Hi there, This year I finished two semesters of E&M, and think I understood much of it but had something of a problem understanding something concering fields and EM waves. Something always seemed sort of odd to me when reading about retared potentials and how it takes time for the field to travel, I tried explaining my problem to the professor (who happened to be one of the best I've ever had) but I don't think he knew what I meant, or maybe my question just didn't make sense. So what bothered me was how the EM field travels. At first when you learn about static fields you learn that they are instantly transmitted. Then you learn that actually they travel at the speed of light, and in the form of a wave. So for example I have a long straight wire where the current was just turned on. It will take time for the field to travel out so I have a sort of double cone (two cones with the round sides touching) of where the field has gotten to which depends on the speed of light and how long I've waited after turning it on. So the field travels out in a wave right? And after a long enough time the parts closer to the wire wil start to only have the typical static mag field of a long straight wire. The wave part dies down near the wire and there's just a field there now? Before the field needed to travel out there in a wave, but after it is just maintained there, and there's no more waves emenating from the wire? I have a feeling that this may not makes sese but oh well. Another thing that confused my about this was reading feynman's lectures. At some point he says " The electromagnetic field can carry waves...", This totally through me off. Is he trying to say that the EM field is the medium through which the waves are travelling? I thought that the EM field isn't there until the wave goes by? I thought there was no medium needed for it to travel though? Is it wrong of me to think of the EM waves as sort of carryying the field to everywhere in space? I'd really like to understand this and any help would be greatly appreciated. thanks.