霜降を 公転してる 地球で捉える

　今日は二十四節気のひとつ「霜降」です。その名が示す通り、今朝、地区のラジオ体操会へ行くとき手が凍え、今年になって初めて手袋をしました。

　天文学的に考えると「霜降」とは、公転してる地球から見た太陽が黄道十二星座の「てんびん座」のすぐ近くになる日です。もちろん眩しくて直接は確認できません。しかし、半年前の４月２３日の午前０時に「てんびん座」が真南より少し東にあったことでこれを証明できます。

　ところで、「てんびん座」は紀元前のバビロニア時代に赤道上空にあり、北半球と南半球を天秤で測って、丁度、釣り合ってたように位置してたことに由来します。現在の２１世紀ではそれから２１００年以上経過し、「てんびん座」は赤道上空から南にずれてます。この原因は地軸がコマのように円を描くように振れる現象によるもので歳差運動と言われます。

　歳差運動の周期は２万５千年ほどで元に戻ると言われてます。この時間は２５０世紀です。現在はバビロニア時代から２１世紀経過しており、およそ１２分の１「てんびん座」の位置が命名当時よりずれてます。このため、現在の秋分の日に太陽は「てんびん座」になく、「乙女座」にあります。

Dear my friends abroad

 Today is one of the 24 solar calendars named "Sohkoh" in our tongue. "Sohkoh" means the season when frost comes. As the name indicates, I felt cold when I went to the district radio gymnastics this morning, so that I wore gloves for the first time this year.

 From the astronomical viewpoint, "Sohkoh"is the day when the sun seen from our revolving earth is in the near vicinity of the "Libra" that is "the Balance" of the Zodiac constellation. Of course, it is dazzling so it cannot be confirmed directly by us. However, this can be proved by the fact that "Libra" is a little east of the due south at midnight on April 23 that was half a year ago.

 By the way, "Libra" was located above the equator during the Babylonian era in BC. Therefore it is derived from the fact that it was located just as if it was balanced by measuring the northern and southern hemispheres. More than 2100 years have passed since the current 21st century, and "Libra" has shifted a little south from the equator. This is due to the phenomenon that the earth's axis swings in a circular motion like a top, which is called precession.

 The cycle of precession is said to return to the origin in about 25,000 years. This time is the 250th century. The 21st century has passed since the Babylonian era, and the position of "Libra" which has shifted from about one-twelfth. For this reason, the sun is not in "Libra" but in "Virgo" on the current Autumnal Equinox Day.

上の英文をネイティブの発音で聴くには英文をドラッグしてコピーし、次に貼り付けて下さい。なお、右上の欄を必ずUS Englishにしてください。

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