The new discovery helps the Amazon River become the world's longest river

Instead of relying on length, scientists have come up with a more precise criterion to compare the 'level of crisis' between rivers.

If asked what is the longest river in the world, would you say that it is the Nile? Because you think that the length of the Nile is 6,650km, while the Amazon River only reaches the 2nd destination with 6,400km.

But with this amazing discovery, the Nile is no longer the longest river in the world.

How to determine the length of a river?

In order to determine the length of a river, it is normal to assume that just determining the headwaters, finding the river mouth and conducting a distance measurement will result.

According to Professor Laurel Larsen from the Department of Geography, California Berkeley University, the length of a river is the longest seamless distance connecting the headwaters to the river mouths, along the deepest trench of the river.

In particular, the watershed is the furthest point and the current flow is independent, no input source. It sounds simple, but this is extremely difficult because rivers are often not a perfect single system. Typically, Mississippi - considering historical reasons, the Mississippi River is completely separate and independent from Missouri. But according to common definitions, these two rivers share a common system.

Mississippi River and Misouri share the same system.

Similar to estuaries. For some small rivers, the determination of estuaries can be quite easy, but with great rivers flowing into the sea like Amazon is extremely complicated.

In 2007, an analysis by Brazilian scientists showed that the Amazon estuary should indeed belong to the Pará river in the southern island of Marajó, instead of the North as previously studied. This observation was quickly rejected by new studies. But it also shows that it is not easy to determine the exact estuary .

Determining the river mouth is also a difficult thing.

Not only affected by the identification of watersheds and estuaries, the length of one river is still hidden by errors by the measurement method.

According to coastline paradox: "The length of a complex object is basically indeterminate, because the larger the length, the smaller the measurement." And with rivers up to thousands of kilometers long, the error is even bigger.

For the above reasons, researchers have concluded that the length of a river is no longer a big thing.

Instead, the only really important factor is the river basin - the mainland provides water for rivers. Because unlike length, this criterion has metrics for easy and more accurate calculations.

The longest river is not standard yet.The widest river is the standard without correction.

Based on this evaluation criterion, hydrologists have launched a new ranking of rivers in the world.

Accordingly, the Nile fell from the top and modest position, the fifth largest river in the world, behind Congo, Mississippi, and Ob.

Leading the table is the Amazon River, with a basin of 6.3 million km2 - enough to be the seventh largest country in the world, after Australia - according to an analysis in Nature.