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> What if the universe were entirely empty except for two astronauts. One of them is spinning, the other is stationary. The spinning one feels dizzy, doing cart
by vorg 9y ago
> What if the universe were entirely empty except for two astronauts. One of them is spinning, the other is stationary. The spinning one feels dizzy, doing cartwheels in space. But which one of the two is spinning? From either astronaut’s perspective, the other is the one spinning. Without any external reference, Einstein argued, there is no way to say which one is correct
There is a 50% chance each is spinning, and we'll know which is correct when an external reference "observes" them. The fact that there's no external reference is what makes this situation be "quantum". If the conscious astronauts are conceptually incapable of being 50% "feeling dizzy", then that would mean conscious beings also require the external reference in order to exist.
- phs2501 9y agoWouldn't the spinning one see the other "orbiting" rather than spinning? If gravity is not strong enough to cause that orbit and there's no thrust evident that could explain the delta-V causing the orbit, couldn't you then conclude that you're spinning without an external reference?
- styrophone 9y agoI think this thought experiment assumes the astronaut is spinning around an axis orthogonal to their belly. From the cartwheeling astronaut's perspective, the other one is also cartwheeling in their own plane.
- SomeStupidPoint 9y agoBut if you tuck in your knees and the other guy spins differently, that's a sign you're the one spinning, no?
- styrophone 9y agoYeah, the choice of a non-inertial reference frame for this example is a little confusing to me too. I also haven't been able to find an independent mention of the spinning astronaut experiment.
- dogma1138 9y agoNo because you technically performed an action which changes the system. Relativity states that there isn't a measurement you can take if you change the system however it's a different story.
- cobbzilla 9y agoThis example totally confused me. An object spinning in space experiences centripetal acceleration, relative to its own center of mass. For sake of example, let's say that instead of spinning in cartwheels, the one spinning astronaut is spinning like an ice skater. OK, which astronaut feels their arms being pulled outwards due to centripetal force, and which one has their arms hanging limply at their sides? Wouldn't that answer the question?
- trhway 9y agoin the model where inertia is a result of interacting with all the other gravitational fields empty Universe would mean no inertia and thus no centripetal force. (of course there is another model - that of Higgs boson - for which i haven't so far been able to find how it explains equivalence of inertial and gravitational masses and thus it is so far non-starter for me, i mean not the boson itself - that of course exists, i mean the boson's role in inertial mass story until of course the boson happesn to be the main carrier of the "gravitational charge" then all would fall nicely in place)
- cobbzilla 9y agoCorrect me if I'm wrong, but without the Higgs boson and its corresponding scalar field, the concept of mass/inertia does not exist. Without mass, can matter still exist? How would this "matter without mass" behave? My mind is close to exploding.
- trhway 9y agoimagine that there is only gravitational force in the Universe and the matter has only gravitational mass("charge"). Accelerating any given piece of matter with respect to all the other matter would cause propagation of change (ie. wave) in the gravitational field of the whole system (Universe). Wave is energy and to generate wave a work is required, ie. a force has to be applied to the piece of matter being accelerated - the requirement for that force is what we call inertia. Now of course the question - what is the carrier of that "gravitational charge". It would be great if Higgs boson was the carrier of that charge.
- deleted 9y ago[deleted]