The response to the question “What is the (xxx?)?” might sound simple—find the source measurement, mouth, and source, but between those steps there are many definitions, fractals, and hydrology and, perhaps most important, national pride. This is a problem that’s so complex that many hydrologists interviewed by Mental Floss explained that river length isn’t even considered a reliable measure any more. What is the longest river on earth? Clicking here: https://www.freejobalert.com/longest-rivers-in-the-world/994260/ for new information.