Lunation Lunacy

Zebulon, NC

Tonight's perigenal full moon was in the news today.

Do I seem obsessed by lunation phenomona?  If so, that is because it's true.  I think it is great fun to see the wonders of nature in a way that science and mathematics predict so accurately.

Spring tides are extra high/extra low tides that occur when the moon and the sun are aligned (new moon) or opposed (full moon).   When sun and moon are 90 degrees out of phase, we have neap tides.  Actually, spring tides happen a couple of days after new/full moons because of local effects.

Below, you see the tides for 30 days at Bridgeport, Connecticut.  The spring/neap tide variations are very plain.

The moon's orbit is not circular.  It is closest ad perigee and furthest at apogee.  The biggest spring tides occur when full or new moon correspond to perigee.  They are called perginal spring tides.  Below you see the tides at Bridgeport, Connecticut for a period of 400 days.  At that scale you not only see the spring tide cycles, but the variations in spring tide levels and thus the perigenal spring tides.  Cool huh?

Regular readers also know that I've written several times about perfect moonrises.  I define a perfect moonrise as being the time when the moon rises in exact syncronism as the sun sets.  That happens, of course, on the evenings of full moons.  However, at the moment of full moon, there is only one longitude on earth where the moon is rising at that exact minute.  The coincidence of that date, time and longitude give you the time and place of the perfect moonrise.  I calculated those dates, times and longitudes for the next several years.  See the table below.

--Date----- -Latitude- --Approximate Place-- 

2012 May  6       054W Suriname

2012 Jun  4       168W American Somoa

2012 Jul  3       077E New Delhi, India

2012 Aug  2       052W Cayenne, French Guiana

2012 Aug 31       151E Sydney, Australia

2012 Sep 30       050W Sao Paulo, Brazil

2012 Oct 29       062E Western Afganistan

2012 Nov 28       138E Papua, New Guinea

2012 Dec 28       156W Hawaii

2013 Jan 27       070W Buzzards Bay, Rhode Island, USA

2013 Feb 25       053E The Caspian Sea

2013 Mar 27       143W Chugach Mountains, Alaska, USA

2013 Apr 25       060E Ural Mountains, Russia 

2013 May 25       067W Bar Harbor, Maine, USA

2013 Jun 23       174W Aukland, New Zealand

2013 Jul 22       086E Kathmandu, Nepal

2013 Aug 21       026W Thule, Greenland

2013 Sep 19       168W Midway Island, Pacfic

2013 Oct 18       006E Luxembourg

2013 Nov 17       131E Kyusu, Japan

2013 Dec 17       142W Marquesas Island, Pacfic

2014 Jan 16       074W New York City

2014 Feb 14       001E London, England

2014 Mar 16       102E Bangkok, Thailand

2014 Apr 15       116W Las Vegas, Nevada, USA

2014 May 14       070E Kabul, Afganistan

2014 Jun 13       064W Virgin Islands, Atlantic

2014 Jul 12       172W Midway Islands, Pacfic

2014 Aug 10       087E Rangpur, India

2014 Sep  9       025W Azores Islands, Atlantic

2014 Oct  8       163W Aleutian Islands, Bering Sea

2014 Nov  6       024E Athens, Greece

2014 Dec  6       173E Midway Islands, Pacific

2015 Jan  5       074W New York City

2015 Feb  3       013E Rome, Italy

2015 Mar  5       088E Dhaka, Bangaladesh

2015 Apr  4       178E Fiji, Pacific

2015 May  4       056W Buenas Aires, Argentina

2015 Jun  2       115E Hong Kong

2015 Jul  2       036W Mouth of the Amazon River, Brazil

2015 Jul 31       162W Nome, Alaska, USA

2015 Aug 29       081E Sri Lanka

2015 Sep 28       043W Rio De Janerio, Brazil

2015 Oct 27       179E International Date Line, Pacific

2015 Nov 25       019E Budapest, Hungary

2015 Dec 25       168W Niue Islands, Pacific

Unfortunately for me, none of those are the time and place where I'm likely to be.  In fact, for a given longitude, one gets to see a perfect moonrise only once every 30 years.  A perfect perigean moonrise happens once every 225 years at a given longitude.  Therefore, the chances of seeing any of these events is very rare unless you are willing to travel to the given longitude to see it.