The discovery of gravitational waves follows closely on the Higgs boson affair, and marks a grave watershed in the story of science. In essence, the scientific method has been redefined, and consequently, many of the words in the scientific lexicon change their meaning too. One of those words is discovery, which changes its meaning in line with the earlier redefinition of physics. I try not to quibble about cosmology because it would be no more than an expression of my uncertainty regarding the really big answers. That said, Id like to turn to my query to the CMBR, because my concern is really about methodology. Specifically, I wonder about ambiguity. If a model predicts a uniform, circumextant radiation fog in the microwave band, it is in some sense testable. However,the question remains: Is the models prediction that explicit that observation of the so-called CMBR can be accepted as a solution to that particular model, to the exclusion of competing solutions? At a fundamental level, observation of the microwave background (or backgrounds in any of the other wavebands) is simply evidence of surrounding radiation at that wavelength, nothing more. Linking the observation to a particular model ought to be thoroughly robust, in my view. I consider the CMBR patterns to be indirect observation because any connection to the Big Bang is hypothetical. Indeed, the BB itself is hypothetical. The connection to the Big Bang is a critical assumption. Without it, the image of gravitational waves is in fact just a spurious pattern in the microwave power spectrum. It is model-dependent physics, something I remain extremely uncomfortable with. Late last year, Hendrik Schatz et al published results in Nature announcing the discovery of nuclear cooling in the subsurface crust of neutron stars. They are quite explicit, and the word discovery passed rigorous peer review. No doubt is left in the mind of a reader that these scientists have seen evidence of nuclear cooling in a neutron star. Excerpt from Stephen Hawking Smoked My Socks ((c) Hilton Ratcliffe, Muse Harbor Publishing, 2014): The great danger in theoretical modelling lies in the seductiveness of having one’s personal opinions raised to the level of universal relevance. Before long, theorists start to believe that what they imagine is actually real, and that the novel products of their conjecture may legitimately be termed “discoveries”. In more arcane realms of science, this sort of delusion is rampant, and syncopated thoughts are called discoveries without embarrassment or shame. A recent announcement by the well-respected science forum Phys.org is a pertinent example of what we talking about. The press release was greeted with enthusiasm in world of theoretical astronomy. Cosmologists were happy. Here is an excerpt: “Nuclear cooling in neutron stars deepens mystery of hot surface “Writing in the journal Nature, Hendrik Schatz and colleagues describe a newly discovered process that happens within the stars crust, located just below the surface. Until now, scientists thought that nuclear reactions within the crust contributed to the heating of the stars surface. ’We previously thought that these reactions were strong enough to heat up the crust,’ said Schatz, an MSU professor of physics and astronomy. ’But thats not the case.’ “What the team of scientists found is that in the stars crust near the surface there is a layer where nuclear reactions cause rapid neutrino cooling. Neutrinos are very elementary particles that are created through radioactive decay and pass very quickly through matter.” Reading the quoted passage, I am given the strong impression that these gentlemen have actually discovered something in the crust of a neutron star. They are talking as if they have studied an event on an actual neutron star, and that it increases our understanding of these mysteriously fascinating cosmological objects. As an astrophysicist intensely interested in neutron stars and with privileged access to the literature surrounding them, I know that the assertion being put forward by the authors of the quoted study is patently false, and it tweaks the word discovery in a terribly misleading way. It is crucially important to emphasise that the discovery of nuclear cooling in a neutron star is not an empirical event, but merely a nuance of the developing model, seen nowhere but on a computer screen. I think the issue is that the discovery was not made on a neutron star. No discoveries have ever been made on a neutron star. Apart from an ambiguous spectral signature assigned to them by the developers of the model, they have never been observed, much less studied in detail. It is just a model, with arbitrarily tunable parameters. Thats fine, but they should make it clear in their announcement. I would suggest that theorists would serve us better if they referred to observational data in developing models of hypothesised entities. The Sun is potentially a candidate progenitor of a neutron star, and what happens on the Sun can guide us in trying to imagine what would remain after the end game of a normal star.
Posted on: Thu, 20 Mar 2014 06:26:47 +0000
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