  What science does, what science could do, and how to make science work? If we
want to know the answers to these questions, we need to be able to uncover the
mechanisms of science, going beyond metrics that are easily collectible and
quantifiable. In this perspective piece, we link metrics to mechanisms by
demonstrating how emerging metrics of science not only offer complementaries to
existing ones, but also shed light on the hidden structure and mechanisms of
science. Based on fundamental properties of science, we classify existing
theories and findings into: hot and cold science referring to attention shift
between scientific fields, fast and slow science reflecting productivity of
scientists and teams, soft and hard science revealing reproducibility of
scientific research. We suggest that interest about mechanisms of science since
Derek J. de Solla Price, Robert K. Merton, Eugene Garfield, and many others
complement the zeitgeist in pursuing new, complex metrics without understanding
the underlying processes. We propose that understanding and modeling the
mechanisms of science condition effective development and application of
metrics.
