For example, to the occupants of the shuttle orbiting the Earth, it can look like they're traveling on a straight line through space.
例如，对于环绕地球的航天飞机内的宇航员而言，他们似乎是以直线方式在太空中运行的。
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This would be the "high ground" for any number of space operations, space manufacturing, construction and commercialization; it could be a "space dock" straight out of the Star Trek universe.
Relativity says that light always moves in a straight line through empty space, and always at the same speed in a vacuum, no matter what your observation point.