What Did I Just Watch? Ferrofluids Explained

Gregory F. Maxwell via Wikimedia Commons // GFDL 1.2

The black fluid looks like common oil or ink. But suddenly, it leaps from a shallow pool to form a phalanx of rotating spikes. It's somehow soft and sharp at the same time. What on Earth is going on here?

This is a ferrofluid: a liquid that becomes strongly magnetized in the presence of a magnetic field. Ferrofluid is a portmanteau of ferromagnetic—the mechanism that draws certain materials to magnets—and fluid (for obvious reasons). A ferrofluid contains nanoscale particles like magnetite, hematite, or another compound containing iron—all of which are attracted to magnets. The particles have to be small enough to randomly distribute throughout the fluid.

A key feature of a ferrofluid is that it's a colloidal suspension. That means the insoluble particles are suspended in the fluid, so it has two states of matter in one solution. (A more common colloidal is milk, which is butterfat globules suspended in a water solution.)

That dual state is important, because a ferrofluid acts like any other liquid until the particles get near a magnet. Then they force the fluid to behave in ways that are stunning to watch:

Those peaks and valleys reflect the magnetic field, as well as the effects of surface tension and gravity.

The ferrofluid was invented by NASA scientist Steve Papell in 1963. He had hoped to transform rocket fuel into a ferrofluid so it could be magnetically drawn toward a pump inlet in a weightless environment, imposing a sort of artificial gravity. That didn't come to fruition, but today ferrofluids are used in a wide variety of applications, including electronics, engineering, medicine, and art. You can even make your own ferrofluid at home! Mix powdered iron fillings into corn oil, grab a magnet, and let the fun begin. Pro-tip: don't get the ferrofluid too close to the magnet or it will leap out of the container—and splatter everywhere.

How Did 6 Feet Become the Standard Grave Depth?

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iStock

It all started with the plague: The origins of “six feet under” come from a 1665 outbreak in England. As the disease swept the country, the mayor of London literally laid down the law about how to deal with the bodies to avoid further infections. Among his specifications—made in “Orders Conceived and Published by the Lord Mayor and Aldermen of the City of London, Concerning the Infection of the Plague”—was that “all the graves shall be at least six feet deep.”

The law eventually fell out of favor both in England and its colonies. Modern American burial laws vary from state to state, though many states simply require a minimum of 18 inches of soil on top of the casket or burial vault (or two feet of soil if the body is not enclosed in anything). Given an 18-inch dirt buffer and the height of the average casket (which appears to be approximately 30 inches), a grave as shallow as four feet would be fine.

A typical modern burial involves a body pumped full of chemical preservatives sealed inside a sturdy metal casket, which is itself sealed inside a steel or cement burial vault. It’s less of a hospitable environment for microbes than the grave used to be. For untypical burials, though—where the body isn’t embalmed, a vault isn’t used, or the casket is wood instead of metal or is foregone entirely—even these less strict burial standards provide a measure of safety and comfort. Without any protection, and subjected to a few years of soil erosion, the bones of the dearly departed could inconveniently and unexpectedly surface or get too close to the living, scaring people and acting as disease vectors. The minimum depth helps keep the dead down where they belong.

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This article originally appeared in 2012.

One Good Reason Not to Hold in a Fart: It Could Leak Out of Your Mouth

iStock/grinvalds
iStock/grinvalds

The next time you hold in a fart for fear of being heard by polite company, just remember this: It could leak out of your mouth instead of your butt. Writing on The Conversation, University of Newcastle nutrition and dietetics professor Clare Collins explains that pent-up gas can pass through your gut wall and get reabsorbed into your circulation. It's then released when you exhale, whether you like it or not.

“Holding on too long means the build up of intestinal gas will eventually escape via an uncontrollable fart,” Collins writes. In this case, the fart comes out of the wrong end. Talk about potty mouth.

A few brave scientists have investigated the phenomenon of flatulence. In one study, 10 healthy volunteers were fed half a can of baked beans in addition to their regular diets and given a rectal catheter to measure their farts over a 24-hour period. Although it was a small sample, the results were still telling. Men and women let loose the same amount of gas, and the average number of “flatus episodes” (a single fart, or series of farts) during that period was eight. Another study of 10 people found that high-fiber diets led to fewer but bigger farts, and a third study found that gases containing sulphur are the culprit of the world’s stinkiest farts. Two judges were tapped to rate the odor intensity of each toot, and we can only hope that they made it out alive.

Scientific literature also seems to support Collins’s advice to “let it go.” A 2010 paper on “Methane and the gastrointestinal tract” says methane, hydrogen sulfide, and other gases that are produced in the intestinal tract are mostly eliminated from the body via the anus or “expelled from the lungs.” Holding it in can lead to belching, flatulence, bloating, and pain. And in some severe cases, pouches can form along the wall of the colon and get infected, causing diverticulitis.

So go ahead and let it rip, just like nature intended—but maybe try to find an empty room first.

[h/t CBS Philadelphia]

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