Art doll

Astronauts Fly Einstein Doll To Demonstration Physicist’s ‘Happiest Thought’

Albert Einstein’s ‘happiest thought’ has been proven again by four international astronauts and a small doll made in his image (opens in a new tab).

Entering Earth orbit Wednesday, Oct. 5, crew members aboard SpaceX’s Dragon “Endurance” spacecraft (opens in a new tab) revealed their chosen “zero-g indicator,” a plush toy of the late theoretical physicist. Floating on a tether, the doll not only confirmed that the Crew-5 astronauts were safely on their way to the International Space Station, but that one of Einstein’s thoughts was indeed true.

“A few years after coming up with his groundbreaking theory of special relativity, Einstein, in his mind, still had a few loose ends to iron out,” said Crew-5 pilot Josh Cassada, NASA astronaut, US Navy captain and physicist, radioed back to SpaceX Mission Control in Hawthorne, Calif. “While he was sitting [at his job] to the patent office because he wasn’t famous yet – [though he] certainly should have been – Einstein had what sadly was one of his happiest thoughts of his entire life…that a person in freefall could not feel his own weight.”

“That thought, and others he built on, led to general relativity and our understanding of gravity and the curvature of spacetime,” Cassada said.

Related: SpaceX launches Crew-5 astronauts on historic flight to space station for NASA

A tradition started by Soviet-era cosmonauts and later adopted for SpaceX’s crewed spaceflight, zero-g indicators signal to crew members still strapped to their seats that they’ve entered orbit — or are in free fall around the Earth – so that they experience weightlessness. Einstein had his “happiest thought” in 1907, more than 50 years before the first human was launched into space.

“We are continually living Einstein’s happiest thought, as the International Space Station has been doing for over 20 years,” Cassada said. “On Crew-5, we call this little guy our ‘free fall indicator’. We’re here to tell you there’s a lot of gravity here. In fact, it’s what’s keeping us in orbit right now and prevents this trip on Crew Dragon from being a one-way trip.

Crew-5’s Free Fall Indicator was made by The Unemployed Philosophers Guild, a specialty shop offering “thoughtful gifts for thinking people”, as part of its “Little Thinker” line of dolls. (opens in a new tab). The 11-inch (28 cm) tall Albert Einstein plush, dressed in a gray sweater and black pants, features the physicist’s unruly white hair.

Albert Einstein Little Thinker plush doll, from The Unemployed Philosophers Guild, was flown by SpaceX Crew-5 astronauts as a zero-g indicator. (Image credit: The Unemployed Philosophers Guild)

Einstein has now joined a small but growing collection of dolls that have flown on SpaceX missions to the space station. Previous zero-g indicators included a plush globe (opens in a new tab)a glitter dinosaur (opens in a new tab)a Grogu (“Star Wars” ‘Baby Yoda’ toy (opens in a new tab)“), a baby penguin (opens in a new tab)a couple of turtles (opens in a new tab)a stuffed toy dog (opens in a new tab) and a monkey (opens in a new tab).

The Einstein doll, along with Cassada, the commander of Crew-5 and the first Native American woman in space Nicole Mann, Japanese astronaut Koichi Wakata and Anna Kikina, Russia’s only active female cosmonaut, is scheduled to arrive at the space station on Thursday evening.

“Kind of like life, we live in the same world, we live in the same universe,” Cassada said. “Sometimes we experience it in a very different way than our neighbors. If we can all keep that in mind, we can all continue to do absolutely amazing things and do it together.”

SpaceX flight controllers thanked Cassada for sharing her feelings, as well as the significance of Crew-5’s “stowaway.”

“My teammates are just glad we didn’t pull out a dry erase board and dig into the details,” Cassada replied with a smile.

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