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In the left-hand image, an orbit would be a horizontal line, because it's a constant distance. So it's a mirror of the time axis, but translated upwards in spa
by jdmichal 6y ago
In the left-hand image, an orbit would be a horizontal line, because it's a constant distance. So it's a mirror of the time axis, but translated upwards in space. It would be exactly the same axis-mirroring translation in the other images. So, importantly, it would not be a line in the right-hand image.
- bweitzman 6y agoThe concept of a constant distance orbit doesn't make much sense in 1D. A horizontal line in this model wouldn't indicate an orbit, but rather a completely stationary object. It would then make sense for the world line to curved because it must be accelerating in order to resist the attraction of the body it's near. By definition, the world line of a stable orbit would be a line in curved spacetime.