How many times do you hear the phrase “it’s common sense” as a justification for something? For me, even one time is too many, as it is so often used to account for things that have little to no evidence to support them. It is also used to diminish new results from researchers. Some ideas might be common sense but they still need to be tested over and over again.

And testing what we believe to be true over and over again is a good thing. It challenges our biases and helps us become more critical of the way we are naturally bound to think. To help you challenge some common misconceptions, here is a list of common sense "facts" that are just not true.

Meteorites Are Fireballs When They Touch The Ground

Space rocks burn as they fall from the sky through the atmosphere. The heat of the entry is created by adiabatic compression of air in front of the object (not friction) and reaches temperatures high enough to melt the outer layer. But the pace is so fast that the melted material is blown off, so it can’t heat up the whole meteor.

Meteors can then spend several minutes in the lower, cooler, denser parts of the atmosphere. There they experience subsonic velocities so they don't warm up any more. Rocky meteorites are usually bad conductors of heat so depending on circumstance they might be hot, warm, or even covered in ice. None of them will be fireballs when they hit. 

Lightning Never Strikes The Same Place Twice

This is one of the oldest and most persistent "common sense" myths around. And if it were true, then lighting rods, which are used to divert lightning from buildings into the ground, would be single-use creations. In reality, lightning strikes prefer to hit tall structures that rise above the surrounding areas. A lighting strike looks for a path to the ground and when it finds one, the charges move from the clouds down to Earth.

Certain tall buildings and many trees have all experienced multiple lightning strikes. Even a few people have been struck more than once. You get more lightning the closer you are to the equator, and Lake Maracaibo is the world’s capital for lighting with 1.2 million strikes per year.

Microwaves Cook Food From The Inside Out Or The Outside In

This is a double whammy of common sense claims that people – pardon the pun – usually get quite heated about. People swear that food cooks from the inside out (look at how butter melts! It’s common sense) or from the outside in (the center always remain frozen! It’s common sense).

Microwaves cannot reach the center of most of the things we place inside them. They penetrate about a centimeter (0.4 inches) into most food and then the rest is warmed up by internal heat transfer. And on the subject of microwaves, placing metals in them usually doesn’t damage the electronics. The issue with metals is actually just that they heat up significantly, which can damage the microwave and burn your food. 

Assorted Ideas About The Human Body And Cold Weather

You should always cover your head in winter because that’s where you lose the most heat from. Wear a scarf on your neck or you’ll catch a cough. Don’t get your feet wet or you’ll get sick. Don’t go out with wet hair, you’ll get the flu. Well, that’s really not how germs work.

They are not just waiting to jump on you the moment your body's exposed to the elements or your extremities come into contact with water. Being cold and having a cold/cough might have similar effects on the body (runny nose, dry throat) but the link ends there. No scientific research has found a direct link between being cold and getting sick. 

Evolution Makes Species Better

Myths about evolution are two a penny but there’s one that continues to be perpetuated even by people that accept the theory – evolution always means improvement. But that’s just not true. There’s no magic force behind evolution. No grand design. Evolution is blind and not all adaptations are improvements for the better.

Evolution doesn’t care about making species perfect. Random chance gives each creature of each species certain characteristics. If these are good enough a species can survive. Humans, in particular, are not the be-all and end-all of evolution. The position of the optic nerve in front of the retina that creates a blind spot is not ideal for an extremely visual species. Octopuses don't have this flaw, by the way. And our bodies can't produce their own vitamin C anymore, something that our ancestors found out on long sea journeys with deadly consequences.

You Should Never Eat Before Swimming

You should always wait a few hours before going swimming after eating. How many parents have repeated this almost dogmatic motto, even though it probably annoyed them when they were children? And they'd be right to be annoyed. Because it’s nonsense.

A lot of reputable sources admit that the statement doesn’t have any scientific backing. Instead, swimming poses a threat to children in other ways. Swimming is one of the leading causes of accidental death in children but this is to do with them being weak swimmers and a lack of supervision, rather than eating. Talk to your children, explain that the hours after lunch are some of the hottest in the day, so it’s better to stay in the shade. Children are not stupid. They know when you lie.

Exercise Cures Depression

When it comes to discussing mental health, “common sense bullsh*t” has almost been elevated to an art form. People with no understanding of the subject feel qualified to give out “medical” advice like they're trained specialists.

So let’s be completely clear. Exercising doesn’t magically cure depression. Nor does a positive mental attitude. Let’s not even start on willpower. You know what helps? Supportive friends and family. Access to medical help. Sometimes medicine. Sometimes different forms of therapy.

Would you tell diabetic people that they don’t need insulin? That they should go for a run instead? Or maybe someone with a broken foot that it would heal if they only got out more? Unless you’re a horrible person you wouldn’t. So start calling out those who say the same things about depression.