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Re: closed universe, flat space?
Posted:
Apr 25, 2013 9:35 AM


On Apr 25, 7:34 am, Dan <dan.ms.ch...@gmail.com> wrote: > > Let?s look at spacetime. According to GR, it is the curvature of > > spacetime that causes gravity. So, spacetime is curved around a > > gravitating mass. In free space, the Einstein tensor vanishes which > > means the Ricci tensor also vanishes which mean the Riemann tensor > > also vanishes. So, you have vanished Riemann tensor in curved > > spacetime. That means the curvature tensors really do not address the > > curvature thing. The field equations are merely differential > > equations that allow you solve the local geometry and nothing more. > > <shrug> > > http://en.wikipedia.org/wiki/Ricciflat_manifold > The Ricci tensor vanishing does not imply the Riemann tensor does . > > Also ,don't confuse space with spacetime . Space is only a 'slice' of > spacetime . In itself it can be flat, while still being in a curved > spacetime . The metric of space is threedimensional , and embedded > in the four dimensional metric of spacetime. Even factoring out the > gravitational effects (which predominantly affect the timetime > component of the metric tensor, not it's space components ) ,we still > have to consider the expansion of the universe . > > http://en.wikipedia.org/wiki/Metric_expansion_of_space > > Space can be predominantly flat (provided it's free from strong > gravitational effects) , while still being embedded in a curved space > time . > > > Write down the metric for nsphere please. <shrug> > > If the earth were perfectly round , you would return to your point of > origin when going around it . Generalize . Or better yet, use Google > to figure out the metric . > > > At least, you admit your own version of cosmology is purely > > speculation. The socalled experts believe in their speculated > > ?reality? more whole heartedly. > > First, don't underestimate the value of rational speculation .I > speculate that the sun will rise tomorrow . > All science has origin in rational speculation. > Second, the most commonly accepted model of the universe is flat (in > space) and infinite.Observations confirm > the universe 'flat with only a 0.4% margin of error' .http://en.wikipedia.org/wiki/Shape_of_the_Universe#cite_note2 > > ><shrug> > > I find it much easier to read your post with this image in mindhttp://www.bittersweetcandybowl.com/candybooru/_images/1b9e551d747b18... > > If you post had a point to make, I don't see it. <shrug>
It begs the question. What is more reality,space or time? TreBert



