23 February 2011

Science Shorts

Physics News

The news in the land of physics is one of tighter experimental boundaries on potential weird stuff a.k.a. "new physics" without actually finding any or ruling it out.

I've previously mentioned the closing parameter space of SUSY. The LIGO and VIRGO experiments designed to detect gravity waves have similarly not found them but have placed experimental limits on their magnitude (although still about tens times larger that their expected magnitude apparently). Our Secretary of Energy, who is also a practicing physicist, is a co-author of a recent paper putting experimental limits on any potential deviations from the general theory of relativity attributable to quantum gravity theories (any deviations are less than one part per million of a certain kind of atom interferometry measurement).

New measurements have increased with accuracy with which we can determine the distance of some of the farthest galaxies which allows more precision in estimating the amount of dark energy in the universe (or, more or less equivalently, the value of the cosmological constant in general relativity).

The Large Hadron Collider (same source) has also put limits on the maximum size of any preons that could be present if quarks were composite, rather than fundamental particles: "if quarks are made of smaller particles, the constituents are no larger than 60 trillionths of a billionth of a meter in diameter. That new limit, about 60 percent smaller than the previous estimate[.]"

In terms more familiar to most people who work with subatomic physics that is 10^-21 meters. Alternately, in terms of the Plank length, the new limit is about 10^12 Plank length units. The semi-classical diameter of an electron is 10^17 Plank length units, while the semi-classical diameter of a proton is 10^20 Plank length units. (I use the caveat semi-classical because it isn't obvious that it is real meaningful to think of fundamental particles like quarks and electrons as anything other than point-like for most purposes.) Thus, the Large Hadron Collider tells us that any component part of a quark has to be at least one hundred thousand times smaller than an electron. Data gathered but not yet analyzed from LHC should make it possible to probe limits half that size.

Many physicists expect that the "minimum length" called the Plank length, is 1.616252(81)×10^−35 meters, based on natural combinations of Plank's constant (which measures the minimum energy of photons of particular wave lengths), the gravitational constant and the speed of light. String theorists, likewise, often assume that the string of string theory are of lengths on the order of magnitude of the Plank length. Thus, the LHC findings, themselves aren't inconsistent with the possibility of composite quarks and electrons although there is really nothing to indicate that they exist either.

The bottom line from all of these studies is that the Standard Model and General Relativity continue to be accurate descriptions to the universe to remarkable levels of precision, despite some lingering concerns about unexpected CP violations in the Standard Model and some theoretical disconnects between the two fundamental theories that crop up only in domains we don't have a capacity to observe at this point.

The vast majority of physicists I'm aware of who study quantum mechanics and general relativity think that there is something beyond these theories to discover and I agree with them. But, whatever new physics are out there, it is also increasingly clear that it is very subtle. In the same way, one can still do a lot of very good science and engineering in a wide variety of useful areas using classical Newtonian mechanics and gravity, classical thermodynamics, Maxwell's Equations for electro-magnetism, a proton-neutron-electron model of the atom, and the Periodic table.

It isn't that modern physics is irrelevant. Every computer designer relies on quantum tunnelling to make the machines work. Every cell phone and GPS unit makes calculations that require the application of general relativity from moment to moment. Both general relativity and quantum mechanics provide insights critical to making nuclear power plants, nuclear bombs, cancer treatments and carbon dating work. But, the weird physics that goes into making these things work seems a lot less weird when broken down to the particular aspect of them that matters for an engineering application and the average person doesn't need to know the science behind these devices and can simply view them as "black boxes" that produce certain results when used in particular ways.

It isn't at all obvious that "new physics" will have any practical engineering applications at all, even if it would be an immense source of intellectual pride and accomplishment for our species.

Also (from the news link above):

Supermassive black holes at the centers of distant galaxies, previously estimated to range in mass between 10 million to 1 billion suns, may weigh about one-half to one-tenth as much. . . . The downsizing indicates that black holes in distant and nearby galaxies weigh about the same, eliminating what had been a puzzling mismatch.

One of the more interesting experimental facts from astronomy is the close relationship between the size of a black hole and the size of its surrounding matter, and the apparent maximum black hole size that is observed. A finding that black holes in distant galaxies (whose light started moving towards us more deeply in the past) are similar in size to black holds in galaxies that are closer (and hence sending light from a less distant part of the past) would seem to rule out a scenario in which the earliest black holes were very large and have steadily shrunk over time due to Hawking radiation, and also a scenario in which the earliest black holes were very small and have steadily grown over time due to the absorbtion of more surrounding material. Shrinkage and growth appear to be roughly balanced over a long span of the history of the universe.

Psychopathy Starts Young

Finallly, the evidence that psychopathy is an early onset condition that manifests as early as age seven (or even age three!) continues to mount, most recently from a study of 9,578 British school children evaluated by teachers and parents at ages 7, 9 and 12, for behavior problems and callous-unemotional traits. The researchers involved in the latest study on the point specifically disavow the loaded "psychopth" word, because research has not yet established a definitive link between callous-unemotional traits in children with behavior problems and psychopathic traits in adults, but another study found "that 3-year-olds who have difficulties learning to fear impending punishments in lab experiments — a key facet of callous-unemotional traits — commit criminal offenses at much higher rates than their peers by age 23."

When an unrelenting penchant for misbehaving joins forces with lack of emotion, guilt and empathy, 7-year-olds are headed for years of severe conduct problems. . . . Youngsters who regularly misbehave and get into trouble at age 7, and who also display so-called callous-unemotional traits, frequently stay on a troubled course until at least age 12. . . . 5 to 10 percent of schoolchildren persistently engage in antisocial behaviors such as fighting, lying and stealing. . . . A total of 4.4 percent of these children, mostly boys, exhibited high levels of both misbehavior and callous-unemotional traits throughout the study. Compared with their peers, this group of youngsters came from particularly chaotic families that used harsh forms of punishment. These kids also displayed many hyperactive symptoms and got along poorly with peers. Another 4 percent of kids in the study displayed consistent conduct problems with either increasing or decreasing levels of callous-unemotional traits from age 7 to 12. . .

[C]hildren with high levels of callous-unemotional traits almost always misbehaved regularly. In contrast, only about half of the kids who constantly misbehaved also lacked remorse, guilt and empathy, indicating that a variety of influences play into conduct problems. . . . callous-unemotional children respond best to interventions that reward them for good behavior rather than punishing them for misdeeds[.]

"Adult psychopaths similarly show no remorse for crimes and blunted emotional reactions, although they often possess considerable empathy that they use to prey on others." Adult psychopaths respond best to the same kinds of incentives.

An important reason to care is that the DSM-V definition of conduct disorder is being revisited and there is faction that thinks it should distinguish callous-unemotional conduct disorder as something distinct from mere chronic misbehavior.

“I’m not suggesting that these children are psychopaths, but callous-unemotional traits can be used to identify kids at risk of persistent, severe antisocial behavior,” said psychologist Nathalie Fontaine of Indiana University in Bloomington, who directed the study. These findings indicate that callous-unemotional traits should be factored into the definition of a particularly virulent form of childhood conduct disorder in the next manual of psychiatric disorders, Fontaine said. Chronic misbehavior alone defines conduct disorder in the current fourth edition of the psychiatric manual used by doctors to define mental ailments, now being revised.

There are about 3 million children born each year in the United States. About 150,000 to 300,000 of them will persistently engage in anti-social behavior. About 13,000 to 26,000 of them, one or two in every couple hundred, will have notable callous-unemotional streaks. These patterns of behavior, if not in place at birth, are at least in place by the time they are in elementary school.

The extent to which it is becoming clear that both future academic performance and future behavior is predictable in early elmentary school is remarkable. But, we don't really know what to do with this knowledge. The only career paths we seem to have in our society for callous-unemotional children is gang hitman and Ponzi scheme engineer, which aren't precisely the sort of paths we'd like to encourage. Similarly, we aren't really sure what to do in our society with mentally retarded children. We don't even have support groups for parents of children who do things like torture little animals, con teachers and bully peers, much to the consternation of the adults in their lives. Sometimes we try to hold those parents morally responsibile, but we don't offer them a lot of organized resources for coping.

Alas, psychopathy (and close cousins like "borderline personality disorder") isn't anything as simple as some particular gene with a simple inheritance pattern. They've looked. It isn't there. It may be hereditary, and almost certainly has a strong congenital component at the very least, although environmental factors may influence how it develops. But, the family histories that researchers have seen involve a variety of mental health issues in a fairly wide swath of cousins and uncles and aunts, as well as closer relations, rather than a simple parent to child pattern. It isn't uncommon for siblings to be very different in this regard - one typically empathetic, another calleous and unemotional. Apparently, there are a number of pieces of the puzzle, some of which are symptomatic even by themselves, that have to come together to produce a person who has this kind of emotional makeup that are relatively independent of each other. Nobody has found a drug that turns callous-unemotional children into loving empathetic ones either.

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