Arcadian Functor

occasional meanderings in physics' brave new world

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Marni D. Sheppeard

Tuesday, August 04, 2009

The Farce

What counts as an explanation in physics? Consider an historical example. The energy distribution of beta decay is explained by Pauli's hypothesis, based on the principle of conservation of energy, of the existence of the neutrino.

The key words in this example are hypothesis and principle. What counts as an hypothesis? Do we allow ideas that (a) permit more paper publications, and hence career advancement, because they are based on equations that we already know, or (b) consider hypotheses that follow from the principle?

Now what counts as a principle? Do we (a) demand the data be fitted to a mathematical curve as quickly as possible, lack of explanations notwithstanding, or (b) consider carefully which established fundamental concepts are inviolable, and which are not?

The energy distribution itself is neither an hypothesis, nor a principle, but that which must be explained. Lest we forget.


Blogger L. Riofrio said...

Funny how hypotheses gain the force of law with some people. The "faint young Sun" hypothesis is not supported by geological evidence, yet some treat it as fact.

Einstein was quite specific that a constant speed of light was a "stipulation, which I make at my own discretion.". He also worked on theories where changes!

August 04, 2009 11:12 PM  
Blogger Kea said...

Louise, I hope you are enjoying Rio!

August 04, 2009 11:29 PM  
Anonymous bob Coecke said...

Re: "permit more paper publications, and hence career advancement" One should be careful not to trow out the baby with the bath water. Dissemination and disseminability, and hence communication, are at the core of scientific progress. I can't see how a discussion of what counts as a useful hypothesis can be done without reference to the community one addresses, the language and paradigms they use, and the modes of communication and information gathering and access they have established. While obviously these things can be far from ideal and sometimes degenerate, referring to publishing papers merely as career advancement is a bit of an insult to those that put substantial effort in producing papers that provide compelling arguments in a language that makes sense to those one addresses. This may then, eventually, lead to paradigm shifts, language shifts, and maybe even the status of hypothesis and what counts as empirical data.

August 04, 2009 11:51 PM  
Blogger Kea said...

I suppose people are free to transfer comments about radically new cosmologies, or other new physics, to publications in completely different fields, if they really want to. Anyway, Louise's theory is published.

August 04, 2009 11:55 PM  
Anonymous Anonymous said...

Actually, Louise's 'theory' is no theory at all, but just a hypothesis. Even if the acceleration of the expansion rate were due to a variable speed of light, there is no explanation of why the speed of light should vary, nor why it should vary in just the way she claims. Such an explanation would be important because a non-constant speed of light means that the laws of electromagnetism are also non-constant. It also means that energy is not conserved. Also, a varying speed of light probably screws up primordial nucleosynthesis. A real theory would address these issues.

August 05, 2009 1:20 AM  
Blogger Kea said...

You missed the word Principle, which I can assure you that Louise has. And it is not a requirement of a theory that it solve all outstanding problems at once.

August 05, 2009 1:23 AM  
Anonymous Anonymous said...

It is a requirement of any theory that it at least be consistent with known laws of physics. A variable speed of light simply is not compatible with the Principle of Conservation of Energy, among other things.

August 05, 2009 7:48 AM  
Blogger CarlBrannen said...

Anonymous: The most obvious explanation for a changing speed of light is that we know that gravity changes the speed of light. By Mach's principle the amount of matter that influences us increases with cosmological time. Hence the gravitational potential changes and so light would change.

"Conservation of energy" follows from the symmetry of time, i.e. every moment of time is identical to every other (and use Noether's theorem). However, cosmologically, time is not symmetric. There's a big bang at one end. Since then the universe apparently keeps growing. Hence no conservation of energy.

P.S. My new paper on spin path integrals over MUBs, is submitted to FoP.

August 05, 2009 6:53 PM  
Blogger Kea said...

Similarly, hbar should grow in cosmological time, and fundamental local observables, such as the fine structure constant, will remain constant.

August 05, 2009 8:05 PM  
Anonymous Anonymous said...

Gravity bends light, but does not change its speed. As for your statement that conservation of energy doesn't hold because time is asymmetric, do you believe this is really a rigorous argument? If so, why do you suppose conservation of energy works in every experiment that can possibly be performed?

August 06, 2009 12:22 AM  
Blogger Kea said...

Anonymous, which part of the word COSMOLOGICAL did you miss?

August 06, 2009 2:42 AM  
Anonymous Anonymous said...

It doesn't matter how much you throw around words like 'cosmological'. This still does not give you license to change the laws of physics any way you want. If you claim that the speed of light is non-constant, then you are throwing away conservation of energy and Lorentz invariance, and so you can get anything you want.

August 06, 2009 4:06 AM  
Blogger Kea said...


(1) Almost everyone I know who works in quantum gravity understands that (a) Lorentz invariance is an emergent feature of a more fundamental quantum theory (b) as Carl already tried to explain to you, only with ordinary local reversible time does one automatically get energy conservation and (c) that quantum gravity must involve alternative concepts of time.

(2) Read Louise's work more carefully, and you will see that she has carefully considered laws about energy.

August 06, 2009 4:30 AM  
Blogger Kea said...

BTW, I recommend Feynman's enjoyable 1964 lecture, on symmetry and conservation laws, he beautifully recalls the original understanding of the conservation of energy through the experimentation of Joule.

He also discusses non conservation laws, including (1) changes of scale, which were first described in a discussion of gravity's affect on bones, by Galileo in Two New Sciences (2) Mach's principle.

August 06, 2009 4:54 AM  
Blogger L. Riofrio said...

Conservation of energy is maintained as E + U = 0. This result applies for all particles, from the most massive to particles with no mass at all. Trivial objections prevent some people from seeing what is simple. Copacabana Beach is just fantastic!

August 06, 2009 7:22 AM  
Anonymous Anonymous said...

It seems to me that you basically have nothing but hand-waving arguments to back-up your ideas. Isn't it very convenient to claim that Lorentz violation and energy conservation don't hold in your understanding? Appealing to quantum gravity would be great if you actually had such a worked out theory were you could make such definitive statements, which you do not. On the contrary, in the only true candidate theory for quantum gravity that we have, Lorentz invariance is fundamental as is energy conservation. I'm sure pointing this out will provoke accusations of being an evil string theorist.

Louise, I do not see how E + U = 0 could possibly be true if the speed of light is non-constant. It should go without saying that these are fundamental objections, not trivial ones.

August 06, 2009 10:22 AM  
Blogger CarlBrannen said...

Anonymous, regarding the speed of light, the less someone knows about a subject the more certain they become. Read Baez's comments.

Regarding tests of conservation of energy, those tests have been performed over time scales negligible compared to the age of the universe.

August 06, 2009 5:38 PM  
Anonymous PhilG said...

Actually Carl that was written by me as part of the Physics FAQ with some minor updates by Carlip. I wrote it a long time ago so it could be due an update. Which parts in particular did you think was relevant here? Is there any part you think could be wrong?

August 06, 2009 9:11 PM  
Anonymous Anonymous said...

Carl, the theory that pigs can fly has not been tested on cosmological time scales either, but this does not make it any more likely. As for the constancy of the speed of light, this must be maintained even in a gravitational field, which is to say that Lorentz invariance is maintained locally.

Also, keep in mind that the speed of light follows from Maxwell's equations. If you say that the speed of light is changing with time, you are in effect saying that Maxwell's equations are also changing with time. In addition, you have to claim that conservation of energy doesn't hold either. Thus, in order for this idea to work, you essentially have to assume that all of the laws of physics that we know are wrong. Most physicists find this a little hard to swallow.

August 07, 2009 12:37 AM  
Anonymous PhilG said...

A changing speed of light does not necessarily mean that energy is not conserved. Provided it changes in a way that can be described by a time independent Langrangian formulation then energy will be conserved. If you put in a changing light speed by hand then energy would probably not be conserved, but only because such a theory is incomplete. Incomplete is not the same thing as wrong.

I'm not saying that VLS theories can easily be made good, but if you are going to claim they cannot work you need a clear no-go theorem with properly stated assumptions. Just saying that energy is not conserved does not get you far because, (a) it does not follow and (b) it does not matter unless the change predicted is ruled out by observation.

August 07, 2009 7:45 AM  
Anonymous Anonymous said...

You are correct that you could always cook up something in order to maintain conservation of energy. Essentially, you have to explain where the energy lost due to a changing speed of light goes. Whatever the mechanism for maintaining energy conservation, it is necessary to see what effect this would have. For example, suppose the energy lost due to a changing speed of light goes into gravitational potential energy. Would this not cause the expansion to slow, negating any apparent acceleration due to a slowing speed of light?

Aside from energy conservation, what happens to electromagnetism? These laws must be changing too if the speed of light is slowing, and this would effect a number of things such as primordial nucleosynthesis. What about Lorentz invariance?

August 07, 2009 10:16 AM  
Blogger L. Riofrio said...

U = - GMm/R

U = - (tc^3)m/(ct)

U = - mc^2

E + U = 0

I'm having too much fun by the beach to write more.

August 07, 2009 10:17 AM  
Anonymous Anonymous said...

It's hardly necessary to write more since what you have written is complete nonsense.

August 07, 2009 11:09 AM  
Blogger CarlBrannen said...

PhilG, I wasn't saying that Baez's page was wrong, but instead the opposite; I was quoting it as a source. Einstein believed that a constant speed of light only applies in inertial coordinate systems and so do I.

I don't believe that it is reasonable to define an inertial coordinate system for the universe as a whole. The problem is getting it to propagate forward in time without topological crap happening (over billions of years!).

To me the question is: Is cosmology simpler with a fixed speed of light or with light varying according to some formula? I think that the universe is flat, always has been flat, and always will be.

August 07, 2009 11:32 AM  
Anonymous PhilG said...

Anonymous - now you are asking questions rather than just saying the theory is wrong for some reason. I would do the same. I dont really like VLS theories myself because they are hard to make sense of in the context of general relativity which I think is a good theory, but I think they are taking a more radical approach where GR may be wrong.

It is not unusual for new theories to be radical, incomplete and seemingly contrary to well established physics. Bohr's model of the atom would be a good example. When people are prepared to develop ideas which are a genuine attempt to address unexplained observational anomalies and they submit their work to peer review, then they should be allowed to do so.

If you want to debunk it start with a theory independent question like "what is your operational definition of the speed of light?" It makes no sense to say the speed of light changes unless you give a way of measuring it e.g. by defining how to measure time and distance using physical properties of materials. The answer will tell you something about what physics they are assuming to be correct and fixed. If you follow a line of questions starting from there you may catch them out, or maybe they will catch you out. Good luck.

August 07, 2009 8:30 PM  
Blogger Kea said...

The way I see it, until anonymous fully refutes the observational results of Louise's cosmology, which I very much doubt he/she can, it doesn't matter how many years he/she keeps screaming at us that we're all morons, we are probably not going to take too much notice of him/her.

Anonymous seems to have forgotten the historical lesson that Newton's laws break down when relative velocities are high, due to the fixed value of the speed of light, locally in cosmic time. Similarly, one cannot seriously expect Maxwell's equations to apply universally for all future observed phenomena, although they are still completely valid in the local cosmic domain to which they apply. Perhaps anonymous is confusing cosmic time with local atomic clocks, on the standard assumption that these are the same things.

August 07, 2009 8:31 PM  
Blogger Kea said...

Phil, I also have the hope that GR (in twistor guise, via cohomology) will be recoverable from the quantum theory. In this context, the cosmically fixed c idea comes down to the mathematical convenience of classical fibre bundles etc. But of course, nature knows that this very old fashioned mathematics is probably past it's prime.

August 07, 2009 8:44 PM  
Anonymous Anonymous said...

Kea, it is really difficult to respond to your statements which, as stated before, amount to little more than hand-waving. As for Louise's "cosmology", I am certain that it would give incorrect results for the primordial abundances of hydrogen, helium, and lithium. In addition, I imagine that it would conflict with the electromagnetic spectrum from distant stars. Of course, since you and she are willing to violate any law of physics which disagrees with your belief, I'm sure you will dismiss this as just another thing that doesn't hold on cosmological time.

August 08, 2009 3:36 AM  
Blogger CarlBrannen said...

Anonymous, before you go on and on about how well the current model computes the elements created in the big bang at least do a literature search. For example, see Resonant enhancement of nuclear reactions as a possible solution to the cosmological lithium problem.

The problem with cosmology is similar to the problem with the standard model. In cosmology, there are a lot of adjustable parameters and relatively few data points. Conflicts are now arising as more data gets added.

In the standard model, there are a lot of data points but the number of adjustable parameters is immense. It will be some time before contradictions show up in them, but it doesn't matter because the theory is at its heart incompatible with gravity.

As far as "electromagnetic spectrum from distant stars", Louise's idea doesn't distinguish between frequencies so there are no distinguishing differences from any other big bang model.

August 10, 2009 8:51 AM  

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