The mining song Sheldon sings is the same song that is heard at the beginning of the documentary Harlan County U.S.A. (1976) which is about the Harlan County, KY coal miners who were fighting for a union contract with UMWA.
On the desk in Bernadette and Howard's main room, beside their Wedding photo, is a collectible spacecraft Eagle from the 1970's TV series Space: 1999 (1975).
Sheldon's shirt has the number 73 on it which happened to be the year Jim Parsons who plays Sheldon was born.
At the end of these episode, the same Vanity Card (#464) of the previous episode (The Focus Attenuation (2014)) is shown, an almost unique case.
Title Reference: Since there is an opportunity to study dark matter in a salt mine, Raj and Sheldon decide to test themselves under the conditions found in a mine.