Why Are Hammerheads' Heads Shaped Like That?

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iStock

There are 10 species of sharks in the Sphyrnidae family, all of them but one falling into the genus Sphyrna, a Greek word that means “hammer”—an apt description for the head shape of these carcharhiniforms. But why are their heads, called cephalofoils, shaped like that? How does a hammer-shaped head, with eyes on each end, help the shark survive?

According to John S. Sparks, Curator-in-Charge of the Department of Ichthyology at the American Museum of Natural History and co-curator of its newest exhibition, Life at the Limits, there are two hypotheses scientists are working with. One, he says, is that “with its eyes out to the side, [the shark] can maximize its visual capacity, in terms of the area that it can see,” which might help when the animal is hunting.

The other has to do with how the hammerhead hunts: The sharks look for prey by rooting around on the ocean bottom with their heads, which are studded with sensory organs called ampullae of Lorenzini (the hammerhead isn't special, though; all sharks have these organs). “Every organism puts off a weak electric field, and [with these electroreceptors] the sharks can sense them,” Sparks says. “It’s thought that having a broader head allows for more of these ampullae, so the shark can better sense prey.”

There may be some evidence to back up this hypothesis, Sparks says. Not all hammerheads’ cephalofoils are created equal: Some have small hammers, while some, like the great hammerhead, have huge hammers. The scientists behind one grant that Sparks reviewed "have found that sharks with larger hammers are more accurate at detecting prey in the substrate.”

What's the Difference Between Straw and Hay?

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iStock.com/dusipuffi

The words straw and hay are often used interchangeably, and it's easy to see why: They're both dry, grassy, and easy to find on farms in the fall. But the two terms actual describe different materials, and once you know what to look for, it's easy to tell the difference between them.

Hay refers to grasses and some legumes such as alfalfa that are grown for use as animal feed. The full plant is harvested—including the heads, leaves, and stems—dried, and typically stored in bales. Hay is what livestock like cattle eat when there isn't enough pasture to go around, or when the weather gets too cold for them to graze. The baled hay most non-farmers are familiar with is dry and yellow, but high-quality hay has more of a greenish hue.

The biggest difference between straw and hay is that straw is the byproduct of crops, not the crop itself. When a plant, such as wheat or barley, has been stripped of its seeds or grains, the stalk is sometimes saved and dried to make straw. This part of the plant is lacking in nutrients, which means it doesn't make great animal fodder. But farmers have found other uses for the material throughout history: It what's used to weave baskets, thatch roofs, and stuff mattresses.

Today, straw is commonly used to decorate pumpkin-picking farms. It's easy to identify (if it's being used in a way that would be wasteful if it were food, chances are it's straw), but even the farms themselves can confuse the two terms. Every hayride you've ever taken, for example, was most likely a straw-ride.

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How and Why Did Silent Letters Emerge in English?

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iStock/Bychykhin_Olexandr

Kory Stamper:

The easy answer is “"because English can’t leave well enough alone."

When we first started speaking English around 600 AD, it was totally phonetic: every letter had a sound, and we sounded every letter in a word. But English—and England itself—were influenced quite a bit by the French, who conquered the island in 1066 and held it for a long time. And then later by Dutch and Flemish printers, who were basically the main publishers in England for a solid two centuries, and then by further trading contact with just about every continent on the planet. And while we’re shaking hands and stealing language from every single people-group we meet, different parts of the language started changing at uneven rates.

By the 1400s, English started to lose its phonetic-ness: the way we articulated vowels in words like “loud” changed slowly but dramatically, and that had an effect on the rest of the word. (This is called “The Great Vowel Shift,” and it took place over a few hundred years.) Somewhere in the middle of the GVS, though, English spelling became fixed primarily because of the printing press and the easy distribution/availability of printed materials. In short: we have silent letters because the spelling of words stopped changing to match their pronunciations.

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

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