Does Sound Travel Faster or Slower in Space?

iStock/BlackJack3D
iStock/BlackJack3D

Viktor T. Toth:

It is often said that sound doesn’t travel in space. And it is true … in empty space. Sound is pressure waves, that is, propagating changes in pressure. In the absence of pressure, there can be no pressure waves, so there is no sound.

But space is is not completely empty and not completely devoid of pressure. Hence, it carries sound. But not in a manner that would match our everyday experience.

For instance, if you were to put a speaker in interstellar space, its membrane may be moving back and forth, but it would be exceedingly rare for it to hit even a single atom or molecule. Hence, it would fail to transfer any noticeable sound energy to the thin interstellar medium. Even the somewhat denser interplanetary medium is too rarefied for sound to transfer efficiently from human scale objects; this is why astronauts cannot yell to each other during spacewalks. And just as it is impossible to transfer normal sound energy to this medium, it will also not transmit it efficiently, since its atoms and molecules are too far apart, and they just don’t bounce into each other that often. Any “normal” sound is attenuated to nothingness.

However, if you were to make your speaker a million times bigger, and let its membrane move a million times more slowly, it would be able to transfer sound energy more efficiently even to that thin medium. And that energy would propagate in the form of (tiny) changes in the (already very tiny) pressure of the interstellar medium, i.e., it would be sound.

So yes, sound can travel in the intergalactic, interstellar, interplanetary medium, and very, very low frequency sound (many octaves below anything you could possibly hear) plays an important role in the formation of structures (galaxies, solar systems). In fact, this is the mechanism through which a contracting cloud of gas can shed its excess kinetic energy and turn into something compact, such as a star.

How fast do such sounds travel, you ask? Why, there is no set speed. The general rule is that for a so-called perfect fluid (a medium that is characterized by its density and pressure, but has no viscosity or stresses) the square of the speed of sound is the ratio of the medium’s pressure to its energy density. The speed of sound, therefore, can be anything between 0 (for a pressureless medium, which does not carry sound) to the speed of light divided by the square root of three (for a very hot, so-called ultrarelativistic gas).

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

Has An Element Ever Been Removed From the Periodic Table?

lucadp/iStock via Getty Images
lucadp/iStock via Getty Images

Barry Gehm:

Yes, didymium, or Di. It was discovered by Carl Mosander in 1841, and he named it didymium from the Greek word didymos, meaning twin, because it was almost identical to lanthanum in its properties. In 1879, a French chemist showed that Mosander’s didymium contained samarium as well as an unknown element. In 1885, Carl von Weisbach showed that the unknown element was actually two elements, which he isolated and named praseodidymium and neodidymium (although the di syllable was soon dropped). Ironically, the twin turned out to be twins.

The term didymium filter is still used to refer to welding glasses colored with a mixture of neodymium and praseodymium oxides.

One might cite as other examples various claims to have created/discovered synthetic elements. Probably the best example of this would be masurium (element 43), which a team of German chemists claimed to have discovered in columbium (now known as niobium) ore in 1925. The claim was controversial and other workers could not replicate it, but some literature from the period does list it among the elements.

In 1936, Emilio Segrè and Carlo Perrier isolated element 43 from molybdenum foil that had been used in a cyclotron; they named it technetium. Even the longest-lived isotopes of technetium have a short half-life by geological standards (millions of years) and it has only ever been found naturally in minute traces as a product of spontaneous uranium fission. For this reason, the original claim of discovery (as masurium) is almost universally regarded as erroneous.

As far as I know, in none of these cases with synthetic elements has anyone actually produced a quantity of the element that one could see and weigh that later turned out not to be an element, in contrast to the case with didymium. (In the case of masurium, for instance, the only evidence of its existence was a faint x-ray signal at a specific wavelength.)

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

Can You Ever Truly Lose Your Accent?

DGLimages, iStock via Getty Images
DGLimages, iStock via Getty Images

You may be able to pull off a Spanish accent when showing off your Antonio Banderas impression, but truly losing your native accent and replacing it with a new one is a lot harder to do. The way you speak now will likely stick with you for life.

According to Smithsonian, our accent develops as early as 6 months old—accents being the pronunciation conventions of a language shaped by factors like region, culture, and class. When a baby is learning the words for nap and dad and play, they're also learning how to pronounce the sounds in those words from the people around them. Newborn brains are wired to recognize and learn languages just from being exposed to them. By the time babies start talking, they know the "right" pronunciations to use for their native language or languages.

As you get older, your innate understanding of foreign accents and languages gets weaker. If you're an English speaker raised in Boston, you may think that the way someone from Dallas speaks English sounds "wrong" without being able to articulate what it is that makes them sound different. This is why pulling off a convincing foreign accent can be so difficult, even if you've heard it many times before.

Around age 18, your ability to learn a second language takes a steep nosedive. The same may be true with your ability to speak in a new accent. If you immerse yourself in a foreign environment for long enough, you may pick up some ticks of the local accent, but totally adopting a non-native accent without making a conscious effort to maintain it is unlikely as an adult.

There is one exception to this rule, and that's Foreign Accent Syndrome. Following a head injury or stroke, some people have reported suddenly speaking in accents they didn't grow up using. The syndrome is incredibly rare, with only 100 people around the world having been diagnosed with it, and medical experts aren't sure why brain injuries cause it. But while patients may be pronouncing their words differently, they aren't exactly using foreign accents in the way most people think of them; the culprit may be subtle changes to muscle movements in the jaw, tongue, lips, and larynx that change the way patients pronounce certain vowels.

[h/t Smithsonian]

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