Yes, something as tiny as 0.0000000000000000001 meter, which demands a damned precise ruler. And this would be the wave connected to the merging of two black holes
I never knew black holes can actually merge. Is this phenomenon related to the "Binary Black Hole"?
A binary exactly means a pair of black hole. They rotate around each other, and then accelerate because of their respective gravitational field. As a result, gravitational waves are emitted.