What Is Quantum Mechanics?

For those who are not shocked when they first come across quantum theory cannot possibly have understood it.

- Niels Bohr, in 1952, quoted in Werner Heisenberg's Physics and Beyond

Podcast of the Day

Melvyn Bragg examines the physics of reality. When Quantum Mechanics was developed in the early 20th century reality changed forever. In the quantum world particles could be in two places at once, they disappeared for no reason and reappeared in unpredictable locations, they even acted differently according to whether we were watching them. It was so shocking that Erwin Schrodinger, one of the founders of Quantum Theory, said "I don’t like it and I'm sorry I ever had anything to do with it." He even developed an experiment with a cat to show how absurd it was. Quantum Theory was absurd, it disagreed with the classical physics of Newton and Einstein and it clashed with our experience of the everyday world. Footballs do not disappear without reason, cats do not split into two and shoes do not act differently when we are not looking at them. Or do they? Eighty years later we are still debating whether the absurd might actually be true. But why are features of quantum physics not seen in our experience of everyday reality? Can the classical and quantum worlds be reconciled, and why should reality make sense to us?

Listen to Melvyn Bragg and guests discuss The Physics of Reality on the In Our Time podcast

Video of the Day

Short Article of the Day

...Quantum mechanics (QM) developed over many decades, beginning as a set of controversial mathematical explanations of experiments that the math of classical mechanics could not explain. It began at the turn of the 20th century, around the same time that Albert Einstein published his theory of relativity, a separate mathematical revolution in physics that describes the motion of things at high speeds. Unlike relativity, however, the origins of QM cannot be attributed to any one scientist. Rather, multiple scientists contributed to a foundation of three revolutionary principles that gradually gained acceptance and experimental verification between 1900 and 1930...

Continue reading Robert Coolman's article: What is Quantum Mechanics?

Further Reading

Quantum mechanics is, at least at first glance and at least in part, a mathematical machine for predicting the behaviors of microscopic particles — or, at least, of the measuring instruments we use to explore those behaviors — and in that capacity, it is spectacularly successful: in terms of power and precision, head and shoulders above any theory we have ever had. Mathematically, the theory is well understood; we know what its parts are, how they are put together, and why, in the mechanical sense (i.e., in a sense that can be answered by describing the internal grinding of gear against gear), the whole thing performs the way it does, how the information that gets fed in at one end is converted into what comes out the other. The question of what kind of a world it describes, however, is controversial; there is very little agreement, among physicists and among philosophers, about what the world is like according to quantum mechanics...

Continue reading the Stanford Encyclopedia of Philosophy article on Quantum Mechanics by Jennan Ismael

Related Topics

Black Holes | Dark Matter | The Multiverse | Particle Physics

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