I’d like to talk about nothing. To be more accurate, I’d like to talk about Sean Carroll talking about nothing. To be more precise, I’d like to talk about Sean Carroll talking about Lawrence Krauss and David Albert talking about nothing, and their disagreement about it.
Sean Carroll recently wrote an article (“A Universe from Nothing?”) discussing an ongoing controversy surrounding Lawrence Krauss’ new book “A Universe from Nothing" (no question mark). Carroll is a theoretical physicist and writer, as is Krauss. Carroll’s article provides the background, but I’ll quickly summarize:
- Lawrence Krauss wrote his book based on his popular Youtube lecture. In both he describes the evidence gathered over the last few decades for how our universe came from nothing, for various definitions of “nothing”.
- David Albert, a science philosopher with a physics background, wrote a critical review of it in the New York Times attacking it for not really addressing the question of “true” nothingness from a philosophical point of view.
- Krauss responded, suggesting the problem is with philosophy which puts abstract ideas above reality. (There is a little irony here given that Krauss is a theoretical physicist, which is essentially a philosopher armed with math.) There have been ongoing clarifications, apologies (of sorts), and comments from other interested parties.
Carroll’s article is yet another attempt to address the controversy, but I don’t think it does so accurately. I don’t think Carroll or Albert give Krauss his proper dues in addressing the issue of “nothing”.
Early in the article Carroll suggest that the issue is a difference in questions:
One question is, within some framework of physical laws that is flexible enough to allow for the possible existence of either “stuff” or “no stuff” (where “stuff” might include space and time itself), why does the actual manifestation of reality seem to feature all this stuff? The other is, why do we have this particular framework of physical law, or even something called “physical law” at all? Lawrence (again, roughly) addresses the first question, and David cares about the second, and both sides expend a lot of energy insisting that their question is the “right” one rather than just admitting they are different questions.
I think this is simply wrong, or at least misleading. If you read Krauss’ book or watch his video lecture he does address the question of why there are physical laws at all. He explicitly addresses three definitions of “nothing”:
- Classical “nothing” where space and time exist and matter and energy emerge from this empty vacuum.
- Relativistic “nothing” from which space and time (“spacetime”) emerge.
- Lawless “nothing” from which laws of physics themselves emerge.
Carroll recognizes that Krauss addresses the first two (though lumps it into one category) but seems to miss the third. Albert seems to miss it too. Krauss talks about the “environmental” science of a multiverse, makes use of the anthropic principle, and fully describes the limitation of physics to address the question any further. He even espouses his own dissatisfaction with the direction that form of answer is heading but that he can’t rule it out. He is honest about what types of questions can and can’t be answered.
It isn’t that Krauss doesn’t address it, but rather that he doesn’t have a full answer for it and suggests that any definition of “nothing” beyond this is an abstraction. He suggests the “nothing” of philosophy doesn’t have value when the “nothing” of reality doesn’t match it.
This is where I think Carroll and Albert miss Krauss’ point, or at least my interpretation of it. Neither really addresses how far a definition of “nothing” can go before it becomes meaningless. Carroll reaches his limit of detail at vague “deep-down laws”:
We are still left with the question of there are those deep-down laws that create a multiverse in the first place.
Here Carroll is talking about a specific form of multiverse based on “deep-down” laws, presumably referring to the fundamental field equations used in physics or any comparable mathematical description. This doesn’t seem to be quite the same context that Krauss uses “multiverse”. Rather, Krauss’ version seems more aimed at all possible universes that can add up to nothing. Granted, describing them as possible requires some sort of “deep-down” law. (This foreshadows the problem.) Albert goes into much more detail than Carroll, but it at this point where I think the question itself begins to lose coherence, as I think Krauss suggests.
Before getting to Albert’s description, let’s try an exercise. Try to define a “nothing” that has no properties or “deep-down” laws. What words do you use to describe it? What math could you use? I propose that it is impossible to define such a “nothing”, one from which you’d expect that “something” cannot spontaneous emerge. That restriction alone would constitute a law of physics, and then one simply asks where that law comes from, as Carroll explicitly does above (“…or even something called “physical law” at all”).
The problem, I think, isn’t with definitions. It’s with intuitions. We have an intuitive dislike for “something from nothing”, probably as an evolved mental approximation to the conservation of matter which may have aided in keeping track of things. (Nowadays this would be folded into the conservation of energy and further folded into the First Law of Thermodynamics.) In this context, our philosophical distaste for “something from nothing” is tied up in laws of physics of the Earth we evolved in, not some sort of philosophical first principles.
I think this is why some people keep trying to re-define what “nothing” means. They aren’t interested in an actual answer because their intuition tells them an answer isn’t possible. Something just can’t come from nothing, and if it can then we need to re-define “nothing” so that it can’t. That is trivially easy to do because any answer for “something from nothing” must contain properties of this “nothing” and we can then simply ask where those properties came from. This explains why we go from classical “nothing” (no matter or energy) to relativistic “nothing” (no space or time) to lawless “nothing” (no physical laws at all). Each time we understand one level we need to re-define “nothing” to be beyond that so that we can feel safe that something just can’t come from nothing.
It’s easy to see where David Albert attempts this in his critical NYT article. He even tries to spin this as a positive feature. Albert suggests that as we learn more we need to adjust the definition. I can see why this might sound enticing in the sense of refining scientific questions but it is a subtle play on concepts. In the scientific context, answers do lead to refining the question, not re-defining it. To see the difference, ask what end is possible in Albert’s version? What would an answer possibly look like? Once you define the question as one that simply takes any answer and tacks on “but why this?”, you turn the question into something useless and meaningless, a forever moving boundary just beyond wherever you currently are. We become Achilles forever chasing Zeno’s tortoise.
Take Albert’s suggestion that Krauss’ version of “nothing” consists of quantum fields at vacuum states, and says the problem is that Krauss doesn’t address why such fields exist at all. But they don’t really exist, at least not in the sense that Albert claims he is talking about “physical stuff”. What he and Carroll are really talking about here is the concept of virtual particles. But even these don’t really exist in the context of “physical stuff”. They are merely a manifestation of fundamental uncertainty, which is a concept. They aren’t “real” particles that exist in any tangible form; they merely act as a language by which we can describe the fundamental properties from which any reality can exist. (There are even many different ways to describe or view these fundamental properties. The concept of vacuum energy derives from the concept of virtual particles which derives from the concept of the energy-time uncertainty principle.)
You don’t need to be a quantum physicist to understand the problem here. Imagine that we have an equation that describes all possible universes, and setting the parameters to zero describes a lack of any universe. Albert’s point is effectively where did the equation come from, and why that equation and not another one. But the equation is not “physical stuff”. It is a symbolic representation of a descriptive concept of what it means for a universe to exist. If you get rid of the “words” to describe things you aren’t left with “nothing”, you are simply left without a language to describe the nothingness.
Yet this is what Albert and Carroll seem to be attempting. They don’t describe what this nothingness is, only what it isn’t. The mathematics allow us to describe what “nothing” actually is. Without this language the question itself is incoherent.
This is where the weakness in that approach lies and can be used to defeat itself, in my opinion. It works both ways. You can put a stop to it by recognizing that laws of physics don’t just define what is possible; they also define what is impossible. Without physical laws, anything and everything is possible. You can’t define a nothing from which something can’t emerge without using laws of physics. Any such restriction is a law of physics.
I challenge David Albert (and perhaps Sean Carroll) to describe the properties of this philosophical nothingness. Describe what it does have, not what it doesn’t have. Does it have statistical properties? Probability properties? Conservation properties? What restriction exists to keep “something” from happening? Now I ask where did those properties and restrictions come from, and why those restrictions and not others? Why do you consider that form of nothing to be some sort of default from which we need to explain where something came from? Isn’t the onus is on you to explain why that form of nothing, whatever it may be, should be the default case? Where is the evidence for that?
It seems to me implausible to describe the nothingness that Albert and Carroll are looking for. Their version of nothingness, some form of reality without properties, is self-contradictory and incoherent. I think this is Krauss’ point. It is certainly mine.
I think the only coherent questions one can ask is what are the barest coherent properties anything can have, what are all of the possible forms of reality these properties can provide, and why do we exist in this particular possible reality. In this coherent context, the base concepts have to be things like uncertainty and probability distributions. You can’t go simpler than that without losing coherent meaning.
Krauss does a decent job of describing reality at this level and is clear he’s talking about plausible answers that work with useful definitions of “nothing”. In fact, he provides a good paradigm shift. The plausible answer is that in fact there is nothing. It is simply that “nothing” can be decomposed into smaller somethings that add up to nothing. Vacuum energy (aka, Cosmological Constant), or plausibly quintessence, acts over the largest distances to push galaxies apart. Gravity acts over smaller scales to keep galaxies, solar systems, stars, and planets together. Electromagnetism acts at scales of molecules and is largely responsible for chemistry, and so on with weak at strong nuclear forces at the atomic and sub-atomic scales. The structures of the universe exist at different scales with different complexity, but it all adds up to zero like some sort of cosmic Maclaurin series expansion of nothingness. Albert has not provided any definition of nothingness that precludes this decomposition from happening, and Carroll stopped the conversation before getting that deep.
Albert’s question, and repeated by Carroll, essentially asks why the plausible exists instead of the implausible, and to me that is the kind of question that answers itself.