September 14th 2015, 09:50 GMT. A far spread out distortion of space crossed earth's path. The distortion had traveled at the speed of light for more than a billion years, all along the way spreading out spherically and diluting its energy density inversely proportional to the spherical area covered. Still, when distorting the space occupied by earth, it did so with a peak power equal to the total electrical power consumption of human mankind.

Earth responded by undulating, expanding in one direction, shrinking in a perpendicular direction, and then reversing. And reversing. The frequency of undulation increased like a coin wobbling on a table top. And then suddenly, like a wobbling coin coming to rest, space became quiet again, and earth's shape stabilized.

Despite the considerable power passing earth, no one would have noticed, were it not for two giant precision rulers, both being completed just in time to catch the expansion and shrinking of matter in response to the distortion of space passing by. Locally earth's diameter grew and shrunk by a tiny amount not exceeding the diameter of the nucleus of a gold atom. 

Yes, these LIGO rulers are that precise. And yes, they need to be that precise. Spacetime is malleable. Malleable against a stiffness far beyond imagination.