1. The twice-in-a-lifetime event: Transit of Venus 2012 http://www.skyandtelescope.com/observi ng/objects/daylightphenomena/3308756.ht ml

2. Venus takes 224.7 days to orbit the sun Earth takes 365.24 days (1 calendar year) Earth, sun and Venus are realigned every 583.92 days, a synodic year 5 Venus synodic years  8 Earth calendar years

3. Venus’ 5 synodic years since 2004

4. Why isn’t there a transit every inferior conjunction? For a transit, Earth, Venus and the sun must line up almost EXACTLY in all 3 dimensions Venus’ orbit plane is tipped with respect to Earth’s – the planes intersect at 2 points (Earth’s location in June & December)

6. 8 years from now? Graphics and reality checks from Royal Astronomical Society of New Zealand’s web page on Venus transit

7. Why has this been an important event in astronomical history?

8. A means to measure the scale length of the solar system Copernicus supplied correct scale model of the solar system; he did not know that the “scale unit” (the AU, or Astronomical Unit) was about 150,000,000 km

9. If Earth is 1 AU from the sun, Venus’s average distance from sun is 0.62 AU At inferior conjunction, Venus is 0.28 AU from Earth

10. Now we’re cooking: