Thursday, June 09, 2005

Time Again

Part 2 of a series on the nature of Time

As I said in a prior post, recent notoriety of one Peter Lynds and a paper he wrote in 2003 has caused me to revisit my assumptions about time.

While I still like the Universe As Simulation theory, it does have some weak points. (Do you know what they are?) Mr. Lynds "theory" (if writing a philosphy paper and publishing it in a physics journal makes a theory) is that there is no such thing as a point in time.

Now I agree that the concept of a point having physical reality is one I've struggled with as well. Even in my Universe as Simulation theory, the smallest unit of distance (or the smallest cell of the simulation) is a Planck Length. This would mean that, even though very small, there is still a "distance" covered by the smallest unit of space. I don't think there is any physical manifestation of this mathematical concept called a point. Neither does Mr. Lynds.

As a result, neither is there a physical manifestation of a point in time. According to Mr. Lynds, there is only Interval.
For example, if two separate events are measured to take place at either 1 hour or 10.00 seconds, these two values indicate the events occurred during the time intervals of 1 and 1.99999... hours and 10.00 and 10.0099999... seconds, respectively.
He goes on to say that no matter how small you make the interval, it can't be zero. So there is no static instant in time at which the position in space a body in relative motion can be precisely determined.

(In fact, this same concept applies to space. When you say an object is at a set of spatial coordinates, it is really "smeared" over an interval of coordinates determined by the size of the object. So even if time were quantized, it's still meaningless to say that an object is at a precise set of coordinates at a specific point in time.)

Mr. Lynds goes to say that it is this very fact, that there isn't a real physical "instant" in time that allows for movement in the first place. Something about if there really were static instants, then objects would be frozen in place in a given instant, with no way to "advance" or move to the next discontinuous instant. (Clearly he hasn't seen the Universe aas Simulation concept, where objects "move" from static instant to instant because they are just calculations of properties that say the position changes).

This indeterminacy of time and position means that either can only be measured as bounded by uncertainty within the limits of Heisenberg's uncertainty principle and quantum uncertainty. Physics experiments (so far) don't disagree with these limits on real world measurements, although whether the limits are due to this "interval" theory or some other fundamental physical principles (say derived from string theory) has not been shown.

Although I'm not sure I understand exactly what he is driving at, it seems that he is almost saying that really time, which can only be represented as intervals, is a derivative measurement of movement through space. It is only the movement through space that causes the illusion of time, and only the order of the positions of bodies in motion that provides the illusion that it flows in a particular direction.

As a result of there not being any reality behind the concept of a static point in time, so to do all the equations in physics which rely on a static point in time fail to represent reality. And this is all of them: velocity, momentum, acceleration, frequency, wavelength, rest mass, energy...they all need to be rejiggered to handle intervals rather than point values. (But does the concept of point work pretty well in given a reasonably approximate answer, accurate enough for most uses? You betcha.)

The sad news in all of this is that if true, there could never be any such thing as time travel (at least, not in the reverse "direction"). I guess this is why no time travellers showed up to the recent Time Traveller Convention.

But while it may be true that time can only exist in the reality of an interval, this doesn't eliminate the Universe as Simulation, which already had that concept baked in. And it does nothing to explain why we have fundamental limits like c (the speed of light in a vacuum), while this could be consistent with the "clock speed" of the universal computer.

Just because we don't like the Russian matryoshka doll implication of the Universe as Simulation doesn't mean that it isn't true. Just because we can't imagine what the "container" for the universal computer could be like (existing not in time or space), doesn't mean that it doesn't exist. I doubt any of my programs have a concept of the "real" world in which they run. There are just bits flipping according to some rules, each flip at a clock interval.

I'll try to wrap this up this weekend with my modified Universe as Simulation theories. (Ok - they're not theories unless I have math to go with them. Call them hypotheses).

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