Friday, April 13, 2007

Cool experiments

I was absolutely delighted to learn from the latest issue of Physics Today (subscription may be required) that a couple of things I thought I knew are no longer entirely true.

1) Resolution (the ability/separation necessary to distinguish two points as separate) is limited by roughly the wavelength/2.
In fact experiments have shown that resolution on the order of wavelength/30 is entirely feasible given ghost reflections and time reversed signal transmissions. Ghost reflections are signals that bounce off obstructions (buildings or mountains) which effectively provide a time delayed signal. A time reversed signal is one in which the signal is played in reverse order. If AEIOU is the “forward” signal the time reversed signal would be UOIEA.

2) Diamonds are the hardest substance.
Over a narrow temperature range experiments have shows that a tin alloy (containing 10% barium titanate) achieves a stiffness, or resistance to compression (measured as Young’s modulus) 7-8 times that of diamond and ~ 40 times that of steel.

Both of the results appear to be far from optimized, expect substantial improvement in the years to come.


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