  We constrain the evolution of Newton's constant using the growth rate of
large-scale structure measured by the WiggleZ Dark Energy Survey in the
redshift range $0.1 < z < 0.9$. We use this data in two ways. Firstly we
constrain the matter density of the Universe, $\omms$ (assuming General
Relativity), and use this to construct a diagnostic to detect the presence of
an evolving Newton's constant. Secondly we directly measure the evolution of
Newton's constant, $\Geff$, that appears in Modified Gravity theories, without
assuming General Relativity to be true. The novelty of these approaches are
that, contrary to other methods, they do not require knowledge of the expansion
history of the Universe, $H(z)$, making them model independent tests. Our
constraints for the second derivative of Newton's constant at the present day,
assuming it is slowly evolving as suggested by Big Bang Nucleosynthesis
constraints, using the WiggleZ data is $\ddotGeff(t_0)=-1.19\pm 0.95\cdot
10^{-20}h^2 \textrm{yr}^{-2}$, where $h$ is defined via $H_0=100 h km
s^{-1}Mpc^{-1}$, while using both the WiggleZ and the Sloan Digital Sky Survey
Luminous Red Galaxy (SDSS LRG) data is $\ddotGeff(t_0)=-3.6\pm 6.8\cdot
10^{-21}h^2 \rm{yr}^{-2}$, both being consistent with General Relativity.
Finally, our constraint for the rms mass fluctuation $\sigma_8$ using the
WiggleZ data is $\sigma_8=0.75 \pm 0.08$, while using both the WiggleZ and the
SDSS LRG data $\sigma_8=0.77 \pm 0.07$, both in good agreement with the latest
measurements from the Cosmic Microwave Background radiation.
