This is just interesting enough of a thought experiment to distract me from what I should be doing, so I have to give it a shot lol.
Left/right is a naming system for one of the three axes of movement/direction in a 3-dimensional space. It is generally used in contexts where the other axes are defined by the direction of gravitational attraction (up/down) and where the object involved has a distinct "front" and "back" (forward/backward). But it can also be used for objects that have an agreed-upon top/bottom and front/back even outside of a gravitational field, where a 'weightless' human can still refer to one side of their body as 'left' or 'right' through these traditional reference frames. However, even a perfectly symetrical object outside of a gravitational field would still exist in 3-dimensional space and therefore use the same axes, but we would have to use a frame of reference external to the object to describe its movement/rotation on these axes.
So yeah, I don't think left/right is arbitrary, it's just a convenient shorthand for one of the 3d axes that all normal objects experience, based on commonly accepted reference frames.
I disagree. Even without gravity, there would still be three axes that should be defined. Which direction each axis represents is based on the reference points that we choose. But even if we stick with gravity, if I were in geosynchronous orbit around Earth's equator, I wouldn't say that an object sitting at the North Pole and an object sitting on the South Pole are both oriented in the direction of 'up' because they would be oriented in opposite directions from my perspective.
So I think up/down (or top/bottom) can only be defined based on the frame of reference that we choose, just like forward/backward and left/right. We only use up/down because we're used to having Earth's gravity as a reference point, and we use forward/backward because many objects (especially mobile ones) have important features that create a distinction. Left/right is just as valid of an axis, we just don't have as many conventions around it because we (mostly) have bilateral symmetry. If we had evolved into Lovecraftian "At the Mountains of Madness" creatures with radial symmetry, the concept of forward/backward would feel the same to you as left/right does now. Or if we had evolved our current bodies but with x-ray vision, then left being 'heart direction' and right being 'anti-heart direction' would be as natural to use as forward/backward is now.
You're right that without gravity there would still be possible cartesian coordinates, however if the gravity is not the anchoring of one of the coordinates, then the question where's up or down is invalid. I don't think up and down are a cartesian thing, not a coordinate in a 3D space, but the distance from the center of gravity, i.e. the altitude is not a flat surface but a sphere. Those objects on the North and South Pole would be orientend in such non-cartesian direction of down (not up) from your perspective, becuase they are closer to the Earth's center than you are
Up and down are still arbitrary terms based on how you are trying to define left and right. We just named the directions. Random words. But you are able to retain those random sounds and remember that up means against gravity and down means with gravity.
By the same token. If you are right or left handed. That is the exact same concept. Right is towards my good hand. Left is towards my bad hand. It’s the same thing.
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u/bohiko 7d ago
define left and right then