From Scientific American:
There are experimental sciences, and then there are historical and observational sciences. The experimental sciences, like chemistry and physics, are easy to spot. When stuff blows up or systems don’t work right, you’ve got yourself an experiment.
Historical and observational sciences can be a little tougher to get a handle on. The researchers in these fields must adopt the Yogi Berra stance—“You can observe a lot just by watching”—and then interpret reality. Or, as the great scientist Ernst Mayr patiently explained in these pages, “Evolutionary biology, in contrast with physics and chemistry, is a historical science—the evolutionist attempts to explain events and processes that have already taken place.… One constructs a historical narrative, consisting of a tentative reconstruction of the particular scenario that led to the events one is trying to explain.”
More here.