Sub-dimensional physics was a branch of physics studied in the 23rd century. The Vulcans possessed a large amount of knowledge regarding sub-dimensional physics and the field was also studied by Flint on Holberg 917G. Flint taught Rayna Kapec all he knew about sub-dimensional physics, along with other topics such as field density and its relationship to gravity phenomena. Rayna then desired to have a conversation with Mr. Spock upon his arrival with a landing party from the USS Enterprise to Holberg in 2269. (TOS: "Requiem for Methuselah" )