Re:Why Understanding Space Is So Hard (2016)
by trevyn on Sunday January 21, 2018 @03:43PM
(#16199902)
>What pulls the rope taut?
Ok, this seems to be a clash of intuitions explained by reference frames —
When you imagine an object in deep space or its own empty universe, you intuitively use an “inertial reference frame”, where “the physics of a system in an inertial frame have no causes external to the system”. I.e. you do not see any “fictitious” forces like the centrifugal force, so the rope would not be taut.
If you are imagining the rope to be taut, you are imagining a force pulling it taut, but this force that you’re imagining is only explained by physics if you’re using a rotational (non-inertial) reference frame.
So if your system has unexplained “centrifugal” forces, those forces can be modelled as the system rotating within an inertial reference frame, without having any evidence of any “non-rotating” matter.
It just so happens that deep space is pretty close to an inertial reference frame, so your mind sort of makes that assumption.
Or, in other words, you could measure and perceive the rate of the rope’s rotation by analyzing the forces in system, without having any physical external point of reference.
Ok, this seems to be a clash of intuitions explained by reference frames —
When you imagine an object in deep space or its own empty universe, you intuitively use an “inertial reference frame”, where “the physics of a system in an inertial frame have no causes external to the system”. I.e. you do not see any “fictitious” forces like the centrifugal force, so the rope would not be taut.
https://en.m.wikipedia.org/wiki/Inertial_frame_of_reference
If you are imagining the rope to be taut, you are imagining a force pulling it taut, but this force that you’re imagining is only explained by physics if you’re using a rotational (non-inertial) reference frame.
So if your system has unexplained “centrifugal” forces, those forces can be modelled as the system rotating within an inertial reference frame, without having any evidence of any “non-rotating” matter.
It just so happens that deep space is pretty close to an inertial reference frame, so your mind sort of makes that assumption.
Or, in other words, you could measure and perceive the rate of the rope’s rotation by analyzing the forces in system, without having any physical external point of reference.