  In 1859, Le Verrier discovered the mercury perihelion advance anomaly. This
anomaly turned out to be the first relativistic-gravity effect observed. During
the 141 years to 2000, the precisions of laboratory and space experiments, and
astrophysical and cosmological observations on relativistic gravity have been
improved by 3 orders of magnitude. In 1999, we envisaged a 3-6 order
improvement in the next 30 years in all directions of tests of relativistic
gravity. In 2000, the interferometric gravitational wave detectors began their
runs to accumulate data. In 2003, the measurement of relativistic Shapiro
time-delay of the Cassini spacecraft determined the relativistic-gravity
parameter gamma&#947; with a 1.5-order improvement. In October 2004, Ciufolini
and Pavlis reported a measurement of the Lense-Thirring effect on the LAGEOS
and LAGEOS2 satellites to 10 percent of the value predicted by general
relativity. In April 2004, Gravity Probe B was launched and has been
accumulating science data for more than 170 days now. MICROSCOPE is on its way
for a 2007 launch to test Galileo equivalence principle to 10-15. STEP
(Satellite Test of Equivalence Principle), and ASTROD (Astrodynamical Space
Test of Relativity using Optical Devices) are in the good planning stage.
Various astrophysical tests and cosmological tests of relativistic gravity will
reach precision and ultra-precision stages. Clock tests and atomic
interferometry tests of relativistic gravity will reach an ever-increasing
precision. These will give revived interest and development both in
experimental and theoretical aspects of gravity, and may lead to answers to
some profound questions of gravity and the cosmos.
