Can astronomy reproduce the Big Bang? Can biologists reproduce the Cambrian explosion? Can geologists reproduce end of the Mesozoic Era?
It's harder to know things we can't do experiments, but we can still know them. In economics, there is a rich tradition of relying on "natural experiments", which is where something like a natural disaster or a law change allows researchers to examine the effects. This is how it was shown that the effect of minimum wage increases on employment is very small. The financial crisis falsified an entire school of macroeconomics.
