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Science
Friday > Archives
> 2000
> May
> May 5, 2000:
Hour One: Cosmology Update
/ Gravitational Constant
| A report in the journal Nature last week added some
of the earliest images of the universe to its family photo album.
Using an ultra-sensitive telescope mounted to a balloon circling
the South Pole, the international team of researchers on the Boomerang
project were able to obtain much more detailed images of the cosmic
microwave background radiation than had previously been possible.
The images, of pockets of hot and cold areas in the cosmic microwave
background, represent the universe when it was only a few hundred
thousand years old. |
Boomerang project launch in Antarctica. Image courtesy
Boomerang team.
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But it's not just the presence of the images that cosmologists are finding
interesting. By analyzing features in the images, the scientists have
been able to tease important findings from the blotchy color fields.
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Among the data is additional evidence that the universe is "flat"
-- that it will continue to expand with just the right amount
of force to counteract the inward pull of gravity, rather than
eventually collapsing inwards upon itself. The findings also confirm
previous data indicating a mysterious repulsive force that is
driving the continued expansion of the universe.
On this hour of Science Friday, we'll get an update on the findings
of the Boomerang team, and find out what they may mean for cosmology
in general.
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Analyzing the high-resolution maps of the cosmic background radiation.
The blotches represent "hotter" and "cooler"
parts of the microwave background. Courtesy Boomerang team.
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Plus - we'll find out about new research presented at a meeting of
the American Physical Society earlier this week that's very close to
home. Scientists working at the University of Washington have come up
with what they say is a more accurate method of measuring the gravitational
constant. That number, called "G," represents how much any two objects
of known mass and separated by a known distance attract each other
due to the force of gravity. (It's different from "g," the ever-popular
9.8 m/s/s that represents the acceleration of objects toward the Earth
under the force of gravity.)
Using an updated version of an 200-year-old method for determining
G, a Cavendish torsion balance, the University of Washington physicists
say that they've been able to measure the value of G with about 100
times more accuracy than before. And that improved accuracy has allowed
them to refine accepted value for the mass of the Earth. They find that
it is 5.972 sextillion metric tons--that's 5,972,000,000,000,000,000,000
metric tons--a little lighter than the previously accepted 5.98 sextillion
metric tons. We'll find out how they reached these conclusions, and
about why the quest to measure G more accurately hasn't always been
smooth sailing.
Guests:
John Ruhl
Member, Boomerang
Team
Professor, Physics
University of California
Santa Barbara, California
Alan Guth
Author,
"The Inflationary Universe: The Quest for a New Theory of Cosmic Origins
" (Perseus Press, 1998)
V F Weisskopf Professor Of Physics
Massachusetts Institute of Technology
Cambridge, Massachusetts
Jens Gundlach
Research Associate Physics Professor
University of Washington
Seattle, Washington
Books/Articles Discussed:
Related Links:
BOOMERanG
Home Page
NASA
Scientific Balloons Program
Caltech
Press Release, (Boomerang)
Cosmology:
A Research Briefing
The
Controversy over Newton's Gravitational Constant
NIST: Introduction to the constants for nonexperts
APS April Meeting Lay Language Papers - Gravitational Constant
Produced By: Charles Bergquist
Web Producer: Charles
Bergquist
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