Experiments to test the Equivalence Principle: the international context

"Galileo Galilei" GG Home Slide tours Documents	The international context Ground tests of the equivalence principle The most systematic and successful experiments on the Equivalence Principle have been carried out by the so called "Eöt-Wash" group of Eric Adelberger, Blayne Heckel and collaborators at the University of Washington in Seattle. The "Eöt-Wash"apparatus is a torsion balance operated at room temperature.with small test cylinders (10 g each) placed on a turntable whose rotation provides a modulation of the expected signal with the period of about 1 hr. Frequency modulation is crucial in order to check for violation in the field of the Earth, otherwise the signal would be DC, and therefore very hard to detect.No violation has been detected, and the sensitivity of the experiments has steadily improved: from 1 part in 10¹¹ in 1990 (Adelberger et al., Phys. Rev. D, 42, 3267, 1990) to about 1 part in 10¹² in 1994 (Su et al., 50, 3614, 1994), to about 1 part in 10¹³ in 1999 (Baessler et al., 83, 3585, 1999). Many other experiments are ongoing all over the world. Three proposed missions for testing the equivalence principle in space STEP (Satellite test of the Equivalence Principle). STEP has originated at Stanford University (USA) in the early 70s. It is currently in the SMEX competition of NASA with the goal of testing the equivalence principle to 1 part in 10¹⁸ . STEP has been studied twice to Phase A level within ESA. In both cases the final study reports were consistent with a target of 1 part 10¹⁷ (Blaser et al., ESA/NASA SCI(93)4, 1993; blaser et al., ESA SCI (96)5, 1996). Visit the STEP Website at: http://einstein.Stanford.EDU/STEP/ "GALILEO GALILEI" (GG). GG has originated at the University of Pisa (Italy) in the early 90s. It has been studied to phase A level within ASI in 1998. The final Study Report is consistent with the goal of testing the equivalence principle to 1 part in 10¹⁷ (GG Phase A Study Report, ASI, 1998). A prototype of the instrument proposed for flight has been developed and is under testing. GG is currently undergoing an Advanced Phase A Study with ASI funding. This study shall be completed by May 2002. The results will be presented at the International Workshop of Pisa-Florence, May 27-29 2002.Visit the GG Website at: http://eotvos.dm.unipi.it/nobili/ MICROSCOPE. Microscope has originated at ONERA (Chatillon, France) in the late 90s. It is currently in Phase B Study within CNES and ESA financial support with the goal of testing the equivalence principle to 1 part 10¹⁵ . Vist the Microscope Website at: http://www.onera.fr/dmph-en/accelerometre/ For a comparative analysis of the different designs of the proposed space experiments, see a Review (Sec. 7), and follow the opendiscussion on radiometer effect and other issues relevant to all three missions Proposed equivalence principle test from a balloon A free fall experiment named GREAT has been proposed for testing the equivalence principle to 1 part 10¹⁵ inside a vacuum capsule to be released from a balloon at an altitude of 40 km, allowing a free fall time of 30 s. GREAT is a collaboration between SAO (Cambridge, MA USA) and IFSI-CNR (Rome, Italia) and is under investigation with NASA and ASI fundings. The target is comeptitive with that of Microscope. The advantages are easy repeatibility and the comparative low cost of sub-orbital flights. Experimental gravitational physics with drag-free satellites Dr Benjamin Lange runs a Webpage with all possible information about drag-free satellites and their use for experiments in gravitational physiscs.Visit it at the address: http://www.dragfreesatellite.com/ anna nobili Last edited: agosto 05, 2002

"Galileo Galilei" GG
Home

The international context

Ground tests of the equivalence principle

The most systematic and successful experiments on the Equivalence Principle have been carried out by the so called "Eöt-Wash" group of Eric Adelberger, Blayne Heckel and collaborators at the University of Washington in Seattle. The "Eöt-Wash"apparatus is a torsion balance operated at room temperature.with small test cylinders (10 g each) placed on a turntable whose rotation provides a modulation of the expected signal with the period of about 1 hr. Frequency modulation is crucial in order to check for violation in the field of the Earth, otherwise the signal would be DC, and therefore very hard to detect.No violation has been detected, and the sensitivity of the experiments has steadily improved: from 1 part in 10¹¹ in 1990 (Adelberger et al., Phys. Rev. D, 42, 3267, 1990) to about 1 part in 10¹² in 1994 (Su et al., 50, 3614, 1994), to about 1 part in 10¹³ in 1999 (Baessler et al., 83, 3585, 1999). Many other experiments are ongoing all over the world.

Three proposed missions for testing the equivalence principle in space

STEP (Satellite test of the Equivalence Principle). STEP has originated at Stanford University (USA) in the early 70s. It is currently in the SMEX competition of NASA with the goal of testing the equivalence principle to 1 part in 10¹⁸ . STEP has been studied twice to Phase A level within ESA. In both cases the final study reports were consistent with a target of 1 part 10¹⁷ (Blaser et al., ESA/NASA SCI(93)4, 1993; blaser et al., ESA SCI (96)5, 1996). Visit the STEP Website at: http://einstein.Stanford.EDU/STEP/
"GALILEO GALILEI" (GG). GG has originated at the University of Pisa (Italy) in the early 90s. It has been studied to phase A level within ASI in 1998. The final Study Report is consistent with the goal of testing the equivalence principle to 1 part in 10¹⁷ (GG Phase A Study Report, ASI, 1998). A prototype of the instrument proposed for flight has been developed and is under testing. GG is currently undergoing an Advanced Phase A Study with ASI funding. This study shall be completed by May 2002. The results will be presented at the International Workshop of Pisa-Florence, May 27-29 2002.Visit the GG Website at: http://eotvos.dm.unipi.it/nobili/
MICROSCOPE. Microscope has originated at ONERA (Chatillon, France) in the late 90s. It is currently in Phase B Study within CNES and ESA financial support with the goal of testing the equivalence principle to 1 part 10¹⁵ . Vist the Microscope Website at: http://www.onera.fr/dmph-en/accelerometre/

For a comparative analysis of the different designs of the proposed space experiments, see a Review (Sec. 7), and follow the opendiscussion on radiometer effect and other issues relevant to all three missions

Proposed equivalence principle test from a balloon

A free fall experiment named GREAT has been proposed for testing the equivalence principle to 1 part 10¹⁵ inside a vacuum capsule to be released from a balloon at an altitude of 40 km, allowing a free fall time of 30 s. GREAT is a collaboration between SAO (Cambridge, MA USA) and IFSI-CNR (Rome, Italia) and is under investigation with NASA and ASI fundings. The target is comeptitive with that of Microscope. The advantages are easy repeatibility and the comparative low cost of sub-orbital flights.

Experimental gravitational physics with drag-free satellites

Dr Benjamin Lange runs a Webpage with all possible information about drag-free satellites and their use for experiments in gravitational physiscs.Visit it at the address: http://www.dragfreesatellite.com/

anna nobili
Last edited: agosto 05, 2002