Connection with real world

 At a fundamental level, quantum physics predicts very unique things about how matter works which are completely at odds with how things work in the real world. Quantum particles behave like particles, in a single place or they can behave like waves, distributed all over space or in several places at once. How they appear seems to depends on how anyone choose to measure them, and first we measure they seem to have no definite properties at all leading us to a basic conundrum about the nature of fundamental reality.

That fuzziness lead to apparent paradoxe such as Schrondinger’s cat, in that thanks to an uncertain quantum physics process a cat is left dead and alive at a same time. But that is not all. Quantum particles also seem to be able to effect each other instantaneous even when they are far away from each other. This truly bamboozling phenomenon is called as entanglement, or in a phrase coined by Einstein, “spooky action at a distance”. That quantum powers are completely uncertain to us, yet are the basis of emerging technologies such as ultra secure quantum cryptography and ultra powerful quantum computing. 

But as to what it all means, no one knows. Some people think we must just accept that quantum physics explains the material world in terms we find impossible to square with our experience in the larger, “classical” world. Others think there must be some better, more intuitive theory out there that we’ve yet to discover.

In all this, there are several elephants in the room. For a start, there’s a fourth fundamental force of nature that so far quantum theory has been unable to explain. Gravity remains the territory of Einstein’s general theory of relativity, a firmly non-quantum theory that doesn’t even involve particles. Intensive efforts over decades to bring gravity under the quantum umbrella and so explain all of fundamental physics within one “theory of everything” have come to nothing.

Meanwhile cosmological measurements indicate that over 95 per cent of the universe consists of dark matter and dark energy, stuffs for which we currently have no explanation within the standard model, and conundrums such as the extent of the role of quantum physics in the messy workings of life remain unexplained. The world is at some level quantum – but whether quantum physics is the last word about the world remains an open question,