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anticorncob28
Post  Post subject: Is the Planck time the shortest possible time?  |  Posted: Thu Oct 20, 2016 4:58 am
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At first I heard that it is, and then read that that is only a common misconception. Wikipedia says that there is nothing special about the Planck time other than that it's a rough time scale of which quantum gravity effects are likely to become important.
But I read Victor Stenger's book "God: the Failed Hypothesis" and he said:
Quote:
In order to measure a time interval smaller than the Planck time, you would need to make that measurement in a region smaller than the Planck length ... According to the Heisenberg uncertainty principle of quantum mechanics, such a region would be a black hole, from which no information can escape. This implies that no time interval can be defined that Is smaller than the Planck time. ... Basically, by definition time is counted off as an integral number of units where one unit equals the Planck time. We can get away with treating time as a continuum variable in our mathematical physics, such as we do when we use calculus, because the units are so small compared to anything we measure in practice. We essentially extrapolate our equations through the Planck intervals within which time is unmeasurable and thus indefinable.

I don't get it, so is there time shorter than the Planck time or not?

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geordief
Post  Post subject: Re: Is the Planck time the shortest possible time?  |  Posted: Fri Oct 21, 2016 10:10 am

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anticorncob28 wrote:
At first I heard that it is, and then read that that is only a common misconception. Wikipedia says that there is nothing special about the Planck time other than that it's a rough time scale of which quantum gravity effects are likely to become important.

I don't get it, so is there time shorter than the Planck time or not?


Just a stab at this**. We may have no method of directly measuring any hypothetical change that follows from a process at a "definition" greater (lesser?) than the Planck length.

Even observing anything close to "this side" of the Planck length may be unrealistic.

However I do not think it has been claimed that the Planck length is the smallest possible length (just the smallest length that can be imagined in a realistic context ) and perhaps via speculation and an incremental build up of knowledge in the area it may be possible to have a clearer picture at some point in the future .

** I know very little about this...I only recently learned how to spell Planck ;)


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anticorncob28
Post  Post subject: Re: Is the Planck time the shortest possible time?  |  Posted: Sun Oct 23, 2016 4:17 am
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So what I'm getting at is that's they're both right. We cannot (even theoretically) measure lengths smaller than the Planck length nor obtain information of what's happening at that scale, so although smaller distances exist they are meaningless to us. Thus we cannot measure change at time intervals less than the Planck time since no object could have moved by more than one Planck length, and therefore time intervals smaller than the Planck time exist but are meaningless to us. Spacetime does NOT consist of "pixels" of smallest non-zero size.

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iNow
Post  Post subject: Re: Is the Planck time the shortest possible time?  |  Posted: Sun Oct 23, 2016 7:33 am
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So, you're asserting that spacetime is continuous not quantized, correct?

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geordief
Post  Post subject: Re: Is the Planck time the shortest possible time?  |  Posted: Sun Oct 23, 2016 9:40 am

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Is it possible for space to be quantized but for time to be continuous?


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wireless
Post  Post subject: Re: Is the Planck time the shortest possible time?  |  Posted: Sun Oct 23, 2016 3:45 pm

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This really is very interesting stuff, but when I measure time I look at my wrist watch.


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marnixR
Post  Post subject: Re: Is the Planck time the shortest possible time?  |  Posted: Sun Oct 23, 2016 5:49 pm
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yes, but is it a Planck watch ?

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anticorncob28
Post  Post subject: Re: Is the Planck time the shortest possible time?  |  Posted: Sun Oct 23, 2016 6:10 pm
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iNow wrote:
So, you're asserting that spacetime is continuous not quantized, correct?

Yes. This is what I meant when I said that spacetime does not consist of "pixels". Spacetime is continuous but meaningless to us after a certain point of magnitud.
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Is it possible for space to be quantized but for time to be continuous?

If space is quantized then it is composed of pixels. Then you need to figure out what shapes the pixels are (cubes would probably be the best option), and also make equations describing discrete transformations under acceleration, rotation, and length contraction. The functions would have to be from time (continuous) to space (discrete). I think this would be pretty difficult. And as far as I know there is no evidence that space is quantized.

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geordief
Post  Post subject: Re: Is the Planck time the shortest possible time?  |  Posted: Sun Oct 23, 2016 7:13 pm

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anticorncob28 wrote:
iNow wrote:
So, you're asserting that spacetime is continuous not quantized, correct?

Yes. This is what I meant when I said that spacetime does not consist of "pixels". Spacetime is continuous but meaningless to us after a certain point of magnitud.
Quote:
Is it possible for space to be quantized but for time to be continuous?

If space is quantized then it is composed of pixels. Then you need to figure out what shapes the pixels are (cubes would probably be the best option), and also make equations describing discrete transformations under acceleration, rotation, and length contraction. The functions would have to be from time (continuous) to space (discrete). I think this would be pretty difficult. And as far as I know there is no evidence that space is quantized.

I am just looking at your post higher up in the thread where you said 'Thus we cannot measure change at time intervals less than the Planck time since no object could have moved by more than one Planck length, and therefore time intervals smaller than the Planck time exist but are meaningless to us'

I was of the impression that movement was not required to measure time (atomic clocks etc -this subject has come up in other forums). Does that undermine your argument?
Cannot time be continuous even if space is not?


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wireless
Post  Post subject: Re: Is the Planck time the shortest possible time?  |  Posted: Sun Oct 23, 2016 8:01 pm

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marnixR wrote:
yes, but is it a Planck watch ?

No , it is an Apple Watch.
"[i][i][i] All scientific experiments and human experiences occur over time scales that are dozens of orders of magnitude longer than the Planck time,[3] making any events happening at the Planck scale hard to detect. As of May 2010, the smallest time interval uncertainty in direct measurements is on the order of 12 attoseconds (1.2 × 10−17 seconds), about 2.2 × 1026 Planck times.[4] "
[/i][/i][/i]https://en.wikipedia.org/wiki/Planck_time
https://en.wikipedia.org/wiki/Planck_time


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