{"id":2346,"date":"2020-07-20T12:12:06","date_gmt":"2020-07-20T19:12:06","guid":{"rendered":"http:\/\/tradewindssailing.com\/wordpress\/?p=2346"},"modified":"2020-07-20T12:12:09","modified_gmt":"2020-07-20T19:12:09","slug":"nautical-terminator-suns-over-the-yardarm-part-3","status":"publish","type":"post","link":"https:\/\/www.tradewindssailing.com\/wordpress\/nautical-terminator\/nautical-terminator-suns-over-the-yardarm-part-3\/","title":{"rendered":"Nautical Terminator – Sun’s Over the Yardarm (Part 3)"},"content":{"rendered":"\n

            <\/strong>Last\ntime we established that the yardarm is not the whole yard, but just the tip of\nit outboard of the leeches, and moreover the commentators are all over the map\nconcerning which yard to use. Yet any part of the rigging, which is constantly\nin motion, is a poor gauge for the altitude of a celestial body compared to the\nsextant. And why use such a clumsy measurement to tell time anyway, since by\n1899 when our phrase first appeared, the chronometer had been in use well over 100\nyears?<\/p>\n\n\n\n

              The\none thing the pundits all seem to agree on is that the sun rises over the\nyardarm at 11:00 AM, sometimes adding for good measure \u201cin the northern\nhemisphere,\u201d though they should know the hemisphere makes no difference.         <\/p>\n\n\n\n

              As\nthe builders of Stonehenge understood, the sun\u2019s altitude varies by the date<\/em><\/strong>.\nAt 1100* at the Tradewinds dock the sun was at a height of 50 degrees, roughly\nthe angle of the main yardarm viewed from the mainmast, on March 24 and again\non September 21. The yardarm will give the correct time twice a year. But by\nOctober it would not rise to this angle even at noon, while at summer solstice\nit would reach 50 degrees by 0916. <\/p>\n\n\n\n

              And\nas Eratosthenes demonstrated in about 240 BC, the sun\u2019s altitude varies with latitude<\/em><\/strong>.\nSo on March 24, the day the sun was at 50 degrees at 1100 here, it reached 50\ndegrees by 1014 local time in Hawaii, and never rose that high in Vancouver. <\/p>\n\n\n\n

              Were\n18th<\/sup> and 19th<\/sup> century navigators such boneheads that they\nwere not aware of these fundamentals? Methinks not.<\/p>\n\n\n\n

              If\nyou\u2019ve ever worked for a living or stood watch, you know the end of your shift\nis not a matter taken lightly, particularly if grog is in the offing. For\nregimentation of life aboard, for establishing the ship\u2019s speed in dead\nreckoning, and for longitude, the accurate measurement of time was crucial.\nNothing as vague as the sun\u2019s proximity to a yardarm could ever have served.<\/p>\n\n\n\n

              But\ndon\u2019t get me wrong. If I overhear you on the dock one day saying, \u201cThe sun\u2019s\nover the yardarm, mate,\u201d I\u2019ll know you\u2019re not doing celestial navigation.<\/p>\n\n\n\n

*Ignoring daylight savings, which would confuse\nthings<\/p>\n","protected":false},"excerpt":{"rendered":"

            Last time we established that the yardarm is not the whole yard, but just the tip of it outboard of the leeches, and moreover the commentators are all over the map concerning which yard to use. Yet any part … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":13,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[31],"tags":[],"class_list":["post-2346","post","type-post","status-publish","format-standard","hentry","category-nautical-terminator"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/posts\/2346","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/users\/13"}],"replies":[{"embeddable":true,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/comments?post=2346"}],"version-history":[{"count":1,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/posts\/2346\/revisions"}],"predecessor-version":[{"id":2347,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/posts\/2346\/revisions\/2347"}],"wp:attachment":[{"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/media?parent=2346"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/categories?post=2346"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.tradewindssailing.com\/wordpress\/wp-json\/wp\/v2\/tags?post=2346"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}