To answer your 3 top questions, "big data" has sometimes been defined as volume, velocity, and variety. I believe other organizations consider more variables when considering what "big data" encompasses. I have worked on several projects using large data sets with geographical information systems linking and analyzing data from multiple relational data sets with spatial data across counties, states, regions, and countries. The time it will take to write 500 word articles depends in large part on the detail require for a particular subject related to big data. I suppose a person could write 500 words relatively quickly if you aren't concerned much with the substance and accuracy level. In addition, you mention the need for graphics/images related to each article. It will take some time to locate pictures suitable for publication. I'd estimate it could take from 1 to 3 or more hours per article, depending on the factors I've mentioned.