieces however,in the interim, people can appreciate the motion of Venus seen from Earth and safely predict what the motions of the Earth will look like from Mars.