ER = EPR. It doesn’t look like much. In fact, it doesn’t look like anything at all. But this is the equation that could unite the two most successful theories describing the universe.

We’ve all heard of quantum mechanics and general relativity. They both explain a range of complicated phenomena exceedingly well, but if you tried to combine them, you would find that the maths just doesn’t work out.

Enter ER = EPR. This new equation, postulated by Susskind, a theoretical physicist from Stanford, could be the answer. The letters don’t represent numbers, but are instead initials of scientists, connecting two papers from 1935, one on quantum mechanics and the other on general relativity. The letters stand for the authors of the papers – E is for Einstein, who worked with Rosen to produce a paper on wormholes and with Rosen and Podolsky on the topic of quantum entanglement.

Wormholes, or Einstein-Rosen bridges, are spacetime tunnels – they connect two distant locations or times. If you fell through one side of a wormhole, you would instantaneously find yourself at the other side, no matter how far away the two locations are.

Quantum entanglement describes how two particles can interact if they are linked by having been created from the same source. Even if these particles are lightyears away from each other, anything that happens to one particle will immediately affect the other. For example, if you have two entangled particles and you measure the spin of one, you now know the spin of the other without making any other measurements.

The two can be combined. What if you had loads of pairs of entangled particles, and you took one from each pair to one point in space and the remaining particles to another, then smashed each group of particles together to make two separate black holes? The black holes would be entangled or, if the equation is right, they would be connected by a wormhole.

The paper is still undergoing peer review, which is required before it can be published, but even now more papers are being churned out, running with the idea. If it turns out to be right, entanglement can be used to describe wormholes, and entangled particles could be explained by wormholes. The fight over how to interpret quantum mechanics might be cleared up. Gravity may be derivable from quantum mechanics, and linking the two more deeply than it was formerly thought. Spacetime may even be built from networks of quantum entanglement in a vacuum.

Sources:

Leonard Susskind, *Cornell University Library*, 23^{rd} April 2016, ‘*Copenhagen vs Everett, Teleportation and ER=EPR’*, http://arxiv.org/abs/1604.02589 (accessed 24th August 2016)

Science Alert,* Futurism*, 18^{th} August 2016, *‘This new equation could help unite the two biggest theories in Physics’*, http://futurism.com/this-new-equation-could-unite-the-two-biggest-theories-in-physics/ (accessed 23^{rd} August 2016)

Tom Siegfried, *Science News*, 17^{th} August 2016, *‘A new ‘Einstein’ equation suggests wormholes hold key to quantum gravity’*, https://www.sciencenews.org/blog/context/new-einstein-equation-wormholes-quantum-gravity (accessed 24^{th} August 2016)