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Old_Geezer: Hmmmmm... I keep getting this kind of answer from people I've asked, and to me, it just seems like a classice example of something the 'Religion vs Science' arguments often designated 'God of the Gaps' (and in this instance, never was a concept more appropriately named!), i.e. when we don't know how to explain something, default to the answer that requires faith without proof. There are clearly only 2 kinds of space - that which contains matter, which is therefore devoid of space (except on the subatomic level), and that which is devoid of matter - which is necessarily a vacuum. Fields are only patterns of interaction between particles, and are not made up of anything identifiable as matter. Maybe the dependable Mr Hawking can sort this one out!
BTW ChuckFickens: Yes, of course, you're absolutely right... I did mean '...molecules of oxygen and nitrogen'. Not hydrogen. The perils of sitting in a noisy, busy internet cafe with pretty girls everywhere to distract!!