So, I have been doing a lot of reading. I have an 8 year old girl that has renewed my interest in physics, chemistry, biology, etc. I find it interesting that we say that Electromagnetic Waves travel through a vacum. We know that mechanical waves like those propagated in liquids and gas travel through a medium. It seems that photons can be created from a vacum if you add enough enegry (http://www.sciencedaily.com/releases/2011/11/111118133050.htm) so... where do they come from... there has to be some medium that they are traveling through doesn't there. We can say that electric and magnetic waves feed off of each other but... I'm not sure how that happens. Are there quantum particles that we simply cannot measure that the EM waves travel through? When we talk about Dark Matter... it's just "stuff" that we cannot bounce something off of, something that doesn't emit anything, and something that we cannot measure interacting with anything else right? So, if the Universe is filled with "Dark Matter" and if it would make sense if EM waves propagated through something... would "Dark Matter" be the medium for EM Waves. And is Dark Matter just a quantum soup? My understanding is that Photons travel through glass by being absorbed and "split out" by many layers of atoms as they travel through the glass. If there was no way for us to measure or "see" glass - and if we only knew about a smalled specturm of the EM waves that are not directly impacted by glass... I guess it would be called "Dark Matter" as well? Simplified but, just trying to get the thought across.