longest-rivers

For over a century, the Nile has been called the longest river on Earth at about 6,650 kilometres. But a stubborn group of scientists argues the Amazon is actually longer — and the disagreement isn't sloppiness. It comes down to a genuinely hard question: where does a river begin, and where does it end? The answer changes the ranking, and reveals why even something as basic as 'how long is this river' has no single correct number.