Earlier quoted context omitted.
A large chunk of physics is theoretical in nature. Sometimes you simply cannot experimentally validate a phenomenon, so you instead propose a theory that attempts to explain it using physics. Then in the future, when the phenomenon is testable, your peers determine whether your theory was correct or not.
Atomism is a good example of how philosophy first made up a theory that was later confirmed (in a changed version). https://en.wikipedia.org/wiki/Atomism You could also derive the Atomic nature of matter through math though, as infinitely devisable sets end up with paradoxes that don't match up with reality (think banarch-tarski) You can do all this without an idea how to test it.
The philosophers that invented atomism probably thought about how the might see their atoms directly. I wonder how many "crazy" ideas were dreamed up that sounded impossible, that are now easy experiments to do today.
Theory is important, even if it sounds impossible today, because we have a history of redefining what is "possible" throughout the history of science.