Posted: Apr 25, 2012 4:19 pm
THWOTH wrote:Lawrence Krauss wrote:I carefully tried, in 3 steps, to progressively explore different versions of what one might operationally call nothing from a physicists perspective.. The first version is indeed the empty vacuum of space–the eternal void of the bible if you wish. Such a version of nothing can quickly be dispensed with as easily leading to something, and not really that different from something.. as I point out. ( and for some reason this bothers some people who think it shouldn’t be so..) But then I talk about how the complete absence of space itself, of our universe, can lead to the creation of space.. our universe.. when quantum gravitational considerations are included….
Nevertheless, Krauss explains something in terms of something else rather than in terms of nothing. Anyway, to explain something in terms of nothing would be to explain nothing, i.e. not to explain anything.
"If the explanation cannot begin with some entity, then it is hard to see how any explanation is feasible. Some philosophers conclude ‘Why is there something rather than nothing?’ is unanswerable. They think the question stumps us by imposing an impossible explanatory demand, namely, Deduce the existence of something without using any existential premises. Logicians should feel no more ashamed of their inability to perform this deduction than geometers should feel ashamed at being unable to square the circle."
(http://plato.stanford.edu/entries/nothingness)
As for the alleged absence of space itself in theories of quantum gravity, it turns out that even those theories aren't ontology-free.
"Quantum theory in general resists any straightforward ontological reading, and this goes double for quantum gravity. In quantum mechanics, one has particles, albeit with indefinite properties. In quantum field theory, one again has particles (at least in suitably symmetric spacetimes), but these are secondary to the fields, which again are things, albeit with indefinite properties. On the face of it, the only difference in quantum gravity is that spacetime itself becomes a kind of quantum field, and one would perhaps be inclined to say that the properties of spacetime become indefinite."
(http://plato.stanford.edu/entries/quantum-gravity)
Quantum fields are something rather than nothing!
Quantum fields have various physical properties, and physical properties are something rather than nothing!
"Einstein’s discovery is that Newtonian space and time and the gravitational field are the same entity. There is a tradition of expressing this discovery saying that 'there is no gravitational field: space and time become dynamical’'. I think that this is a convoluted and misleading way of thinking, which does not do justice to Einstein’s discovery, and has the additional flaw of becoming meaningless as soon as we take into account the fact that the gravitational field has quantum properties. The clean way of expressing Einstein’s discovery is to say that there are no space and time: there are only dynamical objects. The world is made by dynamical fields. These do not live in, or on, spacetime: they form and exhaust reality. One of these fields is the gravitational field."
(p. 27)
"Conceptually, what disappears with GR is the idea of space as the 'container' of the physical world. As mentioned, this disappearance is not so revolutionary after all: to some extent it amounts to return to the pre-Newtonian view of space as a relation between equal-status physical entities. …With or without such an explicit reference to God, for three centuries space has been regarded as the preferred Entity with respect to which all other entities are located. In the 20th and 21st centuries and with GR we have been learning that we do not need this frame to keep reality in place. Reality keeps itself in place. Objects interact with other objects, and this is reality. Reality is the net of these interactions. We do not need an external entity to hold this net. We do not need Space, to hold the universe."
(p. 32)
(Rovelli, Carlo. "The Disappearance of Space and Time." In The Ontology of Spacetime, edited by Dennis Dieks, 25-36. Vol. 1 of Philosophy and Foundations of Physics, edited by Dennis Dieks and Miklos Redei. Amsterdam: Elsevier, 2006.)
This is the relationist view of space plus the view that the fundamental physical objects are (quantum) fields. particularly the gravitational field. And fields are spatially extended entities, so even if space is ontologically reducible or decomposable, spatiality (spatial extension) is not. According to the theory of loop quantum gravity, there are discrete space atoms with a tiny volume, and so spatiality, again, remains unreduced and irreducible. Rovelli rejects the absolutist container/occupier view of space, according to which space contains physical objects (particles, fields) that occupy it. His quantum fields are spatially unlocated but still spatially extended.