It's a good question. The blue whale is the largest known animal to ever grace the planet (they may be twice as big as Megalodon was! Their tongues are as heavy as elephants!), but they're still mysterious. Learn what science knows (and doesn't know) about blue whales in today's classic episode of BrainStuff, based on this article: https://animals.howstuffworks.com/mammals/blue-whale.htm