# Time at the Planck scale **URL:** \ **Category:** Factual Questions\ **Created:** [June 3, 2011, 11:30pm UTC](https://boards.straightdope.com/t/time-at-the-planck-scale/584259 "2011-06-03T23:30:43Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Patrick\_Mc](https://avatars.discourse-cdn.com/v4/letter/p/5e9695/32.png) [@Patrick\_Mc](https://boards.straightdope.com/u/Patrick_Mc)\ **Post date:** [June 3, 2011, 11:30pm UTC](https://boards.straightdope.com/t/time-at-the-planck-scale/584259/1 "2011-06-03T23:30:43Z")
How would time be exerienced at the Planck scale? If there was a dimension smaller than the Planck scale would it be worth studying? ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [June 4, 2011, 3:06am UTC](https://boards.straightdope.com/t/time-at-the-planck-scale/584259/2 "2011-06-04T03:06:22Z")
[Planck time.](http://en.wikipedia.org/wiki/Planck_time) > [@](#): > > The Planck time comes from a field of mathematical physics known as dimensional analysis, which studies units of measurement and physical constants. The Planck time is the unique combination of the gravitational constant G, the relativity constant c, and the quantum constant h, to produce a constant with units of time. For processes that occur in a time t less than one Planck time, the dimensionless quantity tP / t is greater than one. Dimensional analysis suggests that the effects of both quantum mechanics and gravity will be important under these circumstances, requiring a theory of quantum gravity. 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. > One Planck time is the time it would take a photon travelling at the speed of light to cross a distance equal to one Planck length. Theoretically, this is the smallest time measurement that will ever be possible,[3] roughly 10−43 seconds. Within the framework of the laws of physics as we understand them today, for times less than one Planck time apart, we can neither measure nor detect any change. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [June 4, 2011, 3:12am UTC](https://boards.straightdope.com/t/time-at-the-planck-scale/584259/3 "2011-06-04T03:12:15Z")
In _Thief of Time_ Pratchett riffed off of Planck Time with the concept that between each smallest possible unit of time the universe was literally destroyed and recreated. Not his very best book but a good one. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 4, 2011, 3:41am UTC](https://boards.straightdope.com/t/time-at-the-planck-scale/584259/4 "2011-06-04T03:41:43Z")
**Chronos** has schooled me in the past that the Planck limits are merely hard coded limits on what we could conceivably probe to (and we’re not close to probing those scales as is). He told me it is quite possible to go smaller than the Planck size which would then of course mean shorter than the Planck time and so on. We just can’t go there. ---
**Author:** ![Washoe](https://avatars.discourse-cdn.com/v4/letter/w/ecae2f/32.png) [@Washoe](https://boards.straightdope.com/u/Washoe)\ **Post date:** [June 4, 2011, 3:42am UTC](https://boards.straightdope.com/t/time-at-the-planck-scale/584259/5 "2011-06-04T03:42:35Z")
> [@DSeid](#): > > Not his very best book but a good one. I read once on a wiki page though (damned if I’ll ever find it again), that there are theoretical models of cosmology which allow for the entire universe to simply spontaneously vanish. What was I reading? ---
**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:** [June 4, 2011, 8:20pm UTC](https://boards.straightdope.com/t/time-at-the-planck-scale/584259/6 "2011-06-04T20:20:57Z")
I’m afraid you took home the wrong message from what I was saying, then, **Whack-a-Mole**. The short answer is that we don’t know. The long answer is that there might (or might not) be some minimum scale of length and time, or some scale below which things get wonky, and if there is such a length scale, it’s as good a guess as we have that it’s probably (but might not be) somewhere in the general vicinity of the Planck scale. ---
**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:** [June 4, 2011, 8:24pm UTC](https://boards.straightdope.com/t/time-at-the-planck-scale/584259/7 "2011-06-04T20:24:17Z")
> [@](#): > > I read once on a wiki page though (damned if I’ll ever find it again), that there are theoretical models of cosmology which allow for the entire universe to simply spontaneously vanish. What was I reading? The closest I know of to that is a collapse of a false vacuum state. The idea is that what we think of as the lowest energy state of the vacuum might not actually be the lowest, but just a semi-stable excited state. If somehow the true vacuum (or a lower false vacuum) were ever achieved in some spot, it would induce nearby regions to also fall down to the true vacuum, and so on, expanding out at the speed of light. It wouldn’t actually happen everywhere at once, but since it propagates at c, we’d have no warning of it happening before it actually hit us. ---
**Author:** ![Washoe](https://avatars.discourse-cdn.com/v4/letter/w/ecae2f/32.png) [@Washoe](https://boards.straightdope.com/u/Washoe)\ **Post date:** [June 4, 2011, 8:41pm UTC](https://boards.straightdope.com/t/time-at-the-planck-scale/584259/8 "2011-06-04T20:41:16Z")
Yes, I’m pretty sure I was reading something about false vacuum. I’ll poke around tonight and see if I can find it again.