National Geographic Daily News
The LARES satellite is prepared for launch.

The LARES satellite undergoes preparations for launch at Europe's spaceport in French Guiana.

Photograph courtesy Stephane Corvaja, ESA

Davide Castelvecchi

for National Geographic News

Published February 13, 2012

Launched today aboard the European Space Agency's new Vega rocket, a low-cost space probe will test Albert Einstein's general theory of relativity—and could do so better than a recent NASA mission that cost nearly a hundred times more, managers say.

In the mid-2000s, after more than 40 years of development, the $800-million Stanford University-led Gravity Probe B detected frame dragging. This effect, predicted by Einstein's theory, is caused by Earth's rotation dragging the fabric of space and time along with it.

(Related: "'Death Dance' Stars Found—May Help Prove Einstein Right.")

But because of a technical glitch, the NASA craft was able to measure frame dragging with an estimated accuracy of no better than 20 percent.

Scientists working with the new Italian probe, which cost $10 million (U.S.) to build, hope to improve on those readings.

"If we reach one percent [accuracy]—and I am fairly confident we will—we'll have an order of magnitude's improvement" over Gravity Probe B's measurement, said mission leader Ignazio Ciufolini, of the University of Salento in Lecce, Italy.

LARES, for Laser Relativity Satellite, lifted off from a spaceport in French Guiana at 7 a.m., local time. Now in orbit, the probe will provide data on frame dragging for several years. (Lares, pronounced LAR-ries, were local guardian gods in the pagan religion of ancient Rome.)

"Achieving the LARES design sensitivity would allow an impressive confirmation of general relativity," said Alan Kostelecky, a theoretical physicist at Indiana University in Bloomington who's not on the LARES team.

"Disco Ball" to Help Validate Einstein

LARES is essentially a really heavy disco ball: The totally passive probe is a solid sphere of metal—a tungsten alloy—that packs 880 pounds (362 kilograms) in a ball just 14 inches (35.5 centimeters) wide.

The probe is covered with reflectors so that, as the craft orbits Earth, an international network of laser-ranging stations will be able to track its position with millimeter-scale precision.

The craft's orbit around our planet will be tilted at an angle to Earth's Equator. From calculations based on Einstein's theory, Ciufolini's team expects that frame dragging will make LARES's orbital plane slowly precess, or rotate, around Earth as the probe gets dragged along with our planet's distortion of space-time.

(Also see "Einstein's Gravity Confirmed on a Cosmic Scale.")

Over a year, this effect should add up to just a few tens of millionths of a degree, meaning that it would take about ten million years for the probe's orbital plane to complete one full twist around te planet due to frame dragging alone.

Still, the small shift should amount to about 13 feet (4 meters) of displacement a year, which the laser-ranging system should be able to measure to less than one percent accuracy.

Don't Stop Testing General Relativity

LARES's high density makes the probe less sensitive to atmospheric drag, which at about 900 miles (1,450 kilometers) above Earth's surface will be very small but not negligible, Ciufolini said.

The dense sphere will also be virtually unaffected by radiation pressure from sunlight.

Other effects, such as the fact that Earth is not a perfect sphere, will actually make the probe's orbit precess by much larger amounts—one full twist every three years or so.

But the researchers will use various data-analysis techniques, together with data from previous missions, to extract the frame-dragging measurement.

In the end, Einstein's theory will probably pass the test: Scientists believe that general relativity should eventually break down, but only at scales so small that quantum physics comes into play.

Still, in science there's never such a thing as absolute certainty, Ciufolini said. (Also see "Particles Moved Faster Than Speed of Light?")

"General relativity has been confirmed spectacularly by all experiments for nearly a hundred years now," he said. "But that does not mean that one should stop putting it to the test."

3 comments
Lorenzo Iorio
Lorenzo Iorio

A NEW case of scientific misconduct by Mr. Ciufolini as reported by ArXiv. Read the comment by moderators at

http://arxiv.org/abs/gr-qc/070...
It is: " This submission has been made by G. Felici, a pseudonym of Ignazio Ciufolini, who repeatedly submits inappropriate articles under pseudonyms, in violation of arXiv policies " PS. About the OTHER case, the CiuForst one at http://arxiv.org/abs/0712.3934, now ArXiv has reinstated the original comment explicitly exposing Mr. Ciufolini. Let's wait for the next episode...

Lorenzo Iorio
Lorenzo Iorio

The ArXiv moderators  tried to get clever with all of us, to say the least, by censoring their own previous comment mentioning Mr. Ciufolini by invoking alleged "changed ArXiv policies" (what? when? After 5 years and 4 months, respectively, that they kept their own comments there?)  in a private communication to me. So, here are all the screenshots


https://www.facebook.com/GPBframedraggingArXivCiufolini





Lorenzo Iorio
Lorenzo Iorio

The ArXiv moderators, in their comment to this submission  by G. Forst, reported a case of scientific misconduct pertaining the outcome of the GP-B mission by Ignazio Ciufolini, author of the competing LAGEOS tests. They write: ''This submission has been removed because 'G.Forst' is a pseudonym of Ignazio Ciufolini, who repeatedly submits inappropriate articles under pseudonyms. This is in explicit violation of arXiv policies.''

Please note that this version of the ArXiv comment is recent in that it was posted certainly not before May 2011, evidently after that ArXiv staff knew some further pieces of information. Before, the original comment by ArXiv was: "This submission has been removed because ''G.Forst'' is a pseudonym of a physicist based in Italy who is unwilling to submit articles under his own name."

Share

How to Feed Our Growing Planet

  • Feed the World

    Feed the World

    National Geographic explores how we can feed the growing population without overwhelming the planet in our food series.

See blogs, stories, photos, and news »

The Innovators Project

See more innovators »

Latest Photos Galleries

See more photos »

Shop Our Space Collection

  • Be the First to Own <i>Cosmos: A Spacetime Odyssey</i>

    Be the First to Own Cosmos: A Spacetime Odyssey

    The updated companion book to Carl Sagan's Cosmos, featuring a new forward by Neil deGrasse Tyson is now available. Proceeds support our mission programs, which protect species, habitats, and cultures.

Shop Now »