"The Geographer" and "The Astronomer" are the only two paintings of solitary men by Vermeer. Painted in 1668 and 1669, Vermeer obviously intended the two men to be scholarly types. Although the astronomer has no telescope (which probably explains why this painting was originally called "The Astrologer"), he is shown touching a celestial globe. The painting of the geographer was originally called "A Mathematical Artist". He is holding a pair of compasses and has a terrestrial globe nearby. The light flows in from left to right. He appears to be caught looking up in abstract thought.
The model for both paintings is widely presumed to be Antony van Leeuwenhoek. Leeuwenhoek was a draper who became an official civil surveyor in 1669 and gained a reputation for skills in navigation, astronomy and mathematics. Best known for improving the microscope, he is commonly referred to as The Father of Microbiology. 
For many years sold as a pair, the paintings are now separated. I find this quite sad. I think they should be re-united.
"The Geographer" is currently on display at The Stadel in Frankfurt, Germany.
"The Astronomer" is housed in The Louvre in Paris.
For more info on the possible connection between painter and scientist, see Leeuwenhoek and Vermeer. For an interesting interactive analysis using your mouse to highlight various objects in "The Geographer", click here. For "The Astronomer", click here.
Click here for Vermeer's biography. If his name sounds familiar, but you can't quite place it, you've probably seen the movie, "Girl with a Pearl Earring" with Scarlett Johansson.
So, if you could own one piece of original art, what would it be?
Here are some interesting paintings to consider ... more than 500 years of "Women in Western Art" (in 3-minutes):
