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PBS News Hour / YouTube

The world's largest instrument exists deep inside the Luray Caverns in the Appalachian Mountains, and it's 400 million years in the making, Scientific American reports. It's called the Great Stalacpipe Organ, but it's unlike a typical organ, which forces air through pipes to create music — this instrument rhythmically strikes the cave's stalactites to create beautiful sounds.

How it works: Large, rubber mallets sit next to the 37 stalactites. When the organist strikes a key on the instrument, the corresponding mallet strikes the stalactites, all coordinated via a hidden mechanical device that receives electrical signals from the organ. The organ's inventor sanded down 35 of the 37 stalactites to perfect their tone (two didn't need it) and the 3.5-acre cave lends natural acoustics for the songs.

Because the acoustics are not uniform throughout the cavern, it can be difficult to play by ear. So an automated system — using a plastic sheet with holes in it that rotates around a metal drum — plays songs similar to a player piano. When the metal meets the drum, corresponding stalactites sound off.

Go deeper: A combination of Mother Nature's work, time and a skilled mathematician helped create the Great Stalacpipe Organ. The large, echoey chambers of Luray Caverns have formed naturally over the past 400 millions years. Calcium-rich water droplets eventually formed the large stalactites that hang from the cave's ceiling and now act as an integral part of this instrument. Back in 1954, mathematician and electronics engineer Leland Sprinkle visited the caverns. As was customary during these tours, the guide would strike the stalactites to show visitors how each one gave off a unique sound. That moment sparked an idea in Sprinkle's head — create the Great Stalacpipe Organ, which he did in three years.

Go deeper

U.S. economy added 379,000 jobs in February

Data: FRED; Chart: Axios Visuals

The economy added 379,000 jobs in February, while the unemployment rate dropped from 6.3% to 6.2%, the Labor Department said on Friday.

Why it matters: The first Biden-era jobs report shows hiring surged as coronavirus cases eased — though a full recovery remains far off. Economists expected the economy to add roughly 182,000 jobs last month, after adding a paltry 49,000 in January.

This story is breaking news. Please check back for updates.

Dion Rabouin, author of Markets
1 hour ago - Economy & Business

Workers are getting a really bad deal

Illustration: Eniola Odetunde/Axios

This week's spate of data highlighted the difficulties Americans who have lost their jobs have had bouncing back from the coronavirus pandemic, and just how much those who have managed to keep their jobs have been working.

What's happening: The Labor Department reported Thursday that the productivity of American workers fell by a revised 4.2% annual rate in the fourth quarter, the largest decline in 39 years.

FBI: Trump appointee arrested in connection with Capitol riot

Photo: Samuel Corum/Getty Images

The FBI on Thursday arrested former State Department aide Federico Klein, a Trump appointee who worked on the former president's 2016 campaign, on charges related to the Jan. 6 storming of the Capitol, according to a court filing.

Why it matters: The 42-year-old Klein is the first member of the Trump administration to be arrested in connection with the insurrection, which led to the former president's second impeachment and charges against over 300 people.