Figure 1:
Selected tests of the weak equivalence principle, showing bounds on , which measures fractional difference in acceleration of different materials or bodies. The freefall and EötWash experiments were originally performed to search for a fifth force (green region, representing many experiments). The blue band shows evolving bounds on for gravitating bodies from lunar laser ranging (LLR). 

Figure 2:
Selected tests of local Lorentz invariance showing the bounds on the parameter , which measures the degree of violation of Lorentz invariance in electromagnetism. The Michelson–Morley, Joos, Brillet–Hall and cavity experiments test the isotropy of the roundtrip speed of light. The centrifuge, twophoton absorption (TPA) and JPL experiments test the isotropy of light speed using oneway propagation. The most precise experiments test isotropy of atomic energy levels. The limits assume a speed of Earth of 370 km^{–1} relative to the mean rest frame of the universe. 

Figure 3:
Selected tests of local position invariance via gravitational redshift experiments, showing bounds on , which measures degree of deviation of redshift from the formula . In null redshift experiments, the bound is on the difference in between different kinds of clocks. 

Figure 4:
Geometry of light deflection measurements. 

Figure 5:
Measurements of the coefficient (1 + )/2 from light deflection and time delay measurements. Its GR value is unity. The arrows at the top denote anomalously large values from early eclipse expeditions. The Shapiro timedelay measurements using the Cassini spacecraft yielded an agreement with GR to 10^{–3} percent, and VLBI light deflection measurements have reached 0.02 percent. Hipparcos denotes the optical astrometry satellite, which reached 0.1 percent. 

Figure 6:
Constraints on masses of the pulsar and its companion from data on B1913+16, assuming GR to be valid. The width of each strip in the plane reflects observational accuracy, shown as a percentage. An inset shows the three constraints on the full mass plane; the intersection region (a) has been magnified 400 times for the full figure. 

Figure 7:
Plot of the cumulative shift of the periastron time from 1975 – 2005. The points are data, the curve is the GR prediction. The gap during the middle 1990s was caused by a closure of Arecibo for upgrading [272]. 

Figure 8:
The six polarization modes for gravitational waves permitted in any metric theory of gravity. Shown is the displacement that each mode induces on a ring of test particles. The wave propagates in the +z direction. There is no displacement out of the plane of the picture. In (a), (b), and (c), the wave propagates out of the plane; in (d), (e), and (f), the wave propagates in the plane. In GR, only (a) and (b) are present; in massless scalartensor gravity, (c) may also be present. 
http://www.livingreviews.org/lrr20063 
© Max Planck Society and the author(s)
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