Why Do Optometrists Blow Puffs of Air Into Your Eye?

iStock
iStock

I’m basically blind without my contacts, so every year I dutifully schlep to the optometrist to get my eyes tested and outfitted for a new prescription. And every year, I dread it—not just because of the pressure to read the tiniest lines without squinting (just me?), but because of the part of the exam where the doctor has me sit in front of a machine and blasts two puffs of air into each eye. I recently sat through the torturous puffs of air again, and I asked my optometrist: Is this necessary? Can I skip it next time?

Unfortunately for me, this part of the eye exam helps the doctor determine the fluid pressure inside my eyeball, and is therefore totally necessary. High pressure in the eye can cause glaucoma, or vision loss due to damage to the optic nerve. So the doctor asks me to put my chin on the chin rest, stare at a green light, and then uses a machine called a non-contact tonometer to administer two gentle (but totally startling) puffs of air onto the surface of my eye. The machine measures the air that bounces back and then calculates my intraocular pressure. No one likes this part of the test; it was even the subject of an episode of Friends:

There are other ways to test for glaucoma, but many optometrists opt for the air puff test because it’s quick and painless for the patient. So I guess next year, I'll just have to open my eyes up wide and bear it.

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Why Are Barns Often Painted Red?

iStock/Ron and Patty Thomas
iStock/Ron and Patty Thomas

Beginning with the earliest American settlements and continuing into the 18th century, most barns weren't painted at all. Early American barn builders took sun exposure, temperature, moisture, wind, and water drainage patterns into account when placing and building barns, and they seasoned the wood (that is, they reduced the moisture content) accordingly. The right type of wood in the right environment held up fine without any paint.

Toward the end of the 1700s, these old-school methods of barn planning and building fell by the wayside. People sought a quicker, easier fix for preserving their barns—a way to coat and seal the wood to protect it from sunlight and moisture damage. Farmers began making their own coating from a mix of linseed oil (a tawny oil derived from the flax seeds), milk, and lime. It dried quickly and lasted a long time, but it didn't really protect the wood from mold and wasn't quite like the "barn red"we know today—it was more of a burnt orange, really.

Turning Red

The problem with mold is that it decays wood and, in large quantities, can pose health risks to people and animals. Rust, it turns out, kills mold and other types of fungi, so farmers began adding ferrous oxide (rusted iron) to the linseed oil mix. A little bit of rust went a long way in protecting the wood, and it gave the barn a nice red hue.

By the late 19th century, mass-produced paints made with chemical pigments became available to most people. Red was the least expensive color, so it remained the most popular for use on barns, except for a brief period when whitewash became cheaper and white barns started popping up. (White barns were also common on dairy farms in some parts of Pennsylvania, central Maryland, and the Shenandoah Valley, possibly because of the color's association with cleanliness and purity.)

Throughout Appalachia (a historically poorer region), many barns went unpainted for lack of money. In the tobacco regions of Kentucky and North Carolina, black and brown barns were the norm, since the dark colors helped heat the barn and cure tobacco.

Today, many barns are still painted the color traditionally used in a given region, with red still dominating the Northeast and Midwest.

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This story was updated in 2019.

Is There An International Standard Governing Scientific Naming Conventions?

iStock/Grafissimo
iStock/Grafissimo

Jelle Zijlstra:

There are lots of different systems of scientific names with different conventions or rules governing them: chemicals, genes, stars, archeological cultures, and so on. But the one I'm familiar with is the naming system for animals.

The modern naming system for animals derives from the works of the 18th-century Swedish naturalist Carl von Linné (Latinized to Carolus Linnaeus). Linnaeus introduced the system of binominal nomenclature, where animals have names composed of two parts, like Homo sapiens. Linnaeus wrote in Latin and most his names were of Latin origin, although a few were derived from Greek, like Rhinoceros for rhinos, or from other languages, like Sus babyrussa for the babirusa (from Malay).

Other people also started using Linnaeus's system, and a system of rules was developed and eventually codified into what is now called the International Code of Zoological Nomenclature (ICZN). In this case, therefore, there is indeed an international standard governing naming conventions. However, it does not put very strict requirements on the derivation of names: they are merely required to be in the Latin alphabet.

In practice a lot of well-known scientific names are derived from Greek. This is especially true for genus names: Tyrannosaurus, Macropus (kangaroos), Drosophila (fruit flies), Caenorhabditis (nematode worms), Peromyscus (deermice), and so on. Species names are more likely to be derived from Latin (e.g., T. rex, C. elegans, P. maniculatus, but Drosophila melanogaster is Greek again).

One interesting pattern I've noticed in mammals is that even when Linnaeus named the first genus in a group by a Latin name, usually most later names for related genera use Greek roots instead. For example, Linnaeus gave the name Mus to mice, and that is still the genus name for the house mouse, but most related genera use compounds of the Greek-derived root -mys (from μῦς), which also means "mouse." Similarly, bats for Linnaeus were Vespertilio, but there are many more compounds of the Greek root -nycteris (νυκτερίς); pigs are Sus, but compounds usually use Greek -choerus (χοῖρος) or -hys/-hyus (ὗς); weasels are Mustela but compounds usually use -gale or -galea (γαλέη); horses are Equus but compounds use -hippus (ἵππος).

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

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