  The chiral anomaly is a purely quantum mechanical phenomenon that has a long
history dating back to the late 1960s. Surprisingly, it has recently made a
macroscopic appearance in condensed matter physics. A brief introduction to the
relevant features of this anomaly is given and it is shown that its appearance
in condensed matter systems must involve force-free magnetic fields, which may
help explain the long current relaxation times in Dirac and Weyl semimetals.
