Tag Archives: simultaneity

The Alkindian Line

As my main work is being written for publication, and I’ve little time to reproduce it here, or to investigate separate issues with as much academic exactitude, I’m using this site for a while to do side things. This is one of them.

One of the tropes of science fiction, problematic so-far-as-we-know since relativity, is of traveling at many times the speed of light from one place to another. But let’s say for the sake of it that we do have this ability to move so much faster than light. Let’s say that we can move at what I’ll call alkindian speed.

By alkindian[1] speed I mean the speed that everyone up to Rohmer thought to be the one at which light actually traveled: infinite speed. With alkindian speed, when you leave is when you get there (but where you get to isn’t where you left). We arrive at a place at the same time we left somewhere else.

That is, our leaving and getting there is simultaneous. In relativistic physics, this is a problematic idea; it can’t happen with normal (“tardyon”) matter or light. So, lets modify it at little. We can say instead that we move as fast as possible and faster than light — we are moving tachyons (faster than light particles). We move so fast that there is a minimum duration to our motion, such that it can be treated as zero for all practical purposes (also, due to being tachyons, we travel backwards in time, but never mind — we only travel a little bit backwards, since we move so fast).

If we could do this — for all practical purposes, travel almost-instantly from one place to another — then clearly traveling through the universe would be just grand. There would be no more problems with how long it takes to get to very far away places. There would be a significant reduction in children complaining ‘are we there yet?’

However, there would probably be a lot more queuing. Everyone would keep arriving around the same time, then have to wait to get in. The more hip would probably deliberately move more slowly.

Look Up and What Do You See?

Cathal comes home from a business meeting near Betelgeuse, hurrying back on the Alkindian Line. At this stage, Betelgeuse is gone. It has finally collapsed under its own mass and exploded. There is nothing there. It is an ex-star. The meeting is held in the still burning dying system of clouds and debris.

Cathal arrives back on Earth. When he does, he looks up to where he just came from in the sky. He sees Betelgeuse there, in all its glory as it was over six hundred years ago; a bright glow on the belt of Orion.

I wonder: how would the star seem to Cathal? And what would he say? Would he say ‘I see the star up there now’? Or would he say ‘of course, that star is not up there now, so I do not see it’? If he denies seeing it, what would he say he really see, or would he say that he does not see anything? If he says that he does not see anything, then what does he say his experience is? Does he deny his experience outright?

These are questions I cannot answer — even though for all I know I am in the same position. When I look up at where Betelgeuse is, I say now that I see the star shining up there. But there might be nothing there — the star might have died already.

I do not know what I would think if I could interact with whatever is at that place where I see Betelgeuse to be, Perhaps the absence of anything there would make it seem illusory or dreamlike to me when I look at it shining back on Earth. Could I still think of myself as seeing it, once I know it to be gone?

One phenomenon you can easily produce for yourself like this is the after-image. Stare at a bright scene, then look a blank and darker wall. After a while, you will seem to see on the wall a similarly shaped thing to what you were looking at but with complementary colours.[2]

I say ‘seem to see’ because, as many theorists argue, you cannot be seeing anything on the wall. It must be something to do with your vision — inside your eye or brain (or mind). You aren’t seeing anything.

But the effect is quite strong. It does seem to me that I see something. However, as I don’t believe there is anything there to see, many would deny that I do in fact see it.

So, knowing there is nothing out there, I look up at the gone things in the night sky, and think: oh, I must not really see them.

Or perhaps, I look up and think: they were there. I am experiencing the past. What I am experiencing when I look up at the night sky is a memory of stars. Just as my after-images, if I experience anything, are experiences of something inside me. I just don’t know it.


1. I name this after the medieval arabic scholar Al-Kindi, who, like his predecessors, thought light traveled infinitely fast, but also theorized about optics in general. There’s a relatively recent ‘In Our Time’ about Al-Kindi (http://www.bbc.co.uk/programmes/b01k2bv8). Posts about him can be found on both The Stanford Encyclopedia of Philosophy (http://plato.stanford.edu/entries/al-kindi/) and in Wikipedia (http://en.wikipedia.org/wiki/Al-Kindi).

2. For anyone interested, the poet Goethe seems to be one of the first people to notice, describe and theorize about this.

Metaphysics of Time

Previous post: Introduction.

Roughly, one might say that the metaphysics of time concerns whether or not various attributes or features that define time, and so time itself, are possible and/or actual. This breaks down into (i) what is fundamental to time and (ii) whatever this is, whether or not it is possible or actual. The debates about these subjects have led to philosophers developing and/or taking on various metaphysical positions on time. The most notable are A-theory, B-theory, presentism and eternalism. For reasons I hope to make clear as we go along, there are others as well which are less relevant to my project here: the growing block theory, substantivalism vs. relationalism, continuity vs. discrete time, and the debates about temporary intrinsics, composition over time and persistence.

Temporal Passage

Some philosophers (A-theorists) argue that what is variously called temporal passage, the passage of time, the flow of time (or what I sometimes call A-change, e.g., Power 2009) is necessary for time. If you deny the reality of such passage, as some philosophers (B-theorists) do, then, claims the A-theorist, you deny the reality of time. Or, at least, you deny the dynamic aspect of time, of which passage is at least a necessary condition.

The point here is not that you oughtn’t deny the reality of this passage. It is just that doing so denies the reality of time. Our concept of what it is for there to be time, or for time to be real, is that there is this passage. A-theorist argue for this, but also that time is not unreal (and thus there is temporal passage). B-theorists disagree; they deny temporal passage, but not time.

Unreal Time

However, quite eminent philosophers insisted this passage is necessary for time, but deny that it and time are real.

  • One is the formulator of this terminology, John McTaggart Ellis McTaggart. Childhood atheist, Hegelian idealist, believer that ‘man is immortal’, eater of liver for breakfast — in the early 20th Century, McTaggart wrote a(n in)famous paper called ‘the Unreality of Time’. Unsurprisingly given its title, this paper presents an argument that time is unreal (McTaggart 1908).
  • Another is Kurt Godel. He thought the consequences of relativistic physics lead to the the past, present and future being, in reality, indistinguishable (Yourgrau 2005).
  •  There is also some cause to think that Einstein and Minkowski thought something similar: in debate with Bergson, Einstein states that Bergson’s concerns mean that relativity denies the time of the philosophers (meaning, so far as I can tell, the absolute distinction between past, present and future) (see the appendix of Bergson 1999). And Minkowski states that time and space are destined to be mere shadows of their former selves, reducing only to aspects of a four-dimensional manifold, spacetime.

Still, others are not so casual about denying the reality of time, and there has been some debate about what it is for time to be real. These, then, are very brief statements of the main metaphysical positions.

1. Reality in time: Presentism and Eternalism

The debate between presentists and eternalists concerns the reality of things — events, particulars, states, etc. — in any time other than a present time.

  • Presentism holds that only the present exists or is real. The past and future do not exist or are not real.

This means that anything in particular, cats, dogs, a sandwich, the big bang, feelings of irritation, my pot-belly or that great haircut I had in the late nineties: if these are only past or future (e.g., my haircut, the big bang), then they are not real; if these are present (e.g., sigh….my pot-belly, that cat staring at me, half of this sandwich by my laptop), then they are real.

  • Eternalism holds that, whatever time we call past, present or future, anything at any time exists or is real.

This means that anything in particular, cats, dogs, a sandwich, the big bang, feelings of irritation, my pot-belly or that great haircut I had in the late nineties.

Even if these are only past or future (or however else we might want to put it, see below), it is still the case that they are real. Of course, if these are present (e.g., sigh….my pot-belly, that cat staring at me, half of this sandwich by my laptop), then they are real, too.

2. Reality of temporal properties, relations and passage: A-theory and B-theory

One distinction used in the metaphysics of time is between two ways that we think of events as being ordered in time. The two ways events are ordered are described by McTaggart as two series in which think of events in time: the A-series and the B-series.

  • The A-series is the series of events running from the far past, through the recent past, through the present, through the near future, to the far future. According to different moments in time, events have different positions in the A-series. Positions in this series are sometimes also called tenses or A-properties.
  • The B-series is the series of events ordered by B-relations: precedence, simultaneity, ‘earlier than’, ‘later than’, ‘at the same time as’. No matter the moment in time, events stand in the same B-relations to each other, and thus in the same position in the B-series.
  • A-theory is the theory that there is a fundamental difference between the past, present and future.

There are two claims made by the A-theorist.

1. Tenses/A-properties/positions in the A-series/positions in the past, present and/or future are real: Things that are past are really and irreducibly past; things that are future are really and irreducibly future; things that are present are really and irreducibly present. The present and the past and future (including degrees of the latter two, e.g., ‘two days past’ or ‘three years in the future’) are sometimes called tenses. They are also sometimes referred to as A-properties or positions in the A-seriesthe name McTaggart gives to the series of events that is through the future, present and past. This position is sometimes also called the tense theory.

2. A-theorists/Tense theorists also typically advocate the idea that time needs change in events from one of these tenses to another, i.e., temporal passage (what I call ‘A-change’ above). And, also, being A-theorists, and not McTaggart, they argue that such change is real — and thus time is real.

  • B-theorists do not think that such temporal passage or A-change is real; nor do they think it is necessary for time. Only temporal relations are needed for time.

For a B-theorist, there can be real time without there being real tenses, tensed facts, change in tenses, temporal passage etc, or all the other structure endorsed by A-theorists. Instead, all that are needed and all that there is are temporal relations of precedence, simultaneity and succession: ‘before/after’, ‘at the same time’, and so on. These temporal relations are not tensed relations, and sometimes B-theorists are called detensers or tenseless theorists. Again, one is such a theorist because one holds the relevant temporal structure to be real. But it’s not as clear that B-theorists think that such a structure is necessary for time. It is more that B-theorists think it is sufficient for time and that the A-theorist’s structure — passage, fundamental tense — is not necessary for time.

The presentism and eternalist debate is often identified closely with a debate about the whether or not the A-series or the B-series is more fundamental to one’s concept of time. But there are subtle differences: in the debate about temporal properties and relations, the reality of events at other times might be held by both sides. What is at issue is whether or not the difference between the past, present and future is a real distinction, and also whether or not it is fundamental to our concept of time. The issue not whether or not the past and future are unreal. However, the latter is a question which depends somewhat on an answer to the former. For if there is no real distinction between the past, present and future (as implied by the standard interpretation of relativistic physics), it is hard to see how one can say only what is present is real.

A brief statement on the relevance of these distinctions to the project

A central point of this project is that, in shifting between A- and B- theory (or what we might also call tense and tenseless theory) as well as shifting between presentism and eternalism, one shifts between different views of what is real or exists. In doing this, one shifts between different views of what is illusory. The metaphysical condition is satisfied in different ways, leading to different discrepancies with the same phenomenological condition, i.e., the same appearance. This is what leads to different cases of illusion.

A much-discussed example in the metaphysics of time is that of temporal passage, which is supposed to be a problem for tenseless theory. But as will be seen as these posts progress, this is not the only discrepancy. There are other conflicts between concepts of time and phenomenology. This project makes what I consider to be two important claims:

(a) Not all discrepancies are due to the claimed ‘counter-intutive’ conceptions of time; the intuitive conceptions have the own particular discrepancies.

(b) Such discrepancies do not all concern what we might understand as the appearance or phenomenology of time. Because of the role time plays in the structure and occurrence of other entities, particularly concrete particulars, ones concept of time changes what it is that one can claim to perceive, to be conscious of, or even the structure of experience itself. In making the case for any illusion,  one ought to consider how one’s thinking about time plays a role.

My position in this debate

I have sympathy with B-theory over A-theory, and eternalism over presentism. But I am motivated to my views on time by relativity which means that I am not sure that I am entirely sympathetic with B-theory.

For example, simultaneity between spatially separated things is relative given modern physics and I wonder if we should strictly speaking talk about this simultaneity as a temporal relation. In relativity, simultaneity is like spatial co-location along one dimension but not along others. If I hold my hand up in front of the moon, and ignore the distance between them, I might say that both my hand and moon are in the same place, to be co-located. But is this co-location a real spatial relation, be it relative or otherwise, between my hand and the moon. If it isn’t, I feel simultaneity (again, specifically) between spatially separated things is not a real temporal relation.

Also, less relevant to relativity, I think that, actually, in practice, we move between different conceptions of time in our thinking, without necessarily noticing that we do, and this can lead to confusion about time. I think this is the source of our thinking of one view advocating a ‘static’ view of time.

I do not think we should think, as some B-theorists seem to think, that time is a static block. Whatever we are talking about in talking about temporal relations such as ‘simultaneity’ and ‘succession’, they cannot be said to either persist or desist, or remain fixed or changing, or anything else with temporality built into its expression (recently, from a conference in Durham, I’ve become aware that Oaklander is expressing similar thoughts, and I will probably post on that in future).

Other metaphysical issues regarding time: