#448 World's Longest River?

Here's a not-so-simple question.  Which river is the world's longest? 

Above is an 1854 Victorian Infographic made widely available by David Rumsey, a remarkable map collector and proponent of cool historic maps on the web.  Nineteenth century scientists thought the Missouri to be the world's longest with River Amazon second and the Nile fifth.

Our understanding of river length changes over time and the Nile took the length crown for many years.  Now Brazilian scientists claim the Amazon is longer than the Nile. 

Measuring river length is a question of scale as Michael Goodchild from the University of California Santa Barbara Center for Spatial Studies explains in the second half of this talk on spatial thinking.

No matter how long, River Amazon is one beautiful ride.

Yours in traveling the world's longest or second longest river,
Kelly