On 6/5/12, Huddleston, Scott <scott.huddleston@intel.com> wrote:
Do Venus transits ever occur in triples?
Yes, the last triple was in 1275, 1283, and 1396 according to Fred Espenak [1]. OEIS sequence A171467 [2] gives a list of transit years.
If not, is there some orbital resonance, or extremely precise orbital tilt, that assures Venus transits can only happen in pairs?
There *might* a resonance between Venus and Earth, but it's different: When Venus is at inferior conjunction (closest to the Earth), it always presents the same face towards Earth. According to [3], "Whether this is a resonance effect or merely a coincidence is not known.". The abstract of [4] agrees with this, but I don't want to pay for the paper (hint: Elsevier). - Robert [1] Fred Espenak, Transits of Venus: Six Millennium Catalog: 2000 BCE to 4000 CE. http://eclipse.gsfc.nasa.gov/transit/catalog/VenusCatalog.html [2] http://oeis.org/A171467 [3] http://nineplanets.org/venus.html [4] http://www.sciencedirect.com/science/article/pii/0019103569900682 -- Robert Munafo -- mrob.com Follow me at: gplus.to/mrob - fb.com/mrob27 - twitter.com/mrob_27 - mrob27.wordpress.com - youtube.com/user/mrob143 - rilybot.blogspot.com