A leading figure in scientific circles during the French Revolution, in 1792, de l'Ombre was tasked with measuring the length of the arc of the meridian from Dunkirk to Barcelona.

法革命期间科学界的重要人物，德·隆在1792年被委任测量从敦刻尔克到巴塞罗那的子午线弧长。

Well, if you stare at this picture, maybe, just maybe, you might notice that all the arc-lengths between the points of this circle seem to be about the same.

好吧，如果你盯着这张图看，也许，仅仅是也许， 你会注意到这个圆上各点之间的弧长似乎都差不多。

High in the heavens, certainly at an altitude of many miles, the flaming things swept across my view, comet-shaped and stretching over at least ten degrees of arc.

高悬于天际， 确切地说，在数英里的高空，那些燃烧的物体的视线，形似彗星，延展至少十度弧长。

When that angle is really small, the width is basically 1, and the height is basically the same as the arc length along the circle, which by definition is theta.

当那个角度非常小的时候， 宽度基本上是1， 高度基本上和圆上的弧长相同，根据定义这就是θ。