Assertion: magnetic field's field line | /r/HasAspect | no start
Facets:
Source sentences:
text: A magnetic field has no sources or sinks (Gauss's law for magnetism), so its field lines have no start or end: they can only form closed loops, extend to infinity in both directions, or continue indefinitely without ever crossing itself.
text: Magnetic field lines have no beginning or end, they always form closed loops.