I am an Engineer and I thought I knew what force was. You learn all about

F =M*a

but then the problems start when you begin consider that it is a vector quantity and has a direction. Where does that come form? And what causes force?

Then because I am an Electronic Engineer you consider applying a static force, no acceleration, to the end of a longitudinally stiff body. In the instant that you do so the remote end does not know about the force being sent to it. So the force goes off but what determines the amplitude as it has no reaction force and nothing constrains it. It presumable has a propagation velocity like a transmission line and an experiment should be able to show that the force is reflected from the distant end.

Has this experiment ever been done and what is the result?

If you consider a Bowden cable coiled up how is it that the force turns round a corner and seems to be constrained by the material of the core. The core is mostly nothing and some protons with electrons suspended around them. Is it the atomic forces between the atoms that is transmitting the applied disturbance form one end to another?

Finally how does all this work on an Astronomic scale?