Re: [Phys-L] Fwd: [PTSOS] spacetime simulator: flexible conduit?

["Anthony Lapinski" <Anthony_Lapinski@pds.org>]

Nice informative video of curved spacetime!

Anyone know what's under the blue spandex sheet? Some kind of raised
circular platform? It's not a table as he goes underneath to place a PVC
pipe. And where does one purchase such a large sheet?

Phys-L@Phys-L.org writes:
> In the context of
>  http://www.youtube.com/watch?v=MTY1Kje0yLg
>
> On 07/17/2012 01:03 PM, Bernard Cleyet wrote:
> > I don't understand how this is a space time simulator?  I though it
> > was simply an (approximate) inverse square model (1/r, potential),
> > nothing to do w/ special relativity.
>
> (and/or general relativity)
>
> > bc needs to go back to school?
>
> BC is being ultra-polite.  The trampoline model represents a serious
> misconception as to the structure of spacetime and the relationship
> between curvature and motion.  
>
> Here's a three-sentence proof of what I am saying:  Deform the trampoline 
> upward instead of downward.  The intrinsic curvature would be the same
> and the geodesics would be the same, so the prediction of real general 
> relativity would be the same.  However the trampoline demo makes opposite 
> predictions about the motion.
>
> A much more apt model of motion in curved space can be found here:
>  http://www.av8n.com/physics/geodesics.htm
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