The Vast Unknown

As we know, there are known knowns: There are things we know we know. We also know there are known unknowns; that is to say, we know there are some things we do not know. But there are also unknown unknowns, the ones we don't know we don't know.

- Former Secretary of Defense Donald Rumsfeld, news briefing, Feb. 12, 2002

Some people in the media ridiculed the above statement when "Rummy" said it back in 2002. And as a response to questions about the Iraq War, it certainly had some inadequacies. But from a purely epistemological point of view, it's not entirely lacking in merit. Certainly, "we know there are some things we do not know," and I would add that there are some things we cannot know.

I mean this in a strictly rational, scientific sense (at least for now): There are some things that are inherently unknowable. Heisenberg's principle of uncertainty (or indeterminacy) provides a famous example: In quantum physics, it's impossible to know simultaneously the position of a particle and its velocity; the more precisely you measure one property, the less you know about the other. And Werner Heisenberg, the physicist who first formulated this principle, called attention to the fact that this uncertainty isn't just a result of insufficiently precise measuring tools or processes, it's a fundamental property of quantum systems; that is, of matter as such.

Equally fundamental, and possibly even more so, are Kurt Gödel's incompleteness theorems. Without going into great detail (partly because trying to do so would probably give me a severe headache), these theorems prove that many formal logical systems cannot prove all of their own possible axioms and/or cannot prove their own consistency. One reading of the implications is that if the result of a formal logical proof is something we can label as "knowledge," Gödel's theorems show that there must remain some things that are "unknowable" in this sense.

These examples may seem somewhat nitpicky or irrelevant: Surely it doesn't matter much in the larger scheme of things if we can't precisely locate every particle of matter/energy in the universe or if we can't absolutely prove or disprove every possible statement.

But what if one of the inherently unknowable things is the largest scheme of things itself - the universe? In other words, what if there's an inherent unknowability at the smallest scale, the microcosmic, and also at the largest, the cosmic, and an unprovability about any guesses we might make as a substitute for direct knowing?

Within my limited and decidedly math-impaired understanding, this does appear to be precisely the case.

When we look up at the sky on a clear night, we can see millions of glowing objects in the sky - and not one of them is actually located where it appears to be. The reason, of course, is that it takes time for light to travel through space, and during the time the light is traveling from its source (a star, galaxy or planet, for instance) to our eyes, we and that source are moving. Even our nearest neighbors in space are far away enough for there to be a time lag, and thus a displacement, between their emission of light and our reception of it: It takes light about 9 minutes to travel from the sun to the Earth. And obviously, the farther away the emitter is, the longer the time lag and the larger the spatial displacement become.

What this means is that the picture our perceptions (even as we extend them through technology such as telescopes) give us of the universe is inevitably geocentric. We can adjust the picture to some extent, in effect creating a mental or conceptual map of the real current locations of celestial bodies, and this procedure obviously works well enough for us to send space probes to the Moon, Mars and so on. But as the distance involved increases, so must the uncertainty of our conceptual map.

In other words, any model we propose for the structure of the universe in its entirety will always have a major theoretical component. It's likely that we are safe in supposing that the natural physical laws that operate within our zone of certainty will also operate outside that zone, so it's fairly safe to hypothesize that the most distant regions of the universe will be like ours in a general, qualitative sense. But we cannot know the precise structure or appearance of those regions, or of the universe as a whole, in "real time," that is, as they are at any one moment.

One implication of this unknowability is that we (and by "we" I mean all intelligent beings who happen not to be blessed with supernatural omniscience) may ultimately have to accept multiple, and possibly mutually contradictory, models of the universe. As long as a conceptual model doesn't conflict with natural universal laws, insofar as we can understand those, and does account as much as possible for the phenomena that we can observe directly, we probably must accept that it's "true," even if there exist one or more alternative models with equal claims to be "true."

In some sense, we already do live with multiple universes - that is, with multiple explanations of the structure and origin of the cosmos - though there's considerable argument about which, if any, are true. And maybe a realistic understanding of the limits of certainty should prompt us to be a bit less fiercely argumentative about our varying understandings.

Perhaps to add fuel to the fire, or perhaps to help diffuse it, I'll be writing next time about an alternative model that as far as I know - and obviously, that can't be very far - hasn't previously been proposed and is very unlikely to be provable.