I've just read an interesting, but ultimately unsatisfying article in New Scientist about string theory and loop quantum gravity and how these two theories might agree with each other. This agreement may be a great mathematical achievement, but it is only that, because neither theory is testable.
I have blogged about string theory before (here). It imagines every particle in nature is made of a string (in 11-dimensions) and the waves on the string determine the properties of the particle. I admire its ambition, since it tries to explain all the particles, including the graviton, the particle assumed to be responsible for gravity, and tries to be a theory of everything, but it is really a theory of nothing, since it has so many variations you can pick whatever version agrees with what you are looking at, and it makes no specific testable predictions. The one sort-of prediction made, supersymmetry, has now been falsified by the LHC (see here).
Loop quantum gravity is the other popular theory and it is simpler and bolder. A great simplification of Einstein was that he made space-time dependent on the mass within it. A bit like making the stage one of the actors in a play. He did this because space-time is something you cannot directly see anyway, so it's fair game for tweaking and this process means that general relativity is neatly 'background independent': the background space-time is determined by the mass. Loop quantum gravity continues this simplification by saying that spacetime is quantised and so, as in commercial airflight, there is a minimum distance you can travel. Loop quantum gravity is neat but has not yet made a good testable prediction. In the article they claim bouncing black holes might be a test, and there are a lot of 'may's and 'might's, but this is not the same as a controllable lab test: how can you be sure you are seeing a bouncing black hole from afar and not a million other possibilities?
Neither of these theories address the huge observations anomalies we can see including anomalous galaxy rotation and cosmic acceleration which are crying out for attention. Both theories focus on the big bang and distant black holes, as if they are afraid of a more down-to-Earth test. Common sense says we need to learn to fix the bathroom tap (eg: galaxy rotation, flybys, emdrive) before we tackle the plumbing on Pluto (eg: the big bang and black holes).
There is a theory that in some sense looks a bit like both these, but it has not come from a theoretical approach. It has come from paying attention to the anomalous observations that the mainstream ignore. This theory is MiHsC/quantised inertia/horizon mechanics (three names, take your pick!). In this theory, incomplete as yet, particle properties (inertial mass) depend on whether the Unruh waves they can see fit inside horizons. This is similar to string theory's waves on strings, but without needing to invent new waves and seven new dimensions! Quantised inertia also has the background independence of loop quantum gravity in that the behaviour of masses determines their space: an observer's acceleration creates horizons that determine what space is for that observer and that leads back to mass. Plus quantised inertia has no lack of tests, predicting galaxy rotation, its redshift dependence and cosmic acceleration perfectly and simply.
In summary, the New Scientist article is interesting and informative, but far too theoretical, as is all of mainstream physics. Too much theory is a mistake: history shows that new physics always comes from thinking about new observations, because the cosmos' imagination is far better than man's.
References
Cartright, J., 2017. When loops become strings. New Scientist, 11th March 2017.
16 comments:
The MiHsC looks best for me, not only because it's already well established (thought somewhat difficult to remember) acronym (it also contains initials of your name, did you even realize it?) - but quantized inertia is the theorem of all quantum gravity theories, i.e. nothing specific. And horizon mechanics denomination could become downright misleading very soon, as your own derivations indicate, that the expansion of Universe has its origin in very local phenomena (inhomogeneity of space-time).
String theory is inconsistent theory, because it's based on assumption of Lorentz symmetry and existence of extradimensions (which would manifest itself just by breaking of Lorentz symmetry). Not surprisingly such a theory is not able to predict anything testable, as it leads into wast landscape of possible solutions. Even the scope of its predictions is significantly off, as the extradimensions manifest itself at much larger scales, than the Planck length.
More than one generation of physicists has been lost chasing the intellectual allure of string theory. What a waste of talent. Periodically physics turns from the empirical science which it is, into philosophical ruminations in coffee houses (maybe they should chosen the more earthy beerhouse like Einstein).
It is hard to understand how so many people with high intellectual ability have been so co-opted. Perhaps the idea of getting one's hands dirty in the thorny reality is not as alluring as mental gymnastics in a virtual world of imagined perfection. The situation is reminiscent of Saint Thomas Aquinas and religious scholars of the past trying to calculate how many angels could dance on the head of a pin.
Mental gymnastics and philosophical concepts certainly have a place in intellectual endeavor. They are however not science as defined in the Scientific Method. The Scientific Method was the concept that allowed us to make earthly progress by abandoning Sophist and Religious methods when it came to problems in the real world.
I suspect that one reason for the lost generation(s) is due to the fact that the Scientific Method is not taught in schools. I understand how this could come about in the school environment where political correctness, personal relationships, and apples for the teacher are given far more weight than actual ability and performance.
While it is easy to understand the forces that have driven the Scientific Method off the educational stage, that does not mean that non-sense is science, progress will be likely, or that wishing it was so philosophically will cause it to be so in actuality. There is nothing wrong with building castles in the sky, just as long as you do not try to move in.
Keep up the Good work!
Jimmy Johnson
I pick Horizon Mechanics. It rolls off the tongue easier.
Untestable theories are no different to belief systems. Their apparent validity comes from a belief that mathematically robust models describe reality, even if we can't test them them yet. Perhaps this belief derives from Dirac's success in predicting antimatter. The positron emerged as a consequence of the math and was subsequently discovered, however, I am unaware of any similar successes. Maybe Dirac was fortunate, perhaps too fortunate.
String theory and Loop Quantum Gravity are interesting mathematics. Maybe Horizon Mechanics will finally make them testable...
Zephir: I chose the name MiHsC objectively (standing for, of course: Modified inertia from a Hubble scale Casimir effect). It nicely emphasises the physical process, but to me the word MiHsC also had the connotation of being a 'miscellany' of things not usually mixed together (relativity and q. mechanics), and also something seen as from afar through the 'mist'. These reasons are becoming less relevant now as the theory is becoming more coherent and slightly clearer, and horizons are becoming more central. It may also be true that it appealed to me subconsciously because of its similarity to my name but that was not deliberate.
Jimmy: Good comment. The age is becoming an ideological one, and I don't know why. Maybe as you say it is education, but I think it may go deeper. For the ancient world too, the scientific era lasted only 400 years. Maybe as soon as societies become comfortable and detached from physical work, either with slaves in ancient times, or today with computers, inquiry also becomes too detached.
Mike: Regarding ideology, I believe it's due to the increased magnitude of communication (and the rapid nature of that communication) that the internet has brought about. This instant communication leaves no room for detailed thought or reflection on mooted ideas. 100 years ago, it might take years for a consensus to form (scientific or otherwise), but these days it can happen in hours or days. So inevitably such short term consensi are based around initial gut feelings, and immediate emotional reactions. It doesn't bode well, in my view.
Matthew: I can see that. Technology has isolated people from nature, and as you say has put them more in contact with each other. The result is a mental goose-step.
Herd instinct has always been around. Rapid communication just makes it quicker to organize. Vanguards of new ideas will always find the isolation they need, if so desired. A friend once called it "the philosopher's curse".
"Too much theory is a mistake: history shows that new physics always comes from thinking about new observations, because the cosmos' imagination is far better than man's."
That's a lesson that can never be repeated too often...shame it's too long for a tattoo!
qrall: I suppose you're right, I do hope so. My worry is that something akin to a phase transition in society's thought occurs. When ice begins to freeze, you get the odd crystal (lockstep herd thinking) occurring, but then as the temperature creeps a little lower, suddenly it will all freeze.
Hi Mike
Ok, how does this fit in with Horizon Mechanics?
https://phys.org/news/2017-03-dark-influential-galaxies-early-universe.html
http://www.nature.com/nature/journal/v543/n7645/full/nature21685.html
Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago
Abstract
In the cold dark matter cosmology, the baryonic components of galaxies—stars and gas—are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark-matter halo1. In the local (low-redshift) Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius—a hallmark of the dark-matter model2. Comparisons between the dynamical mass, inferred from these velocities in rotational equilibrium, and the sum of the stellar and cold-gas mass at the peak epoch of galaxy formation ten billion years ago, inferred from ancillary data, suggest high baryon fractions in the inner, star-forming regions of the disks3, 4, 5, 6. Although this implied baryon fraction may be larger than in the local Universe, the systematic uncertainties (owing to the chosen stellar initial-mass function and the calibration of gas masses) render such comparisons inconclusive in terms of the mass of dark matter7. Here we report rotation curves (showing rotation velocity as a function of disk radius) for the outer disks of six massive star-forming galaxies, and find that the rotation velocities are not constant, but decrease with radius. We propose that this trend arises because of a combination of two main factors: first, a large fraction of the massive high-redshift galaxy population was strongly baryon-dominated, with dark matter playing a smaller part than in the local Universe; and second, the large velocity dispersion in high-redshift disks introduces a substantial pressure term that leads to a decrease in rotation velocity with increasing radius. The effect of both factors appears to increase with redshift. Qualitatively, the observations suggest that baryons in the early (high-redshift) Universe efficiently condensed at the centres of dark-matter haloes when gas fractions were high and dark matter was less concentrated.
https://www.sciencenews.org/article/distant-galaxies-lack-dark-matter-study-suggests
One more clue. @Mike, afair, you did wrote on that matter some month ago.
qraal & czeko: This is exactly the sort of data I need. MiHsC is the only theory that predicts a link between cosmic size and galactic spin, so I will be looking at this over the next few days. A complication is that these systems seem to be turbulent.
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