We have quantum mechanics -- lots of them -- and they are extremely good at what they do. A bazillion transistors, lasers, and solar cells leave no room for doubt.
Wikipedia is your friend. The eye-crossing graphic nearby is from the double-slit-experiment article at Wikipedia.)
And Roman engineers built extremely good roads, bridges, and aqueducts without any clue about material science.
After almost a century, quantum mechanics (QM) theory can't tell us what any of it means. Wave/particle duality. Probability waves and the collapsing of the wave function. The dual-slit experiment. Quantum entanglement and spooky action at a distance. Undead cats. Quantum foam and virtual particles.
When one shouts down the "shut up and calculate" advocates of the Copenhagen interpretation of QM, we're left with, what? Many Worlds Interpretation: every time a photon or electron could do more than one thing, the universe splits. Or the transactional interpretation: forward- and backward-in-time waves invisibly combining to produce the quantum events we observe. Quantum consciousness: some observer behind the collapse of every wave function. And on and on ... with, so far, no explanation amenable to proof or disproof.
Uncertainty (pun intended) is great for SF authors -- but as a onetime scientist, it's frustrating in the extreme.
General relativity -- our best shot at what gravity is, is about as old as QM -- and the two stubbornly refuse to be reconciled. GR and QM must each be an incomplete theory, no matter how successful each is in problem-solving in its own -- and only its own -- domain.
Much effort has been spent in past decades trying to reconcile the two -- without success. String theory -- the notion of a fundamental physical "explanation" quantizing time and space -- has yet to offer anything either verifiable or falsifiable. It's math, not science. Don't take my word for it. Try Lee Smolin's The Trouble With Physics: The Rise of String Theory, The Fall of a Science, and What Comes Next. I haven't yet read Peter Woit's Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law, but I can't resist the title.
So what's going on? Can I do more than take cheap shots?
QM and modern electronics/photonics are the modern analogy to those Roman engineers. One can't argue with success -- but that's no reason to ignore the lack of science -- as in, understanding -- behind the engineering.
This morning I came across a fascinating article at New Scientist, Is quantum theory weird enough for the real world? Some iconoclastic theorists are looking for the science beneath QM. In a wonderful analogy, they point to an earlier scientific revolution: Tycho Brahe gathering meticulous data about planetary movements, followed by Johannes Kepler extracting the patterns of planetary motion and encapsulating them in his three laws, followed by Isaac Newton's beautiful and elegant theory of gravity. Newtonian gravity held as an explanation for centuries, until new measurements in domains very unfamiliar to Newton became possible.
QM has been stuck for decades in the Keplerian "here are patterns that work" stage. We await a Newton to explain what is happening in the quantum world. When he or she comes along, perhaps GR and QM will meld into a single, more powerful -- and understandable -- scientific theory.
I can't wait.