Has Gravity Probe B been a waste of money?

[Garth]

Yep, it's turtles all the way down.

Perhaps the last turtle is standing on the first?

 

[Garth]

, don't just 'tell us what your theory is', also tell us what 'analysing the best available data, we find that our model is consistent, and estimates of the key parameters are {list, inc error bars, with a statistical metic}.'

Sorry my quip about drinking to that was in response to your previous post. I take this post seriously and say I'm working on it - but I could do with some help! Perhaps the work will never be completed, or perhaps if GPB comes up trumps for SCC others will take on the baton!
Garth

 

[turbo]

Perhaps the last turtle is standing on the first?

Good one!

 

[Chronos]

I do not know where your concept of the SCC universe came from. In the Einstein frame it expands linearly, more slowly than the GR model R(t) =t, and does not contract at all, in the Jordan frame it is static R(t) = Ro. An expanding universe with fixed rulers is replaced by a fixed universe and shrinking rulers. Garth

I may have misinterpretted what SCC was saying. I read it to mean there was no exponential expansion of the early universe. On that point I disagree. It is very difficult to avoid an expansion model that makes any sense. I don't see where an Einstein frame expands or contracts, until you add a cosmological constant.

 

[Garth]

I may have misinterpretted what SCC was saying. I read it to mean there was no exponential expansion of the early universe. On that point I disagree. It is very difficult to avoid an expansion model that makes any sense. I don't see where an Einstein frame expands or contracts, until you add a cosmological constant.

Okay - the presence of the scalar field and the violation of the Equivalence Principle - it is replaced in SCC by the postulate of the Principle of Mutual Interaction (PMI)* - results in a different, though related theory to GR. The Friedmann equations are modified and the SCC cosmological equations have to be solved from scratch. The result is, in the Einstein Frame of measurement in which particle masses are conserved, that the universe expands strictly linearly R(t) = t. This model has already been examined by the Indian team mentioned elsewhere and it is surprisingly concordant with cosmological constraints. It does not need Inflation, there are no horizon, density or smoothness problems in this model, as there are in the GR models, for Inflation to 'fix'. In that sense it requires less extra hypotheses than the standard theory. It does make sense, I find it is Inflation that is difficult to make sense of, especially as the Higgs boson is so elusive!
Because the cosmological field equations have changed these results are obtained without adding a cosmological constant, although it depends how you define the scalar field, its effect could be interpreted as such. The scalar field is that which endows particles with rest energy, or (rest) mass, it is all gravitational potential energy, the work necessary to 'lift' the particle 'out of the Big Bang'. You may not like or agree with these postulates, it is only a suggested alternative gravitational theory but it does work and it is testable, hence the value for me of the GPB.
- Garth

* The PMI :- "The scalar field is a source for the matter-energy field if and only if the matter-energy field is a source for the scalar field."

 

[Chronos]

Thanks Garth. I think I get it now. I ran across this rather bold paper the other day. For some reason, it got me to thinking about SCC. You may find it amusing.
http://arxiv.org/abs/gr-qc/0406023

 

[Garth]

Thanks Garth. I think I get it now. I ran across this rather bold paper the other day. For some reason, it got me to thinking about SCC. You may find it amusing.
http://arxiv.org/abs/gr-qc/0406023

Chronos thank you, I have already downloaded that paper when it first came out on the arXiv but I must confess I have not had the time to study it and do it justice.

There are one or two points of contact with SCC. The implication that GR does not fully include Mach's Principle, and therefore GR has to be revised, is one thought; and the cosmological preferred frame of reference another albeit a related one.

My point I have made elsewhere in these forums is that the basis of SR is "no preferred frame of reference", which manifests itself in GR as the Equivalence Principle and the conservation of energy-momentum. However SR is formulated for an empty universe, flat space-time. As soon as you put matter into such a universe you can select a preferred frame of reference, the Centre of Mass/Momentum of that matter! So as soon as you introduce gravitational fields the basic premise falls down. In SCC the field equations are manifestly covariant, however in order to solve them you have to select a frame of reference, normally for convenience the Centre of Mass/Momentum of the system. In SCC, as soon as you do this, then, in its Jordan conformal frame, energy is locally conserved. In the Einstein frame, which is canonical GR, this feature is lost and it is energy-momentum that is conserved as normal.
As Unnikrishnan points out in his paper this preferred Machian frame of reference also identifies an absolute time, and therefore, as he says, introduces a second Mach's principle for time. (But I would see the two MPs as one)
-Garth