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.

Looking to Downsize? You Can Buy a 5-Room DIY Cabin on Amazon for Less Than $33,000

Five rooms of one's own.
Five rooms of one's own.
Allwood/Amazon

If you’ve already mastered DIY houses for birds and dogs, maybe it’s time you built one for yourself.

As Simplemost reports, there are a number of house kits that you can order on Amazon, and the Allwood Avalon Cabin Kit is one of the quaintest—and, at $32,990, most affordable—options. The 540-square-foot structure has enough space for a kitchen, a bathroom, a bedroom, and a sitting room—and there’s an additional 218-square-foot loft with the potential to be the coziest reading nook of all time.

You can opt for three larger rooms if you're willing to skip the kitchen and bathroom.Allwood/Amazon

The construction process might not be a great idea for someone who’s never picked up a hammer, but you don’t need an architectural degree to tackle it. Step-by-step instructions and all materials are included, so it’s a little like a high-level IKEA project. According to the Amazon listing, it takes two adults about a week to complete. Since the Nordic wood walls are reinforced with steel rods, the house can withstand winds up to 120 mph, and you can pay an extra $1000 to upgrade from double-glass windows and doors to triple-glass for added fortification.

Sadly, the cool ceiling lamp is not included.Allwood/Amazon

Though everything you need for the shell of the house comes in the kit, you will need to purchase whatever goes inside it: toilet, shower, sink, stove, insulation, and all other furnishings. You can also customize the blueprint to fit your own plans for the space; maybe, for example, you’re going to use the house as a small event venue, and you’d rather have two or three large, airy rooms and no kitchen or bedroom.

Intrigued? Find out more here.

[h/t Simplemost]

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Who Was Jim Crow?

Wikimedia Commons, Public Domain
Wikimedia Commons, Public Domain

The name Jim Crow appears throughout many U.S. history books. It's used in reference to both the laws that segregated Black and white Americans in the Southern United States and the region itself during the period when these laws were enforced. Jim Crow Laws and the Jim Crow South were very real from the late 19th through the mid-20th centuries, but a real person named Jim Crow never existed. The name comes from a fictional character used to perpetuate racist stereotypes before the Civil War.

According to Ferris State University, a white performer named Thomas Dartmouth Rice originated the Jim Crow caricature in the 1830s. Rice, known as "the Father of Minstrelsy," would don blackface and affect an exaggerated African American dialect while performing his musical act. Jim Crow was meant to be a racist stereotype of an enslaved person: Like many minstrel personas that came after him, the character was portrayed as a clumsy buffoon.

Though Rice didn't invent minstrelsy, his success helped popularize the stage show format. Inspired by Rice, other minstrel actors borrowed his Jim Crow routine, and soon whites were using the name as a derogatory term for African Americans.

Even after slavery was abolished and minstrel shows faded into obscurity, the Jim Crow character lived on as a label. According to History, the first Jim Crow laws were passed in the Reconstruction Period as a way to limit the rights and resources of newly freed Blacks in the South. Such laws imposed literacy tests on Black voters, segregated public schools, and made it legal for businesses to segregate their customers by race.

How exactly these laws became associated with Jim Crow is unclear, but the phrase Jim Crow Laws was being used by the late 19th century. An 1892 article from The New York Times used the wording when reporting on Louisiana's segregated railroad cars.

Though most people may not be aware of the name's origins, Jim Crow still comes up today when discussing this dark period in U.S. history and its lasting effect on the country.

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