To immortalize the legacy of renowned physicist and cosmologist Stephen Hawking, a commemorative 50-pence coin bearing his name and a black hole will be available in the United Kingdom.
Black Hole In Your Pocket
The attractive coin features a drawing of concentric circles that represent a black hole and the equation describing the entropy of a black hole.
Although the coin features a 2D image, its surface appears to be forming deep notches toward the center of the black hole. It features the name of Stephen Hawking on the concentric circles, and above it, his signature theorem on black holes.
"It's a 2D surface that seems to have a 3D image on it. It's as though you could fall into the black hole," according to Lucy Hawking, Stephen Hawking's daughter.
Lucy and Tim Hawking, the physicist's younger son, attended the launch where they struck their own coins.
"I am thrilled to know that there is a coin commemorating his work," says Tim.
"It's very beautiful, it's very elegant, it's very appropriate, and I think we feel enormously privileged and honored that the Royal Mint has passed this coin in his memory," Lucy added.
The formula used to define black holes entropy known as the Bekenstein-Hawking formula was created by Hawking and Jacob Bekenstein in the 1970s.
Their formula describes the thermodynamic entropy of a black hole with a given mass. The two scientists found that the entropy of a black hole is proportional to the area of its event horizon. They said that as an object falls into a black hole, its entropy increases.
The commemorative coin will not be in circulation but will be available for sale at the UK Royal Mint website for £10 pound sterling or around $13.
The coins that are meant for collectors will come in gold proof, silver proof, silver proof piedfort, and "brilliant uncirculated" at prices ranging from £55 or about $72 to £795 or about $1050 each.
The coin's designer Edwina Ellis said the initial inspiration was Stephen Hawking's description of black holes.
Ellis was inspired by one of Hawking's lectures in which she said the scientist invited the audience to contemplate peering into the black hole before diving in.
"I wanted to fit a big black hole on the tiny coin and wish he was still here chortling at the thought," says Ellis, the engraver of the Stephen Hawking coin.
The coin's release coincides with Hawking's first death anniversary. It is part of the UK Royal Mint's celebration of British innovators in science. Hawking's commemorative coins will join the ones made in honor of Sir Isaac Newton and Charles Darwin.
Hawking died at the age of 76 on March 14, 2018.