The Importance of Being Empirical

The problem with mainstream theoretical physics today is a lack of connection to reality. String theory or loop quantum gravity, for example, are like constructed virtual realities that bear no direct relation to the real world. The proof is that neither of the theories are testable: they cannot be disproven, and this has given them a longevity they do not deserve.

There is a related trend in modern art and this is interesting because both art and science are ways of modelling the world. In a similar way, art used to be testable. An artist draws a face or and lanscape and there is an objective test. Does it look like the real thing? If so, we can say that the artist has skill. Then the camera came along and this skill became obsolete. Art reappeared in a form detached from reality: abstract art. I won't attempt to judge modern art, but a science detached from reality is a disaster, and takes us back before Empiricism and Roger Bacon!

String theorists may say it is not their fault that the theory cannot be tested. But it IS their fault. If they are scientists they need to work on theories that are testable. Either devise a test or forget the theory and start looking at the real world. This used to be the first rule of science, but it has been allowed to lapse. It reminds me of a comment I once read about ancient Greek science when it had passed its peak and humanity was heading for the dark ages: "Speculation ran way beyond the testable and dwindled into metaphysics" (McEvedy, 1961). I hope we are not drifting into a dark age where smug scholars in ivory towers discuss uselessly what came before the big bang, when they can't explain how local galaxies behaved last week, or even why the turbulence in a pipe starts when it does. The best progress has always come from a little thought applied to interesting observations: a prism experiment lead to a better theory of light, a view of Jupiter's orbiting moons through a telescope inspired heliocentricity and gravity, and the null result from the Michelson-Morley experiment lead to relativity.

On a positive note, I worked for ten years at the UK Met Office, in the ocean forecasting section (not climate research) and the ethos in this Ocean Forecasting section and also in the NWP (Numerical Weather Prediction) was healthy, because the ocean or atmosphere models had to forecast data that was continually coming in from satellites, weather stations and ocean buoys in the real world, so there was a constant check from reality to test and improve the models. This is the best way to do science: lots of data, some anomalies, and a little thinking applied.

I'll leave the last word to Sherlock Holmes' creator: "It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts." - Sir Arthur Conan Doyle.

References:

McEvedy, C., 1961. The Penguin Atlas of Ancient History. Penguin Books. (Page 92).

Predictability and Understanding

I've drawn a schematic that classifies how I see various physical theories. The y axis shows how successful the theory is at predicting the real world, or its testability. For example quantum mechanics (QED) can be tested and is very accurate, whereas Lovelock's Gaia Theory is not very predictive or testable, yet, and string theory is not at all. On the x axis I have Understanding, which is supposed to be a rough measure of whether the theory comes with a physical mechanism that explains intuitively how it works. So, thermodynamics is well explained as being due to the statistical motion of atoms, but the onset of turbulence in fluid dynamics is not at all understood:

The top left box is for empirical theories which predict the world quickly, but without the need for an understanding. They usually have adjustable parameters. Many models have been born in this box and end up migrating to the right into the physics box when they are understood better, eg: quantum mechanics originated from Planck's empirical formula, with the adjustable parameter being Planck's constant.

On the top right is the physics box, which mixes predictability with some understanding. The ideal physics is in here. Ideal physics can predict nature, but also includes an intuitive mechanism which helps us to extrapolate the ideas to other parts of nature. I've listed thermodynamics and special relativity very high on both axes since the mechanisms for both are well understood and they both make testable predictions that fit nature.

On the bottom right is the box for philosophy which is all about understanding, without necessarily a need for directly predicting details of the real world. Some beautiful ideas that end up as part of theories start off here, like Mach's idea about observables which helped to produce special relativity.

I'm not sure what to call the bottom left quadrant, but here the theories are neither well understand, nor do they make any testable predictions about nature. This is the worst kind of model: untestable. The kind that Pauli would have called: "Not even wrong". Most of contemporary theoretical physics is here. This is probably the case in every epoch: the only theories we remember from the past are the better ones that survive. These tend to be born in the fertile empirical box and migrate slowly to the right, sometimes with a dash of insight from the philosophical box.

Explaining MiHsC: Whirling a Ball around on a String

Imagine you are standing there in your garden with a ball tied to a string. Slowly you whirl the ball around you so it is pulled outwards. What it pulling it outwards? No one understands the mechanism, but this effect is called inertia. The idea is that objects tend to keep going in the same direction at the same speed until something pushes on them. The ball has inertial mass so it wants to go in a straight line, but you and the string are pulling it towards you. A balance is reached: an orbit, until you let go of the string and send your friends running for cover.

Zooming out by a factor of a million million million, galaxies are similar. Balls of fusion (stars) mutually orbiting, with inertia pulling them apart and gravity pulling them together. The problem is that galaxies spin around so fast that the inertia as we know it, should win over gravity and tear the galaxies apart. Yet galaxies remain stably intact. The small amount of matter we can see lit up in fusion (ie: stars) seems to hold all the stars together. How?

In the 1930s a Swiss called Fritz Zwicky proposed that matter that we cannot see is responsible: dark matter. This sounds fair enough, but the dark matter is needed only in the outer edges of galaxies, and no particles have been detected that could provide the very specific new physics, and the extended distribution (the halo), needed to account for the observed galactic rotations. Dark matter is also not a satisfying theory because it is not predictive or falsifiable. Given any galaxy you can add dark matter wherever you want to fit your predicted rotation curve to the one observed.

If we come back to you whirling a ball around in the garden for a minute. Imagine you could whirl the ball so fast it becomes a blur. Surely the string would break under the inertial pull outwards. What if it didn't? Well, you could conclude that the string was made of strong carbon fibre so it can pull inwards without breaking (just like extra matter in a galaxy provides extra inwards pull), or otherwise you could conclude that the ball is hollow and has less inertial mass than you thought. This means it is less inclined to follow a straight line and zoom off, and more easily bent into a curved orbit even by an ordinary string.

Similarly, instead of adding extra gravitational mass to the galaxy, can we reduce the inertial mass of its stars? There is a way to do this using what is called: "Unruh radiation". This is similar to the Hawking radiation you get in a gravitational field, but you see Unruh radiation only when you accelerate. You also see inertia only when you accelerate, so maybe inertia is linked to Unruh radiation.

Unruh radiation is a wave with a wavelength that depends inversely upon the acceleration. At the edge of galaxies the acceleration is tiny and the Unruh waves become so long that a smaller proportion of them can be measured, and Ernst Mach once said that if you cannot measure something you should discard it, and this kind of thinking led Newton to discard Descartes' vortices and led Einstein to discard the aether, so let us say that if the Unruh waves cannot be seen, then they cannot contribute to inertia, so galactic edge stars lose inertial mass in a new way. On galactic "scales" they have lost mass (forgive the pun). A lower inertial mass means the stars can be more easily bent into a bound orbit, even by the small amount of stellar mass we see in the galaxy.

To cut a long story short, such a model, called MiHsC or quantised inertia, works and fits galaxy rotation curves without dark matter (see the paper below). It also does this without adjustable parameters, which means it gives only one answer, and that happens to be the right one.

McCulloch, M.E., 2012. Testing quantised inertia on galactic scales. Astronomy and Space Science. Vol. 342, No. 2, 575-578.
Journal paper: http://www.springerlink.com/content/1778177x0570j647/

Preprint: http://arxiv.org/abs/1207.7007

MiHsC and entropy?

A paper has just been published by J. Gine called "The Holographic Scenario, the Modified Inertia and the Dynamics of the Universe" (see the link below). I haven't understood the two-screen holographic model he is suggesting yet (I always find these so called 'holographic screens' to be very contrived and unnatural), but I found the last section of the paper particularly intriguing (especially eq. 44) because he uses MiHsC :) He takes the usual MiHsC expression for inertia and rewrites it in terms of Unruh temperatures (though in the paper he doesn't quite complete this conversion..) which allows MiHsC to be thought of in a more overtly thermodynamic way. Whether this will prove useful or not I don't know! Gine's paper is here:

http://www.worldscientific.com/doi/abs/10.1142/S0217732312502082?journalCode=mpla

All this thermodynamics reminds me of a thermal experiment I suggested in 2007: the effect of MiHsC on Unruh radiation (disallowing the longer, colder, wavelengths) should also apply to normal radiation, so the energy radiated by a very cold object should be very slighly less than that expected from the Stefan-Boltzmann law. For more details see the last part (around eq. 13) of this paper:

http://arxiv.org/abs/astro-ph/0612599
McCulloch, MNRAS, 376, 338-342.

Forks in the Road

Newton had his prism, and knew just what it meant.
Darwin saw some finchs' beaks, differently bent.
Einstein had Lenard's data, Michelson-Morley's too.
Reading these anomalies, they worked out what is true.

The cosmos has an imagination, greater than anyone.
It is difficult to outguess it, so what is to be done?
Rather: set up crucial experiments, like forks in a road.
The direction nature takes, will reveal the cosmic code.

The Irrelevance of Craziness

There's a interesting discussion going on over at Backreaction over a craziness factor for new theories. The proposal is that one should check how crazy (different to the standard model) is a new theory, and if it is a bit crazy that's good, but if it is very crazy it is bad. As I've said in a few comments over at Backreaction, I think this is misguided, since in my opinion the sole criteria for judging a new theory should be whether it "predicts nature better and is simpler" than the old models. These things can be determined objectively, whereas the agreement of the theory with human expectations is subjective, and should not be used to judge it.

There's a song, by Seal, that contains the line: "but we're never going to survive, unless we get a little crazy", and that's right in my view. The deeper workings of the cosmos probably would seem mad, if suddenly revealed, relative to our quaint conceptions, so our minds are going to have to learn to 'think crazy' relative to our current modes of thought, to understand the universe as we move out into new regimes, as we already do a little to understand relativity and quantum mechanics. Our world view is better than that of the ancient Greeks, but they would see our worldview as bizarre. Plato would have difficulty imagining that people are standing upside down in the antipodes. Who knows what parochial views we are a victim to?

Some will always try to fit the universe into our present notions of sanity, or stay close to them, by adding patches where they can, but this will eventually be inadequate. I'm not saying that we should deliberately try to be crazy, but I am saying that subjective measures like apparent craziness should not be considered when judging theories. Crazy or not, if they predict nature, and are simpler, then let them stand.

There is a pleasure sure, in being mad, which none but madmen know.
- John Dryden.

The Star Trek London Convention

This last Sunday I went to the Star Trek Destination London convention. It is only the second Star Trek meeting I have been to, but it was extremely interesting, also when I assess my own reaction to it: I wandered around in awe. There was Chekov (Walter Koenig) walking around smiling broadly with a cap on, Data (Brent Spiner) looking out of this world with his bright white hair, all five Captains in booths, hidden by autograph queues. I paid particular interest to the characters from Enterprise (Bakula, Keating, Mongomery, Trineer). I like that series since in many ways it is more realistic, and closer to home timewise, and I like Scott Bakula's portrayal of Captain Archer, I saw his blond hair and big nose from afar. Archer is less decisive and passionate than Kirk, less Professional than Picard, maybe less caring then Janeway, who I also saw from afar (I haven't seen much DS9), but for me Scott Bakula gave the most realistic portrayal of all the captains of an explorer: someone trying to push the human envelope despite huge obstacles, and trying to work out how to do something right, that has never been done or imagined (note: I had only seen Enterprise Seasons 1 & 2 at this time).

I paid to get the autograph of William Shatner, who I have adored since childhood, and paid to see his talk, which was characteristically entertaining. When asked which film was his favourite he said of course: his own Star Trek V. For this film he'd ordered a rock monster breathing fire, but after paying $250,000 a guy in a monster suit showed up with a couple of rocks on his back and instead of breathing fire he emitted a wisp of smoke that blew away in the desert wind. I've read this story before, but Shatner's telling of it was as white-hot passionate as ever. His final comment was that he'd tried to play Kirk with "Awe and Wonder" at the universe, even when faced with death. I looked down at my four year old son, who was asleep draped across me and my dear wife (who reluctantly, but kindly, accompanied me to the convention). Awe and wonder: that is indeed what the universe deserves... No, Shatner didn't dissapoint me. Earlier in the day I got his autograph, and after thanking him I said I'd written a paper (and submitted it to a journal) suggesting that faster than light travel is possible, but he just said "You're very welcome". He was probably in a daze having thousands of people traipse past his booth.

I was certainly in awe and wonder, but also at my own reaction. I am well aware that these are actors and are paid to pretend to be explorers, so why do they affect trekkies this way? Well, sometimes as children we see a situation that we'd love to be in when we grow up. Like my son, who'd love to drive a train. Maybe Star Trek is like that for humanity (the technically-minded part of it anyway). It is a good future for us, with decent morals, interesting explorations and the possibility of healthy growth, and these actors remind us of this future. We are fooled by it, of course, because it is just imaginary, but we allow ourselves to be fooled, since it makes us happy.

There's a saying by Johnny Cash: "You gotta be what you are. Whatever you are, you gotta be it". I think this means that, while feelings may indeed seem to be based on rubbish or even illogic, if it makes you happy: go with the flow. This is like going with the grain of your internal nature instead of across it. More importantly, feelings can be wise in ways that logic can never hope to follow. The initial impulse for research can be irrational too, and although ultimately logic and data must be shown to agree, it may be true that if we believe in the possibility first, it may just be the thing needed to make it all come true.

Anyway, I had a good few hours wandering around in my irrational nirvana.