It requires a much higher degree of imagination to understand the electromagnetic field than to understand invisible angels. … I speak of the E and B fields and wave my arms and you may imagine that I can see them … [but] I cannot really make a picture that is even nearly like the true waves.

volume II; lecture 20, "Solution of Maxwell's Equations in Free Space"; section 20-3, "Scientific imagination"; p. 20-9 to 20-10 - The Feynman Lectures on Physics (1964)