In the sixth instalment of his exclusive monthly series for the South China Morning Post, American theoretical physicist and Nobel laureate Frank Wilczek asks if there really is any fundamental distinction between the universe we know and quasi-worlds, and the undeniable, routine proliferation of quasi-multiverses. Read his previous articles here.
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The fact that physics inside materials can be described using the same ideas we use to describe fundamental physics in empty space – and vice versa – has been amazingly fruitful. It has made modern electronics and computer technology possible. Today, it continues to inspire big innovations in technology and discoveries in fundamental physics.
The notion that we should think of the world as a material is ancient. Aristotle famously declared that “nature abhors a vacuum”, and Plato conceived of the whole world as a stupendous, rather unusual animal. I think it is fair to say that those ideas are, as Wolfgang Pauli liked to put it, not even wrong.
More recognisably scientific and rational ideas of this kind were hotly debated in the seventeenth century, at the dawn of the Scientific Revolution, when natural philosophers struggled to understand planetary motion.
Rene Descartes proposed that the planets were embedded in an invisible swirling ether, whose vortices carried them along.
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Isaac Newton devoted Book 2, of 3, of his masterwork The Mathematical Principles of Natural Philosophy to refuting Descartes’ theory, concluding that “the hypothesis of vortices is pressed with many difficulties”. In Issac Newton’s much more successful mathematical theory of planetary motion, gravity is a universal force that acts directly between separated bodies. In Newton’s vision, space was thoroughly immaterial – a passive, empty void.
For nearly two centuries, Newton’s ideas dominated physics. But in the nineteenth century, space filled up again. In 1862, inspired by Michael Faraday’s experimental discoveries and visionary ideas, James Clerk Maxwell made, that is, imagined, a space-filling medium – in other words, an ether – that could mimic the observed behaviour of electric and magnetic fields.