Washington: Since Charles Darwin’s time, scientists have speculated that the solid Earth might be expanding or contracting. But now, a new NASA study has essentially laid those speculations to rest.
The NASA-led research team has confirmed what Walt Disney told us all along: Our Earth really is a small world, after all.
Using a cadre of space measurement tools and a new data calculation technique, the team detected no statistically significant expansion of the solid Earth.
To make these measurements, the global science community established the International Terrestrial Reference Frame. This reference frame is used for ground navigation and for tracking spacecraft in Earth orbit.
An international group of scientists led by Xiaoping Wu of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., set out to independently evaluate the accuracy of the International Terrestrial Reference Frame and shed new light on the Earth expansion/contraction theory.
The team applied a new data calculation technique to estimate the rate of change in the solid Earth’s average radius over time, taking into account the effects of other geophysical processes. These data were then combined with measurements of Earth’s gravity from NASA’s Gravity Recovery and Climate Experiment (GRACE) spacecraft and models of ocean bottom pressure, which help scientists interpret gravity change data over the ocean.
The scientists estimated the average change in Earth’s radius to be 0.004 inches (0.1 millimeters) per year, or about the thickness of a human hair, a rate considered statistically insignificant.
“Our study provides an independent confirmation that the solid Earth is not getting larger at present, within current measurement uncertainties,” said Wu.
The study has been detailed in Geophysical Research Letters.