The Star Geezer: Longer days await
December 10, 2009
This week expects to be an especially active one on the night-sky viewer’s celestial calendar. In addition to the shows that Jupiter, Mars, Mercury, Saturn and the moon will be putting on, this week also features the usually prolific Geminid Meteor shower as well as the earliest sunset of the year.
This last phenomenon – the idea that the earliest sunset is not on the solstice, the shortest day – is succinctly described by one of the Star Geezer’s favorite phrases: It happens because the equation of time is zero. Now that’s a cosmic phrase but what, really, does it mean?
In trying to explain the somewhat confusing “equation of time” being zero, it is important to understand that the time that our watches and clocks keep does not necessarily match the time a sundial measures. That means that our “clock” midday – noon – doesn’t jibe with the actual solar, or “sundial,” midday, and the discrepancy ultimately combined to give us the earliest sunset by our clocks on the 7th, while the shortest day remains the 21st.
It is often “explained” (quite un-scientifically, to these ears) by astronomers as occurring because of a “wobble’ in the Earth’s orbit around the sun. Get it? Well, neither does the Star Geezer completely. But the result still happens whether we fully understand it or not: Our earliest sunset – by the clocks we time our lives by – occurred on the 7th and thus by the 21st we are already well on our way ( by about 4 minutes) to those later sunsets that signal longer days … even if the actual longer days don’t actually begin until after the 21st.
The peak of the Geminid Meteor Shower occurs this Saturday through Monday nights, with Sunday being the best of the three. These nights should be fairly dark owing to a new moon on the 16th. For best viewing look to the northeast, especially after midnight, and expect to see up to 75 shooting stars per hour ( assuming clear skies).
Planet-wise, Jupiter is visible just after sunset in the west while Mars rises a bit later in the east and is getting brighter by the night.
Recommended Stories For You
Mercury was near the crescent moon on the 7th, while Saturn will be near an even thinner moon tonight. Enjoy our night sky!