This visualization is based on the research for Pedro M Cruz's master thesis. He's interested in using scientific and statistical number-crunching and then displaying the data in visual ways that straddle the very thin line between art and science.
In this case, the data behind the visualization is the evolution of the four leading maritime empires of the nineteenth and twentieth centuries—the British, Spanish, Portuguese, and French navies. Most of the historic data regarding dates of historic events is from Wikipedia; this is thus, more a proof of concept than a demonstration of scholarly data utilization.