Uncertainty principle
Mathematically, Einstein has been proven wrong. In 1964 John Stewart Bell developed a math method to distinguish between the behavior of two particles that have determinate states that are merely unknown to the two individuals that investigate them, and two particles that have entangled states that are indeterminate or uncertain until they are measured. His method shows that the probabilities for getting certain results are different under the two different assumptions. His work is called Bell's theorem or Bell's Inequality. Experiments have shown that nature behaves as Bell describes it.