There are a number of old wives’ tales out there regarding some basic scientific principles. Though most of them were refuted years ago, these rumors just won’t go away. Here are some of the top myths floating around out there that just aren’t true:

We only use 10% of our brains.

It's true that there’s a great deal we don’t know about the brain, but we certainly do know that we use our entire brain. Even if we didn’t have a wealth of data from brain scans to show this 10% figure is completely false (we do), it doesn’t even make sense using basic logic. Though the brain only weighs a couple of pounds, it is incredibly energetically demanding, requiring about 20% of all of the oxygen and glucose brought into the body. It is extremely unlikely that the brain would have evolved as it did if it were mostly useless.

Additionally, there is no evidence that someone was ever diagnosed with a brain tumor but was told: “Great news! The tumor is in a part that you don’t use!” Trauma to the brain would also rarely have devastating results if it were mostly unused, but very few survive gunshot wounds to the head, and it isn’t without some serious side effects.

While you might not be using every bit of your brain at all times, but you do use the entire brain over the course of the day. Feeling like someone isn’t living up to his or her full potential is a different matter, but that still doesn’t mean they aren’t using their entire brain each day.

There is a dark side of the moon.

Oh, Pink Floyd, how you have led us all astray.

From our perspective on Earth, we are able to view about 59% of the moon’s surface (though not all at the same time). The remaining 41% is completely hidden from this vantage point. That 41% must be shrouded in freezing darkness, never to feel the Sun’s warmth, right? No.

This confusion is due to tidal locking, which makes it seem as if the moon isn’t rotating. The moon actually is spinning quite slowly, completing a rotation in about the amount of time it takes it to make a revolution around Earth. While one side (more or less) is forever shielded from Earth, that has nothing to do with the amount of sunlight it receives. After all, we do have different phases of the moon.

Except in the case of a lunar eclipse, sunlight falls on half of the moon (exactly how half of Earth receives daylight at once) all of the time. While the Sun fully illuminates the side of the moon we can see, we appropriately call it the full moon. When parts or all of the moon appear to be missing, some or all of the sunlight is falling on the side of the moon we can’t see. While there is most definitely a region we could refer to as “the far side of the moon” it is no more or less dark than the side we can see.

The full moon affects behavior.

It has been a longstanding myth, particularly among individuals working with the elderly or those with mental disabilities, that the full moon draws out strange behavior in people. This myth has a wide variety of supposed causes, including that the water in the brain is affected by tidal forces of the moon. Many people claim that violent crime increases during this time, and even police stations in the UK once increased staffing for a full moon to prepare for the influx of crime and accidents.

The topic has been studied many times over, and there is very limited correlation between the full moon and increased erratic behavior and certainly no causation discovered. While a few studies have indeed shown a spike in crime and the full moon, it was typically explained by falling on a holiday or weekend. Once that was taken into account, the connection crumbled. There is nothing to fear about erratic behavior and the full moon, unless, of course, you are a werewolf.

Sugar makes children hyperactive.

Attending any child’s birthday party where cake, ice cream, and sugary drinks about would make just about anyone a believer that sugar influences hyperactivity. There has not been much evidence to suggest that the so-called “sugar buzz” is actually real for children (aside from a small subset with an insulin disorder coupled with certain psychiatric disorders). The ramped-up energy seen following birthday parties or Halloween could be excitement over getting a treat or being around other kids. It is also possible that other ingredients, such as caffeine, are to blame.

That’s not to say that sugar intake shouldn’t be limited. The average American consumes 156 pounds of sugar every year. As a comparison, Americans 200 years ago consumed about 3-5 pounds per year. Too much sugar is associated with weight gain, insulin resistance, hypertension, and even an increased risk for certain cancers.

Lightning never strikes the same place twice.

“Lightning never strikes the same place twice” is a common idiom used say that something bad happened once, but it can’t happen again. Unfortunately, it has nothing to do with actual lightning strikes.

Lightning is a huge electrostatic discharge searching for a way down, and it isn’t particularly interested in whether or not it has been hit before. Taller objects, such as trees and skyscrapers, are usually choice targets because there is a shorter distance between that and the origin of the lightning. The tallest tree in a forest can get struck several times until the storm passes. In fact, lightning strikes the Empire State Building around 100 times per year.

NASA released a study in 2003 involving 386 cloud-to-ground strikes and found that over a third of the strikes branched and hit multiple locations at once. Not only does lightning strike twice, but it can also strike two places at the same time!

Dropping a penny from a tall building will kill someone.

If you were to head to the top of the Empire State Building (hopefully after it’s done being bombarded with lightning) and fling a penny down to the sidewalk below, it won’t kill anyone. Pennies are fairly lightweight at around one gram and being a flat circle doesn’t bode well in terms of aerodynamics. Because it would tumble and flip the entire way down, its low mass and relatively low terminal velocity (105 km/h) wouldn’t do much damage to the bystander on the sidewalk. It would feel similar to getting flicked in the head. Annoying, yes; but not lethal.

However, throwing items down to the ground that are more massive or more aerodynamic would increase the object’s terminal velocity and could do quite a bit of damage. Construction zones require hardhats in order to protect workers from stray rocks or bolts that are accidentally dropped from great heights.

Hair and fingernails continue growing after death.

In order for fingernails and hair to grow after someone is dead, the person would need to still be eating and digesting nutrients and performing cellular processes. Of course, that would interfere with the whole “being dead” thing. So there’s no way the body is producing more keratin in order to make hair and fingernails.

However, skin and hair can appear to grow post-mortem. As the dead skin begins to dry out, they retract and pull away from the hair shafts and nail beds. The hair and fingernails are not affected by the lack of moisture and do not shrink, which can make it seem as if they had grown. This also makes clean-shaven men appear to have grown stubble. Many funeral homes will apply moisturizer after the corpse has been washed in order to reduce the amount of drying prior to the memorial service.

Cracking your knuckles gives you arthritis.

While it makes sense on the surface that repeatedly pushing and stretching joints to make them crack would eventually lead to osteoarthritis, which is the painful deterioration of the joints, studies that have been performed on the topic have not been able to show a connection. In 1998, Donald Unger published a paper that revealed he had been cracking the knuckles in his left hand every day for 60 years, but not at all on his right hand. There was no difference in the joint health between the two hands, and Unger received the 2009 Ig Nobel Prize in Medicine for his work.

Synovial fluid is a substance that acts as a cushion and reduce friction in synovial joints, such as knuckles, elbows, knees, and hips. When the joints are stretched and the joint capsule separates, the decreased pressure within the capsule releases gas, forming a bubble to make up for the dead space. Pressing on the joint can create a loud, audible pop as the bubble breaks and the joint capsule returns to its normal size. If cracking knuckles is associated with pain, it may indicate damaged joints that need to be addressed. The cracking sound can also come from tendons, which can reduce their strength over time.

It takes seven years to digest swallowed chewing gum.

Chewing gum does not take seven years to digest. In fact, you don’t even digest it at all. Aside from a small amount of sweeteners and flavorings, there’s really not a lot inside the gum that the human body can actually break down and use. The bulk of gum is made out of rubbery polymers known as elastomers along with glycerin and vegetable oil-based ingredients to keep the gum soft and moist. Once the body has extracted what little it can from the gum, the rest is passed along as waste, just like anything else.

However, that doesn’t mean swallowing gum is a great idea. Swallowing large amounts of gum can cause constipation and gastrointestinal blockage that needs to be removed by a physician. Gum can also fuse with other non-digestible items in the digestive tract such as coins, small toys, and sharp sunflower seed shells, which could contribute to gastrointestinal blockage or injury. While gum won’t stick around in your gut for seven years, it’s probably still safer to spit it out in a garbage can and wait to give it to children until they are old enough to know not to swallow it.

Antibiotics kill viruses.

This one pops up every cold and flu season. Antibiotics, by their very definition, kill bacteria. The common cold and influenza are viruses and are not affected by antibiotic use. While some might think that taking antibiotics could be helpful on some level and want them for viral disease, that is dead wrong and could actually bring on more problems. Taking antibiotics in a manner contrary to their intended purpose or dosage instruction could cause other common bacteria within the body to become drug-resistant, which has become critically important. This could create “superbugs” that cause illness much worse than the primary

The CDC has reported that physicians write tens of millions of antibiotic prescriptions each year for illnesses that are viral. This is partly due to uncertainty of the cause and badgering from the patients (or the parents of children). Some doctors are slightly more justified in prescribing antibiotics for a condition that can be bacterial or viral without making the patient wait days for lab results to return determining the cause. However, it is important for patients to understand why antibiotics don’t kill virus and to not demand drugs that will likely do more harm than good.