薄明光線 (Crepuscular Rays)

　一昨日、上掲の写真に向って右側の光景を撮った写真を掲載し、そこに見られる放射状の光の筋の集合を何と呼べばよいかという疑問を記しておいた。これに対して、一人の方からコメント欄で「天使の梯子（はしご）」、「レンブラント光」、それに「雲間からの光芒」（彼自身が使用しているもの）という呼び方を教えて貰った。

　そこで、「天使の梯子」でインターネット検索をしたところ、『ウィキペディア』 の「薄明光線」の項［2010年11月13日 (土) 21:43］が見つかった。これが気象現象としての名称で、一般的には「天使の梯子」がよく知られている、と説明されている。そして、他に「天使の階段」、「ヤコブの梯子」、「レンブラント光線」、「光芒」の名も挙げてある。

　ヤコブの梯子、天使の梯子という名称は、旧約聖書創世記28章12節に、ヤコブが夢の中で、雲の切れ間から差す光のような梯子が天から地上に伸び、そこを天使が上り下りしている光景を見たという記述があることに由来するそうだ。また、レンブラント光線という名称は、レンブラント (1606–1669) がこれを好んで描いたことに由来するという。

Two days ago, I posted a photo of the scenery at the right of that of the above photo and wrote the question what we should call a group of radial light-rays seen there. In reply to this, one person wrote in the comment column the following names: "天使の梯子 (angel's ladder)," "レンブラント光 (Rembrandt ray)" and "雲間からの光茫 [light beams through gaps in clouds (the commenter's own words)]."

Thus, I made an Internet search of "天使の梯子" and found the page "薄明光線 (crepuscular rays)" of Wikipedia [Japanese edition, 13 November 2010 at 21:43]. The phrase "crepuscular rays" represents the atmospheric phenomenon just in my photos of Tuesday and today. According to the above Web page, crepuscular rays are better known by the name of "angel's ladder" [in Japan], and other names of this phenomenon are "angel's stairs, angel's stairway," "Jacob's ladder," "Rembrandt ray" and "light beams."

The names "Jacob's ladder" and "angel's ladder" come from the following description in the Book of Genesis (28:12): Jacob dreamed that there was a ladder set up on the earth, and the top of it reached to heaven, like the light beam through clouds; and the angels of God were ascending and descending on it [adapted from "Jacob's ladder" page of Wikipedia (English version, 5 December 2010 at 22:08)]. The name of "Rembrandt ray" comes from the fact that Harmenszoon van Rijn Rembrandt (1606–1669) liked to draw crepuscular rays.

From tweets of yesterday (edited by rephrasing, adding words, etc.)
About Astrophysics

"Japanese space craft misses Venus." A Japanese space probe on a £190 million mission to orbit Venus has missed the planet completely – but could be more successful when it next passes by in six years' time, scientists said. Telegraph (December 8, 2010).

About Books

"Not just a pretty face." physicsworld (December 6, 2010). —Review of the book: Shing-Tung Yau and Steve Nadis The Shape of Inner Space: String Theory and the Geometry of the Universe's Hidden Dimensions.

"Inside Penrose's universe." physicsworld (December 6, 2010). —A provocative review of Roger Penrose's Cycles of Time: An Extraordinary New View of the Universe.

"Archimedes coins 'Eureka!' in the nude—and other crazy ah-ha moments of science." Scientific American (December 7, 2010). —An excerpt from John Monahan's They Called Me Mad.

About Fluid Dynamics

"Physicists solve cloud formation puzzle." Clouds sometimes form more quickly than the laws of physics seem to allow. Now atmospheric physicists think they know how. Technology Review Physics arXiv Blog (December 7, 2010).

About Particle Physics

"Quark–gluon mania returns to CERN." physicsworld (December 7, 2010). —The task of interpreting the LHC's first year of data is far from over.