Number 659, October 28, 2003
by Phillip F. Schewe, Ben Stein, and James Riordon
A Map of the Universe
A map of the universe produced by the Sloan Digital Sky Survey contains
200,000 galaxies at distances of up to two billion light years, and
spread out across 2400 square degrees of sky. According to Sloan astronomer
Michael Blanton (NYU), this is "the best three-dimensional map
of the universe to date." The Sloan effort uses a telescope in
New Mexico optimized to record spectra from many galaxies at the same
time. One of the standout features of the map is the Sloan Great Wall
of galaxies, some 1.37 billion light years long and the "largest
observed structure in the universe" (preprint:astro-ph 0310/0310571)
Combined with data from other telescopes, such as the Wilkinson Microwave
Anisotropy Probe (WMAP), the new Sloan observations help tamp down uncertainties
in several pivotal astronomical numbers. The new best value for the
Hubble constant is 0.70 with an uncertainty of about 0.04; the amount
of energy in the universe vested in matter is 30% with an uncertainty
of 4%; the upper limit on neutrino mass is 0.6 eV; and the age of the
universe is 14.1 billion years with an uncertainty of 1 billion (Preprint
astro-ph/0310/0310723; visit Sloan
website).
An Electrical Micro-Generator
An electrical micro-generator might provide electric power for portable
microscale devices. At a modern power station, high pressure fluids
(water, steam, or gas) are dashed against turbine blades, thus turning
a shaft which cranks out electricity. At an MIT lab, all of this is
done on a centimeter-size scale. At an upcoming meeting of the AVS Science
and Technology Society in Baltimore, Carol Livermore will describe a
micromotor with a 4-mm rotor which puts out 20 milliwatts of power,
far more power than any other existing rotating micromotor. The motor
may be incorporated into a microscale gas turbine generator. This is,
in effect, a tiny jet engine: air and gas mix in a small combustion
chamber and the resultant explosion powers the turbine (see
figure). The MIT researchers expect that soon the output will be
at the level of 300 volts, and 1 watt of mechanical power or 0.5 watt
of electrical power. The device might not yet be as compact as the best
micro-batteries currently available, but it will be able to do what
batteries cannot, namely supply power over long periods. (Paper MM-TuA3,
Carol Livermore, 617-253-6761;
meeting will be held November 2-7; visit
website; background
article)
The High and Low Notes of the Universe
The Cornell nano-guitar, first built in 1997 but only now played for
the first time, twangs at a frequency of 40 megahertz, some 17 octaves
(or a factor of 130,000) higher than a normal guitar (see
figure). Researchers at Cornell University used laser light to set
the 10-micron-long silicon "strings" (actually slender planks
of silicon) of the guitar in motion. There is no practical microphone
available for picking up the guitar sounds, but the reflected laser
light could be computer processed to provide an equivalent acoustic
trace at a much lower frequency. The laser light could excite more than
one string, creating megahertz "chords." The playing of the
nano-guitar will be described by Lidija
Sekaric (now at IBM) at the AVS
meeting (paper MM-WeM1; 914-945-1802). If the nano-guitar's natural
tones are among the most high-pitched sounds in the universe, some of
the lowest pitched are to be found in the vicinity of the black hole
in the Perseus galaxy cluster. The Chandra x-ray telescope recently
saw concentric circles in the inter-galactic gas cloud surrounding the
cluster core; some astronomers interpret the ripples as being sound
waves (with a frequency some 57 octaves below human hearing, and possibly
"the deepest note ever detected from an object in the universe")
caused by jets from the black hole shooting outwards into the nearby
matter. (see Chandra
press release)
Enlarge text
Shrink text
Print
Digg this
Del.icio.us
Furl