What Makes #2 Pencils So Special?

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iStock

Most of us pick up pencils—and lose them—without giving them a second thought. Pencils are a bit more interesting than you might, think, though. Here are a few not-so-frequently asked questions about everyone's second-favorite writing implements, including the story of a time when pencil sharpeners were illegal.

WHAT MAKES #2 PENCILS SO SPECIAL?

When it comes to pencils, #2s are actually the absolute middle of the road. While we number our various grades of pencils in the U.S., the rest of the world uses a system of numbers and letters to describe how hard and how black a pencil's lead is. An American #2 pencil (roughly) corresponds to an HB pencil on the rest of the world's scale. The lead is not too dark and not too light, and it's not too hard or too soft.

Pencils numbered higher than 2 have harder leads and are often used by engineers, architects, and draftsmen because of their harder points. The underlying logic here is that the harder point gives the user greater control of the lead. You'll find softer leads in pencils numbered below 2, which are popular with artists because they can help create a wider spectrum of tones than one would achieve by sticking solely to a #2 pencil.

ACK! I USED A #3 PENCIL ON THE SAT! IS MY LIFE OVER?

A student takes a test with a pencil
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No ... but you're probably destined for a life of hard labor rather than college. No, not really. It's hard to get a straight answer on this question, but there are quite a few reports from people online who messed up by using the wrong grade of pencil and still did just fine on their SATs. The general consensus seems to be that the SAT's scanners will read a #3 pencil's mark just the same as it would read one from a #2 pencil. Some people do feel, however, that the harder lead in a #3 pencil makes erasing tougher and ups the chances that a stray smudge or incompletely erased mark will be read by the scanner and end up hurting your score. So it's probably best to err on the safe side and double-check your pencil type before heading into the exam.

IF THE REST OF THE WORLD USES A SYSTEM OF NUMBERS AND LETTERS TO GRADE PENCILS, WHY DO WE USE JUST NUMBERS?

Thank Henry David Thoreau and his old man. When graphite was discovered in New Hampshire during the 1820s, John Thoreau and his brother-in-law Charles Dunbar built their own pencil factory. The only problem was that New Hampshire graphite was pretty crummy; it smeared and made for pretty poor pencils.

Enter a young Henry David Thoreau. Before he wrote about civil disobedience and spent his time at Walden Pond, he worked at the family pencil company. Thoreau perfected a process of using clay as a binder to make the soft, loose graphite hard and suitable for pencils. Suddenly the New England graphite could be used to make a pencil that didn't leave giant smears, and the Thoreaus' business took off. By the middle of the 19th century, the Thoreaus were selling pencils with varying graphite hardness, which they numbered one through four.

IF THE CENTER OF THE PENCIL HAS BEEN MADE OF GRAPHITE FOR SO LONG, WHY DO WE CALL IT "LEAD"?

Photo of the tip of a pencil
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Blame shoddy 16th century chemistry for this one. When a giant graphite deposit was found in England during the 16th century, it eventually found a use as a writing implement. However, early chemists weren't exactly sure what the useful gray substance actually was. They assumed it was some sort of lead, and the term "pencil lead" came into use—even though there wasn't any lead involved.

WHY ARE PENCILS PAINTED YELLOW?

According to most stories, our pencils are yellow as a result of a clever marketing gimmick. In 1889, the Hardtmuth company of Austria introduced a new line of fancy pencils at the World's Fair in Paris. The pencils were named Koh-i-Noor after a famed Indian diamond, and they contained the world's finest graphite from the Far East. They were also painted yellow, which was unusual at the time.

Some historians claim that the Austrian company painted their pencils yellow as a subtle nod to the yellow on the flag of Austria-Hungary. Others claim the yellow was an even subtler nod to the Far Eastern graphite in the pencils; the color yellow is associated with royalty in China. In either case, the new yellow pencils were a hit, and soon other companies began painting their own wares yellow in an attempt to swipe some of Hardtmuth's business.

DOES THE LITTLE METAL BAND THAT HOLDS THE ERASER ON THE PENCIL HAVE A NAME?

A pencil eraser
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It sure does. It's called a ferrule, a combination of the Latin words viriola ("small bracelet") and ferrum ("iron").

HAVE PENCIL ERASERS GIVEN US ANY COMMON WORDS?

You bet. According to records from the 18th century, the elastic substance from tropical plants got its name thanks to its common use of being rubbed over pencil marks to erase them. Since using this substance as an eraser required a lot of rubbing, people began calling it rubber. Another name for rubber from the same era that didn't catch on quite as well was lead-eater

WHEN WAS IT ILLEGAL TO OWN A PENCIL SHARPENER?

If you owned a pencil sharpener in early 20th century England, you had a hot little piece of contraband. At the time, the supply of the red cedar that had historically been used in pencils was getting perilously low, so the government briefly outlawed pencil sharpeners in order to limit waste from overzealous sharpening. Eventually the mechanical pencil and the discovery of incense-cedar's usefulness in making pencils solved this problem, and pencil sharpeners became street legal once again. Phew!

What Do the Numbers and Letters on a Boarding Pass Mean?

iStock.com/Laurence Dutton
iStock.com/Laurence Dutton

Picture this: You're about to embark on a vacation or business trip, and you have to fly to reach your destination. You get to the airport, make it through the security checkpoint, and breathe a sigh of relief. What do you do next? After putting your shoes back on, you'll probably look at your boarding pass to double-check your gate number and boarding time. You might scan the information screen for your flight number to see if your plane will arrive on schedule, and at some point before boarding, you'll also probably check your zone and seat numbers.

Aside from these key nuggets of information, the other letters and numbers on your boarding pass might seem like gobbledygook. If you find this layout confusing, you're not the only one. Designer and creative director Tyler Thompson once commented that it was almost as if "someone put on a blindfold, drank a fifth of whiskey, spun around 100 times, got kicked in the face by a mule … and then just started puking numbers and letters onto the boarding pass at random."

Of course, these seemingly secret codes aren't exactly secret, and they aren't random either. So let's break it down, starting with the six-character code you'll see somewhere on your boarding pass. This is your Passenger Name Reference (or PNR for short). On some boarding passes—like the one shown below—it may be referred to as a record locator or reservation code.

A boarding pass
Piergiuliano Chesi, Wikimedia Commons // Public domain

These alphanumeric codes are randomly generated, but they're also unique to your personal travel itinerary. They give airlines access to key information about your contact information and reservation—even your meal preferences. This is why it's ill-advised to post a photo of your boarding pass to social media while waiting at your airport gate. A hacker could theoretically use that PNR to access your account, and from there they could claim your frequent flier miles, change your flight details, or cancel your trip altogether.

You might also see a random standalone letter on your boarding pass. This references your booking class. "A" and "F," for instance, are typically used for first-class seats. The letter "Y" generally stands for economy class, while "Q" is an economy ticket purchased at a discounted rate. If you see a "B" you might be in luck—it means you could be eligible for a seat upgrade.

There might be other letters, too. "S/O," which is short for stopover, means you have a layover that lasts longer than four hours in the U.S. or more than 24 hours in another country. Likewise, "STPC" means "stopover paid by carrier," so you'll likely be put up in a hotel free of charge. Score!

One code you probably don’t want to see is "SSSS," which means your chances of getting stopped by TSA agents for a "Secondary Security Screening Selection" are high. For whatever reason, you've been identified as a higher security risk. This could be because you've booked last-minute or international one-way flights, or perhaps you've traveled to a "high-risk country." It could also be completely random.

Still confused? For a visual of what that all these codes look like on a boarding pass, check out this helpful infographic published by Lifehacker.

Have you got a Big Question you'd like us to answer? If so, send it to bigquestions@mentalfloss.com.

Does Having Allergies Mean That You Have A Decreased Immunity?

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iStock.com/PeopleImages

Tirumalai Kamala:

No, allergy isn't a sign of decreased immunity. It is a specific type of immune dysregulation. Autoimmunity, inflammatory disorders such as IBS and IBD, and even cancer are examples of other types of immune dysregulation.

Quality and target of immune responses and not their strength is the core issue in allergy. Let's see how.

—Allergens—substances known to induce allergy—are common. Some such as house dust mite and pollen are even ubiquitous.
—Everyone is exposed to allergens yet only a relative handful are clinically diagnosed with allergy.
—Thus allergens don't inherently trigger allergy. They can but only in those predisposed to allergy, not in everyone.
—Each allergic person makes pathological immune responses to not all but to only one or a few structurally related allergens while the non-allergic don't.
—Those diagnosed with allergy aren't necessarily more susceptible to other diseases.

If the immune response of each allergic person is selectively distorted when responding to specific allergens, what makes someone allergic? Obviously a mix of genetic and environmental factors.

[The] thing is allergy prevalence has spiked in recent decades, especially in developed countries, [which is] too short a time period for purely genetic mutation-based changes to be the sole cause, since that would take multiple generations to have such a population-wide effect. That tilts the balance towards environmental change, but what specifically?

Starting in the 1960s, epidemiologists began reporting a link between infections and allergy—[the] more infections in childhood, [the] less the allergy risk [this is called hygiene hypothesis]. Back then, microbiota weren't even a consideration but now we have learned better, so the hygiene hypothesis has expanded to include them.

Essentially, the idea is that the current Western style of living that rapidly developed over the 20th century fundamentally and dramatically reduced lifetime, and, crucially, early life exposure to environmental microorganisms, many of which would have normally become part of an individual's gut microbiota after they were born.

How could gut microbiota composition changes lead to selective allergies in specific individuals? Genetic predisposition should be taken as a given. However, natural history suggests that such predisposition transitioned to a full fledged clinical condition much more rarely in times past.

Let's briefly consider how that equation might have fundamentally changed in recent times. Consider indoor sanitation, piped chlorinated water, C-sections, milk formula, ultra-processed foods, lack of regular contact with farm animals (as a surrogate for nature) and profligate, ubiquitous, even excessive use of antimicrobial products such as antibiotics, to name just a few important factors.

Though some of these were beneficial in their own way, epidemiological data now suggests that such innovations in living conditions also disrupted the intimate association with the natural world that had been the norm for human societies since time immemorial. In the process such dramatic changes appear to have profoundly reduced human gut microbiota diversity among many, mostly in developed countries.

Unbeknownst to us, an epidemic of absence*, as Moises Velasquez-Manoff evocatively puts it, has thus been invisibly taking place across many human societies over the 20th century in lock-step with specific changes in living standards.

Such sudden and profound reduction in gut microbiota diversity thus emerges as the trigger that flips the normally hidden predisposition in some into clinically overt allergy. Actual mechanics of the process remain the subject of active research.

We (my colleague and I) propose a novel predictive mechanism for how disruption of regulatory T cell** function serves as the decisive and non-negotiable link between loss of specific microbiota and inflammatory disorders such as allergies. Time (and supporting data) will tell if we are right.

* An Epidemic of Absence: A New Way of Understanding Allergies and Autoimmune Diseases Reprint, Moises Velasquez-Manoff

** a small indispensable subset of CD4+ T cells.

This post originally appeared on Quora. Click here to view.

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