The Elusive Theory of Everything

Physicists have long sought to find one final theory that would unify all of physics. Instead they may have to settle for several

By Stephen Hawking and Leonard Mlodinow 

Image: Illustrations by Barron Storey

In Brief
  • Stephen Hawking’s work on black holes and the origin of the universe is arguably the most concrete progress theoretical physicists have made toward reconciling Einstein’s gravitation and quantum physics into one final theory of everything.
  • Physicists have a favorite candidate for such a theory, string theory, but it comes in five different formulations, each covering a restricted range of situations.
  • A network of mathematical connections, however, links the different string theories into one overarching system, enigmatically called M-theory: perhaps the network is itself the final theory.
  • In a new book, The Grand Design, Hawking and Caltech physicist Leonard Mlodinow argue that the quest to discover a final theory may in fact never lead to a unique set of equations. Every scientific theory, they write, comes with its own model of reality, and it may not make sense to talk of what reality actually is. This essay is based on that book.


A few years ago the city council of Monza, Italy, barred pet owners from keeping goldfish in curved fishbowls. The sponsors of the measure explained that it is cruel to keep a fish in a bowl because the curved sides give the fish a distorted view of reality. Aside from the measure’s significance to the poor goldfish, the story raises an interesting philosophical question: How do we know that the reality we perceive is true?

The goldfish is seeing a version of reality that is different from ours, but can we be sure it is any less real? For all we know, we, too, may spend our entire lives staring out at the world through a distorting lens.



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