"Galileo Galilei" GG

Home

A review

The international context

A slide tour

A prototype in the lab

Open discussion on
radiometer effect

International Workshop
May 27-29, 2002

Documents

People

Theses

Evaluation of GG

What's going on....

 

gg_fisso_bluscuro_small.gif (6094 bytes)

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.

 

anna nobili   
Last edited: February 21, 2002