It's not clear why you think electromagnetism can't be everywhere in space. Electromagnetic waves are one of the basic ingredients of the universe. Sure the waves that are around now have sources, in that there was some last interaction with other matter. The universe is filled with electromagnetic radiation that last interacted strongly with matter some 13.8 billion years ago. The main thing that has happened to that radiation since then is that it has gotten to be more dilute and lower frequency as the space it's in has stretched out.
(published on 04/13/2017)
I don't understand the reasoning that leads to your points (1) and (2).
This question I understand: "How can electromagnetic waves be one of the ingredients of the universe if it is a side-effect of the universe?" It raises an important philosophical issue.
The distinction between ingredients and side effects is pretty much arbitrary. Two photons can collide and turn into an electron and a positron. In the early seconds, that happened a lot. Then an electron and a positron can collide and make two photons. That also happened a lot. Which (photons or electron/positrons) is the basic stuff and which is the side effect? Does nature have any idea what those words mean?
The distinction between ingredients and other things is a bit more meaningful. For example, we say that sound waves (phonons) are not a basic ingredient because we understand them as one of the ways things like air or steel can behave. You can't have phonons with some sort of medium like that. Photons are a basic ingredient because they can exist in a vacuum without any underlying medium, as least so far as we currently understand the world. Maybe someday what we now call a vacuum will be thought of in terms of some deeper structure, in which case we'd have to revisit this question.
(published on 04/16/2017)