Four Seasons Before Lunch Gauteng (Pretoria)

 I have lived in Pretoria for half my life, but even at almost 50, l still am not ready for mornings like this . I step out of  home in the morning at 7 a.m., greeted by a warm, gentle breeze and sunshine so golden it felt like summer had arrived overnight. The sky was clear; the jacaranda trees glowed purple; the air smelled of warmth and possibility. “Perfect day,” l muttered, locking his door. By the time l drive out—five minutes later—the sky starts to be darkened. A cold wind came crawling in from nowhere, sweeping dust across the pavement. The temperature dropped so suddenly that  l have  to switch the heater for warmth. Laughing. “Ah, Pretoria… you never disappoint.” Halfway to the office, the heavens opened. Not soft rain— a storm . Sheets of water hammered the road, street gutters overflowed instantly, and distant thunder rolled like a grumpy giant waking up too early. People scattered, hiding under bus shelters already too full.  “Ten minutes ago...

Happy Pi Day! Here's how the famed math concept helped NASA's Perseverance rover land on Mars

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In this June 2017 photo, the supersonic parachute design that landed the Perseverance Mars rover on Mars on Feb. 18, 2021, underwent testing in a wind tunnel at NASA's Ames Research Center.
In this June 2017 photo, the supersonic parachute design that landed the Perseverance Mars rover on Mars on Feb. 18, 2021, underwent testing in a wind tunnel at NASA's Ames Research Center. (Image credit: NASA/JPL-Caltech/Ames)

If you're not properly appreciative of pi, NASA is here to help. 

Pi is the ratio of a circle's circumference to its diameter, a mathematical constant that rounds off to 3.14. The actual number goes on forever, but two decimal places will suffice for most of us

Pi is famous and important enough to be celebrated by nerds around the world — on March 14 (3/14) in the United States and on July 22 in Europe and other places that write dates in the month-day-year format. (22 July in such systems is 22/7, a division problem that works out to about 3.14.)

Related: 10 surprising facts about pi

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And NASA doesn't restrict its celebration of the constant to a single day. 

"NASA uses pi every day!" agency officials wrote in a statement on Friday (March 12). 

"Pi is instrumental in developing the size of parachutes to land on the Red Planet," they added. "In fact, pi helps engineers determine how big the parachute needs to be in order to generate the drag needed to slow down craft landing on Mars. It also helps researchers map and explore Earth and planets in our own and other solar systems."

NASA officials adorned that update with a visual aid — a June 2017 photo of a parachute test in a wind tunnel at NASA's Ames Research Center in Silicon Valley, California. The parachute being tested shared a design with the one that helped the Perseverance rover land on Mars last month. 

That 70.5-foot-wide (21.5 meters) supersonic chute opened about four minutes after Perseverance hit the top of the Martian atmosphere on Feb. 18. And you can watch that dramatic otherworldly deployment, thanks to video the rover captured during its descent.

Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook. 

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