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

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Koobee Wublee

Posts: 1,417
Registered: 2/21/06
Re: closed universe, flat space?
Posted: Apr 24, 2013 7:39 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

On Apr 24, 2:11 pm, Dan <dan.ms.ch...@gmail.com> wrote:

> Space can be 'closed' , and also , 'locally flat' , in the sense that
> the Riemann tensor vanishes ,or there exists ,for any point of the
> space, a non-infinitesimal spherical section around that point that's
> indistinguishable from flat space .


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>

> The only metric I can think of where the traveler in a straight line
> *must always* return to his starting point for every possible starting
> point is some sort of n-sphere, though it would have to have
> exceedingly small curvature to match experiments. It would be
> interesting to find another metric where this is valid, though I doubt
> another one exists .


Write down the metric for n-sphere please. <shrug>

> I for one think of the universe as infinite in extent, and mostly
> flat, though my reasons tend to be philosophical :
> Our world should be the most perfect, that is "the one which is at the
> same time the simplest in hypothesis and the richest in
> phenomena" (Leibniz) . And , like it or not, an infinite (and 'roughly
> isotropic') universe matches these criteria.


At least, you admit your own version of cosmology is purely
speculation. The so-called experts believe in their speculated
?reality? more whole heartedly. <shrug>


Date Subject Author
4/23/13
Read closed universe, flat space?
Rich Delaney
4/23/13
Read Re: closed universe, flat space?
Poutnik
4/24/13
Read Re: closed universe, flat space?
Shmuel (Seymour J.) Metz
4/29/13
Read Re: closed universe, flat space?
Rich Delaney
4/23/13
Read Re: closed universe, flat space?
kenseto
4/24/13
Read Re: closed universe, flat space?
JT
4/24/13
Read Re: closed universe, flat space?
herbert glazier
4/24/13
Read Re: closed universe, flat space?
Double-A
4/23/13
Read Re: closed universe, flat space?
Nicolas Bonneel
4/29/13
Read Re: closed universe, flat space?
Rich Delaney
4/29/13
Read Re: closed universe, flat space?
Mike Terry
4/23/13
Read Re: closed universe, flat space?
xxein
4/23/13
Read Re: closed universe, flat space?
Brian Q. Hutchings
4/23/13
Read Re: closed universe, flat space?
Butch Malahide
4/23/13
Read Re: closed universe, flat space?
Newberry
4/24/13
Read Re: closed universe, flat space?
Koobee Wublee
4/24/13
Read Re: closed universe, flat space?
dan.ms.chaos@gmail.com
4/24/13
Read Re: closed universe, flat space?
Koobee Wublee
4/24/13
Read space is locally curved, as has been measured
Brian Q. Hutchings
4/25/13
Read Re: closed universe, flat space?
dan.ms.chaos@gmail.com
4/25/13
Read Re: closed universe, flat space?
herbert glazier
4/25/13
Read Re: closed universe, flat space?
dan.ms.chaos@gmail.com
4/25/13
Read Re: closed universe, flat space?
bradguth@gmail.com
4/27/13
Read Re: closed universe, flat space?
Brian Q. Hutchings
5/4/13
Read Re: closed universe, flat space?
bradguth@gmail.com
5/5/13
Read Re: closed universe, flat space?
Brian Q. Hutchings
4/25/13
Read Re: closed universe, flat space?
Koobee Wublee
4/25/13
Read Re: closed universe, flat space?
dan.ms.chaos@gmail.com
4/25/13
Read Re: closed universe, flat space?
Koobee Wublee
4/25/13
Read closed universe, flat space, ignore Minkowski's worse nD geometry;
thank you
Brian Q. Hutchings
4/26/13
Read Re: closed universe, flat space, ignore Minkowski's worse nD
geometry; thank you
Brian Q. Hutchings
4/27/13
Read curved space and/or curved time (time is the "real, scalar" part of
vector mechanics -- like a God-am clock
Brian Q. Hutchings
4/27/13
Read Re: curved space and/or curved time (time is the "real, scalar" part
of vector mechanics -- like a God-am clock
Brian Q. Hutchings
4/27/13
Read Re: closed universe, flat space?
Tom Roberts
4/27/13
Read Re: closed universe, flat space?
Koobee Wublee
4/27/13
Read Re: closed universe, flat space?
Brian Q. Hutchings
4/29/13
Read Re: closed universe, flat space?
Rich Delaney
4/29/13
Read Re: closed universe, flat space?
dan.ms.chaos@gmail.com
4/29/13
Read Re: closed universe, flat space?
Koobee Wublee
4/30/13
Read Kepler uncovered the curvature via his three orbital constraints
(reciprocal of diameter)
Brian Q. Hutchings
4/30/13
Read Minkowski was an otherwise-great geometer!
Brian Q. Hutchings
5/1/13
Read Minkowski, Minkowski, Minkowski -- say it, againsville
Brian Q. Hutchings
5/1/13
Read Kepler's cosmological curvature thingies
Brian Q. Hutchings
5/3/13
Read Re: closed universe, flat space?
Rich Delaney
5/4/13
Read Re: closed universe, flat space?
dan.ms.chaos@gmail.com
5/4/13
Read Re: closed universe, flat space?
dan.ms.chaos@gmail.com
5/4/13
Read Re: closed universe, flat space?
dan.ms.chaos@gmail.com
5/5/13
Read Re: closed universe, flat space?
Koobee Wublee
5/5/13
Read eight to the bar -- Daddy!
Brian Q. Hutchings

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