$[-/1$ Points$]$

Why is the following situation impossible? An electromagnetic wave travels through empty space with electric and magnetic fields described by

$E=9\mathrm{.}00{10}^{3}cos[(9\mathrm{.}00{10}^6)x-(3\mathrm{.}00{10}^{15})t]$

$B=3\mathrm{.}00{10}^{-5}cos[(9\mathrm{.}00{10}^6)x-(3\mathrm{.}00{10}^{15})t]$

where.all.numerjcal.values. and variables.are.in$.$SL$.$units.