If you’re one of those people who knows that an ‘Einstein–Rosen bridge’ is the formal name for a wormhole, then you probably know that neither Albert Einstein nor Nathan Rosen would set foot in their theoretical namesake because they knew it might not stay stable long enough to get from one side of the universe to the other through a wormhole-connected black hole and white hole – the mirror image of a black hole at the exit. However, if astronomer Arthur Stanley Eddington and physicist David Finkelstein were here, they might convince Einstein and Rosen to follow them down the wormhole because a new paper maintains that it will remain stable and the proof is in their Eddington-Finkelstein metric. Wait … what?
“The Eddington-Finkelstein metric is obtained from the Schwarzschild metric by a change of the time variable. It is well known that a test mass falling into a black hole does not reach the event horizon for any finite value of the Schwarzschild time variable t. By contrast, we show that the event horizon is reached for a finite value of the Eddington-Finkelstein time variable t′. Then we study in Eddington-Finkelstein time the fate of a massive particle traversing an Einstein-Rosen bridge and obtain a different conclusion than recent proposals in the literature: we show that the particle reaches the wormhole throat for a finite value t′1 of the time marker t′, and continues its trajectory across the throat for t′>t′1. Such a behavior does not make sense in Schwarzschild time since it would amount to continuing the trajectory of the particle "beyond the end of time."
There … now do you understand? That’s the abstract from “Infall time in the Eddington-Finkelstein metric, with application to Einstein-Rosen bridges,” the paper written by Pascal Koiran for publication in the journal General Relativity and Quantum Cosmology on how those four geniuses plus Koiran and any of you brave enough to follow them would survive a trip through space-time in a stable wormhole. Fortunately, Live Science was able to explain the concept in terms non-geniuses can kind of understand.
A metric is a way to get from here to there. For most points in space, there are a lot of metrics (think of the options offered by your GPS – by car, by bus, on foot). For wormholes, Einstein and Rosen used the Schwarzschild metric from general relativity, which predicts that an object passing though a wormhole will break down (i.e. be destroyed) when it reaches the black hole’s event horizon – the point where not even light can escape. Koiran, a Ecole Normale Supérieure de Lyon (a French institute of higher learning) computer scientist, took a different path – the Eddington-Finkelstein metric provides a route for a particle to cross the event horizon, enter the wormhole and exit out the white hole at other side in a finite amount of time without any instability or destruction.
Did Koiran drop the mic and book a trip through the nearest wormhole? Unfortunately, metric didn't misbehave at any point in that trajectory. The Eddington-Finkelstein metric only solves the gravity challenge of getting past the black holes at either end of the wormhole – it doesn’t address the thermodynamics – heat and energy -- inside the wormhole which other theories suggest would break the lack-hole-wormhole-white-hole apart before anyone could set foot in it. What Koiran's paper does prove is that traveling through a wormhole is not impossible nor a death sentence – general relativity says so. All we need is the right metric.
Can you plug a black hole and a white hole into Google Maps?