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Topic: closed universe, flat space?
Replies: 48   Last Post: May 5, 2013 2:45 PM

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 herbert glazier Posts: 192 Registered: 7/26/10
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/Ricci-flat_manifold
> The Ricci tensor vanishing does not imply the Riemann tensor does .
>
> Also ,don't confuse space with space-time . Space is only a 'slice' of
> space-time . In itself it can be flat, while still being in a curved
> space-time . The metric of space is three-dimensional , and embedded
> in the four dimensional metric of space-time. Even factoring out the
> gravitational effects (which predominantly affect the time-time
> 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 n-sphere please.  <shrug>
>
> 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 so-called 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_note-2
>

> ><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