(phone ringing) - Hi, it's Danni. I've always been curious
about mega-sized creatures, like this supersized African land snail or this massive rabbit in England. Oh, and check out this cat named Barivel. It's one of the world's
biggest house cats. So cool. Someone named Austin is curious about really big animals too, the kind that live in the ocean. Let's give Austin a call now. (phone ringing) - Hi, Danni. - Hi, Austin. - I have a question for you. What is the biggest shark that ever lived? - Ooh, that's a great question, and it's a surprisingly
hard question to answer because there are hundreds of
sharks living in the ocean. Sharks that can fit in your hand, like this dwarf lantern shark, and sharks with huge mouths,
like this megamouth shark. There are even some sharks
with interesting looking faces, like this goblin shark. And the number of sharks in the ocean isn't the only problem when it comes to finding
the biggest shark. The fact is sharks aren't
all that easy to measure. Think about it. It's not like you can just
go up to a shark and say, "Hey, stay still for a
second so I can measure you." Hmm, so is it even possible
to answer this question? I mean, how do we even
know how big sharks are? Before I move on, I'm curious. How do you think
scientists measure sharks? Now would be a good time to
pause the video and discuss. Okay, you ready? I don't know what you answered, but some of you might have said, "You can capture them to
figure out how big they are." And you're right. One way scientists have used to figure out how big a shark is is to capture it, measure it, then throw it back in the water. But that's not always easy to do. I mean, some sharks are really
big, and strong, and heavy and they don't appreciate
being pulled out of the water, like this great white. Great white sharks are super strong. Strong enough to hunt whales
that are twice their size, and they're really big. They can grow up to 23 feet long. That's almost the length
of 6 second graders laying head to toe, which means they're really hard to catch. So, scientists have invented other tools to measure sharks more
accurately, like this camera. When this special video camera
is attached to a computer, it can measure how big a
shark is when they swim by. Tools like these have allowed scientists to measure even bigger
sharks than the great white. Sharks like this one. You're looking at a whale shark. You can tell by the white
spots all over its body. I got to swim with whale
sharks in Mexico once, and let me tell you, they were huge. Whale sharks can grow as long as 46 feet, which is almost as long
as 12 second graders laying head to toe. Whoa, that makes the whale
shark the biggest living shark in the ocean today. But notice I said "living." What about sharks that
aren't around anymore? Sharks that swam the seas
millions of years ago? Were any of them bigger? Hmm, that's a really
tricky question to answer. I mean, scientists can't measure sharks that aren't around anymore
with special cameras, and they definitely can't catch them. Now, you might be thinking, "We could measure ancient shark fossils like scientists have done with other extinct
creatures like dinosaurs." But here's the thing. Shark bodies are mostly
made of soft cartilage, the same thing your nose is made out of. And that cartilage falls
apart after the shark dies. So, prehistoric shark skeletons are almost impossible to find. But luckily scientists
have figured out a way to estimate the size of sharks
that aren't around anymore by looking at something
that doesn't break apart, shark teeth. Check this one out. Isn't it huge? You're looking at the tooth of a shark that scientists think
could have been even bigger than whale sharks. It's called the megalodon. Now, no one's ever found
a megalodon skeleton, but by comparing the size of their teeth to sharks that are alive today, scientists have been able to estimate that they may have grown
up to 60 feet long, which is like an incredible
15 second graders laying head to toe. Wow. That would make the
megalodon the biggest shark that ever lived. So, in summary, it's not easy
to measure how big a shark is because they're big and strong, and they don't leave a lot
of fossils behind to measure. But by using special tools, like shark measuring video
cameras attached to computers and by studying ancient shark teeth, we've been able to figure
out how big sharks are without ever having to
take them out of the water. That's all for this week's question. Thanks, Austin, for asking it. Now, for the next episode, we reached into our question jar and picked out three
questions sent into us that we're thinking about answering next. When this video's done playing, you'll get to vote on one. You can choose from, "What's the longest
anyone's ever stayed awake? How do mirrors work?" Or, "How were the first roads made?" So, submit your vote
when the video's over. We want to hear from all of you watching. There are mysteries all around us. Stay curious, and see you next week.
