WORMHOLES, ENTANGLEMENT AND THE HUNT FOR QUANTUM GRAVITY
Einstein’s general relativity and quantum mechanics are the two foundations of modern physics. Gravity operates at large scales while quantum mechanics operates at very small scales. The two have never played nice together but work exceedingly well in their respective realms. Quantum Gravity, a physical theory still ‘under construction’, is intended to unify the principles of general relativity with those of quantum theory. A successful theory of quantum gravity is one of the foremost goals of modern physics.
Now a recently introduced theory which may help achieve that goal proposes a new kind of wormhole. Entanglement is a feature of quantum mechanics that links distant objects. According to this new theory wormholes – tunnels through space-time that connect black holes – may be a consequence of quantum entanglement.
The connection between entanglement and wormholes was first proposed a month ago. As early as 2009, however, Mark Van Raamsdonk at the University of British Columbia in Vancouver, Canada, suggested a way to connect the flexible space-time of general relativity, Einstein’s theory of gravity, with quantum mechanics, which generally assumes an unrealistic, rigid space-time.
Van Raamsdonk’s innovation involved the fields that appear in a quantum view of the universe, such as the electromagnetic field and the more exotic Higgs field.
Neighbouring fields are generally more entangled with each other than with regions farther away in space or time. This led Van Raamsdonk to wonder if entanglement has a role in space-time’s geometry. Sure enough, he was able to show that altering the entanglement of quantum fields can alter the shape of space-time, making it flexible. “If you change the pattern of entanglement, you also change the geometry of space-time,” says Juan Maldacena of the Institute for Advanced Study in Princeton, New Jersey. [New Scientist]
The new addition last month added wormholes to the picture by the suggestion that wormholes, previously only described by general relativity, could also result from entanglement which could be responsible for spacetime itself, the very fabric of our universe.
It all sounds a little wild, but the ideas are gaining traction and sparked lively discussion at a recent meeting of the top minds in theoretical physics and philosophy at the University of California, Santa Cruz. “This is all crazy,” Leonard Susskind of Stanford University in California, one of the brains behind the new kind of wormhole, told the conference on 5 July. “It’s also believed to be correct." [New Scientist]
The irony in all this is that Einstein, who was not a big fan of quantum mechanics, famously derided entanglement, referring to it as “spukhafte Fernwirkung" ("spooky action at a distance”). Like Einstein, Schrödinger, who was one of the originators of quantum mechanics, was dissatisfied with the concept of entanglement, because it seemed to violate the speed limit on the transmission of information implicit in the theory of relativity.
Image credits: (C) American Physical Society / Illustration: Carin Cain