When it comes to measuring the "hardness" of a material, most tests are distinctly low-tech and basically involve pressing a diamond tip into the surface and measuring the size of the dent produced.
Virtual particles may not be real, but they help physicists track how forces move, and allow for incredibly precise measurements in particle physics.
Sometimes you think you have a complete understanding of something and then BOOM—a simple problem throws everything out the window. Let's consider a very basic physics problem involving pushing a ...