Michael Disney and the case against cosmology

Iconoclasts in cosmology seem to be rather thin on the ground at the moment. Michael J. Disney, however, Emeritus Professor in the School of Physics and Astronomy at Cardiff University, attempts to damage the credibility of the Magical Kingdom in the current issue of American Scientist.

Disney claims that the number of independent observations in cosmology is much smaller than the number of independent free parameters in current cosmological theories, and argues from this that "modern cosmology has at best very flimsy observational support." Seven years ago, Disney wrote 'The Case Against Cosmology', along rather similar lines, making the notable point en route that only "one per cent of the light in the night sky comes from beyond our Galaxy."

However, I don't think Disney has really done anything here other than: (i) re-discover that all scientific theory is under-determined by data; (ii) re-discover that cosmology is a data-starved science; and (iii) re-discover that cosmological theories have to make some rather special assumptions in order to reach any conclusions at all about the universe as a whole. From the emotive language employed, one can detect significant professional jealousy in Disney's diatribe. For example, in his year 2000 paper, Disney wrote:

Much of cosmology is unhealthily self-referencing and it seems to an outsider like myself that cosmological fashions and reputations are made more by acclamation than by genuine scientific debate.

A scientific discipline in which the participants only read and reference each others' papers. Imagine! And in this context, as is oft the case with a scientist writing on philosophical issues, it is noticeable that Disney has made no effort to read or reference the relevant literature on the philosophy of cosmology. That, quite simply, is poor scholarship.

Whither, and from whence, the weather?

The weather today was grim; in fact, it was grimmer than the grimmest spell in a grimoire written by the Brothers Grimm.

The jet-stream moved Southwards this year, and as a consequence, the UK's Summer weather was dominated by a succession of North Atlantic depressions. If the jet-stream remains so over the next few months, a particularly cold Winter is predicted.

It is appropriate, then, to recall Lewis Fry Richardson, the man who invented the modern weather forecast as a numerical solution of a coupled set of differential equations. Fry's astonishing efforts are recalled in Peter Lynch's recent book, The Emergence of Numerical Weather Prediction: Richardson's Dream. Reviewed in the current issue of American Scientist, Lynch points out that:

[Fry] set out to calculate the weather. He built a working mathematical model of the Earth's atmosphere, based on straightforward physical rules. For example, one rule says that if regions differ in barometric pressure, then air will start to flow along the gradient toward the lower-pressure area. Richardson filled in initial values of pressure, wind velocity and so on, and then traced the model's evolution over time.

Models based on essentially the same principles now run on supercomputers capable of trillions of operations per second. Richardson, however, worked entirely with pencil and paper, using a sheaf of forms he had printed up to guide the computations; his only aids to calculation were a slide rule and a table of logarithms. Furthermore, the circumstances in which he did all this arithmetic have made the project legendary. The time was World War I. Richardson, a pacifist, was serving as a volunteer with the Friends Ambulance Unit in the north of France. He performed his calculations between calls to carry wounded from the front. "My office," he reported, "was a heap of hay in a cold rest billet."

Andy Green and Thrust SSC

It's now 10 years since Andy Green broke the world land-speed record, and the sound barrier, in Richard Noble's Thrust SSC at Black Rock Desert, Nevada. Erstwhile fighter-pilot Green is a remarkable individual, and this month's Motorsport magazine carries a gripping account of the difficulties (those are 'challenges', for younger readers) he faced.

We went back to Jordan in May 1997...We started to use some quite high-end acceleration, and on the first full afterburner run I'm taking it nice and steady, 200, 250, 300, max burner, and suddenly it's going all over the place. I just cannot keep it in a straight line.

Driving a normal car, if it diverges, you respond to correct it. But I was getting into what in an aircraft you'd call a pilot-induced oscillation. The vehicle diverges, you put in a response through the steering wheel, it responds, you put in another, but at that point the vehicle is reversing its response, so you get a double input. You and the vehicle are working out of phase. Every time there's the slightest input, say from irregularity in the desert surface or a crosswind, you've got to correct it. But if you start steerting at the frequency of the car it gets worse, not better. I got out of the car that day and I said to myself, I think this project has just finished. The car's unstable. I think we're stuffed.

I didn't feel I could talk to Richard or anyone else about it, so I spent the night thinking it through. And I came up with the conviction that I was simply going to have to bully the car into being stable, go very high frequency with my steering movements to keep it under control, coupled with lower frequency inputs to steer it. I'd have to steer it at two separate frequencies, simultaneously. So that's what I did, and it worked. I'd found a way to drive the thing. The downside was that I was never going to enjoy it. Imagine taking all the hairiest bits out of a three-hour sortie in a Tornado, and doing them all in two minutes. It was the hardest thing I've ever done: like trying to balance the point of a pencil on the end of your finger.

The team moved to Black Rock Desert in September 1997, and on October 15th set a record of 763.035mph, Mach 1.02

We had active suspension because every time the aerodynamic neutral point moves you have to alter the pitch of the car to compensate. And plus or minus one degree of pitch on the car equals plus or minus 10 tons of load on the front wheels. Running the active fully up through the trans-sonic region increased the load on the front wheels by almost 10 tons. The wheels started to plough into the desert.

We were generating some very powerful shock waves in front of the car. We found the wheels were actually going round less fast than the ground speed: we were ploughing the surface in front of the car. The shock wave was digging up the desert, so the four individual wheel tracks disappeared, and we started to get a single ploughed trace 12 feet wide.

Things change so much between Mach 0.8 and Mach 1. When the shock waves start to form, depending on the shape of your vehicle, you've got a mixture of sub-sonic and supersonic flow. If you're doing Mach 0.95 and the air accelerates locally by another five percent, over the cockpit or the curve of a wheel arch, it will form its own little shock wave there. In the trans-sonic period its doing that in various places around and underneath the car. The pressure difference where the air goes from sub-sonic to supersonic is so great that if it happens underneath the car it can lift it off the ground.

And the car may be fractionally different in shape from one side to the other. It's a hand-built car. We measured it as accurately as we could, but the tiniest difference, the thickness of a few coats of paint, can make the shock waves form earlier on one side. It happens with aircraft when you take them supersonic, but tiny corrections with the controls can fix that. With the car, it's the wheels that have to take the differences in load, and you start to realise the magnitude of the forces involved when a tiny difference can translate to an extra ton of load on one of the front wheels. Once you get well over Mach 1, life gets much easier. It's getting there that's the challenge.