The archaic answer is a philosopher, which comes from the word philosophy, where
- philo = love; and
- sophia = knowledge, wisdom:
c. 1300, "knowledge, body of knowledge," from Old French filosofie "philosophy, knowledge" (12c., Modern French philosophie) and directly from Latin philosophia and from Greek philosophia "love of knowledge, pursuit of wisdom; systematic investigation," from philo- "loving" (see philo-) + sophia "knowledge, wisdom," from sophis "wise, learned;" of unknown origin.
- Online Etymology Dictionary
Support for the link between philosophy and science comes from the term natural philosophy:
natural philosophy noun [mass noun] archaic
Natural science, especially physical science.
Note that calling a lover of science a philosopher would now be somewhat misleading. The modern understanding has specialised this usage to an academic context, hence the Ph in the title, Ph.D.
(This answer is an expanded version of a popular comment I made to a very similar question. I'm including it here for historical interest in the term philosopher.)