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Well twelve years later we are no nearer understanding what DM is... Not found in any detector nor in the LHC... My guess would be it is a scalar field, but then what do I know? Garth

O yes! I am really looking forward to drinking some yesterday! :smile: Garth

Such as:- Cosmic Conspiracies, 2 April 2006, Natural Dark Energy[Natural Dark Energy ,30 March 2007, Down-sizing Forever, 31 March 2008, A Farewell to Falsifiability, 1 April 2015, Garth :oldwink:

The clue lies in the date of publication on the web and the author's name!😉 Garth

A new kind of radio transient: ERBs arXiv:1903.12412v1 [astro-ph.HE] 29 Mar 201 Another fascinating paper by Ali Frolop et al. in yesterdays arXiv: Garth :oldwink:

Fair enough, they don't actually travel; perhaps 'teleport' might be a better word! As I said, at the interface of gravitation and quantum mechanics confusion often reigns, only to be resolved when a quantum gravity theory arrives. Garth

Confusion often arises at the interface of gravitation and quantum mechanics. Gravitational forces are transmitted by virtual gravitons as electromagntic forces are transmitted by virtual photons. And in the weird world of QM such particles travel faster than light, as Peter said, in apparent...

So the next obvious question is 'where do they (gravitons) originate?' Garth

It is published in a peer reviewed journal here: Cosmological evolution of the Higgs boson’s vacuum expectation value From that journal's webpage: Garth

Nevertheless the Age Problem in the early universe appears to remain, as does the tension between the CMB derivation of Hubble's Parameter and that derived from weak lensing KiDS-450: testing extensions to the standard cosmological model. The 'Coasting Model' may indeed have problems but it also...

We have discussed here on PF the question of whether there is an Age Problem in the early universe for many years now, since 2005: Is there an Age Problem in the Mainstream Model? (Oct 2005) Cosmic age problem ? (Nov 2008) Is There An Age Problem In The Early LCDM Model? (Jun 2010) Massive...

But there are other reasons to work on alternatives. Testable science requires alternative models for the standard model to be testable against. Although that is difficult when the standard model is as flexible as Inflation. A less flexible alternative that also passes observational tests...

It does seem that we live in a favourable 'cosmological time zone' in which the universe is old enough for intelligent beings to evolve and discover cosmological history and yet not too old that the neccesary information (CMB etc.) has become undetectable... Garth

May we have the references to the papers you quote? Garth

As I have said in other threads you might be interested in the Introducing the Dirac-Milne universe paper. It has great problems, though it does explain the matter-anti-matter asymmetry. Garth

I am imagining theories in which G may vary - such as in the Brans Dicke theory or in which atomic/particle masses may vary such as in Hoyle's...

I agree, I was not introducing any new physics here, just defining a second by two different methods, using two different physical processes to define two different clocks, but ones that would not remain synchronised. I mean that as measured by a gravitational clock, that defined in my post as...

I would like to make a few observations. In order to measure a clock drift you need two different types of clock that run on different physical principles. If part of the Pioneer anomaly is caused by a clock drift then there would be a discrepancy between the 'atomic clock' (the period of the...

May it be that the aliens are silent because they are sensible? - That is the ones that are sensible enough to manage to survive the technology crisis and not wipe themselves off the face of their planets. These would be sensible enough to have sustainable technologies, sustainable over...

Sending signals might turn out to be a pretty risky business, you never know who might turn up! Having said that we have been broadcasting powerful radio and tv transmissions into the aether for some time now (not to HD 164595 though)... wait, on second thoughts that explains why nobody has...

Hear me now? 'Strong signal' from sun-like star sparks alien speculation Interesting... Wait though With only one signal you just can't tell, and it certainly doesn't come up to scratch as "Extraordinary claims require extraordinary evidence.". It might have been just the cleaner in the...

Why is the Sun important? Because we are observing these exo-planets and at these distances we are to all purposes co-incident with the Sun. Garth

Most exo-planets have been discovered by transits, but that requires the planet to pass between Sun and the parent star, for the Sun to lie in the plane of the exo-planet's orbit, which is only a small percentage of the total. The Sun is not thought to be in the plane of Proxima b's orbit...

More on the James Webb telescope and observing the planet: Prospects for Characterizing the Atmosphere of Proxima Centauri b. Garth

This eprint today suggests even a thin atmosphere is sufficient to prevent this happening to Proxima b: Tutorial models of the climate and habitability of Proxima Centauri b: a thin atmosphere is sufficient to distribute heat given low stellar flux. Garth

There are a number of interesting papers on today's physics ArXiv: The habitability of Proxima Centauri b I. Irradiation, rotation and volatile inventory from formation to the present The habitability of Proxima Centauri b II. Possible climates and observability Exploring plausible formation...

What I am saying is that, without evidence, the hypothesis of a multiverse based on the assumption of the characteristics of this universe being determined solely by a stochastic process is not good science. And I'm not the only one Are Parallel Universes Unscientific Nonsense? Insider Tips for...

Really? I would have thought any scientist would have said the fact that we can presently observe our universe (unique or not) but not any others would be quite a good reason... Garth

Agreed - but that is a big "if". Primordial B-Mode polarisation in the BICEP 2 data perhaps? :wink: Garth

In which case I would not call such galaxies beyond our light cone "devoid of observational evidence". Exactly what observational evidence is there for other universes? Garth

Not because it doesn't lead to a multiverse but because the symmetry breaking process might have been explicit. We haven't observed any of the other universes of the multiverse. Therefore, if we explain features of the early universe simply by chance, by the stochastic process of spontaneous...

Obviously spontaneous symmetry breaking events take place, it's just when they are invoked in speculative theory about the very early universe to "predict" the existence of a multiverse that I have reservations. Its not that I don't like the implication of a multiverse, it's just that I think...

Cosmologists certainly do take spontaneous symmetry breaking in the very early universe seriously and the concept of it being 'spontaneous' (in other words stochastic - 'by chance') is contingent on there being an infinite ensemble of other possible outcomes that inevitably lead to the concept...

Reference?

The 'Bullet Cluster' showed DM still associated with the visible matter after two galaxies that had 'colllided', that is the two galaxies passed through each other but with a X-ray source that had been left between them. This is interpredted as the non-interacting DM staying with the stars of...

We may indeed have to modify the theory; one unexplained feature of the standard \LambdaCDM model is the presence of several puzzling coincidences. The energy density of the cosmological constant is of the same order of magnitude as the density of matter today: \Omega_M \sim \Omega_\Lambda ...

The negative findings of the Large Underground Xenon (LUX) dark matter experiment, which is a 370 kg liquid xenon time-projection chamber that aims to directly detect galactic dark matter and which were published at the international dark matter conference in Sheffield, UK, raises questions...

The standard formula for mass transformation under a conformal transformation: {g*}_{{\mu}{\nu}} = \Omega ^2 g_{{\mu}{\nu}} is {m}* = \Omega^{-1} m. See for example Cosmological Models in a Conformally Invariant Gravitational Thgeory Its just basic physics, the Bohr radius of an atom being...

I agree but some might say that about the \LambdaCDM theory, what with the undiscovered dark sector, the coincidence problems - \Omega_M \sim \Omega_\Lambda , \Omega_m + \Omega_{DM} + \Omega_\Lambda = 1 , Age of Universe = H-1, and built on GR which has proved so far incompatible with quantum...

The conceptual question behind VSL is how are are time and space measured? A natural consequence of SR's assumtion that there is a space-time continuum is to set c as the conversion factor between time units and distance units; its value depending on whatever arbitrary system of units you...

BH's have been suggested as DM before, they would be a form of MACHO. It is generally thought that not enough micro-lensing events have been observed to verify the existence of such objects. However there is a window of possible mass for IMBHs in which their larger masses would require a low...

The TeVeS theories were proposed after MTW was published and are not inconsistent with solar system tests, papers can be found here: The Tensor-Vector-Scalar theory and its cosmology and A tensor-vector-scalar framework for modified dynamics and cosmic dark matter except, as that latter paper...

But the paper discusses whether photons with a small mass could explain Dark Energy not Dark Matter. The original question was confused, yes, and if such photons are thought to be DM, not DE, then that, as Hot Dark Matter, has been ruled out. Basically HDM wouldn't clump as required to form the...

We can do a bit better than that with the original question. Photons are generally thought of as massless although some heterodox theories such as that discussed in Massive Photon and Dark Energy suggest they may have a small mass: Let us limit our discussion to that paper, which should...

Actually energy-density is frame dependent; it is the energy-momentum tensor that is frame independent and conserved w.r.t. covariant differentiation: T^{\mu}{\nu}{;\mu} = 0. The energy-density is just the T00 component of this tensor T{\mu}{\nu} . In order to extract this component of the...

Energy is a frame dependent concept. For example: The Apollo spaceship hurtling towards the Earth had a large kinetic energy as measured in the Earth's frame of reference which had to be dissipated by the heat shield when it decelerated before splashing into the ocean. However as measured by...

You can read Adam Reiss et al.'s paper on the physics ArXiv here:Abstract A 2.4% Determination of the Local Value of the Hubble Constant and .pdf paper. Garth

You will find the paper on the physics ArXiv here:ALFALFA Discovery of the Most Metal-Poor Gas-Rich Galaxy Known: AGC 198691. Garth

What a loss - a truly inquisitive mind - a great loss to PF and to me personally, tamwuff please pass on all our condolences to your family. Garth

Following on from Chalmoth's comment, we can also add that as a logical tautology time can only pass at "one second per second" for any particular observer. Relativity deals with the measurement of time in one observer's frame of reference as measured by another observer in a different frame of...