THE USM SOUTHWORTH PLANETARIUM

207-780-4249        www.usm.maine.edu/planet
70 Falmouth Street   Portland, Maine 04103
43.6667° N                   70.2667° W
Founded January 1970
Julian date:    24581450.5

Sunrise -  6:58 a.m.      Sunset - 4:52 p.m.

           "To maintain the supreme sense of self confidence I have cultivated, I repeat, 'I am strong, able, and calm."           

            -Robin Sharma

THE DAILY ASTRONOMER

Thursday, February 1, 2018

Groundhog's Day

is tomorrow.    Must of us know of it as the day when a groundhog in Pennsylvania emerges from its subterranean hovel to either observe or not observe its shadow.  If Phil, said groundhog, does see his shadow, he will retreat to his lair and we above-ground dwellers will experience six more weeks of winter-like weather.   (This will only apply to those select few Mainers who decide in Mid March to vacation in Hell.)   If Phil doesn't see his shadow, he will remain above ground, thereby indicating spring's early arrival.

This delightful American tradition is well known throughout the country and celebrated rather boisterously in Punxsutawney, PA, Phil's home turf.  Less known, however, is the astronomical aspect of this minor hiemal holiday.      Groundhog's Day is a cross- quarter day, defined as the day approximately midway between successive seasonal points.  Groundhog's Day is the CQ day between the winter (December) solstice and vernal (March) equinox.   We have reached the halfway mark through this later winter.  Cheerfully, this means that we are now in the process of moving out of, instead of into, winter. (Much like a person can only walk into a forest until reaching the mid point, at which point the person begins walking out of it.)

This time of year we notice that the sky isn't pitch black at 5 p.m, anymore.  Each day the sun is rising progressively earlier and setting later, heralding the eventual, though, lamentably, not imminent, arrival of the warm season.   February 2nd also marks an important meteorological nadir.    The graph describing the average high temperatures each day throughout the year is an undulating curve that reaches a minimum on February 2nd.   Even though February is generally a very cold month, the average high temperature will start to increase on February 2nd.  The increase continues until reaching a maximum on August 2nd.  

Groundhog's Day is the cross quarter day that marks a turning point from the frigid winter cold toward the enveloping summer warmth.  It is true that we're not there quite yet, but at least we (and our planet) are moving in the right direction.

_____________________________________________

FROM THE CATACOMBS OF INFINITE KNOWLEDGE

The Other Cross Quarter Days

Along with Groundhog's Day, we have 

  May Day (Beltane), the CQ day between the vernal equinox and the summer solstice

 Lammas , the  CQ day between the summer solstice and the autumnal equinox 

and

Halloween (Samhain), the CQ day between the autumnal equinox and the winter solstice.

__________________________________________________