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FQXI ARTICLE

October 19, 2017

The Spacetime Revolutionary

Carlo Rovelli describes how black holes may transition to "white holes," according to loop quantum gravity—a radical rewrite of fundamental physics.

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December 13, 2016

Carlo Rovelli

CTP Luminy, Marseille

Rovelli, now at the Centre for Theoretical Physics, in Luminy, Marseille, France, certainly didn’t think it would become his career—or that he might one day be known for co-founding a radical new theory to explain the origins of spacetime, loop quantum gravity. He is now investigating whether evidence for this model could be found in the form of "white holes," formed as black holes turn themselves inside out, spewing, rather than swallowing, matter.

Rovelli recounts that he only went to university in order to delay enrolling in Italy’s compulsory military service. So he freely concedes that he was far from a model student. Attending university in the Seventies he was swept up in political activism, a legacy from the halcyon days of the late Sixties. "I was more into trying to change the world than studying," he admits. But Rovelli soon realised he wasn’t getting vary far with his political revolution. It was only then that he started studying relativity—Einstein’s ideas on gravity that involve weaving space and time together into a four-dimensional fabric—and quantum mechanics—the theory governing the world of the very small—in more detail. He describes what came next as a flash. "It was incredibly beautiful," Rovelli says. "I fell in love with it."

Carlo Rovelli discusses his international bestseller, "Seven Brief Lessons on Physics," with Colin Stuart.

LISTEN:

Rovelli then went on to do a PhD, at the University of Padua, Italy, but unusually for a doctoral student he didn’t publish any papers, instead choosing to focus on mastering the different approaches to quantum gravity. Doctorate complete, he set out on his own, initially without being attached to a school or research group. Instead Rovelli upped sticks and traveled the world, visiting Isham in London as well as journeying to the US.

The network of interacting

quantum events can be

identified with the very

fabric that weaves spacetime.

quantum events can be

identified with the very

fabric that weaves spacetime.

- Carlo Rovelli

So to crack the conundrum of quantum gravity, Rovelli argues, we shouldn’t be formulating our equations in terms of things, but in terms of events. In loop quantum gravity, spacetime itself emerges from fundamental discrete quantum events. Although this approach is followed by a large number of researchers worldwide, "the precise formulation of the theory is still discussed, and I’d like to make this all more precise," says Rovelli.

Black Hole to White Hole

To this end, Rovelli has recruited a postdoc who will spend a year with him in Marseille chiseling the equations. He then hopes to test his results by comparing them to a concrete physical situation describing the fate of black holes. In Einstein’s standard theory of gravity, black holes form when stars die, and their matter is crunched down into the black hole’s infinitely small and dense core. In Rovelli’s analysis, in terms of loop quantum gravity, this matter still gets compressed, but only to an extent. Rather than being squeezed into an infinitely tiny point, the compression hits a limit and then the matter bounces out again.

White Hole

Could the antitheses of black holes exist—and provide evidence of loop quantum gravity?

Credit: JPL/NASA

"The network of interacting quantum events can be identified with the very fabric that weaves spacetime," says Rovelli. Analysing events it is easier to see how spacetime itself may turn inside out, transforming from a black hole to a white hole.

Can black holes turn into white holes? Carlo Rovelli chats about the possibility with Zeeya Merali.

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David Sloan, from the University of Oxford, UK, thinks Rovelli’s is a well-founded, if ambitious, project. "Carlo has met with remarkable success in the past, and is known for taking on hard conceptual issues," Sloan says. "One can never guarantee success in these things—that’s the nature of research—but I’m confident that he will make some significant headway."

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Please read the important Introduction that governs your participation in this community. Inappropriate language will not be tolerated and posts containing such language will be deleted. Otherwise, this is a free speech Forum and all are welcome!

Recent Comments

ANONYMOUS wrote on May 9, 2017

Ever notice the dependence of SR and GR on Lorentz Transformations arbitrarily specifies spherical symmetry be maintained for bodies in motion when inertially they should be expected to flatten to a shape like a discus with the minor axis in parallel with the vector of motion?

Ever notice the dependence of SR and GR on Lorentz Transformations arbitrarily specifies spherical symmetry be maintained for bodies in motion when inertially they should be expected to flatten to a shape like a discus with the minor axis in parallel with the vector of motion?

LEE BLOOMQUIST wrote on April 30, 2017

"…Rovelli’s interpretation of quantum theory is hard to overlook." (F. Mercati, see above.) "… consider a reformulation of quantum mechanics in terms of information theory." (Rovelli, Relational Quantum Mechanics, see arXiv.) Algorithms produce information. So inferring from G. 't Hooft's**Cellular Automaton Interpretation of Quantum Mechanics** that *algorithms may underlie Hilbert space*: *learning algorithms may underlie Hilbert space*. So with a quantum mechanics based on...

"…Rovelli’s interpretation of quantum theory is hard to overlook." (F. Mercati, see above.) "… consider a reformulation of quantum mechanics in terms of information theory." (Rovelli, Relational Quantum Mechanics, see arXiv.) Algorithms produce information. So inferring from G. 't Hooft's

STEVE DUFOURNY wrote on February 24, 2017

Professor Rovelli has an wonderful creativity.It is important like the imagination.We search after all answers and all ideas are of course welcome.I am not a big supporter of whormholes but I respect these mathematical mirrors.In fact that can permit to better understand our Black holes.A BH for me is a spherical volumes of matter not baryonic cold in logic.This mass not baryonic has properties and rules Inside this universe.They embark the galaxies these supermassive BHs central to...

Professor Rovelli has an wonderful creativity.It is important like the imagination.We search after all answers and all ideas are of course welcome.I am not a big supporter of whormholes but I respect these mathematical mirrors.In fact that can permit to better understand our Black holes.A BH for me is a spherical volumes of matter not baryonic cold in logic.This mass not baryonic has properties and rules Inside this universe.They embark the galaxies these supermassive BHs central to...

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