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1. How could they conduct an experiment on 'nothing' as the Casimir experiment seemed to have done ? Surely if there are virtual particles, then there isn't nothing , there is something. Besides, surely its impossibly to create 'nothing' in the first place so that we can test it?
The term "creation from nothing" is a bit misleading here. The particles are not created out of some prior energy being transformed, but that doesn't mean the vacuum itself is nothing. Even in the complete absence of virtual particles, matter and energy, a vacuum is still something, namely the gravitational field.
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2. Why has there no been more 'BIG BANGS', from nothing ? If the Big Bang originated from nothing and essentially created the universe, then what is to prevent another random 'BIG BANG'?
To add to the confusion, the nothing prior to the big bang is a different concept. This void is a state where there is no spacetime, but the laws of physics still exist. This creation ex nihilo, is not compatible with an infinite universe. What is stopping another big bang from happening? Well, nothing. Under inflation models, big bangs will occur continuously into the future, allowing spacetime to be immortal, so to speak.
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The assumption is that time only started with the Big Bang and the assumption now that the universe will not contract by dark energy and will expand indefinitely. If that is the case, then this universe is either unique (IE: first universe not to contract back to nothingness) or it it not the only universe?
Under the same inflation models, certain regions in empty space can inflate to expanding universes like our own. In that sense, our universe may just be a small part of a larger, expanding multiverse.
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