  Solar prominences are cool 10$^4$ Kelvin plasma clouds supported in the
surrounding 10$^6$ Kelvin coronal plasma by as-yet undetermined mechanisms.
Observations from \emph{Hinode} show fine-scale threadlike structures
oscillating in the plane of the sky with periods of several minutes. We suggest
these transverse magnetohydrodynamic waves may represent Alfv\'en waves
propagating on coronal magnetic field lines and these may play a role in
heating the corona.
