  The density variations in thin stellar streams may encode important
information on the nature of the dark matter. For instance, if dark matter
aggregates into massive sub-halos, these perturbers are expected to scatter
stars out of dynamically cold stellar streams, possibly leading to detectable
gaps in those structures. Here we re-examine the density variations in the GD-1
stream, using Gaia DR2 astrometry, Pan-STARRS photometry, together with high
precision radial velocities measured with the CFHT/ESPaDOnS and VLT/UVES
instruments and complemented with public radial velocity catalogs. We show that
after correcting for projection effects, the density profile exhibits high
contrast periodic peaks, separated by $2.64\pm0.18$ kpc. An N-body simulation
is presented that reproduces this striking morphology with simple epicyclic
motion in a smooth Galactic potential. We also discuss the reliability of
measuring density variations using ground-based photometric surveys, and for
the particular case of GD-1 we highlight some of the artifacts present in the
Gaia DR2 catalog along its track. Massive dark subhalos do not appear to be
required to explain the density clumping along GD-1.
