# Three Spatial Dimensions, Only One Time Dimension-Why? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [September 14, 2012, 11:38pm UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738 "2012-09-14T23:38:24Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [September 14, 2012, 11:38pm UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/1 "2012-09-14T23:38:24Z")
Shouldn’t time also have three dimensions? Of course, having time dimensions perpendicular to each other is a bit confusing. Anyway, have three time dimensions ever been postulated? What does such an assumption do to General Relativity? ---
**Author:** ![StGermain](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/stgermain/32/2868_2.png) [@StGermain](https://boards.straightdope.com/u/StGermain)\ **Post date:** [September 14, 2012, 11:56pm UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/2 "2012-09-14T23:56:35Z")
Who say it is? (Or actually, Who says it isn’t). "People assume that time is a strict progression of cause to effect, but _actually_ from a non-linear, non-subjective viewpoint - it’s more like a big ball of wibbly wobbly… time-y wimey… stuff. " StG ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [September 15, 2012, 12:50am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/3 "2012-09-15T00:50:15Z")
Can’t find a cite now but more than one time dimension screws up causality. Lemme hunt through my old back issues of Scientific American… ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [September 15, 2012, 2:05am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/4 "2012-09-15T02:05:58Z")
Takes me back to Fritz Leiber’s time-travel science-fantasy novel “The Big Time.” The idea was that there was ordinary time – A.D. 1900, A.D. 1901, etc. – wherein people could do ordinary time travel. i.e., I could go back to 1900 and assassinate Woodrow Wilson before he ever ran for President. But there was also a “bigger” time dimension, in which I could go back in time “before” another assassin went back in time, to stop him from assassinating Joseph Carroll. (Who is Joseph Carroll? Well, you never heard of him; he was assassinated before he ever had a chance to run for President!) ---
**Author:** ![emeraldia](https://avatars.discourse-cdn.com/v4/letter/e/c2a13f/32.png) [@emeraldia](https://boards.straightdope.com/u/emeraldia)\ **Post date:** [September 15, 2012, 3:33am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/5 "2012-09-15T03:33:24Z")
Time is a subjective construct. I don’t think it exists independent of our minds. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [September 15, 2012, 3:51am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/6 "2012-09-15T03:51:23Z")
I don’t think that quite makes sense. You could say the same of “light.” Light doesn’t exist, except as a construct of our minds. Except that plants can sense it too. Time, as an objective thing, is evidenced by motion. Landslides, the melting of icicles, the raging of forest fires, etc. Without time, how can you have motion? Time can be measured in any rhythmic event: days, lunar months, years, the cycles of the precession of the earth’s poles, the passage of the solar system around the galaxy. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [September 15, 2012, 4:10am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/7 "2012-09-15T04:10:55Z")
I’ve wondered exactly that myself on some occasions. I don’t even know if it’s a serious question. But yeah. Why 3 or 4 or 10 or 11 space dimensions, but only 1 time dimension? Why not 2 or 3 or 4 or 10 or 11 or something time dimensions? Imagine it this way: There is all sorts of theory about how there are (or might be) more than 3 space dimensions, yet in the universe as we know it (sort of), we only seem to occupy 3 of those and we only have access to those 3. The other dimensions are either “compact” (i.e., really really tiny) or otherwise inaccessible to us. So why not a similar theory for time? Possibly 2 or more dimensions of time, but we only have access to 1 of them (thus allowing for “causality” as we think we know it). If we were to develop a theory with multiple time dimensions, it would have to be really really weird (compared to the world as we know it) – But when did that ever stop anybody? ---
**Author:** ![Dallas\_Jones](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dallas_jones/32/3277_2.png) [@Dallas\_Jones](https://boards.straightdope.com/u/Dallas_Jones)\ **Post date:** [September 15, 2012, 5:12am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/8 "2012-09-15T05:12:11Z")
Time is a spatial dimension that you can’t point to. The past is ‘over there’ in that general direction and the future is coming right up. ---
**Author:** ![drewtwo99](https://avatars.discourse-cdn.com/v4/letter/d/d07c76/32.png) [@drewtwo99](https://boards.straightdope.com/u/drewtwo99)\ **Post date:** [September 15, 2012, 5:21am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/9 "2012-09-15T05:21:02Z")
> [@Dallas\_Jones](#): > > Time is a spatial dimension that you can’t point to. > > The past is ‘over there’ in that general direction and the future is coming right up. When will “then” be “now”? 😃 ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [September 15, 2012, 1:35pm UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/10 "2012-09-15T13:35:57Z")
We have 3 spatial and 1 time dimension in GR, because that’s what matches our observations. In string theory, I’ve read more than once that the extra dimensions have to all be spatial, or it makes the math all wonky somehow. But they have at least looked into that, and considered additional time dimensions. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [September 15, 2012, 1:50pm UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/11 "2012-09-15T13:50:05Z")
[Max Tegmark](http://space.mit.edu/home/tegmark/dimensions.html) has done work considering universes with a different number of dimensions. The upshot is, that basically only 3+1 dimensions allows for the stability needed to evolve complex observers, so if you are one of those, you should expect to find yourself in such a universe. That doesn’t mean theories with more than one time dimension haven’t been proposed, the most famous one being Itzhak Bars’ ‘two-time physics’. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [September 15, 2012, 2:40pm UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/12 "2012-09-15T14:40:29Z")
> [@emeraldia](#): > > Time is a subjective construct. I don’t think it exists independent of our minds. Eh? It’s what prevents things from all happening at once. Things happen sequentially even when there’s nobody watching. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [September 15, 2012, 6:02pm UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/13 "2012-09-15T18:02:03Z")
A colleague of mine has written a paper that proposes 3 dimensions of time to go with 3 of space. He identifies the resultant 6 dimensional space as the 4 x 4 skew symmetric real matrices. I have read his paper and it makes mathematical sense but could never get any physical meaning from it. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [September 16, 2012, 4:55am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/14 "2012-09-16T04:55:10Z")
> [@Mangetout](#): > > Eh? It’s what prevents things from all happening at once. Things happen sequentially even when there’s nobody watching. If a Big Bang happens and there’s nobody there to observe it, does it make any noise? ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [September 16, 2012, 5:22am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/15 "2012-09-16T05:22:47Z")
Time is what happens when you don’t travel at _c._ Or to put it another way: if you have mass. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [September 16, 2012, 5:33am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/16 "2012-09-16T05:33:11Z")
> [@Dallas\_Jones](#): > > Time is a spatial dimension that you can’t point to. > > The past is ‘over there’ in that general direction and the future is coming right up. However, in space we can go up or down, left or right, forward or backward. In time, it’s 1 dimension, but a temporal one, in that it seems we can only move in one direction: forward, and in traveling through space, time dialates to compensate any acceleration, so it appears from the traveling observer light is always traveling at _c._ So, calling it spacial, I believe, is incorrect. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [September 16, 2012, 6:01am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/17 "2012-09-16T06:01:19Z")
> [@Half\_Man\_Half\_Wit](#): > > [Max Tegmark](http://space.mit.edu/home/tegmark/dimensions.html) has done work considering universes with a different number of dimensions. The upshot is, that basically only 3+1 dimensions allows for the stability needed to evolve complex observers, so if you are one of those, you should expect to find yourself in such a universe. > > That doesn’t mean theories with more than one time dimension haven’t been proposed, the most famous one being Itzhak Bars’ ‘two-time physics’. I’m really partial to this theory, especially since it can explain singularities like black holes. If a second timeline is perpendicular to our own, it would be invisible to us, since a line has no circumference. When gravity becomes so strong to overcome c, it reduces mass to a zero-dimensional point (raising its density to infinity, yet keeping its gravity the same), perhaps allowing the mass to redirect along the 2nd timeline, yet its mass is all still really there, but now being within 4 dimensions, its “3 dimensional shadow” (of what was the star) has been reduced to a point, like a 4 dimensional sphere sitting on a 3 dimensional surface. And somehow gravity can permeate all dimensions. Hrmmm. A “4 dimensional” Riemann sphere comes to mind. Also, if indeed quantum particles are zero dimensional points of pure energy (or 1 dimensional loops of “strings”), it might explain the very strange behavior of the quantum world. Correct me if this comes across as non-sense. ---
**Author:** ![Kozmik](https://avatars.discourse-cdn.com/v4/letter/k/8dc957/32.png) [@Kozmik](https://boards.straightdope.com/u/Kozmik)\ **Post date:** [September 16, 2012, 6:53am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/18 "2012-09-16T06:53:19Z")
> [@Lumpy](#): > > Can’t find a cite now but more than one time dimension screws up causality. Lemme hunt through my old back issues of Scientific American… What if… you could hunt through _all_ issues of Scientific American… ---
**Author:** ![MEBuckner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mebuckner/32/2896_2.png) [@MEBuckner](https://boards.straightdope.com/u/MEBuckner)\ **Post date:** [September 16, 2012, 7:10am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/19 "2012-09-16T07:10:39Z")
Robert Heinlein’s novel [_The Number of the Beast_](http://en.wikipedia.org/wiki/The_Number_of_the_Beast_%28novel%29) features the discovery of two extra time dimensions, and the invention of a “continua” device that can travel along the two extra time dimensions into various alternate universes. (Heinlein used this as an excuse to have his characters visit assorted fictional universes created by other authors, including the Land of Oz, on the grounds that with 10,314,424,798,490,535,546,171,949,056 accessible parallel universes–6[sup]6[sup]6[/sup][/sup]-- you’re bound to find something corresponding to just about anyplace anyone has ever conceived of. He also used it as an excuse to tie together characters from different fictional continuities of his _own_ previous novels.) ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [September 18, 2012, 4:43am UTC](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738/20 "2012-09-18T04:43:13Z")
There are also timeless models of the universe that some people really like, at least, according to the author of Harry Potter and the Methods of Rationality. (And, no, he was not talking fictionally–all of his science is accurate, and he even included a footnote on that particular point.) [Next page](https://boards.straightdope.com/t/three-spatial-dimensions-only-one-time-dimension-why/634738.md?page=2)