Yes, it's a cheap and old pun. I don't care.
I've mentioned how

extra dimensions are one of the main ways particle theorists

~~pad out their publication list~~ conjecture new physics might arise. But I spoke mostly in generalities, about the basic concept of more dimensions, and how it differs from the pop scifi ideas. But there's lots of fun to be found in the details!

The idea of extra dimensions goes all the way back to 1921, when

Theodor Kaluza suggested identifying electromagnetism as the gravitational effect of the extra dimension. Five years later,

Oskar Klein expanded on his idea, which is thus known as

Kaluza-Klein theory. More generally, the process of taking a five- (six-, etc) dimensional theory and figuring out what it looks like in four dimensions is known as the Kaluza-Klein expansion. The specific model of these two men is no longer in favour, as it implies that electric charge and mass should be correlated (they are not).

Modern theories relevant to experiments like the LHC go back to only 1998, when

Nima Arkani-Hamed

, Savas Dimopoulos

, and Gia Dvali proposed the existence of

large extra dimensions. They where inspired by string theory, so

*large* means at most millimetre-sized. This is still much, much bigger than the

Planck scale; more to the point, it can lead to phenomena observable at current experiments.