  In this short article we discuss the properties of electromagnetic fields in
heavy-ion collisions and consequences for observables. We address
quantitatively the issue of the magnetic field lifetime in a collision
including the electric and chiral magnetic conductivities. We show that for
reasonable parameters, the magnetic field created by spectators in a collision
is not modified by the presence of matter. Based on this, we draw definite
conclusions on observed effects in heavy-ion collisions.
