The first term in the formula for E represents the Coulomb's law for the static electric field. The second term is the time derivative of the first Coulombic term multiplied by r ′ c which is the propagation time of the electric field. Heuristically, this can be regarded as nature "attempting" to forecast what the present field would be by linear extrapolation to the present time. The last term, proportional to the second derivative of the unit direction vector e r ′ , is sensitive to charge motion perpendicular to the line of sight. It can be shown that the electric field generated by this term is proportional to a t / r ′ , where a t is the transverse acceleration in the retarded time. As it decreases only as 1 / r ′ with distance compared to the standard 1 / r ′ 2 Coulombic behavior, this term is responsible for the long-range electromagnetic radiation caused by the accelerating charge.