I haven’t written anything for this site in a few months because my efforts to secure a funded PhD place in the competitive field of quantum gravity have taken up all of my time. Now I’ve been granted such a place in York, I can return to writing here. What makes quantum gravity such a competitive field for would-be graduate students is its relevance to many of the most important outstanding problems in fundamental theoretical physics. Since religious people have a tendency to treat “we don’t understand X” and “God did X” as synonyms, in a fallacy known as the argument from ignorance, I felt a discussion of these issues from a genuinely scientific perspective would be of some value to this site.
Lawrence Krauss has done for how something can come from nothing what Richard Dawkins did for Darwinian evolution – not so much contributing to scientists’ knowledge as disseminating that knowledge to the public. This is not to denigrate either man’s work; it is to observe that the science is well-established consensus among the relevant experts, rather than an individual’s opinions. (Another physicist whose scientific atheist publications have a personal presentation, while still covering the work of many other scientists, is Victor Stenger.) The basic idea for how something can arise from nothing is that conserved quantities – energy and “Noether charges” (why energy is treated separately would take too long to explain here), and so-called “Poisson brackets” thereof – exist in positive and negative amounts that, according to all our observations, cancel in our universe, which means a splitting of nothing into aggregates can occur without violating conservation laws. In particular, gravitational attractions provide negative contributions to the universe’s energy budget, which led Einstein to be the first physicist to propose its possible role in the universe’s origin. But a full understanding of how gravity operates at the subatomic level, which still eludes us, is crucial for filling in all the gaps.
Religious people love to crow at every individual “we don’t know” concession in science. They never stop to think whether “a magic man who hates human genitals did it” is even a remotely evidenced or plausible answer to outstanding questions. It’s not. Nor does it gain either virtue if the genitals comment is omitted, a point I shouldn’t have to make to the deists in the audience. All the details we already know are suggestive instead of a purely natural explanation applying, whatever it may be. To be sure, there are outstanding difficulties with the current mathematics; but that is precisely why it is mathematical, not literary, answers which will be needed.
Another common mistake of religious people is to assume “we don’t know” is a synonym for “we haven’t a clue”. The argument from ignorance always assumes that no decent explanations are available, whereas with quantum gravity the problem is we have multiple explanations but we can’t evidentially distinguish between them, because their predictions differ only at very high energy scales. This evidence issue also raises an important way science is better than religion. We cannot currently specify how we could test any quantum gravity models with experiments it is in our power to feasibly do in the present, but this “how would you test it?” objection, which scientists call the falsifiability criterion (after the philosopher Karl Popper), is mainly brought up against string theory because it is the leading approach in the subject. Creationism, depending on how it is formulated, can also often be unfalsifiable. (Its falsifiable versions have already been falsified.) But here’s why creationism is pseudoscience but string theory isn’t: string theorists are working hard to come up with a decent answer!