In the ATM section in the "Is Venus Bugging Us?" thread someone is passing on a theory that influenza outbreaks coincide with the conjuctions. As I'm kind of being ignored there I'd thought I'd ask this here.

One: What the heck is a inferior conjuntion of Venus with Earth?

Two: Do they ever occur outside of the Autumn/Winter months?

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"The beauty of that discussion of averages is that you don't have to be an expert in Apollo or in photography in order to see where this time study "analysis" breaks down. You just have to be, well...not an idiot." -JayUtah

Earth and Venus orbit the sun. At some points one planet is on one side of the sun while the other planet is on the other. Far away from eachother. Bad time to launch a probe. Or a bug.

At other points they are on the same side during their orbits and that is when they are closest to eachother.

It's where Venus passes "between" the Earth and the Sun. Due to orbital inclinations, Venus usually winds up either above or below the Sun as seen from Earth, although this wasn't the case in June, 2004.Sure. They can happen any day of the year (see above re the June, 2004 inferior conjunction). It's all a product of orbital periods and mechanics.

The bit about flu, etc., is, at best, malarky.

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Graphically, here's what an inferior conjunction of Venus in respect to the Earth looks like, as seen from above the plane of the ecliptic (the plane of the Earth's orbit). (not to scale):



Also here's what a superior conjunction looks like:



Remember, the orbital plane of Venus is not identical to Earth's, therefore Venus rarely appears to cross the Sun.

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Just for fun, I will say they always do occur inside the Autumn/Winter months.

Owing to the fact that this planet has a northern and a southern hemisphere, it is always Autumn or Winter somewhere here.

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0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0....

And some of us are already in line for June 2012

D'oh! You got me on that one. (What a minute, what's down there? The Prison Continent, The Land of the Hairy Potato-shaped Bird, The Big Icebox and South America. Oh okay South America counts)

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"The beauty of that discussion of averages is that you don't have to be an expert in Apollo or in photography in order to see where this time study "analysis" breaks down. You just have to be, well...not an idiot." -JayUtah

Yup, and my diagrams were actually from below the plane of Earth's orbit. Ha!

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Is Venus' entire orbit below the Sun's equator? Or just dips below for part of the cycle.

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"The beauty of that discussion of averages is that you don't have to be an expert in Apollo or in photography in order to see where this time study "analysis" breaks down. You just have to be, well...not an idiot." -JayUtah

Due to Venus' orbit not being coplanar with the plane established by the Sun's equator, it is either "above" or "below" (i.e., not in) the solar equatorial plane, except for twice an orbit, when it crosses the equatorial plane of the Sun.

Here's a wiki article that elaborates on orbital inclinations.

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But is it Autumn or Winter when it's above?

Is it always June when it's "in"?

Due to the difference between the orbital periods of the Earth and Venus, Venus can be "above" on any day of an Earth year. It's not constrained by the seasons of the Earth.

One item of clarification re the transits of Venus: for the past couple of thousand years they have been occurring mainly in either June or December. This is due to the way the nodes of Venus' orbit line up as seen from Earth. For example the last non-June/December transit was on May 23rd in the year 1526 CE. This June/December pattern will continue for many more thousands of years, unless there's an event that perturbs either Venus and/or the Earth.

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The Earth Venus conjunction features interestingly in The Da Vinci Code. Because 13 Venus years are almost precisely equal to 8 Earth years, there are 13/5 = 2.6 Venus years for each 8/5 = 1.6 earth years. The common "0.6" in the two cycles means that when Venus has orbited 2.6 times, the Earth has orbited 1.6 times, so they line up exactly again with the sun. The five inferior or superior conjunctions are therefore at 1.6, 3.2, 4.8, 6.4 and 8 earth years = 2.6, 5.2, 7.8, 10.4 and 13 Venus years. For example, the inferior conjunction of Earth and Venus on 18 August 2007 was the fifth such event since the same date in 1999. These five points form a perfect pentagram in space, the divine shape of Pythagorean lore and the Vitruvian Man by Leonardo, as discussed by Dan Brown. There is reportedly a 0.0789 day slippage of this pentagram every 584 days.

Assuming a single, unambiguous definition of 'inferior conjunction' for the Moon and Venus, do such (always) occur within hours? days? a month? of the corresponding Earth-Venus conjunctions?

Can the Moon ever spoil the fun of watching an "in" Earth-Venus conjunction? If so, has it done so since telescopes were invented? When will it next be a party-pooper?

That part is good information.

The rest is...

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The information is all correct, I think you may be reading more in than is there.

Venus transits of the sun take a quarter day or so, and are visible from almost anywhere on the Earth that is in sunlight. They occur in pairs, mostly now, a hundred years apart. A solar eclipse by the moon doesn't last as long as that--and the eclipse is not visible from everywhere, so it wouldn't obscure the transit for everyone.

Thanks.

Any solar eclipses, somewhere in the world, during at least part of a transit of Venus?

The odds are thin. This 6000 year catalog shows only about 80 transits, that's about one per 75 years, but a lot occur in pairs about eight years apart. The pairs are over 100 years apart. This catalog of "famous" lunar eclipses probably would have included one that had a simultaneous transit.

None since 2000 BCE, and the next is not forecast until 5 April 15,232 (Dynamical Time!).
There was a near miss on 22 May 427 BCE, when a total solar eclipse ended nine hours before the beginning of a transit of Venus, and another on 4 June 1769, when a total solar eclipse started five hours after the transit of Venus ended.
(Information from Jean Meeus' Mathematical Astronomy Morsels III.)

Grant Hutchison