Quantum mechanics is famous for saying that a tree falling in a forest when there’s no one there doesn’t make a sound. Quantum mechanics also says that if anyone is listening, it interferes with and changes the tree. And so the famous paradox: how can we know reality if we cannot measure it without distorting it? An international team of researchers has found a way to do just that by applying a modern measurement technique to the historic two-slit interferometer experiment in which a beam of light shone through two slits results in an interference pattern on a screen behind.