“The BBC reports on something sure to impress your next date — and possibly your last — when you explain it,” writes Slashdot reader dryriver. From the report: Scientists have turned their attention to investigating that most annoying of human habits — the sound made when you crack your knuckles. The characteristic pop can be explained by three mathematical equations, say researchers in the US and France. Their model confirms the idea that the cracking sound is due to tiny bubbles collapsing in the fluid of the joint as the pressure changes. Surprisingly, perhaps, the phenomenon has been debated for around a century. Science student Vineeth Chandran Suja was cracking his knuckles in class in France when he decided to investigate.

“The first equation describes the pressure variations inside our joint when we crack our knuckles,” he told BBC News. “The second equation is a well-known equation which describes the size variations of bubbles in response to pressure variations. And the third equation that we wrote down was coupling the size variation of the bubbles to ones that produce sounds.” The equations make up a complete mathematical model that describes the sound of knuckle cracking, said Chandran Suja, who is now a postgraduate student at Stanford University in California. “When we crack our knuckles we’re actually pulling apart our joints,” he explained. “And when we do that the pressure goes down. Bubbles appear in the fluid, which is lubricating the joint — the synovial fluid. “During the process of knuckle cracking there are pressure variations in the joint which causes the size of the bubbles to fluctuate extremely fast, and this leads to sound, which we associate with knuckle cracking.” The study has been published in the journal Scientific Reports.

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Source: Slashdot – Scientists Explain the Sound of Knuckle Cracking

The Federal Communications Commission on Thursday approved an application by Elon Musk’s SpaceX, allowing the aerospace company to provide broadband services using satellites in the U.S. and worldwide. “With this action, the Commission takes another step to increase high-speed broadband availability and competition in the United States,” the FCC said in a statement. CNBC reports: This marks the first time the FCC has allowed a U.S.-licensed satellite constellation to provide broadband services through low-Earth orbit satellites. “We appreciate the FCC’s thorough review and approval of SpaceX’s constellation license. Although we still have much to do with this complex undertaking, this is an important step toward SpaceX building a next-generation satellite network that can link the globe with reliable and affordable broadband service, especially reaching those who are not yet connected,” Gwynne Shotwell, President and Chief Operating Officer at SpaceX said in a statement. SpaceX will begin launching the constellation it dubbed “Starlink” in 2019. The system will be operational once at least 800 satellites are deployed. Starlink will offer broadband speeds comparable to fiber optic networks.The satellites would offer new direct to consumer wireless connections, rather the present system’s redistribution of signals, transforming a traditionally high-cost, low reliability service.

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Source: Slashdot – FCC Authorizes SpaceX’s Ambitious Satellite Internet Plans