I understand the concept of spacetime being warped (I’ve seen the rubber sheet analogy a thousand times), but does that mean that everything is *technically* always traveling in a straight—albeit warped—line?
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Everything that is operating solely under the influence of gravity is moving in a straight* line. The Moon orbiting around the Earth, for example. However, if there is anything else acting on it, it is no longer moving in a straight line. If you are sitting in a chair, the upward force from the chair causes your worldline to curve relative to spacetime.
*We use the term ‘autoparallel’, because ‘straight’ can have different meanings when the geometry is curved
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