I'm taking E & M II this semester, and one question got me thinking. We know the formulation of the four Maxwell's equations, and that's okay so far. But in the absence of sources, they take the form:
$$\nabla \cdot \mathbf{E}= 0 \\ \nabla \cdot \mathbf{B}= 0 \\ \nabla \times \mathbf{E} = -\dfrac{\partial\mathbf{B}}{\partial t}\\ \nabla \times \mathbf{B} = \mu_{0}\epsilon_{0}\dfrac{\partial\mathbf{E}}{\partial t}$$$$\nabla \cdot \mathbf{E}= 0 \\ \nabla \cdot \mathbf{B}= 0 \\ \nabla \times \mathbf{E} = -\dfrac{\partial\mathbf{B}}{\partial t}\\ \nabla \times \mathbf{B} = \mu_{0}\epsilon_{0}\dfrac{\partial\mathbf{E}}{\partial t}$$
So my question is, theThe electric field is caused by the presence of charged particles, which if it varies, causes the existence of a magnetic field. But if there are noaren't any sources, how can the Maxwell's equations have nontrivial solutions? Wouldn't the electric and magnetic field be always be zero?