[marcosdumay]

It helps that astronomy is a branch of physics. In a sense, astronomers do perform experiments, on different conditions but with the same theory. (By the way, that's what bothers me most about cosmology, it seems to not agree with any small scale experiment performed.)

Well, certainly, natural experiments can lead to knowledge. But that's a much slower and more dangerous path, artificial experiments are better in every sense, except that they are mostly not available for economics. Anyway, I don't think the use of natural experiments are the bottleneck currently holding economics back.