There are multiple ways to define a coordinate system for Earth coordinates; some are better for particular purposes than others.
有多种方式来定义地面坐标系统；有一些在某些用途方面比其他的更好。
2
Shapiro doesn't think it's necessary to invoke multiple universes or life-laden comets crashing into ancient Earth.
夏皮罗认为，没有必要援引多重宇宙或载有生命的彗星坠落到远古地球的事。
3
MESSENGER is now in the last stages of multiple gravity-assist flybys of Earth, Venus and Mercury, en route to an insertion into orbit around Mercury in March of 2011.