A laser-driven tidal wave could test a question that has long plagued physics: is the information inside a black hole lost forever or somehow preserved through the mysterious machinations of quantum mechanics?
The defining feature of a black hole is thought to be that anything that crosses the event horizon – the proverbial point of no return – can never escape and is lost forever.
But in the 1970s, Stephen Hawking discovered that black holes aren’t truly black. If a virtual particle pair pops into existence near the event horizon, and one falls in, the black hole must lose a tiny bit of mass in the form of energy. So black holes will radiate tiny amounts of energy – dubbed Hawking radiation – and evaporate over time. The bigger the black hole, the longer it takes to evaporate.
So what happens to everything that has fallen into the black hole? Logic dictates it, too, should be lost. But quantum mechanics holds that information must be conserved and cannot be lost – hence the paradox.
Unfortunately, there’s no good way to study an actual black hole up close to test what’s really going on. So physicists have been exploring “analogue” black holes that mathematically mimic their celestial counterparts.
One possibility is that the information is preserved via entangled photons, which share a quantum relationship with each other no matter how distant they are, and is released in a burst of energy as the black hole winks out of existence. If physicists could find correlations between the original escaped partner and a photon re-emitted as radiation, this would be strong evidence that information is indeed conserved.
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