The Great Scientist is a Great Person acquired through Specialists or Wonders.
"Great Scientists" figure out how the world works. They discover that the earth orbits the sun. They sequence DNA and invent quantum mechanics. They cure polio and predict eclipses. They make a civilization smarter. They invent the future.
In Gods & Kings and Brave New World, the Great Scientist may use the "Boost Science" ability, which lets you immediately gain a large number of science points based on the science output of your civilization. It is usually enough to finish researching the current technology, and even boost another one! Use this if you need an immediate result.
Alternatively, the Great Scientist can construct an Academy for a long-term Science boost in a city. In the early game, constructing Academies is recommended, as the long-term science gains will surpass the instant gain of Boost Science. In the later game, Boost Science may be worth many tens of turns' worth of Academy science. Since you can see how much science Boost Science is worth by mousing over the button, you can judge its worth based on how many turns you expect are left in the game (or until you get enough tech to go for your desired victory). Since the Academy affects the science output of an individual city, its gains are augmented by all science buildings with a percentage bonus, like the Research Lab.
Unique Unit Replacements
|Andalusian Polymath||Córdoba (Abd-ar-Rahman III)|
|Benevolent Mad Doctor||Asklepieia (Faust)||