今晚將出現藍月亮

Blue moon to appear tonight

今晚將出現藍月亮

A blue moon is generally understood to be second full moon in a month, a phenomenon that won’t happen again until 2018. But the moon won't look blue.

一般來說，人們認爲藍月亮是每個月的第二次滿月，這種現象直到2018年纔會出現。然而，藍月亮並非藍色。

Look out into the sky after midnight tonight, and you will be able to sneak a peek at a “once-in-a-blue-moon” phenomenon: A blue moon, itself.

今晚午夜仰望天空，大家將看到一種千載難逢的現象：藍月亮。

The “blue” moon will be visible on Friday. Its appearance marks the second full moon in the month of July, a phenomenon that won’t happen again until 2018.

本週五將出現“藍”月亮。標誌着7月的第二次滿月，這種現象直到2018年纔會出現。

But what exactly does a blue moon look like, and is it really all that rare? What is a blue moon?

然而，藍月亮到底是什麼樣的？真的那麼罕見嗎？什麼是藍月亮？

When two full moons fall within the same calendar month, that second moon is called a blue moon. The first full moon this month was seen on July 2.

如果在同一日曆月內出現兩次滿月，則稱第二次滿月爲藍月亮。本月第一次滿月出現在7月2日。

“It’s basically because a lunation is 29-and-a-half days . . . that you wind up having a second full moon in a calendar month,” explained Paul Mortfield of The David Dunlap Observatory in Richmond Hill.

“基本是因爲陰曆月有29天半，因此，只在日曆月內存在第二次滿月，” 列治文山大衛鄧拉普天文臺的Paul Mortfield解釋道。

“All it is, is an extra full moon that we get, and that’s been going on for millennia,” Mortfield told the Star.

“藍月亮是額外的滿月，已經持續了千年，”Mortfield告訴《星報》。

Confusingly, the term “blue moon” can also be used to describe the third of four full moons that occur in a single season.

令人困惑的是，如果一個季度中出現四次滿月，“藍月亮”一詞也可用來描述其中的第三次滿月。

Where does the definition come from?

此定義從何而來呢？

NASA says the original definition of a blue moon, detailed in the Maine Farmer’s Almanac, was “so convoluted many astronomers struggled to understand it.”

美國航空航天局稱，《緬因州農夫年曆》詳細介紹了藍月亮的原定義，“非常複雜，以至於很多天文學家都難以理解。”

A 1946 article in Sky & Telescope magazine, however, redefined the term blue moon as a “second (full moon) in a month.”

然而，1946年在天空&望遠鏡雜誌上刊登的一篇文章重新將藍月亮一詞定義爲“每月的第二次滿月。”

Although this was a mistake, the definition stuck, and we have come to use it that way ever since.

儘管這一定義是錯誤的，人們卻從那時起就這樣理解藍月亮。

How often do blue moons occur?

藍月亮多久出現一次？

Two full moons generally appear in the same month once every two or three years: the last occurrence was in August 2012, and the next one is expected in January 2018.

一般來說，每兩年或三年在同一月內出現兩次滿月：上次發生在2012年8月，預計下一次將出現在2018年1月。

The second type of blue moon, the third of four full moons in a season, happens every three years or so. The last was in 2010, and the next one is expected in May 2016.

第二類藍月亮，即如果一個季度中出現四次滿月，則爲第三次滿月，大約每三年出現一次。

譯文屬原創，未經允許，不得轉載。