tana wrote:DrW wrote:
When in their ground state, the covariant quantum fields that underlie QFT (which both create and permeate all space) undergo no excitations and participate in no interactions.
Since there is no excitation, no particles or energy are created (and therefore no gravity or spacetime) these quantum fields are not detectable, even theoretically. Therefore, it can be reasonably claimed that "nothing" is there.
When is When? When can there ever be a moment or point where the field is dormant, un-excited? In an eternal/infinite system, there can be no timeline, no pre or post excitement period.
And now, here's some bonus footage you're sure to like. If the system that makes particles visible is infinite, then particles themselves must also be considered infinite, and also then, the phenomenon of consciousness, that particles when assembled create, must itself be infinite. There can be no timeline. In an infinite system there can be no before point when particles have not yet assembled themselves to project consciousness.
Also, in an eternal/infinite system, if a group of particles can become assembled in a particular pattern, that projects the consciousness of say, "tana", if this can happen once (it has) then it could happen again. A bazillion years from now. In fact, in infinity it has already happened an infinite number of times.
tana,
Your question is probably best addressed by the various multiverse theories. So far these have not been discussed here much. Sean Carroll (SC), whose work pretty much prompted this thread, is a strong proponent. In this model, there would be a sequence in which the various universes were formed - this giving a relative "when". There are a number of other advantages to these versions of cosmology.
Note: these universes would not (as someone asked upthread) constitute those generated by a the "many worlds" interpretation of QM. Physics Guy may wish to comment further.
So, rather than engage in a metaphysical discussion - one for which we are probably both ill equipped, I would suggest trying for a 'Scientific American' level understanding of a some of the theoretical physics concepts being discussed.
As the OP title indicates, this thread started as a discussion of a debate on cosmology and religion between Sean Carroll, a physicist, and a professor of philosophy and theist, William Lane Craig. If you have not been following the discussion prior to this thread, or have not seen the debate, there are several recordings of it on You Tube. Just type in < Sean Carroll William Lane Craig Cosmology > and take your pick.
As we learned in the debate, Sean Carroll is a proponent of a version of the multiverse as a natural consequence of what physics tells us about Inflation and the Big Bang. It is important to keep in mind that things work out best if one assumes that what we call the Big Bang took place after a brief initial inflationary epoch. This initial inflation took place in the first small fraction of a second, as has been mentioned on this and other threads. There is a great deal of physical evidence for the reality of this cosmic inflation.
The main content of the MDB threads on this subject so far has been a discussion of quantum fields, including their role in the inflationary epoch preceding the Big Bang. A number of links to videos on the subject have been posted on this thread and I would suggest that you go back over the thread, pick them out, and view each of them.
If you still have questions after viewing the debate and these linked videos, links to a technical paper, a Scientific American article, and a couple of good blog posts are listed below.
Sean Carroll blog post on the multiverse:
http://www.preposterousuniverse.com/blog/2017/05/10/is-inflationary-cosmology-science/Sean Carroll has also written an excellent book entitled,
"The Big Picture". It is well worth the money and time to read.
Scientific American article:
https://blogs.scientificamerican.com/observations/a-cosmic-controversy/ Blog post on eternal inflation:
https://darkmatterdarkenergy.com/2015/12/06/eternal-inflation-and-the-multiverse/Here is an abstract from the paper at
https://arxiv.org/pdf/1512.01203v1.pdfThe theory of the inflationary multiverse changes the way we think about our place in the world. According to its most popular version, our world may consist of infinitely many exponentially large parts, exhibiting different sets of low-energy laws of physics.
Since these parts are extremely large, the interior of each of them behaves as if it were a separate universe, practically unaffected by the rest of the world. This picture, combined with the theory of eternal inflation and anthropic considerations, may help to solve many difficult problems of modern physics, including the cosmological constant problem. In this article I will briefly describe this theory and provide links to the some hard to find papers written during the first few years of the development of the inflationary multiverse scenario.
