With the stiffness of spacetime being orders of magnitude higher - I found claims of 20 as well as 100 orders of magnitude, no idea what the correct value is -

With the stiffness of spacetime being orders of magnitude higher - I found claims of 20 as well as 100 orders of magnitude, no idea what the correct value is - than the stiffest known materials, one would have to bang on spacetime pretty hard to produce a measurable signal.