THE Y-FILES, Part I: Answers to Satisfy the Most Inquisitive 4-year old

I keep my office like I keep my coffee: dark. So when the door creaked open, and the light streamed in, I knew it was trouble. The dame walked toward me and started firing off questions. She was the pushy sort, and she shot "˜em off rapid-fire: "Why's the sky blue? Why are tennis balls fuzzy? Why do llamas spit? Why? Why? Why?" The gal was merciless, and she didn't take "Go ask mom" for an answer. This was a four-year-old who needed explanations, and she needed "˜em fast. I looked over my shoulder, took a long swig of courage, then opened the drawer. I could see it was time to crack open this case.

THE WHY FILES

WHY ARE OCEANS SALTY BUT NOT LAKES?
Oceans act like big dumping grounds for all the minerals (including salt) that wash off the land and get carried by rivers into the sea. As salt collects in the ocean, some of it evaporates with water, but most of it stays put. Evaporated salt and water take a ride in the clouds back over land, and the cycle continues. This means that rainwater does contain some salt, so, in truth, lakes are a little salty too. So why are the Great Salt Lake in Utah and the Dead Sea in the Middle East excessively salty? It's because they don't have an outlet. All lakes are fed by a water source (usually a river), and, in most lakes, the water flows out through a river as well, eventually reaching the sea. Salt lakes take water in from rivers or rain, but since they can only lose water by evaporation, some of the salt is left behind. Over time, these lakes have developed a high percentage of salt (even more than that of the world's oceans).

WHY DO LIGHTNING BUGS LIGHT UP?
When a male firefly larva finally gets old enough to develop wings, he does what every other male in the animal kingdom does when he can finally get away from home: He goes cruising for chicks. Fireflies can't entice the ladies with fancy dinners or nice cars, but they can emit glowing signals from their bodies because they have a bioluminescent enzyme known as luciferase, which the women just go crazy for. The downside is that fireflies only live for about seven days, which means their nighttime glowing expeditions are particularly frantic. So think twice before stuffing a bunch of those guys into a Mason jar; you may be ruining their one and only chance to "get it on" or, at the very least, seriously cramping their mojo.

More essential answers after the jump...

WHY DOES IT HURT SO BADLY TO CHEW ON ALUMINUM FOIL?
Sure, you're probably not snacking on balls of Reynolds Wrap every day, but most of us have had a little foil trespasser make it into our mouths every now and again. And when it happens, it can hurt really badly, but only if you have fillings in your teeth. Terrible as it is to imagine, when the silver in a tooth filling chomps down on aluminum, the reaction of the two elements creates a tiny electrical charge.

WHY DOES IT HURT SO BADLY WHEN YOU HIT YOUR FUNNY BONE?
Because your funny bone isn't a bone, that's why. It's actually the ulnar nerve, which runs from your shoulders to your hands and is responsible for things like dexterity. The ulnar nerve sits rather close to the skin in the area around the elbow, so—like contact with any exposed nerve—it hurts really bad when you hit it. It's actually one of the body's biggest design flaws because we really could have used some more padding around that nerve. Primates like orangutans and chimpanzees have the same problem. So maybe the person who came up with the nonsensical name saw a chimp hitting his ulnar nerve, because, really, that's just funny.

WHY DO SOME PEOPLE HAVE "INNIE" BELLY-BUTTONS AND SOME PEOPLE HAVE "OUTTIES"?
No, it's not a conspiracy. The disappointing (i.e., boring) answer is that it's pretty random. Only seconds after you were dragged into this world, a doctor placed two clamps on your umbilical cord and cut it off a few centimeters away from your belly-button. Though this was probably your first emotionally scarring experience, the first scarring experience of a physical kind occurs when that little piece of umbilical cord still attached to your body eventually deadens and falls off, leaving—normally—a concave scar, or an innie belly-button. People with outties simply healed differently during this process. If you're bummed about your outtie status, mental_floss would like to remind you that things could be a lot worse: Several conditions, usually developed later in life, can cause urine, blood or, yes, even intestinal parts to leak out of the body by way of the navel.

>> Be sure to come back tomorrow for part II of the Y-Files. Oh, and if you enjoyed this piece, back issues are available for purchase here.