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 ( Posts about him can be found on both The Stanford Encyclopedia of Philosophy ( and in Wikipedia (

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

2 thoughts on “The Alkindian Line

  1. testificor

    Isn’t there an obvious (though perhaps philosophically uninteresting?) difference between a retinal afterimage (effect of saturation of retinal light receptors) and an image of distant object (photons impinging on retinal light receptors)? One is an artifact of biochemistry, the other a consequence of the finite speed of light and the very large distances between stars?

    Isn’t the problem of whether stars we see at night are really “there” or not just the problem of relativistic simultaneity with bigger times and distances?

    1. timeandillusion2012 Post author

      Hi Testificor, thanks for the message,
      That’s not a philosophically uninteresting difference at all! Thanks for raising it.

      However, the context of my point is that, given a certain way of thinking about time, they both have this in common: Both after-images and distant stars SEEM to be things at a distance from us but — given a certain way of thinking — neither are things at a distance from us.

      As for the problem of whether stars we see at night are really there or not*, it isn’t a problem of relativistic simultaneity.

      — The stars as we see them at night are not simultaneous — either relatively or otherwise — with whatever we’re doing now when looking at them. Relativistic physics defines simultaneity by references frames. However, the time-lag of light coming to us from distant stars means that its source is never simultaneous with its reaching us, whatever the reference frame one might pick. In any frame, if there is a distance between the star and us, light takes time to cross it (and always at the same speed).

      — The stars might be doing something at the same time we are seeing them, however, e.g., like being the place for business meetings. In that case, relativity is relevant to how we define ‘at the same time’. But that is a different issue.

      I hope this is useful. And thanks again for the response,

      *Why ‘there’ in quotes, by the way? Do you think there’s no ‘there’ there? What’s there if ‘there”s not there?


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