# What is the shortest time measurable... **URL:** \ **Category:** Factual Questions\ **Created:** [January 14, 2013, 5:21am UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138 "2013-01-14T05:21:07Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Qwertol](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Qwertol](https://boards.straightdope.com/u/Qwertol)\ **Post date:** [January 14, 2013, 5:21am UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/1 "2013-01-14T05:21:07Z")
with current technology? And by ‘current technology’ I mean not only devices that do exist now but also the ones that could be built with current state of knowledge… How precise (what’s maximum deviation) is (would be) that measurement? ---
**Author:** ![penultima\_thule](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/penultima_thule/32/3833_2.png) [@penultima\_thule](https://boards.straightdope.com/u/penultima_thule)\ **Post date:** [January 14, 2013, 5:39am UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/2 "2013-01-14T05:39:33Z")
The Large Hadron Collider provided an estimate for the mean life time for a Higgs Boson particle of about 1.6×10−22 seconds. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [January 14, 2013, 6:14am UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/3 "2013-01-14T06:14:01Z")
The [Planck Time](http://en.wikipedia.org/wiki/Planck_time). 5.4x10[sup]-44[/sup]s. That gets you the absolute limit. Getting shorter than we do now measurable times probably just needs more energy. You are fighting the noise and uncertainly. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [January 14, 2013, 6:25am UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/4 "2013-01-14T06:25:22Z")
> [@Francis\_Vaughan](#): > > The [Planck Time](http://en.wikipedia.org/wiki/Planck_time). 5.4x10[sup]-44[/sup]s. That gets you the absolute limit. Getting shorter than we do now measurable times probably just needs more energy. You are fighting the noise and uncertainly. How would more energy produce a smaller measure of time? Something oscillating at a higher frequency? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 14, 2013, 3:23pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/5 "2013-01-14T15:23:48Z")
> [@](#): > > The Planck Time. 5.4x10[sup]-44[/sup]s. That gets you the absolute limit. Well, maybe. We don’t actually know that the Planck time is an absolute limit. Almost everything that people say about the Planck scales is just educated guesswork. To answer the OP’s question about current technology, the LIGO gravitational wave detectors measure a change in the length of the interferometer arms of 4e-19 meters. Since this change in length measurement is done via phase matching of light waves, it could also be considered as a measurement of time, corresponding to a time of about 1.3e-27 seconds. ---
**Author:** ![AK84](https://avatars.discourse-cdn.com/v4/letter/a/85e7bf/32.png) [@AK84](https://boards.straightdope.com/u/AK84)\ **Post date:** [January 14, 2013, 3:31pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/6 "2013-01-14T15:31:27Z")
Ok please someone explain this is laymans terms, so we can gain perspective. In the following format, the really short periods are to one second as one year is to \_\_\_\_\_\_\_\_ years. ---
**Author:** ![JerrySTL](https://avatars.discourse-cdn.com/v4/letter/j/e274bd/32.png) [@JerrySTL](https://boards.straightdope.com/u/JerrySTL)\ **Post date:** [January 14, 2013, 3:32pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/7 "2013-01-14T15:32:16Z")
The time between the traffic light turning green and the car behind me blowing their horn. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [January 14, 2013, 3:47pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/8 "2013-01-14T15:47:41Z")
> [@AK84](#): > > Ok please someone explain this is laymans terms, so we can gain perspective. In the following format, the really short periods are to one second as one year is to \_\_\_\_\_\_\_\_ years. It isn’t going to help. There are 3x10[sup]7[/sup] seconds in a year. The Universe is say 1.4x10[sup]10[/sup] years old. So the Universe is about 4x10[sup]17[/sup] seconds old. The time period **chronos** cites = 10[sup]-27[/sup]s is thirty billion times smaller than the ratio of one second to the age of the universe. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 14, 2013, 3:47pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/9 "2013-01-14T15:47:59Z")
> [@](#): > > Quoth **AK84** : > > Ok please someone explain this is laymans terms, so we can gain perspective. In the following format, the really short periods are to one second as one year is to \_\_\_\_\_\_\_\_ years. It won’t help. The time I mentioned is to one second as one second is to 10[sup]19[/sup] years. But now you need perspective on what 10[sup]19[/sup] years is. That’s about a billion times longer than the current age of the Universe. > [@](#): > > Quoth **JerrySTL** : > > The time between the traffic light turning green and the car behind me blowing their horn. No, that’s usually about two seconds. I don’t know why that joke persists so, when anyone who pays attention to traffic can tell just how long it really is. ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [January 14, 2013, 6:06pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/10 "2013-01-14T18:06:24Z")
Truth is relative to time & place. Facts are not. So, if you want a true answer, there is one for this moment but tomorrow it likely will be wrong. If you want a factual answer, you must leave time out of it. You can’t do that… yet. ---
**Author:** ![Qwertol](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Qwertol](https://boards.straightdope.com/u/Qwertol)\ **Post date:** [January 14, 2013, 10:27pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/11 "2013-01-14T22:27:03Z")
About the examples given here: could you consistently make one measurement right after another, in other words could you make a clock out of it? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 14, 2013, 10:58pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/12 "2013-01-14T22:58:35Z")
> [@JerrySTL](#): > > The time between the traffic light turning green and the car behind me blowing their horn. Here in Panama, we call that the “Panasecond.” It is theorized that, since cars sometimes start blowing their horns _even before the light has changed_, faster-than-light travel must be possible. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [January 14, 2013, 11:06pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/13 "2013-01-14T23:06:48Z")
_Scientific American_ from 1984 has a [short piece](http://www.scientificamerican.com/article.cfm?id=what-is-the-fastest-event) with same OP. The shortest time interval ever measured appears to 20 attoseconds, 20 billionths of a billionth of a second. In 2010 physicists in Berlin were measuring the delay between excitation of an atom and emission of an electron. [Cite](http://esciencenews.com/sources/popsci/2010/07/27/german.scientists.measure.how.fast.electron.jumps.shortest.time.interval.ever.measured) (from PopSci source, unfortunately, but it was the quickest I could get my hands on, and seems legit). ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 15, 2013, 12:14am UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/14 "2013-01-15T00:14:19Z")
That’s about five orders of magnitude longer than the lifespan of the Higgs, which is a measurement of basically the same sort (interval between an excitation being produced and that excitation decaying). ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [January 15, 2013, 12:27am UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/15 "2013-01-15T00:27:30Z")
> [@penultima\_thule](#): > > The Large Hadron Collider provided an estimate for the mean life time for a Higgs Boson particle of about 1.6×10−22 seconds. (My cite of 20 attoseconds.) > [@Chronos](#): > > That’s about five orders of magnitude longer than the lifespan of the Higgs, which is a measurement of basically the same sort (interval between an excitation being produced and that excitation decaying). Yes, you’re right. Can you describe for laymen what the timing tech–or approach/principles–consists of, broadly, and how the photoemission and the CERN techniques differ? Timing virtual particle existence is the same across the board? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 15, 2013, 1:04am UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/16 "2013-01-15T01:04:40Z")
> [@](#): > > Can you describe for laymen what the timing tech–or approach/principles–consists of, broadly, and how the photoemission and the CERN techniques differ? No. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [January 15, 2013, 5:14am UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/17 "2013-01-15T05:14:21Z")
> [@Chronos](#): > > No. 😃 ---
**Author:** ![ducati](https://avatars.discourse-cdn.com/v4/letter/d/cc9497/32.png) [@ducati](https://boards.straightdope.com/u/ducati)\ **Post date:** [January 15, 2013, 3:14pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/18 "2013-01-15T15:14:14Z")
> [@JerrySTL](#): > > The time between the traffic light turning green and the car behind me blowing their horn. > [@Colibri](#): > > Here in Panama, we call that the “Panasecond.” It is theorized that, since cars sometimes start blowing their horns _even before the light has changed_, faster-than-light travel must be possible. Sorry, but the time between a woman saying “I do” and her realizing she’s given her last blowjob is roughly 1/4 “Panasecond”. ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [January 15, 2013, 9:10pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/19 "2013-01-15T21:10:54Z")
> [@Leo\_Bloom](#): > > Can you describe for laymen what the timing tech–or approach/principles–consists of, broadly, and how the photoemission and the CERN techniques differ? (Some of the following is touched on in your old SciAm link, but I’ll not worry about repetition.) (1) “Direct” timing (10[sup]-10[/sup] s) If you want to time something like you would with a stopwatch, then you’re limited to the smallest intervals available with fancy stopwatches. That is, you could have two signals coming in, and you could click “go” at the first one and “stop” at the second one and see how much time elapsed in between. This approach is limited to a picosecond (10[sup]-9[/sup]) or a bit smaller. (2) Sub-femtosecond light pulses (10[sup]-16[/sup] s) The shortest controlled light pulse ever created is just below 0.1 femtoseconds. These fast flashes are used to take high “shutter speed” images of, say, chemical reactions in progress. (3) The photoemission measurement discussed above (5x10[sup]-18[/sup] s) Things get a bit more complicated here. For the photoemission measurement, they wanted to see how much time passes between the arrival of a “ping” pulse on an atom and the emission of the electron due to that ping. Since times on this scale are too short to measure directly, they did something else. Each electron that will be ejected has an energy that can be measured using an everyday technique (time-of-flight spectroscopy). If that electron, when emitted, experiences an ambient electric field, it will be accelerated. So, such an electric field is introduced by shining a second strong laser pulse (near-infrared wavelenghts) across the atoms of interest. This NIR pulse generates an oscillating electric field that changes the electrons’ energies, with the an electron’s energy being shifted up or down in an oscillatory way depending on when in the NIR wave’s cycle the electron is emitted from the atom. The technological breakthrough of relevance was the ability to make these two pulses (the ping and the probe) such that they have sufficient power _and_ have a controlled phase relationship. Since the phase relationship is known, you can plot the measured electron energies as a function of the phase difference between the ping and probe pulses. For any single electron you can’t tell much, but if you collect tons of samples, you can build up a probability distribution for the energy shift of the emitted electrons relative to the ping arrivals. From the energy shifts, you can infer when those electrons were being emitted relative to the ping arrivals. The 20 attosecond photoemission result, then, comes from looking at the this inferred delay (averaged over many trials). The experiment had sensitivity down to 5 attoseconds, so the technique should be given credit for that. In other words, the fact that they happened to use the technique to measure something that lasted 20 attoseconds isn’t fair to what they _could_ have measured. (3) Particle lifetimes The longest lifetimes (\>10[sup]-9[/sup] seconds or so) are best measured using a stopwatch-type approach. Going lower, down to around 10[sup]-15[/sup] s, you can combine velocity (energy) and position measurements to infer lifetime. That is, you can record where a particle is created, note its energy to infer its velocity, and then see where it decays. The distance it travels and its speed are enough to work out how long it lived. The limiting factor in this approach is the spatial resolution of particle detectors (~10 microns). If you hear a lifetime reported that is shorter than this, it is inferred from quantum mechanics. In particular: a particle that lives for some given amount of time also has some energy during that time. The uncertainty principle limits how precisely I can know its energy during the time it was alive. The shorter the particle lifetime, the less certain I can ever be about its energy. This energy includes its mass. So, particles that live for a very short amount of time have an uncertain mass. So in practice when you measure the mass of a short-lived particle (typically by adding up all the energies and momenta of the things it decays into and noting that these quantities are conserved from before to after the decay), you don’t get the same answer every time. You get a spread of answers. For example, the W boson has a mean mass of 85.4 GeV. If you measure a bunch of W bosons’ masses, you’ll get answers distributed in a [bell-curve-like way](http://en.wikipedia.org/wiki/Relativistic_Breit%E2%80%93Wigner_distribution) around that mean value with a spread of around 2.1 GeV. The lifetime of the W boson can be directly calculated from this mass width as (_h_-bar)/(2.1 GeV) = 3.1x10[sup]-25[/sup]. There are also cases where the lifetime is inferred through knowledge of interaction rates and decay rates, but the story underlying such cases is basically the same. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [January 15, 2013, 9:40pm UTC](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138/20 "2013-01-15T21:40:08Z")
**Pasta** , you’re a prince. **Chronos** , \<_harrumph_\>. [Next page](https://boards.straightdope.com/t/what-is-the-shortest-time-measurable/647138.md?page=2)