Re: News: Earth Is Smaller Than Thought, New Measurements Show.
- From: UC <uraniumcommittee@xxxxxxxxx>
- Date: Tue, 10 Jul 2007 21:24:09 -0000
On Jul 10, 5:12 am, Ye Old One <use...@xxxxxxxxx> wrote:
Earth Is Smaller Than Thought, New Measurements Show.
http://news.nationalgeographic.com/news/2007/07/070709-earth-size.html
Kate Ravilious
for National Geographic News
July 9, 2007
New measurements reveal that Earth is smaller than was previously
thought-though not by much.
If you're a planning a trip around the world, you may be pleased to
hear that you have about 0.1 inch (2.5 millimeters) fewer to travel.
Although the change is tiny, experts say it could have implications
for predicting sea-level rise and the effects of global warming.
Using a suite of sophisticated techniques, a team of international
scientists has spent the last two years measuring nooks and crannies
all over Earth, noting how they have changed and comparing the new
measurements with those taken in 2002.
In addition to revealing Earth's slightly slimmer silhouette, the
results reveal that the Pacific seafloor is the most restless place on
the planet, traveling to the northwest by around two inches (five
centimeters) a year.
Meanwhile, much of Scandinavia and northern Canada are bobbing up in
elevation some 0.2 to 0.3 inch (5 to 8 millimeters) a year, and North
America is pulling apart from Europe at a rate of around 0.7 inch (18
millimeters) a year.
The changes do not indicate that Earth is shrinking but rather that
previous estimates-measured from Earth's core to its surface-were
slightly off, the researchers explained.
"Earth's physical shape hasn't changed since last time, but we have
just shown that on average our 400 observation sites lie around 2.5
millimeters closer to the center of the Earth," said Axel Nothnagel, a
mathematician at Germany's University of Bonn who took part in the
research.
A Mammoth Calculation
One of the techniques used to measure these planetary jiggles involved
more than 70 radio telescopes situated all over the world, each
picking up radio waves from quasars-young galaxies billions of
light-years away.
"Because quasars are so far away, they appear stationary and so they
are an ideal fixed point in the sky," Nothnagel explained.
In the same way that early sailors used stars to navigate, Nothnagel
and his colleagues used the quasars' signals to calculate how far
various spots on Earth have moved from each other.
Another technique used in the study measured the distance between
Earth and various satellites in the sky.
Overall the study used 400 observation sites and compiled data taken
between 1984 and 2005. Analyzing all the data and carrying out the
calculations took two years.
So why do these tiny movements matter, and do we really need to know
Earth's size to the nearest millimeter? The answer is probably yes, if
you live on a sinking continent.
"[The measurement] provides us with access to a coordination system
against which we can measure environmental change," said Marek
Ziebart, a mathematician at University College London who wasn't
involved in the study.
If ice caps continue to melt or water begins to evaporate from the
Amazon Basin, these new exact measurements will enable scientists to
more accurately track the effects, Ziebart explained.
(See an interactive map of the effects of global warming.)
"If you have a tide gauge telling you that the sea level is rising,
how do you know that it is not the continent which is subsiding [or
sinking]?" Nothnagel said.
For scientists who want to determine whether the sea level has risen
by just a millimeter a year, the measurements on the ground have to be
just as precise, he said.
The new measurements also allow scientists to monitor continuing
trends that have been spotted in previous surveys, the research team
noted.
North America and Europe continue their steady parting of ways, as the
Atlantic Ocean grows wider due to the process of continental drift.
Meanwhile, northernmost sections of Europe and North America keep
gaining in elevation, as they buoy up after the huge weight of ice was
lifted at the end of the last ice age.
"Canada and Scandinavia are responding to post-glacial rebound,"
Nothnagel said.
He and his colleagues are now gathering data for the next mammoth
calculation effort, which is due to begin in 2008.
--
Bob.
Maybe Earth should reply to one of those e-mails that read:
"Increase your pen1s size!"
.
- References:
- News: Earth Is Smaller Than Thought, New Measurements Show.
- From: Ye Old One
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