We’ve all heard it, the claim that evolution isn’t science because it isn’t observable. Of course this is just an extremely narrow and convenient definition of science used by members of the creationist community to assure them their belief system isn’t threatened. It’s pretty obvious from the context that this claim is saying that if the evolution of one kind (not species) into another isn’t directly observable it isn’t a scientific theory. The idea that phenomena have to be directly observable to be a part of science seems to be limited to only those sciences that are a threat to theistic worldviews.
Contrary to what creationists want us to believe, there are several different forms of observation available to us. I like to break scientific observation into three categories. Sensory observation where an event, state or object is directly observable by human senses. Measurable observation where the phenomenon is indirectly observable through the use of tools. Trace observation is the observation of changes in an distinct and separate event, state or object caused by the phenomenon we are investigating.
Creationists will frequently mention gravity as an event that is directly observable so it fits into their narrow definition of science. To them the observation proves the science of gravity. However what they are doing is conflating the observable event and the explanation for the event we get from science.