Sometimes you're the horse; sometimes you're the cowboy. Either way, the ride eventually comes to an end.
So it is with calendars, too. Eventually the year ends, we get back up on the horse, and we do it over.
If you are following a certain calendar in the year 2012, you know of significant events happening December 21. Planets are aligning, and intrigued people ranging from astronomers to hucksters are following the movement of the solar system that day, the December solstice.
While NASA has weighed in on end-of-the-world prophecies, it concurrently is deploying its resources to document a rare alignment never before recorded.
On December 21, for the third time in 2012, a transit of Venus occurs in which both Venus passes directly in front of the sun as seen from a planet and the alignment is within the ken of spacecraft optics:
September 20 transit of Venus, as seen from Jupiter; Hubble Space Telescope targeted the giant planet to quantify how much sunlight reflected off Jupiter's atmosphere.
December 21 transit of Venus, as seen from Saturn.
In orbit around Saturn since 2004 is the Cassini spacecraft, equipped per a NASA document with a Visual and Infrared Mapping Spectrometer (VIMS) that "Identifies the chemical composition of the the surfaces, atmospheres and rings of Saturn and its moons by measuring colors of visible light and infrared energy given off by them."
Astronomers Jay Pasachoff and Glenn Schneider, who used images taken at a transit of Mercury with the TRACE spacecraft in 1999 to explain the Black Drop Effect, and who arranged this September's Hubble observations of the transit of Venus as seen from Jupiter, suggested to Cassini scientist Phil Nicholson that Cassini observe the December 21 transit of Venus from afar. The spacecraft will essentially be looking down a long barrel from Saturn to the sun--only three pixels across! Yes, though the Sun is only about 3 pixels across, the team will try to detect the 0.01 percent drop in intensity resulting from the 10-hour transit. They're looking for chemical compounds in the Venusian atmosphere's spectrum, detected by VIMS. See JPL article Cassini Solstice Mission.
Now that's the big alignment of December 21, the winter solstice in the northern hemisphere, a Friday. Not the end of days; rather, the end of long nights. Go out and dance. Read Desiderata.
When you wake up and find the world hasn't ended, get back up on your horse and move on. You've lived to ride another day.