Illustration of the (largely exaggerated) effect a gravitational wave passing by five groups of test-masses.
The masses do not interact between them. They are initially located along parallel circles centered around the same axis. The circles are separated by a quarter of the gravitational wave wavelength. The grid plane and the axis help the eye in order to visualize the modification of the distances between the test-masses.
Credit: Virgo Collaboration/LAPP/D. Buskulic