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“It’s not quantum mechanics” may often be heard, a remark informing the listener that whatever they are concerned about is nowhere near as difficult, as abstruse, as complicated as quantum mechanics. Indeed to non-physicists or non-mathematicians quantum mechanics must seem virtually impossible to appreciate – pages of incomprehensible algebra buttressed by obscure or frankly paradoxical “explanations”.

The post Quantum mechanics – a new lease of life appeared first on OUPblog.

Describing the very ‘beginning’ of the Universe is a bit of a problem. Quite simply, none of our scientific theories are up to the task. We attempt to understand the evolution of space and time and all the mass and energy within it by applying Albert Einstein’s general theory of relativity. This theory works extraordinarily well. But when we’re dealing with objects that start to approach the infinitesimally small – elementary particles such as quarks and electrons – we need to reach for a completely different structure, called quantum theory.

The post Where did all the antihadrons go? appeared first on OUPblog.

This November marks the 100th anniversary of Albert Einstein completing his masterpiece of general relativity, an idea that would lead, one world war later, to his unprecedented worldwide celebrity. In the run-up to what he called “the most valuable discovery of my life,” he worked within a new sort of academic comfort.

The post Max Planck: Einstein’s supportive skeptic in 1915 appeared first on OUPblog.

The great German physicist Max Planck once said, “However many specialties science may split into, it remains fundamentally an indivisible whole.” He declared that the divisions and subdivisions of scientific disciplines were “not based on the nature of things.”

The post Max Planck’s debt appeared first on OUPblog.

In an infinite universe, anything that can happen does happen - an infinite number of times.

Of course, the idea of an infinite universe is a tricky (possibly an infinitely tricky) one to grasp, and there's no proof as yet that our universe is infinite. Some theories propose that we may be part of a multiverse - a (possibly) infinite number of universes embodying all possible physical laws and values of important constants like the strength of gravity. Many of these universes would contain little of interest (a low gravitational constant, for example, makes it impossible for galaxies and stars to form, so life is most unlikely). Other variants would look more like ours. There might even be one in which I don't like chocolate, though I'm not sure that counts as 'possible'.

And then there's the interpretation of quantum theory which says that when you open the box to reveal Schrödinger's cat, the universe splits into the 'cat-alive' and the 'cat-dead' version. By the time a few splits like this have occurred, you get a fair degree of diversity and some interesting narratives evolving.

Which brings me to the connection (there is one, I promise) with writers and writing.

If the universe really is infinite, then all our books, even our wildest fictional fantasies, are true. There is a universe somewhere, or perhaps a pocket of our own universe, where the characters you and I have invented actually exist - and do exactly the things they do in our books. And, in a 'neighbouring' universe, they make slightly different choices and perhaps write themselves into a better book.

This may all sound incredibly far-fetched. I am not an expert, though I did some physics at university long ago. These days, I'm a keen reader of those books that thrill you with the exciting bits of cosmology, quantum physics and neuroscience. They set my imagination alight... and nothing does that more than the idea that every work of fiction ever written has actually happened, somewhere way out there. I'm not sure why this thrills me, but it does.

As I sit and write, often feeling that I am listening in to my characters' conversations and observing their actions rather than making them up, the idea that I am tuning in to something real is a very powerful and poignant one.

I realise that the question of what 'actually exists' plunges one into some deep waters of philosophy. I'm going to stay in the shallows for the purpose of this post, but if anyone wants to wade out deeper, I'd love to know what you think.

Thanks to Brian Greene and his intriguing book 'The Hidden Reality' (Allen Lane, 2011), which gave me some insight into all this stuff and made me marvel all over again at the wonderful place in which we live. It seems safe to assume that the universe is even more amazing than our current theories tell us, and that, for me, feels exactly right.

[Photo of Earth from space by Terra satellite, image copyright NASA]

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By Jim Baggott

If a tree falls in the forest, and there’s nobody around to hear, does it make a sound?

For centuries philosophers have been teasing our intellects with such questions. Of course, the answer depends on how we choose to interpret the use of the word ‘sound’. If by sound we mean compressions and rarefactions in the air which result from the physical disturbances caused by the falling tree and which propagate through the air with audio frequencies, then we might not hesitate to answer in the affirmative.

Here the word ‘sound’ is used to describe a physical phenomenon – the wave disturbance. But sound is also a human experience, the result of physical signals delivered by human sense organs which are synthesized in the mind as a form of perception.

Now, to a large extent, we can interpret the actions of human sense organs in much the same way we interpret mechanical measuring devices. The human auditory apparatus simply translates one set of physical phenomena into another, leading eventually to stimulation of those parts of the brain cortex responsible for the perception of sound. It is here that the distinction comes. Everything to this point is explicable in terms of physics and chemistry, but the process by which we turn electrical signals in the brain into human perception and experience in the mind remains, at present, unfathomable.

Philosophers have long argued that sound, colour, taste, smell and touch are all secondary qualities which exist only in our minds. We have no basis for our common-sense assumption that these secondary qualities reflect or represent reality as it really is. So, if we interpret the word ‘sound’ to mean a human experience rather than a physical phenomenon, then when there is nobody around there is a sense in which the falling tree makes no sound at all.

This business about the distinction between ‘things-in-themselves’ and ‘things-as-they-appear’ has troubled philosophers for as long as the subject has existed, but what does it have to do with modern physics, specifically the story of quantum theory? In fact, such questions have dogged the theory almost from the moment of its inception in the 1920s. Ever since it was discovered that atomic and sub-atomic particles exhibit both localised, particle-like properties and delocalised, wave-like properties physicists have become ravelled in a debate about what we can and can’t know about the ‘true’ nature of physical reality.

Albert Einstein once famously declared that God does not play dice. In essence, a quantum particle such as an electron may be described in terms of a delocalized ‘wavefunction’, with probabilities for appearing ‘here’ or ‘there’. When we look to see where the electron actually is, the wavefunction is said to ‘collapse’ instantaneously, and appears ‘here’ with a frequency consistent with the probability predicted by quantum theory. But there is no predicting precisely where an individual electron will be found. Chance is inherent in the collapse of the wavefunction, and it was this feature of quantum theory that got Einstein so upset. To make matters worse, if the collapse is instantaneous then this implies what Einstein called a ‘spooky action-at-a-distance’ which, he argued, appeared to violate a key postulate of his own special theory of relativity.

So what evidence do we have for this mysterious collapse of the wavefunction? Well, none actually. We postulate the collapse in an attempt to explain how a quantum system with many different possible outcomes before measurement transforms into a system with one and only one result after measurement. To Irish physicist John Bell this seemed to be at best a confidence-trick, at worst a fraud. ‘A theory founded in this way on arguments of manifestly approximate character,’ he wrote some years later, ‘howe