Are Space and Time Identical?

Are Space and Time Identical?

I wish someone would get to the bottom of space and time, because for the life of me I can’t. They reduce me to tears, intellectually (personally, I find them congenial companions). But I think I can ask some intelligible questions about them (at least I think I can). On the face of it, they are separate and distinct aspects of reality—elements, constituents, components (whatever the right word is). You could have one without the other; they have very different properties. That’s how it seems; and yet a dualist ontology creates conundrums. Is it possible to be an identity theorist about them? Is one reducible to the other? Which is basic? Descartes might say the essence of space is extension while the essence of time is duration—and one can exist without the other. God could have created space on a Tuesday and time on a Thursday (he took a break between creating them). But on reflection this is not so obvious. If time stopped, would space continue to exist? If space disappeared, would time march on regardless? Neither of these seems self-evident: how could space continue in a world without time, and how could time continue to pass in the absence of anything in time? Space needs time in order to exist, and time is pointless without anything in it. Space needs some sort of temporal career, and time needs space with which to occupy itself. These counterfactuals suggest a necessary connection between the two, though not an identity. But whence the connection? Space and time have quite different natures and are “distinct existences”, as Hume would say. Yet time seems like an essential property of space, and space seems like an essential property of time—but these things are not identical, apparently. If they were identical, then we would have an explanation of their necessary connection; so, we might wish to think again about an identity theory.

The things existing in space and time encourage such a project: material objects and minds. For these things inextricably involve both elements; they have space and time woven into them. The spatial thing is a temporal thing and the temporal thing is a spatial thing. The material thing in space changes over time, and the mental thing in time is embodied in a spatial object (the body). Extension and duration belong to the same thing, necessarily so: what changes in time is extended in space. There is not an extended thing and a changeable thing—as if there is a spatial chair and a separate temporal chair. Material objects and minds are where space and time come together, inextricably. Might not space and time also come together in some underlying unity? And not because time is just another spatial dimension, but because its essence is bound up with space—as the essence of space is bound up with time. But I have no idea how this could be. It seems that it has to be, but I can’t imagine how. The idea seems preposterous on its face. It would require a complete rethinking of the nature of space and time, as if common sense must be wide of the mark. What if both space and time had a fine structure way beyond anything conceived in physics (and mathematics), and that this structure formed a bridge between them? What if our senses distorted the objective realities to an undreamt-of degree? What if time were a wobble in the fine structure of space, and space were a geometrization of the fine structure of time? Yes, I know this is hopelessly metaphorical and wildly speculative, but we are trying to see how the universe as we know it is so much as possible. Space and time strike us as deeply connected but resolutely disjoined—a difficult combination to pull off (compare electrons as both particles and waves).

Here is a mind-bending thought experiment: suppose you existed outside space and time (a type of god) and that you were about to enter a spatial and temporal world—what would you notice first, space or time? Would you see space first or time first or both together? Answer: I don’t know. I rather think it would be time by a small margin, but space would loom into view very quickly. According to an identity theory, it would be a simultaneous perception of the two things (really one thing)—the Hesperus of space and the Phosphorus of time. Or try to imagine a fetus having its first experience of the world: I picture it as a kind of undifferentiated perception of what we might, from the outside, describe as space-in-time. We never perceive space without an impression of time, or time without an intimation of space. Maybe our concepts of space and time are a kind of grid we lay over the world that disguises its essential unity—spacey time and timey space (noumenal space-time). But, as I say, space and time leave me baffled and lachrymose, speechless and bereft. They badly need to be got to the bottom of.[1]

[1] Would other things fall into place if space and time were rendered transparent? Would consciousness become limpidly intelligible? Would the origin of the universe become plain for all to see? Would the jigsaw puzzle of the world resolve itself into a simple pattern? Who the hell knows. Space and time are the original mind-fuck (in the technical sense of my little treatise Mindfucking, 2008).