  The use of probe molecules to extract the local dynamical and structural
properties of complex dynamical systems is an age-old technique both in
simulations and experiments. A lot of important information which is not
immediately accessible from the bulk measurements can be accessed via these
local measurements. Still, a detailed understanding of how a probe particle's
dynamics are affected by the surrounding liquid medium is not very well
understood, especially in the supercooled temperature regime. This work shows
how translational dynamics of a rod-like particle immersed in a supercooled
liquid can give us information on the growth of the correlation length scale
associated with dynamical heterogeneity and the multi-body static correlations
in the medium. A unified scaling theory rationalizes all the observed results
leading to the development of a novel yet simple method that is accessible in
experiments to measure the growth of these important length-scales in molecular
glass-forming liquids.
