Exploring the Invisible
Much of modern physics has been about exploring inherently invisible things, which seem to be far more common than the obvious things we experience with our senses. Yet these invisible things follow rigorous laws that allow us to test their existence in many ways. Here is a very short list of some of the "invisible" things that we routinely work with.
Dr. Sten Odenwald, ContributorAstronomer, NASA Heliophysics Education Consortium