I am tempted to write:  &quot;what part isn&#x27;t?&quot;<p>Seriously, just about everything we do in computer science is experimentation, at least if it involves...<i>physical computers</i>.<p>Every time we run a program, we run an experiment.  At least if we have some expectation of what we want the program to do.  Every time we write a test, or run a test suite, we are running an experiment.<p>Every time we implement some sort of abstraction, every time we vary a parameter, every time we optimize a program, we are running experiments.<p>At least if we&#x27;re doing it right.<p>If you&#x27;re not doing experiments, I have a hard time categorizing what you are doing as <i>computer</i> science.