Next they had to decide on a "natural" length. They chose one ten-millionth of the distance from the Equator to the North Pole.

接下来他们必须决定一种“自然的”长度，他们选择了从赤道到北极距离的一千万分之一，他们将它称作一米。

youdao

How do natural variations such as the changing day length make such profound alterations to physiology and behaviour?

昼夜长短之类的自然变化是如何对野生动物产生如此深刻的生理变化及行为变化呢？

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What excites ophthalmologists most, and what every lens-making company wants to achieve, is an “accommodating” lens that can change its focal length in the same way that a natural lens does.

最让眼科学家兴奋的，而且每一家人工晶体制造公司都想获得的，是一种“善于适应新环境的”晶体，能像天然的晶体一样改变它的焦距。

youdao

Springs have a natural length; x is measured from that length.

弹簧是有原长的,x 就是从这里起算的

耶鲁公开课 - 基础物理课程节选

It's possible to change the length of the entire tube on a natural horn, but only by adding lengths of tubing called "crooks, " or by switching one crook for another.

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