Levels of science investigation are threefold. Science may be classified as experimental, observational, or historical. This sounds simple enough, but public confusion about these terms may match their uncertainty about what scientists mean by fact, hypothesis, and theory, or even about "scientific method" and when or how it is used. Let's try to bring more clarity to the picture.
You may recall your early science courses as being mostly "experimental." Simple experiments affirmed the behavior of water when it froze, salt when it dissolved, or objects when they fell. You were able to control the conditions. Mathematics helped quantify the results beautifully. "Observational" sciences were a little different. You studied the motions of stars and planets. You made field visits to study rocks or plants and collected a few specimens. Perhaps you did experiments to illustrate apparent movement of stars or duplicate rock forming processes. Methods of observing and reporting observations were of primary importance.
Finally, we have the "historical" sciences such as evolutionary biology. Such sciences do not possess the same opportunity for testing and proof. Therefore, we gain knowledge in a more subtle way. We study events which occurred long ago when no one was present to see what actually happened. Events of long ago cannot be duplicated and observed. We must rely heavily on inference and weight of evidence. This is not to say historical sciences are not useful, but the certainty of knowledge is more tentative, even controversial. Scientists keep searching for new and better explanations. Whether we study history of life on earth in the distant past or history of events in the early Christian church, we must still view our study as a search for objective truth.
Evolutionists think their historical science conclusions about origins are completely certain. They confidently claim successive forms of life arose from each other. But what do evolutionists actually see when they look at fossil history? They observe that the fossil column does not manifest gradual changes, but rather, sudden changes with no antecedents. Our blog has previously noted this reality, dubbed "punctuated equilibrium" by scientists. Evolutionary gurus Eldredge, Mayr, Dawkins, Gould, and Dennett have been having an intramural "food fight" for years over how the process is supposed to work. Their disagreement over theoretical process apparently does not trouble the evolutionary science community. Their reaction is to tout the certainty of evolution, promote it ever more stridently, and force-feed the public education system with evolution, evolution, and more evolution.