Monday, March 27, 2006

About Time

Paul Davies is a physicist and science communicator and populariser with a penchant for metaphysics. I've heard him speak on both his own research as well as his musings on time when his book About Time was released. In a recent special edition of Scientific American, he considers that time, is an illusion. Ford Prefect said the same thing in The Hitchhiker's Guide to the Galaxy, "Time is an illusion, lunchtime doubly so".

Part of the reason according to Davies is due to special relativity. This theory combines space and time for an observer (which can be a sentient being or simply a measuring device) in a metric (a way of measuring things) as ds2=dx2+dy2+dz2-c2dt2. ds is the measure in this space, which includes measures of distance in (x,y,z) space and in time. Viewed like this, we see that time is in some ways a bit like space, and can be thought of as block time, in the same way that space can be thought of as a point in a cubic space. This leads Davies to suggest that a view of time as flowing is a function of the brain only.

Further, we know that physical equations are time invariant, that is, nothing changes if you run them forwards or backwards. This is not to say that things running backwards are equally likely (coffee cups don't rise to your desk and reassemble). So if there is a sense of time, it is statistical in the sense that it relies on thermodynamics, global entropy (disorder) increasing if you will.

So far, so good. However, this is where Davies descends into what New Testament scholar Tom Wright would call soggy pantheism. Davies suggests that since the flow of time is a cognitive illusion and that block time exists (incidentally, special relativity (SR) also destroys any concept of things happening at the same time, namely simulataneity), then we should stop worrying about death. This is a large jump for a few reasons.

Firstly, whilst block time may be a given, SR also tells us that there are null geodesics (experienced by photons), spacelike geodesics and timelike geodesics . Timelike geodesics are the paths masses travel when moving more slowly than the speed of light (the theoretical upper speed limit of the cosmos), and hence causality holds. Hence, for a given observer, there is a past, present and future, even if they are some sort of illusion. Anything outside of my lightcone (null geodesic) can't affect me.

Now given most of the time (!) I, and the whole world move much more slowly than the speed of light, simultaneity is a very good approximation, and time is largely linear in my experience and that of everyone else. Likewise, given thermodynamics, dead bodies don't reassemble themselves. Davies metaphysical jump is what Wright would call a folk theology to deny the significance of death.

People crave relationships with others and death ends them in our experience. They are unrecoverable because of physics, not in spite of it! Death matters. If we are going to deal with it, then it will be via technology or theology (or both) - not metaphysical sophistry as Davies expresses it.

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