David Connery asked:

If the universe was created in a Big Bang, before light, matter, and time; if there was no time how can there be a before? If there is no matter how can any reactions, chemical or physical or other, occur? It is impossible to make something with nothing. Is our universe just one of many, in a cycle created out of the death of another? Do you think the Big Bang was part of another cosmic event, i.e. the creation or death of other unknown universe(s)?

Answer by Massimo Pigliucci

The question of what, if anything, was before the Big Bang – or even, as you point out, whether it makes any sense to talk about “before” and “anything” in this case – is one that has vexed both philosophers and physicists for a long time. Recently, for instance, cosmologist Lawrence Krauss has written an entire book dedicated to the topic, aptly entitled A Universe from Nothing: Why There Is Something Rather than Nothing. Krauss thinks that physics is very close to answering that question, as the available empirical and theoretical evidence points to the idea that the universe came out of an essentially featureless quantum vacuum.

Some philosophers, however, think this is too quick. For instance, David Albert, in a critical review of Krauss’ book that appeared in The New York Times, correctly points out that even a quantum vacuum is not “nothing,” and that it does have “features,” at the very least because it behaves according to the laws of quantum mechanics, which is what Krauss helps himself to when he says that physics can explain how the universe came about. Although the specific diatribe between Krauss and Albert is not the main point here, it has to be noted that subsequently Krauss backed away from his initial position a bit, stating (somewhat disingenuously) in an interview with Atlantic magazine that “Well, if that hook [talking about “a universe from nothing”] gets you into the book that’s great. But in all seriousness, I never make that claim.” Regardless, I think it is fair to say that physics is getting closer and closer to understanding how the universe came about, but we are not there yet, and there is a good chance we might never get a complete answer.

Why not? Well, to begin with because there simply may not be enough of what philosophers call “historical traces” left for scientists to work with. Science is an empirical discipline, and whatever theory scientists come up with has to square with the empirical evidence. But we may not be able to recover any evidence at all about whatever was “there” “before” the universe began. It all got wiped out by the Big Bang itself.

Notice that I put “there” and “before” in scare quotes, because you are right that it is at the least a bit problematic on the one hand to say that time and space began with the Big Bang, and on the other hand to ask what was there before that cosmic inception. Nonetheless, I do not think this is an insuperable problem, as physicists have different options available. They could simply say that the meanings of concepts like time and space change (in specifiable ways) before and after the Big Bang, but that we may use the same words anyway for convenience purposes. Or they could say that only local (i.e., of this specific universe) time and space began with the Big Bang, but that a broader conception of those quantities applied even before to the whole multiverse.

Which brings me to your other questions: are there are other universes, and is it possible that ours originated from one of those? The idea that our universe is really part of a much bigger entity, referred to as the multiverse, has been discussed a lot in physics and philosophy of late. (And it is not to be confused with the so-called many worlds interpretation of quantum mechanics, about which you can find a lot more here.)

Physicist Lee Smolin, for instance, has proposed a so-called theory of cosmic natural selection, a summary (and criticism) of which you can find in this article of mine at Rationally Speaking. The basic idea is that collapsing black holes spawn baby universes, and these newly formed universes are characterized by combinations of physical parameters similar but not identical to the one of the “mother” universe. The “selection” bit of the theory comes in because some universes are going to be more stable than others, and hence will be more likely to “survive” longer, and in turn to spawn more baby universes.

Notice the language that Smolin imports straight from the Darwinian (biological) theory of natural selection. But there are important disanalogies between the two, which is why Smolin’s theory is far from being accepted. In biology, selection is triggered by competition of organisms for a common set of limited resources; it is not clear in what sense, if any, universes compete for resources with each other. Also, the theory of biological evolution requires a mechanism of inheritance (genetic transmission), which makes possible the creation of new generations inheriting characteristics of the old ones. No similar mechanism is known in black holes physics.

Finally, there is the issue that – so far at least – not only nobody has observed any other universe (other than our own) within the multiverse, but it isn’t even clear whether such observation, even indirectly, is in principle possible. If it isn’t, then the idea of a multiverse is bound to remain mathematical speculation, i.e., basically metaphysics, not science.