**Albert Einstein famously said that quantum mechanics should allow two objects to affect each other’s behaviour instantly across vast distances, something he dubbed “spooky action at a distance” ^{1}. Decades after his death, experiments confirmed this, but to this day, it remains unclear exactly how much coordination nature allows between distant objects. Now, five researchers say they have solved a theoretical problem that shows that the answer is, in principle, unknowable.**

**The team’s 165-page paper appeared on the arXiv preprint repository ^{2}, and has yet to be peer reviewed. If it checks out, it solves a number of related problems in pure mathematics, quantum mechanics and a branch of computer science known as complexity theory in one fell swoop. In particular, it answers a mathematical question that had been unsolved for more than 40 years.**

**click here.**