Talk:Planck time

message: ==i aint readin allat
==
If someone wants to rewrite this so that is has meaning they are welcome to add it back.
Derivation
Ignoring a factor of  \pi, the Planck mass is roughly the mass of a black hole with a Schwarzschild radius equal to its Compton wavelength. The radius of such a black hole would be, roughly, the Planck length.
The following thought experiment illuminates this fact. The task is to measure an object's position by bouncing electromagnetic radiation, namely photons, off it. The shorter the wavelength of the photons, and hence the higher their energy, the more accurate the measurement. If the photons are sufficiently energetic to make possible a measurement more precise than a Planck length, their collision with the object would, in principle, create a minuscule black hole. This black hole would "swallow" the photon and thereby make it impossible to obtain a measurement. A simple calculation using dimensional analysis suggests that this problem arises if we attempt to measure an object's position with a precision greater than one Planck length.
This thought experiment draws on both general relativity and the Heisenberg uncertainty principle of quantum mechanics. Combined, these two theories imply that it is impossible to measure position to a precision greater than the Planck length, or duration to a precision greater than the time a photon moving at c would take to travel a Planck length. Hence in any theory of quantum gravity combining general relativity and quantum mechanics, traditional notions of space and time will break down at distances shorter than the Planck length or times shorter than the Planck time.
::I think it was a mistake to remove this section. The articles on planck length and planck time imply that these constants have a special physical significance as being some sort of limits to our theory, and not just unit games - but don't explain why. This text (I have no idea who wrote it, by the way) does, or so it seems.Nyh (talk) 14:01, 14 October 2009 (UTC)

message: Does anyone else have an issue with the following under 'Simple Definition':
"The speed of any object is limited by Einstein's laws of relativity, which state that nothing can travel faster than the speed of light in a vacuum (denoted c)."
I understand that this is for a simplified explanation, but it's just plain not true. Einstein only stated that an objects mass would become infinite if traveling at the speed of light. Also, faster-than-light observations and thoughts have been carried out and discussed here:
http://en.wikipedia.org/wiki/Speed_of_light#.22Faster-than-light.22_observations_and_experiments
I didn't want to alter the original article since I'm new to the wikipedia, but wanted to leave note of this in case the author would like to respond and possibly reconsider an edit.
Respectfully,
Dave Quirus          26 Aug 2005
     Infinite mass is the same thing as impossible, and if an object could actually travel >c in a vacuum (ignoring shenanigans like an alcubierre drive or the casimir effct), it would be capable of carrying information, which IS prohibited in relativity, isn't it?
I could be wrong, but I was pretty sure that's how it worked.  The "nothing" could be changed, but other than that...
24.125.105.48 (talk) 03:35, 5 April 2009 (UTC)
thread_title: Concerns regarding following statement

message: So there's the Planck length and the Planck time: does this mean the world can be thought of as a 3 dimensional grid, each cell sized to the Planck length, and iterations running in every Planck time (i.e. the Planck time is the "FPS value" of the universe)?
> The Planck time is the time it would take a photon travelling at the speed of light to cross a distance equal to the Planck length. However, this may not be taken as a "quantum of time."
Please elaborate. If it can't be taken as a quantum of time, there must be a reason. 67.67.250.168 02:41, 19 March 2006 (UTC)
thread_title:  A discrete world? 

message: Time references this topic in the "Time quanta section": Time#Time_quanta.
I think that is misleading and I opened a discussion at Talk:Time#Time_quanta.3F
Your opinion?
206.169.169.1 18:43, 4 October 2006 (UTC)
thread_title:  Referenced from [[Time]] under "Time quanta" 

message: I think the current figure is off by two orders of magnitude. From the beginning:
75y/life * 365d/y * 24h/d * 60m/h * 60s/m * 5.3912 * (10^40)tP/s = 1.27512662 × 1050tP/life.
I think the error came as follows: the tP per person was calculated as 77y/13.7By of 8*1060 tP per universe. But 4.3*1017s/universe (which matches my figures) times 5.4*10^44tP/s gives 2*1062, not 8*1060. Anyone concur? Debivort 20:46, 26 March 2007 (UTC)
replies: text: 75 years times about 3.16e+7 seconds/year gives 2.37e+9 seconds per lifetime. Divided by the Planck time, this is about 4.4e+52 Planck times. The lifetime of the universe, at 13.7 GY, is 4.33e+17 seconds, or 8.0e+60 Planck times. The numbers in the article appear to be consistent with each other. Checking your figures, your quotient for division is not quite correct (you're flipping the exponent and multiplying by Planck time, instead of multiplying by (1/tP)). --Christopher Thomas 21:01, 26 March 2007 (UTC)
replies: text: Yes you are right. I misread the definition as 5.4*10^44tP/s rather than 5.4*10^-44s/tP. Sorry for the confusion. Debivort 22:54, 26 March 2007 (UTC)
thread_title:  person's age in planck units 

message: In the introduction to this article, it is written that:
"One Planck time after the event is the closest that theoretical physics can get to it, and at that time it appears that gravity separated from the other fundamental forces."
The contemporary view of gravity is based on Einsteins theory of general relativity, which states that the observation of gravity is a consequence of the curvature of space-time. As such, is is completely meaningless to discuss gravity separating from other fundamental forces, since it's not a really a "force" per se. i think what the author was intending to say was that gravity would have been created the moment the universe had size larger than a singularity. 
I am refraining from editing this bit until i get some corroboration. any opinions? please CC any replies to my talk page. --Shaggorama 01:29, 13 September 2007 (UTC)
thread_title:  Gravity is not a force 

message: The very last paragraph challenges the existence of planck time based on pictures being too crisp from outer space.  This sounds bogus to me, because the length and time scales involved are truly miniscule, and you should be able to see crisp images just fine even from the most remote regions of space.  We are limited in observation only by the size of the photon, and that size is easily small enough to bring back a high resolution image from space.  What do you say to deletion of this paragraph?--MaizeAndBlue86 (talk) 23:49, 3 March 2008 (UTC)
thread_title:  Planck time challenged? 

message: I have to question that value for the planck time.  Yes, it's true that light can travel the planck length in that amount of time, but no meaningful signal could be interpreted from that short a time (i.e. the wavelength of light is usually so much greater than this length that it would take several, perhaps even billions of planck times to even cover 1 period of oscillation).  The shortest wavelength of light possible is 2x planck length because the signal must be able to go from high to low.  Shouldn't that be the planck time? - The time it takes light to travel 2 planck lengths?  That is the shortest time that one could possibly recover complete information about a signal.--MaizeAndBlue86 (talk) 23:59, 3 March 2008 (UTC)
thread_title:  Correct value for planck time? 

message: That is not significant evidence that light is not particulate.  My telescope gets bad resolution, does that mean that light is particulate?
It has been proven time and time again that light is a particle, and particles have size, hence the planck length and hence the planck time.  You cannot measure something smaller than the measuring particle itself.--MaizeAndBlue86 (talk) 23:40, 6 March 2008 (UTC)
replies: text: I think you cannot compare the hupple telescope to your telescope. The Deep Field picture is the farest and sharpest ever taken. And it is as simple as that: It shouldn't be that sharp! There has been measured something smaller than the planck time, that is a simple fact in this article. And serious scientists are saying that, publishing their findings in serious journals. So, if we take the "No Original Research" principle serious, we can not depend on your or my opinion as long as you haven't published it (or I haven't published it), lets say in a journal. So let us just stay with the facts, which are: The scientists say something's wrong because the Hupple Deep Field picture is sharper than expected. I assume that is a simple principle we can agree on and will undo the undo. If you're still unhappy with that, please explain me why we shouldn't include it, but not on Original Research by yourself or because of what you think or I think. Bring me an article (placed in time after that one) that says: "Oh my god, we were mistaken" or "Uh, we made a serious error in our measurement", than we will delete it ok? Or if you can bring me an article of another scientists saying "That's nonsense" referring to that publishing in another publishing (journal or so) than we can at least print both opinions (but shouldn't delete one of them). As long as that's not the case, lets stay with the facts, even if they are not how we like them to be... it wouldn't be science if we already know everything and wouldn't have a few problems in our theories right? ;) greetings, ColdCase (talk) 01:52, 7 March 2008 (UTC)
replies: text: I wanted to add: If you have a good idea for rephrasing the sentences in a way they would satisfy all of us, just say it. A good compromise is still the best way to end a depate ;) ColdCase (talk) 01:58, 7 March 2008 (UTC)
thread_title:  Hubble telescope challenges planck time 

message: This is my proposed contribution to this article, I do not consider it original research, because it doesn't claim any direct conclusions.  It merely draws a legitimate connection and leaves open the results, which need to be officially "accepted" by the scientific community to be concluded.  I strongly believe it would contribute to the overall quality of the article.  Please read:
===The Universe as a discrete-time system===
The presence of a ‘smallest time’ in the universe means that time moves in discrete segments, and not continuously.  However, since these segments are so small on the scale of human measurability, it is often a good approximation to assume time and space are continuous.  The differences become apparent on extremely small length and time scales, and are therefore important for understanding quantum physics.
Discrete-time sampling theorem says that a discrete signal cannot contain higher frequencies than 1 cycle per 2 samples, where a cycle corresponds to a wave going from ‘high’ to ‘low’.  In other words:
:f_m = \frac{1}{2T_s}
where fm is the maximum possible frequency, and Ts is the period between each sample.  In the case of our universe this sample period is the planck time, and that corresponds to a maximum measurable frequency of 
:9.276 \times 10^{42}\mbox{ Hz}
Not to say that higher frequencies can't happen, only that we can't measure them with the limited ‘sampling rate’ of the universe.
So what happens to all of the higher frequencies?  In discrete signal processing, if one tries to sample a continuous signal whose frequency content is too high, aliasing occurs.  So instead of it being a high frequency, it appears as a low frequency.  In effect, going past this frequency limit is the same as starting over at low frequencies again and moving up from there, with most of the original signal content lost in-between samples.
The relevance of this fact for the structure of the universe is not yet known, but it may have the power to explain several phenomenons in the world of quantum physics.  For example, why space and time seem to become “fuzzy” around distances near the planck length, and times near the planck time (see quantum foam).
:Please post comments, I would like to hear what people think!--MaizeAndBlue86 (talk) 17:18, 18 March 2008 (UTC)
replies: text: I'm not sure what an "entity" would be in physics, nor how one would determine what qualifies and what does not.  It is not a formal concept I am familiar with, can you clarify or define it?  Thanks. Wwheaton (talk) 19:50, 18 March 2008 (UTC)

text: * an entity would be a "thing" (technical definition). Not all nouns refer to things. Saying that "time moves in ..." not only speaks of time as a thing, it is speaking of time as if it were an agent that can "do" something. The main topic in ontology is "what nouns are things?"--JimWae (talk) 23:44, 18 March 2008 (UTC)

text: The vacuum of space and time can, in fact, be modeled statistically as a "sea of photons", or a photon gas.  That is consistent with space and time being made up of smallest entities, or "building blocks".  If the building block is the photon, then it's hard to measure something that's smaller than that.  You definitely can't do it with another photon.--MaizeAndBlue86 (talk) 21:01, 18 March 2008 (UTC)

text: * models are certainly useful, but they do not "tell" us anything about the "real" underlying "structure of the universe" - they only help us model the universe. That which we cannot measure, we might be better off not drawing too many conclusions about --JimWae (talk) 23:44, 18 March 2008 (UTC)
thread_title:  Proposed new section 

message: The presence of a ‘smallest time’ in the universe means that time moves in discrete segments, and not continuously.  However, since these segments are so small on the scale of human measurability, it is often a good approximation to assume time and space are continuous.  The differences become apparent on extremely small length and time scales, and are therefore important for understanding quantum physics.
Discrete-time sampling theorem says that a discrete signal cannot contain higher frequencies than 1 cycle per 2 samples, where a cycle corresponds to a wave going from ‘high’ to ‘low’.  In other words:
:f_m = \frac{1}{2T_s}
where fm is the maximum possible frequency, and Ts is the period between each sample.  In the case of our universe this sample period is the planck time, and that corresponds to a maximum measurable frequency of 
:9.276 \times 10^{42}\mbox{ Hz}
Not to say that higher frequencies can't happen, only that we can't measure them with the limited ‘sampling rate’ of the universe.
So what happens to all of the higher frequencies?  In discrete signal processing, if one tries to sample a continuous signal whose frequency content is too high, aliasing occurs.  So instead of it being a high frequency, it appears as a low frequency.  In effect, going past this frequency limit is the same as starting over at low frequencies again and moving up from there, with most of the original signal content lost in-between samples.
The relevance of this fact for the structure of the universe is not yet known, but it may have the power to explain several phenomenons in the world of quantum physics.  For example, why space and time seem to become “fuzzy” around distances near the planck length, and times near the planck time (see quantum foam).
:Please post comments, I would like to hear what people think!--MaizeAndBlue86 (talk) 17:18, 18 March 2008 (UTC)
thread_title: The Universe as a discrete-time system

message: A Planck Unit is the smallest measurable unit. It does not follow that the smallest MEASURABLE unit is a feature of "space-time itself". There has been no determination that either space or time are entities, no less entities with properties. Planck units have definite implications for the limits of measurement, but since it is not clear there IS any underlying "structure of the universe", it is premature (at the very least) to comment in that regard --JimWae (talk) 17:34, 18 March 2008 (UTC)
replies: text: I'm not sure what an "entity" would be in physics, nor how one would determine what qualifies and what does not.  It is not a formal concept I am familiar with, can you clarify or define it?  Thanks. Wwheaton (talk) 19:50, 18 March 2008 (UTC)

text: * an entity would be a "thing" (technical definition). Not all nouns refer to things. Saying that "time moves in ..." not only speaks of time as a thing, it is speaking of time as if it were an agent that can "do" something. The main topic in ontology is "what nouns are things?"--JimWae (talk) 23:44, 18 March 2008 (UTC)

text: The vacuum of space and time can, in fact, be modeled statistically as a "sea of photons", or a photon gas.  That is consistent with space and time being made up of smallest entities, or "building blocks".  If the building block is the photon, then it's hard to measure something that's smaller than that.  You definitely can't do it with another photon.--MaizeAndBlue86 (talk) 21:01, 18 March 2008 (UTC)

text: * models are certainly useful, but they do not "tell" us anything about the "real" underlying "structure of the universe" - they only help us model the universe. That which we cannot measure, we might be better off not drawing too many conclusions about --JimWae (talk) 23:44, 18 March 2008 (UTC)
thread_title: Replies

message: The Orders of Magnitude table indicates that Planck time is the order of 1E-26 sec, but the text shows this should be the order of 1E-44 sec. The text mentions 1E-26 relative to the attosecond. Please resolve. GilesW (talk) 15:06, 24 August 2008 (UTC)
thread_title:  Orders of Magnitude table 

message: I was wondering if the Plank length could be fine tuned, using the neutrino instead of a photon. Brian Pearson (talk) 13:38, 10 September 2008 (UTC)
thread_title:  Fine tuning the Plank length? 

message: Both articles talk about "measuring" times on the attosecond scale, but both specify it's around 100 attoseconds as far as I can tell.  Here's what the 2006 one said:  
:"The researchers devised a new technique to 'see' the motion of protons, one of the building blocks of an atom, in molecules of hydrogen and methane.  The technique involves firing a very short but intense laser pulse at a molecule, which rips an electron away, leaving the molecule in an excited ionised state.  The electron is then drawn back to the molecule, and when it collides a very short burst of x-rays is released.  'That has encoded information within it about the state of the molecule at the point of re-collision, and can give us information about the motion of the protons in this molecule,' Dr Tisch told the BBC News website.  The process is ultra-fast, and the team was able to observe the effect the laser had on motion in the molecules with an accuracy of 100 attoseconds - the fastest ever recorded.  'Slicing up a second into intervals as miniscule as 100 attoseconds is extremely hard to conceptualise. It's like chopping up the 630 million kilometres from here to Jupiter into pieces as wide as a human hair,' explained Dr Tisch."  
According to the calculation, Planck time is about 5.4E-44 and 100 attoseconds is 1E-16.   By my calculations, that's 1.85E26 different although I could have gotten that wrong.   Please correct if so.  Sln3412 (talk) 19:00, 25 June 2010 (UTC)
thread_title:  Shortest measured time 

message: Can't read the equations.  They come out as fuzzy gray souble-lines on a black background.  Same result in five different browsers.  Any chance of using a more legible font, or maybe presenting them as a simple JPG or GIF graphic?  —Preceding unsigned comment added by 74.92.174.105 (talk) 23:35, 21 October 2010 (UTC)
thread_title:  Better font / graphic for equations? 

message: The article claims:
:All scientific experiments and human experiences happen over billions of billions of billions of Planck times, making any events happening at the Planck scale hard to detect.
Even if that stmt is trying to express "far more", it is an extreme understatement. The human mind is not able to perceive anything shorter than abt 1/24 s, which makes billions³ (= (10⁹)³ = 10²⁷) pretty lame. The number is more like 10⁴² to 10⁴³, which is "one to ten tridecillions" in the short scale of US. Won't an expression like "orders of magnitude more" be more suitable and less malformedly dramatic? Rursus dixit. (mbork3!) 18:38, 28 January 2011 (UTC)
thread_title:  Billions of billions of billions??

message: "Theoretically, this is the smallest time measurement that will ever be possible".  This appears in the article, and is cited to a source which doesn't really go into any detail.  This needs more of an explanation, as I for one don't see why it is "theoretically" the smallest time measurement that will EVER be possible. --T.M.M. Dowd (talk) 17:25, 24 April 2011 (UTC)
replies: text: It is fully explained and as well as possibly can be to people who dont study this rather astoundingly complex system, right under "Physical Significance." You would have to try very hard (not reading half the page) to come away with a question about how it funcitons. 74.132.249.206 (talk) 05:02, 2 September 2011 (UTC)
thread_title:  Theoretically, this is the smallest time measurement that will ever be possible 

message: That all looks really complicated. And Im bad at math. But could someone post what the planck time looks like in standard notation? (as in, 0.0000~1 etc seconds) alternatively if such a page already exists, i'd like to either be pointed to it or have it pointed out on the page here. 74.132.249.206 (talk) 04:56, 2 September 2011 (UTC)
thread_title:  Some sane numbers? 

message: The article talks about "processes which happen at less than Planck Time durations" which, please forgive me if I'm a dullard, I had though were not possible. No event takes place at less than a Planck Time, it's granular to the point where it becomes a logical absurdity to speak of "less than Planck" much as it is a logical absurdity to speak of "before the Big Bang." Am I totally wrong? Damotclese (talk) 19:13, 8 December 2011 (UTC)
replies: text: There is nothing special about Planck Time. It is not the smallest possible time or anything like that. It just a number. Nothing more. 2A02:168:F609:0:7855:CA84:B8D8:C659 (talk) 22:19, 10 August 2019 (UTC)
thread_title:  "Less than Planck Time" 

message: The page says that the smallest time interval that was directly measured was of order of 12 attoseconds, but another source says it is 20 attoseconds. http://www.sciencedaily.com/releases/2010/06/100624144109.htm 
Please confirm.
::, the smallest time interval uncertainty in direct measurements is on the order of 12 attoseconds (1.2 × 10−17 seconds), about 3.7 × 1026 Planck times.
:The one you posted is from June 2010, but writer must not have been aware of May one. Also, 12 attoseconds is the level of accuracy, while 20 attoseconds is the event length.--JimWae (talk) 10:50, 19 April 2012 (UTC)
thread_title:  The smallest time interval that was directly measured was of order of 20 attoseconds. 

message: ...because not to is just ridiculous. I have reverted an edit from March 2013 which removed it. (It may well have been well-intentioned, but was clumsily done.) Richard75 (talk) 22:02, 16 December 2013 (UTC)
thread_title:  This article needs to say how long the Planck Time actually is... 

message: pysics  is the biological meaning to quatum asro nominal  — Preceding unsigned comment added by 80.4.133.105 (talk) 19:01, 6 October 2014 (UTC)
thread_title:  physics 

message: >"The Planck time is considered by many physicists to be the shortest possible measurable time interval; however, this is still a matter of debate."
>"The reciprocal of the Planck time, which is Planck frequency, can be interpreted as an upper bound on the frequency of a wave. This follows from the interpretation of the Planck length as a minimal length, and hence a lower bound on the wavelength."
>"Because the Planck time comes from dimensional analysis, which ignores constant factors, there is no reason to believe that exactly one unit of Planck time has any special physical significance."
--The last claim appears correct to me, but it is contradicted by the other two, which imply (or imply that many scientists believe) that the Planck time and Planck length are something akin to the speed of light, i.e. their specific values _are_ of special physical significance. There are similar claims in the article Orders of magnitude (time):
>"One Planck time [...] is the briefest physically meaningful span of time"
>"[1 Planck time is] Presumed to be the shortest theoretically measurable time interval (but not necessarily the shortest increment of time - see quantum gravity)"
It would not be sensible to presume that an interval of 5.39×10^−44 s could be measured in theory, but not 5.2×10^−44 s, just because this particular number came out of dimensional analysis and was given a name, yet until they are rewritten or removed, that is the substance of these claims and that is what a certain proportion of readers will believe. I shan't edit though because IANAP. Glumblebee (talk) 07:25, 25 June 2019 (UTC)
thread_title:  Exaggerated physical significance 

message: An editor has asked for a discussion to address the redirect Shortest time interval. Please participate in the redirect discussion if you wish to do so.  Steel1943 (talk) 22:04, 20 September 2019 (UTC)
thread_title:  "Shortest time interval" listed at [[Wikipedia:Redirects for discussion|Redirects for discussion]] 

message: An editor has asked for a discussion to address the redirect Smallest time interval. Please participate in the redirect discussion if you wish to do so.  Steel1943 (talk) 22:08, 20 September 2019 (UTC)
thread_title:  "Smallest time interval" listed at [[Wikipedia:Redirects for discussion|Redirects for discussion]]