for National Geographic News
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 (get the facts on 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.
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