Common Myths, Busted

True or false: Lightning never strikes the same place twice. Dogs see in black-and-white. Touching a toad will give you warts.

People have been repeating these ideas for years. You may have heard them from your friends or family or seen them on the internet. But the reality is, they’re 100 percent false!

You might be surprised to learn that many well-known “facts” aren’t facts at all. Certain beliefs have been around so long that they’ve become widely accepted—even though scientific studies have shown them to be wrong. Take a closer look at some popular myths that have been busted by science.

True or false: Lightning never strikes the same place twice. Dogs see in black-and-white. Touching a toad will give you warts.

People have repeated these ideas for years. You may have heard them from your friends or
family. Maybe you’ve seen them on the internet. But the truth is, they’re 100 percent false!

It might surprise you, but many well-known “facts” aren’t facts at all. Some beliefs are widely accepted because they’ve been around so long. But scientific studies have shown them to be wrong. Take a closer look at some popular myths. Then see how they’ve been busted by science.

BUSTED: No matter how long a piece of food has been on the floor, the safest bet is to toss or compost it. Even if the floor seems clean, it might harbor microscopic bacteria that could make you sick. People can easily introduce harmful germs to a room’s floor just by walking across it, explains Donald Schaffner, a microbiologist at Rutgers University in New Jersey. 

Some studies suggest that the longer food sits on the floor, the more bacteria it picks up, says Schaffner. His research also shows that moist foods like fruit salad pick up more germs than dry ones like a cracker. And hard floors transfer more microbes than carpet. But no matter the conditions, bacteria can get onto food in less than a second, so your dropped snack could be contaminated the moment it hits the ground. The bottom line, warns Schaffner, is that “there’s no safe amount of time” for food to touch the floor.

BUSTED: It doesn’t matter how long a piece of food has been on the floor. The safest plan is to toss or compost it. The floor may seem clean. But it might hold microscopic bacteria, and they could make you sick. People can easily introduce harmful germs to a room’s floor. They just have to walk across it, explains Donald Schaffner. He’s a microbiologist at Rutgers University in New Jersey. 

The longer food sits on the floor, the more bacteria it picks up. That’s what some studies suggest, says Schaffner. His research also shows that moist foods pick up more germs than dry ones. For example, fruit salad picks up more germs than a cracker. And hard floors transfer more microbes than carpet. But in any case, bacteria can get onto food in less than a second. So your dropped snack could be dirty the moment it hits the ground. Schaffner warns that “there’s no safe amount of time” for food to touch the floor.

BUSTED: The truth is, dropping a penny from any skyscraper probably wouldn’t do much damage if it were to hit someone. “There are two main forces that act on falling objects,” explains Geoff Martindale, a flight test engineer at Amazon Prime Air in Seattle, Washington. “One is gravity, which accelerates the object toward Earth. The other is drag, caused by surrounding air molecules, which slows the object down.” The faster an object falls, the more air molecules it bumps into, increasing drag.

An object dropped from a great height will eventually reach its terminal velocity. That’s when the force of drag pushing up against it becomes equal to the force of gravity pulling it down. When these two forces are balanced, the object stops accelerating and falls at a constant speed. A penny dropped from the top floor of the 102-story Empire State Building would likely reach a terminal velocity of about 70 kilometers (44 miles) per hour, says Martindale. That’s about how fast it would go if you threw it as hard as you could. “Since a penny is so light, it would do little damage to a human at that speed,” he says. 

BUSTED: If a penny dropped from a skyscraper hits someone, it probably won’t do much damage. “There are two main forces that act on falling objects,” explains Geoff Martindale. He’s a flight test engineer at Amazon Prime Air in Seattle, Washington. “One is gravity, which accelerates the object toward Earth. The other is drag, caused by surrounding air molecules, which slows the object down.” The faster an object falls, the more air molecules it bumps into. That increases drag.

What if an object falls from a great height? In time, it will reach its terminal velocity. The force of drag pushing up against it and the force of gravity pulling it down become equal. When these two forces are balanced, the object stops accelerating. It falls at a constant speed. Take for example, a penny dropped from the top of the 102-story Empire State Building. The penny would likely reach a terminal velocity of about 70 kilometers (44 miles) per hour, says Martindale. If you throw a penny as hard as you can, that’s about how fast it will go. “Since a penny is so light, it would do little damage to a human at that speed,” he says. 

BUSTED: At more than 3,300 km (2,000 mi) long, the Great Wall of China is one of the most impressive structures on Earth. Despite its size, this engineering marvel is very difficult to see from space. That’s because “its color and texture blend into the surrounding terrain,” explains Tim Newman, a program coordinator for the U.S. Geological Survey (USGS).

The Great Wall is difficult to spot in high-resolution photos of Earth taken by USGS satellites, which orbit 700 km (440 mi) above the planet’s surface. Even astronauts aboard the International Space Station, just 400 km (250 mi) above the ground, report that the
Great Wall is visible only with the help of magnifying camera lenses.

Other human-made landmarks are easier to see. For example, says Newman, “China’s Three Gorges Dam is visible not only because it’s large but because its white color stands out against the blue water.” Even smaller structures like roads and crop fields can stand out clearly when their surroundings are a different color, he says.

BUSTED: The Great Wall of China is more than 3,300 km (2,000 mi) long. It’s one of the most impressive structures on Earth. But this giant engineering marvel is very difficult to see from space. That’s because “its color and texture blend into the surrounding terrain,” explains Tim Newman. He’s a program coordinator for the U.S. Geological Survey (USGS).

USGS satellites orbit 700 km (440 mi) above Earth’s surface. They take high-resolution photos of the planet. But the Great Wall is difficult to spot in these photos. Astronauts aboard the International Space Station are just 400 km (250 mi) above the ground. But they need magnifying camera lenses to see the Great Wall.

Other human-made landmarks are easier to see. Newman gives an example. “China’s Three Gorges Dam is visible not only because it’s large but because its white color stands out against the blue water.” And smaller structures can be seen when their surroundings are a different color, he says. Even roads and crop fields can stand out clearly.

BUSTED: This idea comes from the understanding that after you eat, your body diverts some blood from your muscles to your stomach. “The stomach needs extra blood to help digest food,” says Dr. Mark Chandler, a pediatrician at Duke University School of Medicine in North Carolina. 

Doctors used to believe that reduced blood flow to muscles could cause them to cramp. Physicians feared that an uncontrollable muscle spasm could make it difficult to swim and increase risk of drowning. But they now know that there’s more than enough blood in your body—about 5.5 liters (1.5 gallons)—to safely digest food and swim at the same time. So there’s no need to wait 30 minutes after lunch before jumping back into the pool. In fact, eating will give you energy to keep swimming.

BUSTED: This idea comes from what happens after you eat. Your body sends less blood to your muscles and more to your stomach. “The stomach needs extra blood to help digest food,” says Dr. Mark Chandler. He’s a pediatrician at Duke University School of Medicine in North Carolina. 

So the blood flow to muscles gets reduced. Doctors used to believe this could cause muscle cramps. An uncontrollable cramp could make swimming difficult. That would increase the risk of drowning. But now doctors know that isn’t true. Your body contains about 5.5 liters (1.5 gallons) of blood. That’s more than enough to safely digest food and swim at the same time. So you don’t need to wait 30 minutes after lunch to jump back into the pool. In fact, eating will give you energy for swimming.

BUSTED: Accidentally swallowing a small wad of gum won’t do you any harm—and it won’t stay in your body for more than a couple of days. Most gum is made of flavorings, sweeteners, and gum resin—a type of plastic that gives gum its chewiness. Our bodies can digest sugars and other ingredients, but stomach acids can’t break down gum resin (see Chewing on Plastic). 

The resin passes through the digestive system but remains relatively intact as it does. “Gum leaves the stomach in less than two hours and should come out in your stool, or poop, in one to two days,” says Chandler.

Still, ingesting gum isn’t something you should do often. If you were to swallow a lot within a short time period, “it’s possible that a clump of gum could get stuck in your intestines,” says Chandler. A blockage could result in a serious medical problem. When you’re done chewing, your best bet is to throw the gum into a trash can, says Chandler.

BUSTED: If you swallow a small wad of gum by accident, it won’t hurt you. And it won’t stay in your body for more than a couple of days. Most gum is made of flavorings, sweeteners, and gum resin. This type of plastic gives gum its chewiness. Our bodies can digest sugars and other ingredients. But stomach acids can’t break down gum resin (see Chewing on Plastic). 

The resin passes through the digestive system. But it remains mostly intact. “Gum leaves the stomach in less than two hours and should come out in your stool, or poop, in one to two days,” says Chandler.

But you shouldn’t swallow gum often. If you swallow a lot in a short time, “it’s possible that a clump of gum could get stuck in your intestines,” says Chandler. A blockage could cause a serious medical problem. Finish chewing, and throw the gum into a trash can, says Chandler.