Erik Verlinde's (Not Quite) Explanation of Gravity

Erik Verlinde is a String Theorist who recently proposed a theory of gravitation as an emergent entropic force, the entropy being a function of the information stored on holographic screens in higher-dimensional space-time. For the moment, just nod along. A lot of people don't think it makes much sense. According to Verlinde, gravity isn't a fourth fundamental force, it's a consequence of something else. The catch is that his something else is an extended metaphor rather than physics. To see why, we have to have a swift tour of some technical philosophy.

There's distinction between a physical property and a defined property. A physical property is one that exists even if there is no-one or nothing there to measure it: size, weight, mass, electric charge, velocity, being an oxygen atom. A defined property is one that someone needed to think up and define a way of measuring: temperature, decibels, lumens, colour, information, entropy. Many of our physical theories are there to link defined properties with physical ones. We have a theory of temperature as the movement of atoms and molecules, which causes our feelings of hot or cold and makes, amongst other things, thermometers work they way they do. Defined properties don't happen in the world if there are no measurers or definers. If there is no-one to feel the heat, is the kitchen hot? No, but it is full of molecules whizzing all over the place. If a tree falls in the forest and there's no-one there, does it make a sound? No, but it does create a pressure wave in the air (which would be a sound if there was someone there who wasn't deaf). Hold this distinction in mind for a moment.

There are laws of physics, nice-to-have-regularites, models and theorems with empirical content. A nice-to-have-regularity is the one about the speed of sound at sea level on a normal day, or how much effort it takes to cut a wire with a good set of pliers. It's what makes our world predictable and manageable - because you can have a chaotic world that obeys the laws of nature (the atmospheres of Jupiter or Venus, the surface of the Sun). Chemical reactions are nice-to-have regularities. A model is, for instance, Euler's equation for the bending of a beam (the only known instance of a useful fourth-degree differential equation). It starts with assumptions, draws a conclusion and when you measure everything, it works out. A theorem with empirical content is, for instance, information theory and thermodynamics: the terms are defined into existence, and methods of measuring them created to make sure the theorems are true: what you can't guarantee is that the results are useful and interesting. This leaves the laws of physics: these hold all the time, everywhere about everything, and for that reason, they are local and position-indifferent: most laws of physics are equivalent to an instance of the principle of least action.

The laws of physics have to be about physical properties - because they describe how the universe behaves everywhere and all the time, before anyone arrived to define sound, colour or entropy. Models, regularities and theorems with content can be about physical and / or defined properties. Nature doesn't give a hoot about defined properties - we do, cats do, but the dumb stuff that make up us and cats doesn't. Nature works on physical properties.

Verlinde is suggesting that gravity is not a fundamental force, but a consequence of other physical processes: like water pressure, which is a consequence of the mass and velocity of a large number of water molecules. Except his explanation doesn't involve any actual physical properties. Because information, entropy and holographic screens are not physical properties and processes.

Start with "information". As used in these contexts, this is -log(p(x)), where p(x) is the the probability of the event x. The lower the probability, the more information we have when it happens. Probability here is defined in the frequentist sense, as the long-run proportion of the event x happening. Here's where we hit a subtle point: frequencies are "objective" because the counts are a matter of fact, but they are not a physical property of any system, rather, they are the result of the physical properties of that system. The 50% chance of getting heads flipping a fair coin is not a physical property of the coin (and the flipper), it's a consequence of the fact that the centre of gravity of the coin is right in the middle (and of the fact that the flipper picks a random point to apply the force). Taking a mathematical function of a defined property just creates another defined property, so "information" is a defined property.

Entropy is as defined a property as you can get. Whereas the physical explanation of temperature is about the movement and vibration of molecules (physical properties), the physical explanation of entropy is as the proportion of permutations of the particles in a system that leaves certain properties (for instance, its energy and temperature) unchanged: the higher the proportion, the lower the entropy of that state.

The idea of an "entropic force" is that if we subject a system to a slight perturbation, there is a higher probability that it will return to a lower-entropy state than remain in a higher-entropy state. On the outside, this looks like a force - but it isn't. Because the system will remain in the new configuration unless an actual force dislodges it - and that force isn't Nature saying to herself "gee, there are more probable configurations than this one, so I'd better change to one of them". The force is something that, ultimately, will resolve down to lots of quantum mechanics and electromagnetism.

This doesn't mean you can't write down a bunch of equations to define an entropic force and then get gravity out of them - Verlinde does and there's nothing wrong with his maths - though you may find his assumption of some abstruse Black-Hole theory physics less than "first principles". It does mean that those equations might not describe actual physical properties and hence don't describe what happens in Nature. It's the difference between, say, Quantum Mechanics, which tells you not only what the properties of a system are but also why your measuring instruments work for that system, and thermodynamics, which describes the relationships between measurable properties of a system but does not describe what's going on in that system to cause those measurements.

That's what's wrong with Verlinde's paper: there's a lot of mathematics but no actual physics. You can't say "gravity is not a fundamental force, and to prove it I'm going to give you an explanation of it in terms of other things that aren't fundamental forces either". The cutest moment is when he cites the AdS/CFT correspondence and Black Hole theory as "evidence". Last time I looked, speculative physics was neither empirical nor true and so could not be "evidence".

I'm Just A Person On My Own

Would I ever think my life would be better with a drink? No. Do I feel better since I got sober? Yes. Do I feel even better since my blood sugar levels fell back below about six mmol / litre? Oh god yes. Do I feel randomly depressed, sad, unhappy, lonely and despairing like I used to? No. Do I feel happy, fulfilled, content, at peace, at one with the world around me and otherwise accepting of my fate and place in the world? Are you freaking kidding?

Actually, I don't actually feel anything, much. Aside from irritation at the incompetence, crassness and incivility of the world. This is partly because I have grey hair and less testosterone coursing through my system than I used to. It's also because I mind less about all the stuff I don't have, never did and won't be able to do. That isn't acceptance, it's just numbness.

Once upon a time I had a hole, a cavity, in my soul. Actually it felt like it was inside my torso. Some while ago, it stopped hurting and for a couple of years I thought it might have been filled, or at least that whatever it was that kept it empty had stopped. Then I began to suspect that what I feel can't be happiness, or contentment or anything else all the therapists say the normals feel, because if this is all there is, it's as real as white sliced bread.

That cavity in my soul is still there. It hasn't been filled up, though it isn't getting any larger. It's just been cauterised, so it doesn't bleed any more. It's covered in scar tissue and doesn't feel pain like it used to. It's still there. If it wasn't this song wouldn't make the hairs on the back of my neck stand up and fill me with a kind of weird peace...



... and I would be able to sing the third verse  "Sober now, I'm cold, alone / I'm just a person on my own / Nothing means a thing to me / No, nothing means at thing to me" with quite so much relaxed force. Those word express exactly how I really feel when I'm not faking it to make it.

Samantha Morton's The Unloved

Samantha Morton is best known for her performance as the psychic in Minority Report and puts in a remarkable performance in one of my must-see films, Morvern Caller. The Unloved is her first film as a director: it's about a ten-year old girl (Molly) who is put into the care system after her father (Robert Carlyle in a powerful performance) beats her for losing his cigarette money. Molly shares a room with a sixteen year-old (Lauren) who is being sexually used by one of the care workers, tries to persuade her mother to take her in, gets taken in by the Police when Lauren is caught shoplifting, spends nights out of the home and at the end of the movie isn't even back in school yet. The film is cold and accurate without being bleak - a balancing act Morton and her photographer pull off throughout - and for me captures the way isolated moments - cleaning your teeth in the momentary privacy of the bathroom, gazing at a spider's web, looking at the town from a park hill - can provide brief moments of relief from being somewhere you don't want to be. The images contrast cold skies, sun and clouds with the tatty, industrial town that is Nottingham - a town that for many years was the violent / drug crime capital of the country.

The tone of the film walks another fine line, between isn't-it-dreadful sentimentality (which would have required Juliet Stevenson somewhere) and the fake street-life style of Kidulthood. It helps that Molly is not a broken soul - as shoplifting, trick-turning, gas-taking Lauren clearly is. Morton clearly decided to make the film as an aesthetic and dramatic experience rather than a polemical one (as Cathy Come Home was).  A polemic would have been difficult, because the fault with the care system isn't that it's heartless and staffed by abusers, but that it is smothered in denial.

The scene that says it all is the case meeting: Molly surrounded by her social worker, a care worker from the home, and a "senior social worker". The care worker has been seen feeding Molly toast and tea after she came back from running away, taking her shopping for clothes and trainers and generally being a kind young aunt. The meeting reduces her to inarticulate babbling, which is taken as normal speech by the social workers: their professional vocabulary simply doesn't allow them to say the things that we the viewers would say instinctively. Because, of course, Molly's vulnerability has nothing to do with Molly and everything to do with care system run by adults mostly seen doing paperwork.

The film was shown in May 2009 on Channel Four to an audience of two million viewers. I saw this at the ICA at 6:30 on a Friday. There were maybe fifteen people there. I don't know what it looked like on television, but it looked ten times better in the cinema.

Flamenco - Maria Pages

I search in vain for reviews of the current flamenco season at Sadlers Wells - other than Clement Crisp being his usual self in the FT. There are reviews of minor plays that will be forgotten before they even close, but nothing of Eva Yerbabuena's Lluvia or Maria Pages' Autoretrato. What stops the critics seeing it? Is it the frocks? Can't they take the singing? Maybe the audience is the wrong kind of people (the kind who go to Spain for their holidays, not Tuscany)? Is it because they would lose credibility across the dining tables of north London if they said "frankly what these flamenco gals are doing is much more fun and interesting than the latest Arts Council darling"? I suspect the answer is a big YES to that one. If anyone suggests that it is because flamenco is flagrantly heterosexual and modern dance and classical ballet is, well, for those of a more delicate disposition, they would probably get into trouble with the thought police.

Flamenco is a genre with its conventions, and yet it is strong enough to absorb influences ranging from Keith Jarrett (channelled by the pianist with Rafaella Carrasco) to modern dance (Eva Yerbabuena) to John Mclaughlin (via his work with Paco de Lucia) and the Cuban music scene. Plus these guys have to make a living at it without funds from the National Lottery.



Anyway, in the end, do I care? The fans loved Maria Pages on Wednesday and so did I. Her castanet playing was awesome, the footwork fancy, the rapping fun and the whole show a delight. Given the choice between that and Swan bloody Lake, I know which I would take - even if it does mean the 341 bus to Waterloo afterwards.

I Get A "Recognition"

I have been trying not to write about work recently, mainly because it would turn into one long rant about the utter idiocy of our IT department and its outsourced support. This is a major, major bank which does not officially provide or support Oracle, Business Objects and SAS. About which I have spoken.

Our section had an Awayday recently, in the Seven Dials club in Covent Garden (they don't seem to have a website.) It was the usual mixture of "here's how the numbers are" and "bonding by fun" which usually has me reaching for the phone to call in suddenly ill, but this time was actually reasonably bearable. I got to meet a number of the new guys on the team who are due to start soon, and scarily young and bright they are too. As well they should be.

Modesty forbids me to describe the spontaneous round of applause that greeted my presentation on business-as-usual activities in the management information team, but then I did tell a good story vividly.

At the end of the day there were some "recognition" for people who had done above and beyond the call of nine-to-five, and for once I found myself agreeing with the choices: all went to people who were good soldiers, as such things should. Except one. Which went to me, for finally getting all that software to work on the Bank's machines. Which I did not do as a good soldier, but bitching and moaning all the way (which come to think of it, is how good soldiers behave, if Generation Kill is as accurate as they say).

Given that I was in the doghouse a year ago, this isn't bad. My appraisal for last year was "Met Expectations" which is better than it has been for a while. The thing is this: I'm still the same old me. I'm doing pretty much what I always do. It's the managers that have changed. Now they are giving me stuff that can be done, instead of the mission-impossibles that the previous guys came up with.

Here's the take-away: if you set your people up for success, they will probably succeed; if you set them up for failure, they will surely fail.

Why There Should Not Be An Adjustment Disorder

Reading Petra Boynton's blog, I see that the APA are taking comments about the forthcoming fifth edition of its Diagnostic and Statistical Manual, or DSM-V to the masses. In psychiatry this weighty tome has roughly the status that Halsbury's Laws of England does in the legal profession. Most important, if your particular screw-up doesn't fall into a DSM-IV (the current edition), your insurance company is not going to pay out for your treatment.

There's a thing called Adjustment Disorder. You have this if you become overly depressed, anxious or start behaving oddly within three months of a stressful or traumatic event, carry on doing so for at most six months after the event stops, and for that time have difficulty coping with work and life. If the event goes on and on (the boss is a bitch), the condition is chronic. If you go on being depressed, anxious or behaving oddly for six months after the boss moves on (or whatever) then you have something more serious. This looks okay, but...

You can hear the bullies lining up now, can't you? Your employer sacks you with no money - hey, get drunk on the day, curse them, let it go and move on. If you fall into a depression, that's you having an adjustment disorder and has nothing to do with them. They aren't responsible. Or your wife cashes you in, taking the house, kids, half the pension and maintenance. Adjust little buddy, no moping for you. It happened, move on and get on with your life. If you can't, it's not her fault, it's yours, because you have an adjustment disorder. It's all about what counts as over-reaction: who decides that? For the people who hand out the harm, that would be any sign of depression or reduced functioning at all; for the poor bloody victims, that would be all the blues they can feel. Your co-dependant friends would indulge you and your colleagues at work would get irritated if you came in the next day still moping.

Now compare this with the symptoms for a major depressive episode. To have one of these, you need at least five of the following nine symptoms, which must manifest for most of the day: 1) feeling sad, blue or depressed; 2) a loss of interest and pleasure in things you used to do; 3) significant changes in weight and appetite; 4) significant problems sleeping; 5) agitated or lethargic body movements; 6) feeling fatigue at least once a day; 7) low self-worth and inappropriate guilt; 8) persistent difficulty concentrating; 9) thoughts of death or suicide. The symptoms must persist for a two-week period and must include one or other of the first two. But here's the catch, which most casual readers of DSM (if there could be such a thing) miss: if you're hauling your ass out of bed, making it to work, paying the bills, baby-sit your brother's kids, keep the larder and the fridge full and even making it to the gym a couple of times a week, you don't qualify for being depressed. You qualify as feeling like crap and needing a change of life, but not as depressed. Because you're functioning, and if you're functioning, a psychiatrist can't diagnose you as crazy.

Notice that all these symptoms are as "objective" and "observable" as anything about human behaviour and psychiatry ever will be. Weight is objective, so is the time you wake up or the number of hours before you fall asleep; you get to report if you're feeling sad and anyone can see if you don't get as excited by football as you used to, can't concentrate or are dragging your sorry ass around the place instead of being spritely. No-one can impose their ideas of what's "normal" on you, though they can take a swig of denial and say that it's not as bad as you're making out. Imposing their denial is not imposing their values.

Many people criticise the DSM for what they see as the creeping medicalisation of normal behaviour. They have in mind the famous definition of ADHD as "behaviour that irritates primary school teachers". But that's the clue: it's the teachers, social workers, GP's and parents who medicalise the actual boisterous boy, not the DSM-trained psychiatrist, who is most likely to say "he's a boy, and you want him to behave like a girl?". There's a context to the DSM - it's for psychiatrists, not "councillors" or "therapists". On a daily basis psychiatrists see people who are severely fucked-up, people that we never see. They get the context and know what the words mean, we don't.

The real criticism isn't about medicalisation, it's about the use of social norms in psychiatry. It's that use of "overly" in the definition of Adjustment Disorder. It's maybe in the whole idea that we should "adjust" to the slings and arrows of outrageous misfortune at some rate that optimises our social and economic effectiveness while maintaining a facade of feeling humanity. I once read an account of children's attachment to their mothers. It was based round how the kids reacted when Mommy left them at the nursery. "Appropriate adjustment" was when the kid cried for a little - just enough to show it was missing mommy but not enough to be a nuisance to the teacher - and then went to play with the other kids. Too much crying was unhealthy, running straight off without missing mommy was unfeeling. That isn't psychology, it's manners at best and competitive parenting at worst: look at my appropriately-adjused child.

Being screwed-up is one thing, but not fitting in with the straights and normals is another. No-one is under an obligation to do that.

Dumb Security Questions When Buying A Car

The other day I had to call Mastercard to let them know I was going to spend some money on my card, so they didn't automatically block it when someone tried to put the price of a second-hand car through. (That happens all the time with credit cards - which have computer routines to highlight alleged suspicious spending.)  I keyed in my credit card number, the three-digit code on the back and my date of birth. The young man who eventually answered had my details in front of him, but insisted that I give him my name and address and if I there were other people who could use the account. Then he asked me how much I had spent in Foyles a month ago.

Huh? If he'd asked about how much I'd spent at Richer Sounds around a month ago, I would have known. I don't buy electronic kit that often (it was a Sony BDPS 760 and an excellent purchase it was as well, plays well with my Sony Bravia flat-screen and gives new life to DVD's, but I digress). I read over a hundred books a year, most of which I buy in Foyles or Blackwells, so I buy books "all the time" and no more remember what I bought for how much than anyone else would remember what they spent in Sainsbury's a month ago. Maybe it would have been a memorable thing for that young man to have bought books in Foyles in the Wicked West End, but not for me. (In fact on the date he mentioned, I think I bought Being and Nothingness and Being and Time for stock, as reading Hegel's Phenomenology has given me a taste for some heavy continental stuff.) So since I flunked that, he said I'd failed the security question and he couldn't go on.

In the end, it turned out that Cargiant don't take Mastercard, so I called my bank and explained the situation, and they gave me an extra £2,000 on my overdraft, which was enough to pay for the car on my regular debit card.

This does not count as "working out all right" because there's still a silly young man out there who thinks that you can remember what you spent at Sainsbury's three weeks ago. And he may block your card if you don't get it right.