For
the past 30 years, the transport properties in the unusual metallic
phase seen in the cuprate superconductors and many other quantum
critical metals, have defied an explanation in terms of the standard
building blocks of modern physics --- particles with local interactions and conservation laws.
A recent proposal suggests that all of the properties of such `strange
metals' can be understood if the current has an anomalous dimension not
determined simply by dimensional analysis. My talk will focus on trying
to understand this claim. To demystify this claim, I will first show
that even in the standard formulation of electricity and magnetism,
there is an extra degree of freedom, which has remained unnoticed until
now, that can allow, in principle, for the current to have any allowable
dimension. However, I will show that the only quantum theories to
date which exhibit such odd behaviour are holographic models that are
derived from a gravity theory that lives in higher dimensions. The
existence of currents having anomalous dimensions, a direct probe of the
existence of extra `hidden' dimensions, can be tested with the
Aharonov-Bohm effect. I will describe this effect and its potential
impact for unlocking the secret of the strange metal in the cuprates.