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What Makes #2 Pencils So Special?

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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?

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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"?

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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?

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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!

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Big Questions
Do Bacteria Have Bacteria?
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Drew Smith:

Do bacteria have bacteria? Yes.

We know that bacteria range in size from 0.2 micrometers to nearly one millimeter. That’s more than a thousand-fold difference, easily enough to accommodate a small bacterium inside a larger one.

Nothing forbids bacteria from invading other bacteria, and in biology, that which is not forbidden is inevitable.

We have at least one example: Like many mealybugs, Planococcus citri has a bacterial endosymbiont, in this case the β-proteobacterium Tremblaya princeps. And this endosymbiont in turn has the γ-proteobacterium Moranella endobia living inside it. See for yourself:

Fluorescent In-Situ Hybridization confirming that intrabacterial symbionts reside inside Tremblaya cells in (A) M. hirsutus and (B) P. marginatus mealybugs. Tremblaya cells are in green, and γ-proteobacterial symbionts are in red. (Scale bar: 10 μm.)
Fluorescent In-Situ Hybridization confirming that intrabacterial symbionts reside inside Tremblaya cells in (A) M. hirsutus and (B) P. marginatus mealybugs. Tremblaya cells are in green, and γ-proteobacterial symbionts are in red. (Scale bar: 10 μm.)

I don’t know of examples of free-living bacteria hosting other bacteria within them, but that reflects either my ignorance or the likelihood that we haven’t looked hard enough for them. I’m sure they are out there.

Most (not all) scientists studying the origin of eukaryotic cells believe that they are descended from Archaea.

All scientists accept that the mitochondria which live inside eukaryotic cells are descendants of invasive alpha-proteobacteria. What’s not clear is whether archeal cells became eukaryotic in nature—that is, acquired internal membranes and transport systems—before or after acquiring mitochondria. The two scenarios can be sketched out like this:


The two hypotheses on the origin of eukaryotes:

(A) Archaezoan hypothesis.

(B) Symbiotic hypothesis.

The shapes within the eukaryotic cell denote the nucleus, the endomembrane system, and the cytoskeleton. The irregular gray shape denotes a putative wall-less archaeon that could have been the host of the alpha-proteobacterial endosymbiont, whereas the oblong red shape denotes a typical archaeon with a cell wall. A: archaea; B: bacteria; E: eukaryote; LUCA: last universal common ancestor of cellular life forms; LECA: last eukaryotic common ancestor; E-arch: putative archaezoan (primitive amitochondrial eukaryote); E-mit: primitive mitochondrial eukaryote; alpha:alpha-proteobacterium, ancestor of the mitochondrion.

The Archaezoan hypothesis has been given a bit of a boost by the discovery of Lokiarcheota. This complex Archaean has genes for phagocytosis, intracellular membrane formation and intracellular transport and signaling—hallmark activities of eukaryotic cells. The Lokiarcheotan genes are clearly related to eukaryotic genes, indicating a common origin.

Bacteria-within-bacteria is not only not a crazy idea, it probably accounts for the origin of Eucarya, and thus our own species.

We don’t know how common this arrangement is—we mostly study bacteria these days by sequencing their DNA. This is great for detecting uncultivatable species (which are 99 percent of them), but doesn’t tell us whether they are free-living or are some kind of symbiont. For that, someone would have to spend a lot of time prepping environmental samples for close examination by microscopic methods, a tedious project indeed. But one well worth doing, as it may shed more light on the history of life—which is often a history of conflict turned to cooperation. That’s a story which never gets old or stale.

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

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Big Questions
Why Do Cats 'Blep'?
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As pet owners are well aware, cats are inscrutable creatures. They hiss at bare walls. They invite petting and then answer with scratching ingratitude. Their eyes are wandering globes of murky motivations.

Sometimes, you may catch your cat staring off into the abyss with his or her tongue lolling out of their mouth. This cartoonish expression, which is atypical of a cat’s normally regal air, has been identified as a “blep” by internet cat photo connoisseurs. An example:

Cunning as they are, cats probably don’t have the self-awareness to realize how charming this is. So why do cats really blep?

In a piece for Inverse, cat consultant Amy Shojai expressed the belief that a blep could be associated with the Flehmen response, which describes the act of a cat “smelling” their environment with their tongue. As a cat pants with his or her mouth open, pheromones are collected and passed along to the vomeronasal organ on the roof of their mouth. This typically happens when cats want to learn more about other cats or intriguing scents, like your dirty socks.

While the Flehmen response might precede a blep, it is not precisely a blep. That involves the cat’s mouth being closed while the tongue hangs out listlessly.

Ingrid Johnson, a certified cat behavior consultant through the International Association of Animal Behavior Consultants and the owner of Fundamentally Feline, tells Mental Floss that cat bleps may have several other plausible explanations. “It’s likely they don’t feel it or even realize they’re doing it,” she says. “One reason for that might be that they’re on medication that causes relaxation. Something for anxiety or stress or a muscle relaxer would do it.”

A photo of a cat sticking its tongue out
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If the cat isn’t sedated and unfurling their tongue because they’re high, then it’s possible that an anatomic cause is behind a blep: Johnson says she’s seen several cats display their tongues after having teeth extracted for health reasons. “Canine teeth help keep the tongue in place, so this would be a more common behavior for cats missing teeth, particularly on the bottom.”

A blep might even be breed-specific. Persians, which have been bred to have flat faces, might dangle their tongues because they lack the real estate to store it. “I see it a lot with Persians because there’s just no room to tuck it back in,” Johnson says. A cat may also simply have a Gene Simmons-sized tongue that gets caught on their incisors during a grooming session, leading to repeated bleps.

Whatever the origin, bleps are generally no cause for concern unless they’re doing it on a regular basis. That could be sign of an oral problem with their gums or teeth, prompting an evaluation by a veterinarian. Otherwise, a blep can either be admired—or retracted with a gentle prod of the tongue (provided your cat puts up with that kind of nonsense). “They might put up with touching their tongue, or they may bite or swipe at you,” Johnson says. “It depends on the temperament of the cat.” Considering the possible wrath involved, it may be best to let them blep in peace.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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