"Peter L. Peres" wrote: > I am not a physicist ... That's for sure. > ... but for me the fact that vacuum has a dielectric constant at all is a > strangeness by itself. Why? It's mainly a way of resolving the various measurement units involved relating to charge displacement and field strength. The units are Farads per meter, and since Farads and meters are arbitrary units that aren't related to each other, we end up with a proportionality factor of 8.85e-12. > As you know any capacitor stores a part of the charge in the dielectric, > using well-known polarisation mechanisms. No, capacitors store *energy* in the dielectric, in the form of an electric field. They store charge on the plates. If you happen to have a dielectric that can be polarized, then this reduces the field. Some of the energy goes into moving the dielectric charges around, and this may or may not be reversible. (Consider the ferroelectric memory cell.) > Now, try to picture this for vacuum. Oops. And don't say no energy is > stored there. Epsilon0 says otherwise. Nobody says no energy is stored there, but you said that charge was stored there. Big difference. -- Dave Tweed -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics