Question regarding time

[Goodchild]

My kids have been dingdonging me about time tonight after watching the new Star Trek movie (and the time travelling issues therein). I've been able to satisfactorily explain the grandfather paradox to them after they asked about it, but during the course of explaining I came up with a question regarding time myself.

What is the smallest unit of time, essentially? I know about the Planck measurement of time, but what is getting me is whether time flows seamlessly forward or if we are jumping forward in time by Planck units? How, exactly, do we proceed forward through time?

Just something bugging me and not sure if there's even an answer :)

[premjan]

Chances are that the universe gets blurry if you look at too small a time or space interval. The Planck distance / time are candidates for this minimum scale. The flow/directional arrow of time itself may not be fundamental in microscopic terms, but only in large-scale macroscopic terms. If it is like other quantum phenomena, it won't exactly be discrete, but it will cease to be resolvable below a certain scale - sort of like a graphic pixel.

[David B]

No-one really knows, I think.

You might find this interesting, but it isn't mainstream.

http://en.wikipedia.org/wiki/Transactional_interpretation

David

[tjakey]

I kind of like the idea that "time" is a sort of average, a bit like temperature.

[BigEvil]

Just guessing but,

Time is the same as space.

The smallest increment of time would be the same as the smallest increment of space.

That doesn't really answer your question, but might lead to a different way of approaching it.

[Goodchild]

Just guessing but,

Time is the same as space.

The smallest increment of time would be the same as the smallest increment of space.

That doesn't really answer your question, but might lead to a different way of approaching it.

Yeah, it kind of broadens the question a bit because now I'm wondering if we move seamlessly through space (as it feels from our macroscopic viewpoint) or if we jump through space by Planck units.

That's what's really buggering my brain thinking about this. Are we moving through spacetime smoothly or do we, essentially, teleport at a Planck unit level?

[premjan]

There's no grid, just likely a resolution limit.

[Preno]

We don't know. People are working on both discrete and continuous theories of quantum gravity.

[David B]

Just guessing but,

Time is the same as space.

The smallest increment of time would be the same as the smallest increment of space.

That doesn't really answer your question, but might lead to a different way of approaching it.

Yeah, it kind of broadens the question a bit because now I'm wondering if we move seamlessly through space (as it feels from our macroscopic viewpoint) or if we jump through space by Planck units.

That's what's really buggering my brain thinking about this. [/b] Are we moving through spacetime smoothly or do we, essentially, teleport at a Planck unit level?

My bold.

This is a question that bugged me for a while, and I can't of course give a definitive answer, but my working hypothesis is that at the quantum level of reduction individual interactions happen in Planck time jumps, but for macroscopic objects it's smeared out into a continuum, because the planck time jumps are not synchronised, because the distance between the components of a macroscopic object like, say, me or you, means that changes don't all happen at the same time, because the speed of light stops them doing so.

I hope that makes sense of some sort:o

A couple of years ago I ploughed all the way through

http://www.npl.washington.edu/npl/int_rep/tiqm/TI_10.html#1.0

and, in my layman's sort of way, it made more sense to me than my layman's sort of understanding of the Copenhagen interpretation.

I must re-read it.

David

[Jobar]

Our best mathematical understanding of time treats it as quantized, just as is space. (Both are aspects of the same reality, spacetime.) But the truth is that understanding is only describing the measurement of time. We don't know if time is smoothly continuous, and we can only measure it in units of Planck time; or if reality actually corresponds completely to our mathematical understanding of it, and time and space don't flow smoothly but change by discrete ticks and jumps.

[Preno]

Our best mathematical understanding of time treats it as quantized, just as is space.No, it doesn't (unless, of course, you mean some specific, yet unproven theory such as LQG by "our best mathematical understanding of time"). The Standard Model doesn't treat time as discrete. Our current theories break down at Planck scales, but that doesn't mean they treat time and space as quantized.

[Rilx]

Time and space are different things than temporal and spatial properties of phenomena. Planck's measures are segments of a continuum. They exist only as a relation to the continuum. Of course the continuous time and space are "only" our metaphysics. OTOH they are the metaphysical basis of all our physical theories.

[Ray Moscow]

IIRC, the quantum loop gravity (http://en.wikipedia.org/wiki/Loop_quantum_gravity)theory is that neither space nor time are continuous. Lee Smolin seems to be its most well known proponent.