Tryptophan is a component of serotonin, which turns into the sleep-inducing melatonin. Thus, many people believe turkey — which contains tryptophan — makes you sleepy.

In reality, it's likelier an excessive amount of carbohydrates and booze that makes you sleepy after Thanksgiving dinner. Poultry also contains tryptophan — and cheddar cheese actually has more of the stuff than turkey! Do you hear anyone talking about how tired they are after eating a chunk of cheddar? No.

If food is on the ground for less than five seconds, it's safe to eat because the floor germs haven't contaminated it yet, right?

Wrong-o! Although the longer food is on the floor, the more bacteria it can pick up, one study from Rutgers University found that bacteria can contaminate your food instantly.

I was always warned not to crack my knuckles because it would lead to arthritis and other joint problems in the long run. Mainly, I was suspicious that it just drove my family crazy.

It turns out their concerns weren't necessary either way: Several studies have compared arthritis rates among knuckle crackers and non-knuckle crackers and found no relation.

It's long been held that dogs can only see in black, white, and certain shades of gray. However, including to many sources — including the American Kennel Club — this is a big, fat lie.

In actuality, dogs can see yellow, blue, and combinations of these two colors. This makes for a lot of grayish-brown, in their world. So while grass may not be green and red may look more brown, they do see color.

I think a lot of us liked this myth because it meant there's so much more we could do, if we could just learn to "tap into" other parts of our brain. I hate to break it to you, but this one is...

FALSE! Dr. Barry Gordon, professor of neurology and cognitive science, behavioral neurologist, and cognitive neuroscientist explains at Johns Hopkins' Hub site that we use just about every part of our brain nearly all the time. Still not convinced? Dr. Gordon says that the brain is three percent of the body's weight, but uses 20 percent of the body's energy.

As a kid, I'd love to sit right in front of the TV, just to, you know, get closer. I can remember my mom telling me to back up, or else I'd go cross-eyed.

It turns out sitting close to the TV isn't bad for your eyes, according to the American Academy of Ophthalmology. It can cause eye strain, but research has found no damage in children or adults.

A lot of us are warned as young girls to hold off on shaving for as long as we can, because it makes the hair grow back thicker. This is yet another huge misconception.

Hair only appears to grow back thicker. Because shaving cuts it at a blunt angle (as opposed to when it grows naturally with a fine point), it gives off the look and feel of thicker, darker hair. It's the act of constantly chopping off stubble that changes the appearance so much. But the hairs themselves are not thicker.

And for what it's worth: Shave if you like; don't shave if you don't like. It's totally up to you, myths and other people's opinions be damned.

Negative. Gastroenterologist Dr. Rodger Liddle explains that for something to take that long to digest, it would need to be so large that it gets trapped in the stomach or intestine. Chewing gum passes through the digestive system like any other food.

However, worth noting is that swallowing a ton of chewing gum in a short period of time can be dangerous, as it can accumulate and stuff up the digestive tract, causing constipation.

When we were little, our parents sometimes told us to wait at least a half hour after eating to go swimming. The fear for many of them was that the digestive tract needed extra blood pumped to it, which would take blood away from your arms and legs, and you'd lose the ability to swim and find yourself in danger.

While the body does give extra blood to help you digest food, it's not enough to stop your limbs from working. At most, you might suffer a minor cramp, but that's it.

Supposedly, the inevitable extinction of natural blondes and redheads is supported due to the fact that they carry a recessive gene that is becoming more and more rare as the years pass.

However, in order for a gene to become extinct, one of two things needs to happen: Literally every person on the planet carrying that gene needs to die or fail to reproduce (unlikely), or there would need to be some evolutionary disadvantage to that hair color (which there isn't). So, true blondes and redheads might be in the minority, but the chances of them ever disappearing completely are slim to none.

Sharks are known for having a keen sense of smell; but it turns out we've been overestimating their talent.

The myth that they can smell a drop of blood from a mile away is false. In fact, their sense of smell is not much different from any other fish.

Surprisingly, goldfish can be trained to respond to colors, music, and other cues. Furthermore, they've been shown to retain memories for as long as a year! They've been taught to play fetch, push levers, play soccer, and even do the limbo. (Don't ask.) They anticipate feedings when repeatedly fed at the same time of day, and they can recognize their masters.

Beer before liquor, never been sicker. Liquor before beer, you're in the clear. Sound familiar?

The truth is that it doesn't matter which alcohol you drink when; it matters how much you drink overall. As you consume, your inhibition decreases, and you're likelier to drink more. Starting with liquor or beer won't have any effect on how sick you get. One thing to remember is that if you start with a drink that contains more alcohol, your inhibitions are likelier to decrease faster, and you're inclined to drink more, sooner. This could give you the impression that it was the order in which you drank that made you sick, when really, it was simply that you got drunk faster and drank too much in general.

Here's one myth many scientists wish would die. There is no scientific proof that eight is the magic number. Yes, we need water to stay hydrated; but we also get hydration from other sources as well. The quality of the water matters, along with what you eat, where you live, how active you are, and how big you are.

The T-Rex's teeny, tiny arms are the subject of many funny memes today; but science explains that there is a good chance (although some do doubt it) that the T-Rex made good use of its little arms — for holding down its mates and its prey. But to be fair, this one's up for debate.