## Archive for the ‘At the seaside’ Category

### The secret of world class putting

Friday, March 13th, 2009

Watch professional golfers putt and you’ll eventually notice three common features about their style,  says Robert Grober, an expert on the physics of golf at the Yale University.

First, the putter head always moves at a constant speed when it hits the ball. Second, the length of time the putting stroke takes has little impact on the speed of the ball (and therefore the length of the putt). And finally, a professional golfer’s backswing takes about twice as long as the  downswing.

Grober has used these observations to construct a mathematical model of a putting swing and to explore other properties of such a system.

It turns out that the model that best accounts for this behaviour is a simple pendulum driven at twice its resonant frequency.

That explains a number of other observations about professional golfers, says Grober. For example, a common putting tip is that longer backswings equate to longer putts. This model has exactly this characteristic: the length of the backswing is proportional to the speed of the club at impact.

It is also relatively straightforward to get a sense of the tempo of the required putt by swinging the club back and forth in resonance, like a pendulum. The duration of the actual stroke is exactly half the length of the putter cycle (i.e. from the address position moving backward, to the address position moving forward). “In fact, one often observes golfers instinctively doing this before they hit a putt,” says Grober.

So now the secret is out. Make a careful note for next time you’re out on the links.

Ref: arxiv.org/abs/0903.1762: Resonance in Putting

### The telescope that Antarctica broke

Tuesday, February 17th, 2009

First light from any instrument is always exciting but particularly so when exotic locations and exciting goals are involved.  The CORONA experiment offers both.

CORONA is a stellar coronagraph designed to spot extrasolar planets orbiting other stars. It is based at Dome C, some 10,000 feet above sea level in in Antarctica, a location that boasts some of the best seeing on the planet.

The goal of the project is to test the feasibility of operating such a device in the harsh conditions that exist in the Antarctic, where temperatures can drop to -80 degrees C in winter.

The result: at -65 degrees C the telescope showed some strong aberrations in test images of Sirius, probably the result of thermal distortions.

Geraldine Guerri from the Université de Nice Sophia-Antipolis in France and buddies say: “The coronagraph could not be operated in these conditions, and thus, no nighttime images are presently available. CORONA has been sent back to France to be modified.”

That must have been disappointing, although their paper puts a brave face on things. Their plan is to eventually build a much more sophisticated coronagraph with adaptive optics.

That won’t be easy and given their experience so far, it looks highly, perhaps overly, ambitious.

Ref: arxiv.org/abs/0902.2326: First Light from the Dome C (Antarctica) of a Phase Knife Stellar Coronagraph

### What should robots do for us?

Monday, February 16th, 2009

Robots have great potential for assisting the old and disabled (not to mention the rest of  us) .  But if you’re developing one of these devices, where do you start? What kind of assistance you should concentrate on providing?

Young Sang Choi and buddies from the Healthcare Robotics Lab at Georgia Institute of Technology have worked it out for us. They asked a group of people suffering from amyotrophic lateral sclerosis (Stephen Hawking’s condition) what they most wanted a robot to be able to fetch for them.

Here are the top five requests (out of 43)…

1. TV remote
2. medicine pills
3. prescription bottle
4. glasses
5. cordless phone

Seems sensible to compile a list like this. Other notable entries:  14 cellphone, 21 keys, 36 wallet, 38 drinking can (drink not specified)

Does such a list exist for able-bodied  people? And if not, what should be on it?

Ref: arxiv.org/abs/0902.2186: A List of Household Objects for Robotic Retrieval Prioritized by People with ALS

### Simulating Sweden

Tuesday, February 10th, 2009

If you want to model how infectious diseases spread, you need a decent simulator to see how the various coping strategies pan out. Your simulation needs to take into account the population, its age and gender distribution, where people live and how far they travel from home to work and which people share homes.

But making this data realistic would be hard. After all, would anybody willingly agree to have their real data entered into such a simulation?

Actually yes. Swedes. All nine million of them.

Yep, the personal details of the entire Swedish population have been used to create what must be the world’s largest and most realistic computer simulation of the way infectious diseases spread.

Lisa Brouwers at the Swedish Institute for Infectious Disease Control and buddies have built a simulation called Microsim in which every member of the Swedish population is represented with details including their sex, age, family status, school, workplace and their geographic location at these places to within 100 metres.

That makes for potentially fantastic simulations but it also raises extraordinary questions over privacy. The data is only minimally anonymized: each individual is given a random identifier but otherwise their personal data is intact.

Given that the team is combining data from three different sources, this doesn’t sound like nearly enough protection.

But Brouwers must know what she’s doing. Or at least be praying that the rest of Sweden doesn’t find out what she’s done.

Ref: arxiv.org/abs/0902.0901: MicroSim: Modeling the Swedish Population

### Space Station simulator given emotions

Tuesday, February 3rd, 2009

Astronauts training to work on the International Space Station have to have mastered a mind-boggling amount of kit before they leave Earth. One of these devices is the Canadarm 2, a robotic arm used to manipulate experiments outside the station.

On Earth, astronauts train on a Canadarm 2 simulator connected to a virtual assistant that can spot potential errors, such as a move likely to smash the arm into the station. The assistant then offers hints and tips to the astronaut to help him or her make a correction or even issue a command to prevent damage.

The bad news for astronauts is that André Mayers and colleagues at Université de Sherbrooke in Canada who created the virtual assistant, have given it an unusual upgrade. In an attempt to help the simulator learn more about the astronauts who are using it, the team has programmed the assistant to experience the equivalent of an emotion when it records a memory of what has happened.

The problem is that the assistant receives a huge amount of data from each training session. It’s emotional response allows it to determine which of this data is most important, just as humans do. “This allows the agent to improve its behavior by remembering previously selected behaviors which are influenced by its emotional mechanism,” say the team.

The system is called the Conscious Tutoring System or CTS. It’s not clear from the paper how well the system works but how long before one unlucky astronaut hears the phrase: “I’m sorry Dave, I can’t do that.”

Ref: arxiv.org/abs/0901.4963: How Emotional Mechanism Helps Episodic Learning in a Cognitive Agent

### Reinventing the dismal science

Tuesday, January 20th, 2009

The discipline of economics in crisis. The credit crunch has exposed many economists’ most cherished ideas for the nonsense they manifestly are. With its theories in tatters, what now for the dismal science?

It looks as if the best bet is take a a few leaves out of some network science text books. Economies are complex networks, after all, although economists have failed to notice.

Until now! One of the first onto the network bandwagon is Nobel prize-winner Jo Stiglitz from Columbia University and a few pals who have been examining the Japanese credit network between banks and quoted firms in 2004.

Since the collapse of the bubble economy in the early 90s, the Japanese banking system has been going through a similar crisis to the one sweeping the west, so there is plenty to learn (not least of which is the time it can take to turn things around, although most western economists are ignoring this at present) .

The paper makes both heartening and frightening reading. (more…)

### The strange right hand of the universe

Monday, December 22nd, 2008

Is the Universe right handed? If Michael Longo at the University of Michigan in Ann Arbor is to be believed, the answer is yes; and the evidence comes from the right or left-handed shape of spiral galaxies.

Astronomers have images of many thousands of spiral galaxies. But classifying them as left or right handed is tricky for a computer program. So a project called the Galaxy Zoo asks humans to analyse galaxies and mark them as either left or right handed.

It’s fair to say the results have caused some controversy. The Universe, according to this data, seems to prefer right-handed galaxies and by some distance.

Various critics have said this is a result of the way the tests are set up and that we humans have an in-built bias for right-handed spirals. But this has been challenged by other data. Longo has trawled through the lot and and has settled on the conclusion that there is some kind of universal preference for right handedness, an Axis of Evil along which galaxies tend to spin.

What to make of this claim? Longo says that various studies have shown all kinds of biases, some such as the cold spot in the cosmic background radiation, more convincing than others.

But it always pays to tread carefully in areas like this. A number of claimed biases have disappeared after a more thorough analysis of the data.

A fascinating idea it may be, but we need to treat claims of a universal handedness with caution.

Ref: http://arxiv.org/abs/0812.3437: Does the Universe Have a Handedness?

### Levitating gas pipelines

Thursday, December 4th, 2008

Great to see one of the arXiv’s most creative minds posting again today. Alexander Bolonkin–he of “In Outer Space without a Space Suit?” and “Floating Cities, Islands and States” fame–is back with another startling idea.

Methane is significantly lighter than air and so could be used to levitate the pipes it flows through. These aerial pipelines would then be abel to carry heavier than air goods such as oil, coal and even human passengers.

Bolonkin calculates that one projected aerial pipeline coudl carry 24 billion cubic meters of gas and tens of million tons of oil, water or other payload per year.

Why not?

Ref: arxiv.org/abs/0812.0588: A Cheap Levitating Gas/Load Pipeline

### Two new SETI searches see first light

Friday, November 21st, 2008

The Search for Extraterrestrial Intelligence is picking up steam. The folks over at the Berkeley SETI group now have 7 separate searches underway at infrared, visible and radio wavelengths.

Today, Andrew Siemiona and pals outline the two newest programs which have recently seen first light and are hunting for pulses just a few hundred nanosceonds long. By contrast, most searches up till now have looked only for pulses a few seconds long.

The first, a project called Fly’s Eye at the Allen Telescope Array in northern California, can watch huge areas of the sky up to 100 degrees square and spot pulses as short as 0.625 ms

The second is called Astropulse at the Arecibo Observatory in Puerto Rico and will be 30 times more sensitive than any search gone before.

The early results from these searches are being processed on the SETI@Home network which the authors claim is the second most powerful supercomputer on the planet.

Nevertheless, it looks as if they have long hard slog ahead of them: ET hasn’t revealed herself just yet.

Ref: arxiv.org/abs/0811.3046: New SETI Sky Surveys for Radio Pulses

### The terrible truth about economics

Friday, October 31st, 2008

“Compared to physics, it seems fair to say that the quantitative success of the economic sciences is disappointing,” begins Jean-Philippe Bouchaud,  an econophysicist at Capital Fund  Management in Paris. That’s something of an understatement given the current global financial crisis.

Economic sciences have a poor record of success, partly because they are hard (Newton once pointed out that modelling the madness of people is more difficult than the motion of planets). But also because economists have singularly failed to apply the basic process of science to their discipline.

By that I mean the careful collection and analysis of observable evidence which allows the development of hypotheses to explain how things work.

This is a process that has worked well for the physical sciences. Physicists go to great lengths to break hypotheses and replace them with better models.

Economics (and many other social sciences) works back to front. It is common to find economists collecting data to back up an hypothesis while ignoring data that contradicts it.

Bouchaud gives several examples.  The notion that a free market works with perfect efficiency is clearly untenable. He says: “Free markets are wild markets. It is foolish to believe that the market can impose its own self-discipline.” And yet economists do believe that.

The Black-Scholes model for pricing options assumes that price changes have a Gaussian distribution. In other words, the model and the economists who developed it, assume that the probability of extreme events is negligible.  We’re all now able to reconsider that assumption at our leisure.

Bouchaud could also have added the example of economists’ assumption that sustained and unlimited economic growth is possible on a planet with limited resources.   It’s hard to imagine greater folly.

So what is to be done? Bouchaud suggests building better models with more realistic assumptions;  stronger regulation; proper testing of financial products under extreme conditions; and “a complete change in the mindset of people working in economics”.

All these things seem like good ideas.

But Bouchaud seems blind also to the greatest folly, which would be to imply that the roller coaster ride that we have seen in recent weeks can somehow be avoided in these kinds of complex systems.

Various physicists have  shown that stock markets demonstrate the same kind of self-organised criticality as avalanches, earthquakes, population figures, fashions, forest fires…. The list is endless.

And of course, nobody expects to be able to prevent the spread of bell bottoms or earthquakes or avalanches. If you have forests, you’re going to have forest fires.

What people do expect, however, is to have mitigation procedures in place for when these disasters do happen. That’s where econophysicists need to focus next.

Ref: arxiv.org/abs/0810.5306: Economics Needs a Scientific Revolution