Press Release

Spider-web Sensor Reveals a Flat Universe

By SpaceRef Editor
April 26, 2000
Filed under

Contact: Michelle Viotti (818) 354-8774

Inspired by the elegant efficiency of spider webs,
researchers at NASA’s Jet Propulsion Laboratory (JPL), Pasadena,
Calif., have designed a tiny, web-shaped sensor that maps faint
structures in the early universe, reinforcing theories that the
cosmos is flat in its geometry.

(A NASA news release describing the overall results may be found
at .)

Carried on an internationally sponsored balloon experiment
called BOOMERANG (Balloon Observations of Millimetric
Extragalactic Radiation and Geophysics), the dime-sized sensor
known as a “micromesh bolometer” is a prime example of NASA’s
success in developing miniaturized, high-performance technologies
for space missions.

“Just as spiders spin their webs with the least amount of
silk possible, we were able to eliminate 99 percent of the
material used by conventional bolometers,” said Dr. James Bock,
who led in the detector’s development at JPL’s Microdevices
Laboratory. “The supporting material for our detector even has
the same thickness as a strand in a spider’s web — about one
micron thick, or one hundred times finer than a human hair.”

Using advanced micro-machining techniques, each section of
the sensor’s web was designed to be smaller than the millimeter
wavelength of radiation streaming in from the cosmic microwave
background. Created when the first atoms formed in the early
universe, the cosmic microwave background has cooled a thousand
times from its original temperature — comparable to the hot
surface of the Sun — to the cold, faint radiation seen today.

While the cosmic microwave background is almost perfectly
uniform in all directions, the sensitivity of JPL’s bolometer
allows scientists to capture temperature variations of only 100-
millionths of a degree (0.0001 C) in just a few seconds of
observing time.

“That’s sensitive enough to detect the heat given off by a
coffee maker all the way from the Moon,” said Bock.

By measuring one small patch of sky after another over
several days of observation, the bolometers plot a map of the
cosmic background radiation, providing a snapshot of the universe
when the radiation formed about 300,000 years after the Big Bang.
At this time, regions with a higher density of matter and energy
left a record in the background radiation. Wherever dense
regions existed, they left a faint imprint of slightly higher
temperatures. These fluctuations in the background serve as a
kind of fingerprint, allowing scientists to discriminate between
theories of cosmic development.

With the bolometer’s high level of sensitivity, the
BOOMERANG project was able to reveal density patterns in the
young universe that are consistent with an inflationary theory of
cosmic development. This theory proposes that, in the first
moments after the Big Bang, the universe went through a period of
extreme, exponential inflation. The theory further predicts a
“flat” geometry for the universe, because the immense stretching
of space during an inflationary period would have removed any
initially strong curvature in the smaller and denser early

“Think of it this way,” explains Bock. “If we were to
balance on a large ball, we would certainly feel the curvature
beneath our feet. Expand that ball to the size of the Earth, and
we experience that space as flat. Now think about blowing up
that ball to a cosmic scale, and you can imagine how inflation
would vastly flatten the visible universe.”

To test cosmic development theories even further, future JPL
bolometers will fly on the European Space Agency’s Far Infrared
and Submillimetre Telescope (FIRST) and Planck missions, both
scheduled for launch in 2007. Using bolometers with 10 times
higher performance, Planck is expected to provide the definitive
map of variations in the cosmic microwave background, while FIRST
will survey some of the earliest galaxies. In the meantime,
scientists will be studying the BOOMERANG map over the next few
years to gain a better understanding of the nature and
composition of matter in the universe.

The BOOMERANG results were obtained through a balloon
experiment in 1998 that carried JPL’s bolometer in a sensitive
receiver 36 kilometers (23 miles) above the atmosphere in
Antarctica. Because Antarctica provides 24-hour sunlight and
winds that blow in a circular pattern around the continent, the
balloon experiment was able to maintain continuous measurements
over a 10-1/2 day period.

The scientific results will be published in the April 27
issue of Nature. Information on the BOOMERANG project can be
found at and . For images of JPL’s
micromesh bolometer and its results, see .

The BOOMERANG Project was led by Dr. Andrew Lange of the
California Institute of Technology and by Dr. Paolo DeBernardis
of the University of Rome La Sapienza. Primary funding for
BOOMERANG was provided by the National Science Foundation and
NASA in the United States; the Italian Space Agency, the Italian
Antarctic Research Programme and the University of Rome La
Sapienza in Italy; and the Particle Physics and Astronomy
Research Council in the United Kingdom. The Department of
Energy’s National Energy Research Supercomputing Center provided
high-level computer analysis of the data.

The Microdevices Laboratory is a state-of-the-art research
and technology-development facility in the Center for Space
Microelectronics Technology at JPL. Funding for the micromesh
bolometer came from JPL’s Technology and Applications Programs
Directorate. JPL is managed by Caltech on behalf of NASA.


4/26/00 MV


SpaceRef staff editor.