Spend enough time defining and refining the frame list before you start developing the individual frames: it is best to get the story straight in plan text before adding the images.
Since this frame of reference-the earth –is rotating, motions that would be straight in a stationary frame of reference appear curved to the observer on earth.
由于参照系—地球—是旋转的，所以在静止参照系中应是呈直线运动，在地球上的观测者看来就成为曲线运动。
3
These enable use of a straight forward post and beam gravity frame, immediately legible in its simplicity.