Wednesday, March 28, 2012

A few arresting stories:

From SciTech, a few headlines:
  • quantum-interference-pattern Quantum Interference Shown Experimentally in Larger Molecules: A perfectly accurate headline over a sloppy story. (The double slit experiment is explained by a purely wave description of matter: but that's not the only experiment in town. And there is no such thing as "the exact transition between macroscopic physics and quantum physics".) This sort of thing was already done with smaller particles; these are pretty big.
  • Antimagnet Cloak Hides Objects from Static Magnetic Fields is a good enough description of a really cool story: layers of superconductor with a ferrite magnet on the outside keep the field inside zero (or close, for this experiment), and don't perturb the field outside (at least not much). The writer suggested that the technology might let someone "hide metallic weapons from security portals" but given that so far all superconductors demand aggressive cooling, and that one could defeat the "static magnetic field" aspect by pulsing the system, I don't think terrorists will be helped much. (Imagine trying to conceal a knife in a dewar of liquid nitrogen.)
  • Runaway Planets at 30 Million MPH is written as though astronomers had actually seen such beasts. Not so. They calculate that if a binary star system with a planet falls into a black hole, there's a chance that, just as one of the stars could be kicked out at high speed (actually seen), any loose planets could also take a fast ride (not seen, nor likely to be).
  • Crab Nebula Emits Pulses at Unexplainable Levels is about the surprisingly high energies gamma rays from the pulsar attain: up to 400 GeV. For comparison, gamma rays from nuclear decays are typically in the range 100keV to 10MeV. Nobody is sure why they can range so high, but we're not perfectly sure about the mechanism for high energy gammas from the sun either (magnetic field twist and reconnection is the top theory).
  • Rational Thinking Ruled Out as Reason for Children’s Selective Imitation. The headline, and the conclusion, are deeply overwrought and not justified by the story itself.
    In the experiment, a child would observe an adult performing the unconventional action of illuminating a lamp by touching it with the head. Being presented with the lamp later on, 70 percent of the children would copy this curious behavior – but only if the hands of the person were free during the observed action. If the hands were occupied by holding a blanket wrapped around the body, which was before worn loosely over the shoulders, imitation rates dropped to around 20 percent.
    The new results are from revisiting the experiment, after noticing that the sight of an adult wrapped in a blanket was going to be distracting to an infant.
    One alteration underlined how much eye- catching distractions influenced the children’s response: When two red Smileys were put on the table before the experiment, imitation of the “hands-free”-condition dropped considerably. In order to reduce distraction during the second condition, the children were given time to familiarize themselves with the sight of the blanket in a five-minute warm-up phase, which preceded the demonstration of the head touch action. The imitation rate went up to around 70 percent, showing that it made no actual difference whether the model person’s hands were free or not.

    This contradicts the earlier claim that infants were concluding that an adult must have had a good reason for not using his hands. But that doesn't mean infants can't think rationally.

  • I decided not to comment on the article claiming that women could reach orgasm from exercise.

A number of interesting stories, but with a fair bit of chaff and nonsense to weed through...

2 comments:

Assistant Village Idiot said...

That shielding of magnetic fields...

I don't know if you were reading my blog a year ago.

http://assistantvillageidiot.blogspot.com/2011/01/anti-gravity.html

james said...

I was, but that may have been when I was out of town for a while; I don't remember it.
One good description of the effect of a "gravity shield" is that trying to step onto it is like trying to make a high-jump with the bar set at infinity. There's an awful lot of potential energy you have to account for; that has to go into the system somehow.

Just because I can't think of a way to make a gravity shield doesn't mean it is impossible-- I've been surprised too many times. But whatever it is, it has to follow the rules. Each square cm of surface has about 1kg of air above it, which would require about 60MJoules of energy to "shield" completely from Earth's gravity. Of course its momentum would tend to move it up up and away from the surface and out of the shielded region, which would make it tend to fall again--and its potential energy has to go somewhere too.

It might be possible, with gravitational waves, to make a bit of spacetime locally flat for a tiny fraction of a second (though I don't think gravity waves work that way--I should review). But that's not quite the same thing as a shield.