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Why Does Inhaling Helium Make Your Voice Sound Funny?

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Helium's atomic number is 2 and its atomic weight is 4.002602. Its boiling and melting points— -452.1°F and -458.0°F, respectively—are the lowest among the elements. It is the second most abundant element in the known universe (after hydrogen). And it makes your voice sound really funny when you inhale it. Here's why.

A Crash Course in Sound

When you speak, air travels up from your lungs and through the larynx, where it meets the vocal cords (or vocal folds), twin infoldings of mucous membrane stretched horizontally across the larynx, and hits the underside, causing them to vibrate. The vibration of the cords excites air molecules in your vocal tract and sets up resonant frequencies. The vibration of the vocal cords influences the pitch (the perceived fundamental frequency of a sound) of your voice; the vibration of the air in the vocal tract influences your voice's timbre (the quality of a sound that distinguishes different types of sound production—remember that for later, it will be important); and manipulation of the vocal tract—moving your tongue, lips, etc.—creates different resonant frequencies and allows you to make the different sounds of speech, like "oohs" and "aahs." Your voice finally leaves your mouth in the form of waves, oscillations of pressure transmitted through a medium.

Voice, Meet Helium

In addition to the vibrations and manipulations that influence the sound of your voice, what another person hears when you speak also depends in part on what the space where the sound is created contains. The air that fills a room where you might be speaking to someone is made up of roughly 78.08 percent nitrogen, 20.95 percent oxygen, 0.93 percent argon, 0.038 percent carbon dioxide, and tiny amounts of other gases. Nitrogen, which makes up the majority of our air, has a mass roughly seven times greater than that of helium. Because helium is lighter than air, sound waves travel through it faster. In a room where the temperature is 68 degrees Fahrenheit, sound travels at 344 meters a second through air, but 927 meters a second through helium. When you inhale helium, you're changing the type of gas molecules in your vocal tract and increasing the speed of the sound of your voice.

Some people think that helium changes the pitch of your voice, but the vibration frequency of the vocal cords doesn't change along with the type of gas molecules that surround them. When your vocal tract is filled with helium, your vocal cords are vibrating at the same frequency as usual. It's actually the timbre (again, the quality of a sound that distinguishes different types of sound, also known as tone quality or tone color) that changes, because those lighter-than-air helium molecules allow sound to travel faster and change the resonances of your vocal tract by making it more responsive to high-frequency sounds and less responsive to lower ones. Your voice winds up flat and Donald Duck-esque and listeners perceive this as a change in pitch.

More Fun With Gases

If a lighter gas like helium gives us a squeaky-sounding voice, you might to assume that a heavier-than-air gas would amplify the lower resonant frequencies and make it deeper and richer (trading Donald Duck for Barry White, if you will). You'd be correct; gases like xenon and sulfur hexafluoride slow the speed of sound and lower the resonant frequencies of your vocal tract. 

No Fun With Gas

As amusing as the results are, inhaling helium is not so great for you. While you're inhaling it, you're not getting the oxygen you need for normal respiration. Breathing helium continuously can cause asphyxiation within a few minutes. That light-headed feeling you get from a few inhalations is a sign you need to take a break. And please don't ever inhale helium directly from one of those pressurized tanks. The high flow rate can rupture your lung tissue or send a concentrated mass of gas into your bloodstream, after which it can lodge in the brain and cause a stroke, seizures and death.

This story originally appeared in 2009.

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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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