Saturday, April 09, 2005

Epistemology, ontology and FTL travel

On the blogsite ID: The future, Jay Richards is using these terms to talk about the effect of special relativity. He has received a lot of scathing comment - I suspect more because he is a proponent of ID than out of any serious attempt to engage with the issues.

I understand where he is coming from. This isn't a scientific comment, but probably just a reflection of something that I am uneasy about because it hasn't been taught me clearly. Faster than light travel is impossible we are told, because nothing can travel faster than light; light defines the shape of the universe; and if you travel faster than light you would therefore be in two places at once.

But let's suppose you could travel faster than light. Suppose I manage to travel instantaneously to a fictional planet orbiting Alpha Centauri, and look back towards Earth through an infeasibly powerful telescope. I would be able to see myself doing the things I was doing four years ago - this is "Einsteinian"/"epistemological" time, and the argument is that because nothing travels faster than light, and light defines the shape of the universe, I would therefore be in two places at once. But I think this is a circular objection by definition, as far as I can tell - I wouldn't be able to communicate with myself four years ago - because if I then instantaneously travelled back, my "ontological"/"real" time would have moved on, and I wouldn't be four years ago any more. Similarly, if I were to beam back to earth television signals of Alpha Centauri, they wouldn't get there until four years had passed - by which time, according to earth's "ontological"/"real" time, I would already have left for Alpha Centauri.

In other words, I think the sense of this is that there is an "epistemological" line of time - which relates to the fact that communication doesn't take place above the speed of light (I can only look backwards to where I was/something else is at the speed of light). There is also an "ontological" line of time - that is, if I look 13 thousand million light years away, I am looking at what happened 13 thousand million years ago at that point in space - but that the age of the universe there now is not 2 thousand million years, it is the same as it is here - even though there's no way for us to know what it is like there now (other than our Copernican assumption, which is that it is similar to how it is here now). That isn't nonsense - there are many aspects of relativity that are counterintuitive, but to argue that there are parts of the universe "ontologically" "now" that are younger than we are is silly - epistemologically they are, yes - which is how we can find out about the early universe - but that doesn't mean that their "real" age is less than ours - it just means we can't know about what they are like now whilst communcation is limited to the speed of light.


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