The meaning behind Elon Musk and Grimes’ daughter’s name, Exa Dark Sideræl

Elon Musk and Grimes were inspired by supercomputing, dark matter, and ‘deep space time’ when choosing their one-of-a-kind name for their newborn daughter Exa Dark Sideræl, whom they are calling ‘Y’ for short. 

The singer, 33, revealed in a cover interview with Vanity Fair that she and the billionaire SpaceX founder, 50, secretly welcomed a second child via surrogate in December while opening up about the origins of her unique moniker. 

According to Grimes, the baby girl’s three names are all rooted in science, with one nod to the singer’s love of Lord of the Rings and elven mythology. 

Here, FEMAIL reveals the true meaning behind each of the baby girl’s three monikers. 

SpaceX founder Elon Musk, 50, and his on-again-off-again partner, Grimes, 33, secretly welcomed their second child, a daughter named Exa Dark Sideræl, via surrogate in December 

Grimes revealed the news in a cover interview with Vanity Fair while opening up about their daughter’s name, which was inspired by supercomputing, dark matter, and ‘deep space time’ 

The 33-year-old singer, who already has a baby son, X Æ A-12 (pictured) with Elon shared that the former couple will call their daughter ‘Y’ for short

EXA: A nod to supercomputing 

Grimes, whose real name is Claire Boucher, explained their newborn’s quirky first name, Exa, is a reference to the supercomputing term exaFLOPS, the capability of performing one quintillion floating-point operations per second.  

The decimal prefix ‘exa’ denotes the number one quintillion, which is defined in the U.S. as 1000000000000000000 or 1 followed by 18 zeros.

FLOPS, meanwhile, is an abbreviation of floating-point operations per second. It refers to the theoretical peak performance of computers.

DARK: Inspired by dark matter and ‘the unknown’ 

Their daughter’s second name, Dark, is a nod to dark matter and ‘the unknown.’

‘People fear it but truly it’s the absence of photons. Dark matter is the beautiful mystery of our universe,’ Grimes told the magazine.  

Dark matter is an invisible substance that is thought to comprise 85 percent of the universe’s mass, according to NASA. 

It is thought to be the gravitational glue that holds the galaxies together, though it has never been directly observed by scientists. 

The enigmatic material is invisible because it does not absorb, reflect, or emit light. 

Astronomers have been able to infer its existence because of its gravitational effects on known matter — any physical substance that has mass and takes up space. A smartphone and the human body are both examples of matter. 

‘Shine a torch in a completely dark room, and you will see only what the torch illuminates. That does not mean that the room around you does not exist. Similarly we know dark matter exists but have never observed it directly,’ The European Space Agency explained in a 2013 article.  

The newborn’s first name, Exa, is a reference to the computer term exaFLOPS, the capability of performing one quintillion floating-point operations per second

The decimal prefix ‘exa’ denotes the number one quintillion, which is defined in the U.S. as 1000000000000000000 or 1 followed by 18 zeros

Their daughter’s second name, Dark, is a nod to dark matter and ‘the unknown.’ Dark matter is an invisible substance that is thought to comprise 85 percent of the universe’s mass

SIDRÆL: An ‘elven’ take on deep space time

Finally, Sideræl, which is pronounced sigh-deer-ee-el, is a ‘more elven spelling’ of sidereal, which Grimes described as ‘the true time of the universe, star time, deep space time, not our relative earth time.’

Founded by German-British William Herschel, sidereal astronomy is a branch of astronomy that studies the origin, nature, and relationship of the stars.   

‘A sidereal day measures the rotation of Earth relative to the stars rather than the sun,’ according to EarthSky. ‘It helps astronomers keep time and know where to point their telescopes without worrying about where Earth is in its orbit.’  

A solar day — the time it takes for the Earth to make one complete revolution on its axis in respect to the sun — is around 24 hours, while a sidereal day lasts 23 hours 56 minutes and 4.1 seconds.

Their daughter’s third name is also a reference to Grimes’ favorite Lord of the Rings character, the elf Galadriel, who ‘chooses to abdicate the ring.’

The J. R. R. Tolkien character was one of the great elves from Middle-earth who was known for her transcendent beauty, knowledge, and power.    

Actress Cate Blanchett played Galadriel in director Peter Jackson’s Lord of the Rings and The Hobbit trilogies.  

Finally, Sideræl, which is pronounced sigh-deer-ee-el, is a ‘more elven spelling’ of sidereal. Sidereal astronomy is a branch of astronomy that studies the origin, nature, and relationship of the stars. A sidereal day (pictured) measures the rotation of Earth relative to the stars

Their daughter’s third name is also a reference to Grimes’ favorite Lord of the Rings character, the elf Galadriel, who is played by Cate Blanchett in the film adaptations of the series 

Grimes and Musk have also been calling their baby girl Sailor Mars, a reference to the manga cartoon Sailor Moon

REVEALED: Exa Dark Sideræl’s nicknames

Grimes and Musk are calling their baby girl Y for short, similar to how they nicknamed their son, X Æ A-12, ‘X’ after he was born in May 2020. 

They were forced to change the spelling of their son’s name in order to comply with California law, which prohibits the use of any numbers or symbols in a name.  

Just a few weeks after the baby was born, they revealed that his birth certificate would be registered under the name X AE A-Xii, using the Roman numeral version of the number ’12’ and changing the character æ to AE. 

If Musk and Grimes choose to register their newborn daughter’s birth certificate in Texas, they will have to alter the spelling of her name, once again removing the symbol æ in order to comply with state regulations that only allow the use of English characters in a name. 

They have also been calling their baby girl Sailor Mars, a reference to the manga cartoon Sailor Moon. 

Grimes conceded to Vanity Fair that their unique choice of names is not to everyone’s tastes, admitting that she is prepared for her daughter to one day want to change it.  

She added that they might end up changing the name themselves before the interview came out. The mom, who was pushing for the name Odysseus, explained that Exa Dark Sideræl was a compromise, but she thinks it might be boring. 

‘I was fighting for Odysseus Musk,’ she told the magazine. ‘A girl named Odysseus is my dream.’