How do you measure the longest river?

This week on Unexplainable or Not, Sally Helm, the newest member of our team, tries to figure out what's killing mussels, why rivers suddenly change course, and what the longest river in the world is.

Guests: ⁠Douglas Edmonds⁠, professor at Indiana University; ⁠Neel Dhanesha⁠, science reporter 

For show transcripts, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unxtranscripts⁠⁠

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