Big Mystery: Space and Time
What is the most fundamental mystery in the universe? Mind and matter is big, but space and time might be bigger. Each individually is a mystery, as has long been recognized, but there is also the mystery of their connection. How are space and time connected? Are they connected? It might be held that they are separate realities, merely existing alongside each other (“alongside” in what sense?), different in nature, only contingently connected. You could have one without the other: in some possible worlds there is space without time and in others time without space. Why should space require time in order to exist, or time require space? Aren’t they like chalk and cheese or electricity and gravity—distinct existences (to use Hume’s phrase)? Space has three dimensions (possibly more), time has just one; space is extended, time is not; space is static, time flows. When God created space he hadn’t even thought about creating time, and he could have created time without creating space. So it seems: we have such “intuitions of contingency” (compare mind and body). I open my eyes and see space, but I don’t see time (perhaps I feel it in myself); I experience the passage of time (memory, expectation), but I don’t experience the passage of space; I can get lost in space, but can I get lost in time? We apprehend space and time quite differently, and this seems grounded in metaphysical differences: so isn’t there a fundamental dualism here? Not a dualism of the material and the immaterial, but a dualism of the spatial and the temporal: the essence of space is extension (trivially), while the essence of time is continuation (the onward march). We are dealing with two sorts of “substance”: spatial substance and temporal substance (we could also say “stuff” or “quiddity”). It would be crazy to try to reduce one to the other: to claim that space reduces to time or time reduces to space. Such a view would be flagrantly eliminative, false to the facts. So space-time dualism seems the indicated position: non-identity, non-supervenience, non-reducibility. We should be “Cartesians” about space and time.
But this position faces nagging questions (just like mind-body Cartesian dualism). Are space without time and time without space really conceivable? Might there not be “illusions of contingency” here? Is it an accident that both are infinite (infinitely extended and infinitely divisible)? And don’t the two “interact” in certain ways? Material objects exist in both space and time, having both location and history. They could hardly exist in one but not the other: there couldn’t be objects in space that have no history (what kinds of objects would these be?) or objects in time that have no location (where would such objects be?). Material objects straddle space and time, having a foot in both camps. Isn’t causation essentially spatiotemporal? Causation requires contiguity in space and time (or spatial separation in the case of action-at-a-distance). And motion is defined in terms of space and time: how much space is traversed in how much time. These are points of “interaction” between space and time, analogous to perception and action in the case of mind and body. Space and time seem designed for material objects, their sine qua non; so it isn’t as if they never recognize each other’s existence. They cooperate in various ways—as when an organism is born in a certain place and then lives a life over a certain period of time. We also measure space and time using the same kinds of measuring device, viz. physical objects (rods, clocks). Don’t physicists speak of “space-time” and treat both as basically physical? Space is treated as constituted by relations between material objects, and time is regarded as equivalent to periodic processes such as rotations, orbits, and oscillations. This may be found unduly verificationist, but doesn’t it indicate a degree of affinity, commonality? The idea of space without time or time without space will strike physicists as pure mythology, not consistent with Relativity Theory (their touchstone of truth). All in all it appears that space and time can’t be quite as separate as our imaginations may suggest; and yet reducing one to the other seems preposterous. A double-aspect theory suggests itself, obscure as that may be (space and time as two sides of the same coin). The situation resembles the usual dialectic surrounding mind and body, with the same array of (unattractive) options.
We seem headed toward a mysterian position: space and time are intimately connected, necessarily so, but the connection is opaque to us, really opaque. The spatiotemporal “link” is not given to us; there is an “explanatory gap”; and we suffer from “cognitive closure” about the space-time nexus. This may arise from deep ignorance about what space and time are: we just don’t have penetrating knowledge about the nature of these things. Our conception of space is just a patchwork of superficial sensory representations combined with some mathematical artifice; our conception of time is conditioned by the practical concerns of life plus some rudimentary methods of calculation (calculus, for instance). It’s all maps and clocks, basically. We just don’t know much about the real objective deep nature of space and time, so we flounder in our understanding of how the two relate. Some may resort to the analogue of panpsychism: maybe there are little bits of time in all parts of space, or specks of space locked inside all instants. Others may boldly go eliminative (that seems to happen a lot with time). Dualism seems like the commonsense position, but commonsense is often limited when it comes to big cosmological questions (animal minds like ours are not cut out for cosmology given that food and shelter are our paramount concerns). Thus it may be that the nature of space and time lies largely concealed from us, generating misleading intuitions of contingency and impressions of ontological distinctness. Could there be some deeper reality of which space and time are merely aspects? Is this reality knowable by us? In the case of the mind-body relation we do have some relevant knowledge: we know that the brain is vital, that minds evolve and change with bodies, that there are causal relations between the two (often quite specific and intricate). But we have difficulty making sense of this knowledge, creating a viable theoretical edifice out of it. In the case of the space-time relation, however, we don’t even have even this primitive level of knowledge: all we know is that space and time come together in material objects (“the bus was going 30 miles an hour”). We don’t have systematic correlations between space and time, or causal relations, or an analogue of the brain (which at least gives us somewhere to look). We just have broad theoretical reasons for thinking that space and time must have some sort of underlying connection–it can’t be just an accident that they exist together. This is why I say that the mystery of space and time may be bigger than the mystery of mind and body: space and time are bigger in themselves, of course, and we draw an even bigger blank when contemplating their ultimate relationship. They must be connected, yet they seem radically unconnected. Thus we feel queasy when asked to consider their metaphysical separation (as in those alleged possible worlds that have one but not the other), but we are compelled to admit that we have no account of their necessary connection. Perhaps we are convinced that both are necessarily connected to matter (no space without material objects and no time without concrete events), but we hesitate over the question of radical ontological separation. For in virtue of what are the two necessarily connected, and how can they be so connected if they are what they seem? Time is one thing, space is another—how do the two manage to meet in the middle? Did God just slap them together or did he engineer an intelligible interlocking machine? Is the cosmos ultimately made of SPIME? Space stretches out and time ticks by—what have these facts go to do with each other? What is the meaning of their coexistence? Why must a universe be made like that? These are Big Mysteries, even bigger than the “world-knot” of the mind-body problem; we could call them the “cosmic-maze”. We are locked in the maze of space and time trying to find our way out, as we have both a mind and a body and struggle to untangle the conceptual knot they present. We can’t solve the maze and we can’t untie the knot—hence the mystery. But in both cases we can be sure there is a solution out there, even if we can’t produce it ourselves. Space and time fit snugly together somehow, as mind and body also do. We just have a boatload of trouble (possibly terminal) figuring out how the connection works. When I think of space my mind naturally turns to time, and when I think of time my mind naturally turns to space; and I have faith that space and time echo my thoughts in their own way. It’s just that I’m not privy to the way they join together. I have a vague feeling that time infuses space, peps it up, like alcohol in wine; and a feeling that space gives substance to time, beefs it up, like yeast in bread. But I have to confess that I have no idea what I am talking about when I say such things. I just feel that the two belong together in creating a fuller, more complete, world—that they are sadly lacking without each other. Each fills out what would otherwise be intolerably etiolated, hardly meriting the name “reality” at all. But maybe that’s because I would not exist but for their mysterious union: for I know myself to be a creature of both space and time. (Here philosophy makes contact with poetry, to which it is actually quite close, despite the appearances presented by your average philosophy department). If space and time were not connected, the universe would be genuinely meaningless—just static emptiness and transitory futility. Space would have no history and time no point (is there anything more desolate than the idea of time without even space to play with?). Space and time need to mesh if anything is to mean anything.
 Mathematical existence, conceived Platonically, is absent space and time, and perhaps there is a possible world limited to such existence; but it would be a bleak and arid world, despite Plato’s fondness for it. Numbers can’t even move (or be at rest)! What there can’t be is a possible world containing only time or only space—such a world is a mere chimera, though suggested by the appearances (or some of them). Space and time necessarily come as a package deal.