Phil Thrift asks, " Why is there something rather than nothing? Or is that a nothing question?"
It is either a nothing question or an incredibly deep question depending upon the sort of answer you are looking for. "Why" questions may be requests for motivation -- Why did you do that? -- or they may be requests for causes -- What brought that phenomenon about?
If you are looking for the first sort of answer, I ain't got it, but would point out that it is presupposed that existence requires an act of will and the ability of something whose will could create matter. I'm always amused with the version of the question, "But where did it all come from?" I usually reply, "Newark" and then point out that the question presupposes that it came from somewhere and ask where it was before that.
If we treat it as the second sort of question, what caused there to be all this stuff it is an interesting question. On the one hand, it seems as if we may have reached the limit of possible physical explanation. Physics can describe the way bits of matter and energy interact with one another, but we seem to require the assumption that there is at least the stuff there.
At the same time, spontaneous creation of stuff is not only allowed by our best physical theories, it is actually a direct result. In quantum mechanics, we have this thing called the Heisenberg Uncertainty Principle. It is usually set out in terms of position and velocity -- we can determine the exact position of a particle, but nothing about its velocity; we can determine the exact velocity of a particle, but nothing of its position; or we can determine both, but only up to a limit. I use the verb "determine" and not "know" here because the principle is metaphysical, not epistemological, that is fancy philosophy talk for saying it's not that the particle has exact values for both position and velocity and we just can't know both, it's that it cannot have exact values for both.
This needs to be stressed here because we can express the Uncertainty Relationship in terms of pairs of physical quantities other than position and velocity, for example, time and energy. If you take a small enough span of time in a region, we can determine very little about the energy of the reason. Small enough durations and the uncertainty in energy gets quite large, large enough to be the energy of a particle. In extremely short time spans, it is not only possible, but expected that complete particles will simply pop into being.
Before George Gamow's Big Bang Theory became the cosmological gold standard, physicists Thomas Gold, Hermann Bondi, and most famously Fred Hoyle came up with a rival called the Steady State theory which tried to use mechanisms along this line to account for everything in the universe and its continuous expansion. The idea is that there is something instead of nothing, because, well, sometimes, matter happens. But we've long since given up this idea as an explanation for all matter and energy and asking for the source of the stuff that got banged in the Big Bang becomes at best metaphysical speculation and at worst, a dreaded nothing question.
JoeS asked, "Is the statement "The grass is grue" falsifiable only at the time where it our language system would falsify it? Is it falsifiable at all? What about descriptors of from a different language system that don't involve a time trigger in our system? Are they falsifiable?"The" grue" of which he speaks comes from Nelson Goodman's "New Riddle of Induction" in which he argues that the central logical tool in scientific reasoning, induction, is not the language independent thing we think it is. The idea is that if the word "grue" means "green before 1/1/07 and blue thereafter" then all of the evidence we currently have that the grass is green is also evidence that the grass is grue since all observations have come before the year 2007. By using induction from this evidence, speakers of our color language would predict that on New Years' Day, the grass will still be green, but using the very same logical inference, grue-speakers will be lead by their language to argue that all scientific evidence points to it being what we would call blue. So we have different claims about how the world will be based on the same evidence and the same scientific inference, with the only difference being the language we choose to speak -- something that should be innocuous.
Is the statement "Grass is grue" only falsifiable after 1/1/07. In the naive sense, yes, because that is the first point at which there theories make different predictions. But as Duhem, Quine, Kuhn, and Lakatos (amongst many others) point out. No matter what we observe, we haven't necessarily falsified anything in particular. We can hold onto the grue language and grue-based inductions if we are willing to make adjustments elsewhere in our web of belief.
Consider a non-temporal example of the sort you requested. If I start with a glass of water at room-temperature and remove some of the heat, I get colder liquid water. If I remove more heat, I get colder liquid water. If I remove even more heat, I get even colder liquid water. One inductive inference is that removing more and more heat will give me colder and colder liquid water. Another language, atomic language, on the other hand, says I will eventually get ice (there's the grue-like move in a place that doesn't seem so weird). Is the theory in the original language falsified? Not necessarily, I can keep any part of it, it just means that I need to come up with some new kind of explanation in the language for a weird occurrence. If we woke up on New Years' Day to find all the grass was blue, we would not adopt the grue language, but rather, look for a scientific explanation for the change in the color of grass. When we saw water turn to ice, we posited the need for a new mechanism. We can keep whatever language we want, but that language helps define what it is that needs explaining.
So the notion of falsifiablility is not the right sort of approach here. But it is on the right track. I think a better way to look at it is through Imre Lakatos' notion of progressive and degenerate research programmes. We can never completely undermine a scientific theory, but we can say that it is becoming ad hoc, intellectually clunky and when this is the case and there is a sleek, elegant competitor, there is reason to prefer the competitor. We can never rule out grue speak, but the thery of the world that accompanies it is so cumbersome, so ugly that it simply undesirable.