Excerpt from nature.com
By Zeeya Merali

Many researchers believe that physics will not be complete until it can not just the behaviour of space and time, but where these entities come from.

“Imagine waking up one day and realizing that you actually live inside a computer ,” says Mark Van Raamsdonk, describing what sounds like a pitch for a science-fiction film. But for Van Raamsdonk, a physicist at the University of British in Vancouver, Canada, this scenario is a way to think about reality. If it is true, he says, “everything around us — the whole three-dimensional physical world — is an illusion from information encoded elsewhere, on a two-dimensional chip”. That would make our Universe, with its three spatial dimensions, a kind of hologram, projected from a substrate that exists only in lower dimensions.

This ‘ principle’ is strange even by the standards of theoretical physics. But Van Raamsdonk is one of a small band of researchers who think that the ideas are not yet strange enough. If nothing else, they say, neither of the two great pillars of modern physics — general relativity, which describes gravity as a curvature of space and time, and quantum mechanics, which governs the atomic realm — gives any account for the existence of space and time. Neither does , which describes elementary threads of energy.


Zeeya Merali discusses some of the theories that are trying to explain the origins of space and time.

Van Raamsdonk and his colleagues are convinced that physics will not be complete until it can explain how space and time emerge from something more fundamental — a project that will require concepts at least as audacious as holography. They argue that such a radical reconceptualization of reality is the only way to explain what happens when the infinitely ‘singularity’ at the core of a black hole distorts the fabric of space-time beyond all recognition, or how researchers can unify atomic-level quantum theory and -level general relativity — a project that has resisted theorists’ efforts for generations.

“All our experiences tell us we shouldn’t have two dramatically different conceptions of reality — must be one huge overarching theory,” says Abhay Ashtekar, a physicist at Pennsylvania State University in University Park.

Finding that one huge theory is a daunting challenge. Here, Nature explores some promising lines of attack — as well as some of the emerging ideas about how to test these concepts…