Sunday, February 15, 2015

Valentine's Day means a whole hour of extra light in the evening

Sunday, February 15.  Temperature dropping, wind gusty, and snowed-in.  Again. Time to reflect!

What a difference an hour makes!  At my latitude of 42 degrees, we have gained an hour of evening light since the winter solstice on December 21st.  The result, for me at least, is that the oppression of the dark days is lifting, my mood rising with it.  (From late fall through early winter, I seldom see the sun at all during the week except through my classroom windows.  I am sorry for anyone without even decent windows!)  --actually, sunset was earliest a good week before the solstice, although days were still shortening as sunrise got later.  Since mid-December, sunset has been moving back at an accelerating rate, reaching a seasonal high of nearly 2 minutes per day near the end of January.  The sun set here on the 14th at 5:15, but today at 5:17.  

It's worth mentioning that the definition of sunset is not as clear-cut as you might imagine.  It's true that sunset is the moment that the sun finishes disappearing below the horizon, but the lens-like effect of Earth's atmosphere means that the sun is actually well below the horizon before that--its light bending slightly around the curve of the earth as it passes through the air.  The sunset times given by my buddies at the NOAA Solar Calculator are for "apparent sunset."  And I seldom see sunset anyway, since you need a clear horizon without trees or thick clouds that interfere--both pretty rare in the northeast, except perhaps well out at sea.

Short of actually witnessing sunset, we can often get a pretty good idea of the time--not to mention a great experience--as the pink glow of the last light on the undersides of the clouds fades to purple-gray. 

 Sunset on Block Island Sound on a sailing trip from Pt. Judith to Montauk, September 2013.

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