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Thread: Newton's Bucket?

  1. #1 Newton's Bucket? 
    Forum Cosmic Wizard
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    I got wondering after reading some of the threads on relative motion and the one on an absolute reference frame if there is any way to prove or disprove Newton's bucket hypothesis.
    So is there any way Newton's Bucket could be tested?


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  3. #2  
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    I am new to that Bucket too and was trying to make sense of it.

    All I could think was that if there was a massive object that approached the site of the bucket ( and departed) then the amount of(change of ) movement might be measured compared to the initial state without the presence of the mass.

    I think the idea might be that if all massive objects extraneous to the bucket system were removed altogether (ie the entire universe ) then the bucket would no longer move at all.

    Those are just my musings (mutterings?).I would be interested also in a proper explanation.


    Last edited by geordief; August 13th, 2014 at 07:35 AM.
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  4. #3  
    Forum Masters Degree Implicate Order's Avatar
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    Newton's Bucket whilst being a source of great debate between those subscribing to 'absolute space' versus the relativists, when the dust finally settled with Einstein bringing spacetime into the arena, the day was ultimately won by the relativists but there is still a degree of conjecture whether Mach's solution might still hold legs in an empty universe. At the moment Einstein's SR and GR provide a solution to what the water in the bucket is spinning relative to and that is spacetime itself, which is the only 'absolute' invariant that all observers will agree on irrespective of their motion.

    It is quite clear that Einstein was greatly impressed with Mach's view that the water was spinning relative to the average distribution of the content of the universe and this notion is effectively embedded partly in the principle of GR with the degree of spacetime curvature equating to the associated mass-energy distribution however where their views parted was in their interpretation of whether or not acceleration would be detectable in an empty universe. Mach's viewpoint was that in a universe devoid of all matter there is no average distribution to consider therefore no effects of acceleration would be observed for the bucket, whereas for Einstein, acceleration effects are still observed as the solution could still be found in SR whereby spacetime still 'exists' in an empty universe but spacetime is flat and therefore subject only to the special condition of SR......however this thought experiment is strongly suggestive that Einstein perhaps considered that spacetime had an independent existence and this is a bit of a dilema to the 'pure' relativists out there.
    Last edited by Implicate Order; August 13th, 2014 at 09:16 AM.
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  5. #4  
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    Thanks and is it reasonable to say that the thought experiment itself is unreasonable and that an "empty universe" has no basis in reality ?

    Or are there any approximations to that state (it doesn't seem to me to be similar to the "singularity" situations around the time of the Big Bang for example)
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  6. #5  
    Forum Masters Degree Implicate Order's Avatar
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    Quote Originally Posted by geordief View Post
    Thanks and is it reasonable to say that the thought experiment itself is unreasonable and that an "empty universe" has no basis in reality ?

    Or are there any approximations to that state (it doesn't seem to me to be similar to the "singularity" situations around the time of the Big Bang for example)
    My personal view is that the notion of an 'empty universe' can only really be solved once we have a solution for quantum gravity. While GR appears to be able to model this type of universe as a unique form of vacuum solution, it represents a spectral extreme to the Field Equation solutions that should be met with suspicion given that at the other end of the spectral extreme we have a singularity condition where GR breaks down. If the stress energy tensor goes to 0 we may obtain a flat universe however we know with QM that is impossible to reach an exact state of 0 energy due to HUP. Now of course I am neglecting to consider that there is intrinsic energy in spacetime itself with the contribution of energy from the gravitational field itself which according to GR appears to be the case. I really wrestle with this notion. QM certainly concludes that there is energy in the quantum vacuum so I shouldn't be surprised by that but it is still a spanner in the works for my mindset. Furthermore I am *probably deliberately* neglecting to consider a non-zero cosmological constant. Nevertheless if spacetime possesses an independent existence as modelled by SR and GR then we are left with the begging question of 'how was it created?'. Here we are as relativists dispatching the notion of the aether and 'absolute space' yet once again we are left resurrecting a notion of an independent spacetime that 'exists'. It sounds like we are half-pregnant.

    Philosophically it is easier to consider spacetime as simply being a way to express the relations between things but that is just convenience on my part. I am hoping with the emergence of a successful theory of Geometrogenesis that spacetime is deemed to be emergent and thereby relegate this current invariant into the ultimate 'variant bucket' arising from a broken symmetry from an underlying more symmetrical state allowing us to continue our search for a universe emanating from a 'nothing' state. At the moment however, mainstream consensus would conclude that if SR and GR ain't broke, then don't fix it.....which would be contrary to our resident mate MacGuyver who 'fixes shit that ain't broke'. :-))
    Last edited by Implicate Order; August 13th, 2014 at 08:15 PM.
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