Six More Commonly Believed Things That Are False

A few weeks ago I did a post, Six Commonly Believed Things That Are False. One commenter asked for more, and after a few weeks of keeping my eyes and ears open, here it is, “Six More Commonly Believed Thing That Are False”.

1) Medieval people thought that the Earth was Flat

Yes, I know I did this one last time. But I got so many responses from people who disagreed that I had to do it again. This time, I’m just going to quote from Wikipedia:

The late development of European vernacular languages also provides some evidence to the contention that the spherical shape of the Earth was common knowledge outside academic circles. At the time, scholarly work was typically written in Latin. Works written in a native dialect or language (such as Italian or German) were generally intended for a wider audience.

Dante's Divine Comedy, the last great work of literature of the Middle Ages, written in Italian, portrays Earth as a sphere. Also, the Elucidarium of Honorius Augustodunensis (c. 1120), an important manual for the instruction of lesser clergy which was translated into Middle English, Old French, Middle High German, Old Russian, Middle Dutch, Old Norse, Icelandic, Spanish, and several Italian dialects, explicitly refers to a spherical Earth. Likewise, the fact that Bertold von Regensburg (mid-13th century) used the spherical Earth as a sermon illustration shows that he could assume this knowledge among his congregation. The sermon was held in the vernacular German, and thus was not intended for a learned audience.

Reinhard Krüger, a professor for Romance literature at the University of Stuttgart (Germany), has discovered more than 100 medieval Latin and vernacular writers from the late antiquity to the 15th century who were all convinced that the earth was round like a ball.

Is that enough evidence that even common people knew that the Earth was round? Because I certainly think it is. Granted, we’ll never be able to know if everyone thought the earth was round or flat. But every bit of evidence I’ve ever seen has said that people thought it was round, and none of the detractors last time produced a shred saying that they didn’t. So as far as I’m concerned, this is case closed.

2) Spacecraft heat up on re-entry because of the friction of the atmosphere.

I’m going to admit it, this I thought this for a long time. But it turns out that friction has almost nothing to do with the heating of spacecraft upon reentry. It’s nearly entirely due to the compression of the air in front of the craft, which heats the air and the craft.

At speeds exceeding the speed of sound a shock wave builds up, and the spacecraft cannot push it out of the way fast enough, which causes it to compress and heat adiabatically. It’s essentially the same principle that makes a bicycle tire or pump get hot as they’re inflated.

This is why the space shuttle’s nose is blunt, it moves the shockwave further back, causing it to heat the craft less.

3) Men have one less rib than women.

No they don’t. The origin of this one is obvious, Genesis 2:21-22, “And the LORD God caused a deep sleep to fall upon Adam, and he slept: and he took one of his ribs, and closed up the flesh instead thereof; And the rib, which the LORD God had taken from man, made he a woman, and brought her unto the man.”

The ancient Hebrews would surely have known that men and women had the same number of ribs. An interesting explanation I’ve heard for this passage is that the original writers didn’t mean rib.

As it turns out, most animals have a bone in their penis to aid with erections, but humans don’t. (The most likely reason for this is so that unhealthy males are less likely to reproduce, which is advantageous for females. Matt Ridley’s The Red Queen has a more detailed discussion of it).

The Hebrews almost certainly realized this difference, and their explanation is now in Genesis. Of course that’s only a hypothesis, but it’s far superior to the one that the Hebrews thought men were missing a rib.

4) 21 Grams

There’s a popular myth that the body loses 21 grams when we die, and this is widely used as evidence for some kind of soul. Unfortunately for those people, it’s not true

This myth started with Dr. Duncan MacDougall, who conducted some experiments in 1907 that came to this stunning conclusion. But his methods were flawed, his results were inconsistent, his samples were too small, and his ability to measure was not nearly accurate. It is almost a case study in how not to conduct science. Besides, in nearly a century his results have not been repeated. It seems that this is one of those things that people just want to believe, truth be damned.

5) The “Rule of Thumb”

It’s commonly thought that the phrase “rule of thumb” refers to an English law that stated that a man could beat his wife with anything thinner than the width of his thumb. This was stated in the movie Boondock Saints. The problem is that there’s no evidence of this origin, and it appears to have been claimed as common law to justify later lax attitudes toward domestic violence.

The truth is that no one really does know where it originated. Some claim that the most likely origin is from carpenters, who were so skilled that they didn’t use any form of measurement other than the ones immediately on hand. According to one post here, “they measured, not by a rule(r) of wood, but by rule of thumb.” But another further down the page claims that this is mistaken, and that the term originates with using the width of the thumb as an inch in the cloth trade. Yet another claims the measurement origin, citing the Swedish “tum”, meaning inch, which derives from “tumme”, meaning thumb.

The only thing that legal experts seem to agree on is that the phrase almost certainly didn’t begin with domestic abuse in English common law.

6) Eating chocolate leads to acne.

There’s no evidence to suggest that chocolate leads to acne, (although poor diet may), and plenty of evidence saying that it doesn’t. According to Dr. Jerome Shupack, a professor of clinical dermatology at New York University School of Medicine and a member of the American Academy of Dermatology, the medical community has known conclusively for over twenty years that chocolate has no effect on acne.

Dr. Shupack suggests that this myth may have gotten started because chocolate contains theobromine, which is similar to iodine. "There are some people who are sensitive to iodine whose skin breaks out when exposed to it," says Shupack. "Somewhere way back when, some dermatologist, aware that the theobromine in chocolate is similar to iodine, put one and one together and got three." Another possible origin is that someone noticed that kids eat more chocolate than adults and get more acne than adults, and linked the two.

However it got started, this factoid isn’t true.