On Jan 6, 2011, at 12:19 PM, Paul Zielinski wrote:
I think in one option he dispenses with GR but only in the sense that the large scale metric of spacetime is considered to be flat, with only intragalactic matter-induced curvature, rendering GR irrelevant outside the galaxies.
I have not read the paper in detail. 3D space is already flat in the standard cosmology. If he means 4D flat then that's very ad-hoc - not pretty. On the other hand, he claims Martin Rees endorses his model - I find that claim a bit odd. So I am waiting for the real experts to give their opinion. This kind of fitting of models to data can be very tricky and I personally do not have the time nor sufficient expertise to assess the claim.
Although he does seem to be leaning towards the conclusion that neither Newtonian theory nor GR are necessarily accurate in the intergalactic regions. If so he wouldn't be the only one, since we all know that modifications of the inverse square law are currently being entertained by a number of cosmologists in order to solve the "dark matter" problem.
My own opinion is that there is no attractive dark matter or repulsive dark energy problem at all. It's a pseudo-problem. / > 0 is simply because the density of virtual bosons exceeds the density of virtual fermion closed loops at large scale for the very simple elementary reason that virtual bosons anti-gravitate and closed virtual fermion loops gravitate. This is shown by John Peacock in "Cosmological Physics" and by Peter Milonni "Quantum Vacuum" using only battle-tested physics
1) Lorentz invariance
2) Equivalence Principle
3) Elementary quantum field theory - boson vacuum energy is positive with w = - 1, hence 3 x negative pressure
fermion vacuum energy is negative with w = -1, hence 3 x positive pressure
the sign of the gravity attraction or repulsion is ~ (energy density)(1 + 3w)
4) retro-causal hologram principle explains WHY the dark energy density is so small
past light cone dark energy density ~ (area/entropy of post-selected future light cone cosmological event horizon)
in a Novikov loop in time.
On Wed, Jan 5, 2011 at 6:32 PM, JACK SARFATTI wrote:
i posted this already yesterday on stardrive science news
I suspect the paper is not right. Ptolemy's epicycles fit the data at the time pretty well also. However, I have not had time to read it carefully. I still do not understand the basic picture the author is proposing. However he cites Martin Rees helping him so I am not ready to dismiss it as crank. His model seems to dispense with Einstein's GR hence my bias against it.
On Jan 5, 2011, at 6:16 PM, Kim Burrafato wrote:
From the paper's conclusions. Pretty straightforward.
1) The galaxies are attracted to each other by gravity, but there is another repulsive force which cancels it, perhaps called ”dark energy” or ”the cosmological constant”. We then need to explain the origin of dark energy and why it cancels gravity so exactly. This cancellation was apparently valid when the galaxies were closer together, so dark energy would have to follow the same inverse square law as gravity. Why does this repulsive force not show up inside the galaxies? While the observations are indicating zero force, the evidence for a new hitherto unknown force is perhaps not compelling.