I am looking for some help with understanding an aspect of physics which relates to something I want to consider theologically.
Basically, it is to do with the question of existence and time.
There’s a rather nice diagram which, I gather, sums up the present state of understanding in terms of time and space.
Here, the past is ‘the region from which we can receive light’ and the future is ‘the region to which we can send light’.
Thus the longer ago a thing happened, the further the distance from which we can receive light from that event. Hence, the ‘past’ light cone contracts towards us, the observer, in the present, as we can only receive light from recent events that are correspondingly near to us in space, whereas we can receive the light of events that took place billions of years ago from equally immense distances away.
On the other hand, if we point a flash gun at the sky and set it off, the light will spread out (theoretically) throughout the universe, so the ‘future’ light cone expands away from us. After eight minutes it will have reached the Sun. After about four and a half years, it will have reached Alpha Centauri, and so on.
What I am really interested in, however, is that bit of the diagram labelled “hypersurface of the present”, and what the relationship is between ‘the present’, ‘the past’ and ‘the future’.
And here’s my key question: how can we speak of things that are not on the hypersurface of the present actually existing?
It would seem patently obvious (though I may be missing something!) that from a simply physical point of view, nothing on the ‘future’ side of the diagram actually exists at all, even if its ‘coming into being’ is both predictable and inevitable.
Does the same, however, apply to the past? If so, then the only realm in which we can talk about things actually existing is on the plane of the hypersurface of the present.
But then we have to ask the question, just how ‘thick’ is that plane? I believe some people suggest it is just a ‘Planck Moment’, but I’d be interested to know of other ideas.
I am aware that the question is complicated by aspects of Relativity theory, which mean that time is not ‘absolute’. In particular, there is the interesting, though hard to conceive, fact that events which appear simultaneous to one observer may be separated in time from the perspective of another observer.
Considered overall, then, the hypersurface of the present may be ‘wavy’ — a bit ahead for some observers, a bit behind for others, but how far might these ‘waves’ extend?
I am also aware that St Augustine of Hippo wrote a whole chapter on this subject in his Confessions. What he said is very interesting, but I’m trying to get at the physics in the first instance before looking at the theology.
What I am asking is whether it could actually be that, despite our memories of the past and our anticipation of the future, what exists, physically, is confined to a ‘micromoment’.
Thoughts and contributions would be welcome.
John Richardson
14 December 2010
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14 December 2010
