# The Speed Of Time... **URL:** \ **Category:** Great Debates\ **Created:** [November 3, 2001, 4:04pm UTC](https://boards.straightdope.com/t/the-speed-of-time/91318 "2001-11-03T16:04:22Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [November 3, 2001, 4:04pm UTC](https://boards.straightdope.com/t/the-speed-of-time/91318/1 "2001-11-03T16:04:22Z")
We believe time to be the fourth dimension. Take length, turn 90 deg. and you have width. Turn another 90 deg. in repect to the first two and you have depth. Imagine ANOTHER 90 deg. turn in respect to the three, and that unseen direction is time. Say we assume time to progress at a uniform rate; neither speeding up nor slowing down. A point in 3-space becomes a line in 4-space. A line becomes a plane. a plane becomes a solid. And in 4-space a 3- dimensional solid becomes… uh…a tesseract (Right?) Anyway… Measuring time as a distance between two pointsmeasuring one second apart, what speed does that point travel alonf time? The speed of light , or some other speed? ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [November 3, 2001, 4:29pm UTC](https://boards.straightdope.com/t/the-speed-of-time/91318/2 "2001-11-03T16:29:05Z")
> [@](#): > > \*Originally posted by Enola Straight \* > **Say we assume time to progress at a uniform rate; neither speeding up nor slowing down. A point in 3-space becomes a line in 4-space. A line becomes a plane. a plane becomes a solid. And in 4-space a 3- dimensional solid becomes…uh…a tesseract (Right?)** FWIW, a tesseract is a specific 4-d shape, the analogue of a cube. A 3-d solid becomes a hyperplane in 4-d space. I can’t answer the speed question, though. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [November 3, 2001, 4:34pm UTC](https://boards.straightdope.com/t/the-speed-of-time/91318/3 "2001-11-03T16:34:58Z")
My understanding of Einstein’s special relativity of time is not that time is a dimension in the same sense that three orthagonal linear dimensions are. That is to say, there is something more similar between three distance dimensions than between them and time. Geometrically, you can’t make a 90 degree turn from some path and travel along time. This should be obvious in one sense: you can choose any direction to call your first dimension, and you can choose any direction in the plane perpendicular to that to call your second, and only then is there one specific direction that must be considered as the next dimension. A better way to consider four orthagonal dimensions is to say that each of them is made up primarily of distance but also contains some time, and all four of them have the same properties but have their own isolated degrees of freedom. Arbitrarily one can select another set of four with same properties and isolated degrees of freedom. The purpose of this treatment is to be able to describe coordinate systems that work correctly from the point of view of an observer with a location and velocity (necessary because if a system of mathematics breaks down for anybody, then nobody should trust it). Another note: your question actually implies something that isn’t true (because it’s built into our language and most people’s understanding of the world). You can’t say you measure two points at different locations one second apart - it only appears that you can because you don’t realize what’s going on. Any observer’s understanding of whether events in different locations happen simultaneously is not correct for everybody else. This is a feature of the way the universe is put together, not the trivial artifact of how long it takes you to observe things (which is also there). ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [November 3, 2001, 6:25pm UTC](https://boards.straightdope.com/t/the-speed-of-time/91318/4 "2001-11-03T18:25:28Z")
I thought I stated this thread in General Questions. Mr.(MS?)Moderator, please move this thread to the appropriate forum. ---
**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:** [November 3, 2001, 11:24pm UTC](https://boards.straightdope.com/t/the-speed-of-time/91318/5 "2001-11-03T23:24:11Z")
> [@](#): > > \*Originally posted by Enola Straight \* > \*\*We believe time to be the fourth dimension. > > Take length, turn 90 deg. and you have width. > Turn another 90 deg. in repect to the first two and you have depth. Imagine ANOTHER 90 deg. turn in respect to the three, and that unseen direction is time.\*\* I don’t think of time in this way; I don’t think it’s a geometric dimension like the ‘other’ 3. > [@](#): > > **Measuring time as a distance between two pointsmeasuring one second apart, what speed does that point travel alonf time?** Anyway, how _could_ you measure the speed of time’s passing?, that would be like measuring a centimetre in centimetres; time progresses at exactly one second per second. Now as to whether time passes at a constant rate… that’s an interesting almost metaphysical question; if time slows down, so does everything; so time still passes at one second per second. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [November 4, 2001, 12:54am UTC](https://boards.straightdope.com/t/the-speed-of-time/91318/6 "2001-11-04T00:54:52Z")
> [@](#): > > \*Originally posted by Mangetout \* > Now as to whether time passes at a constant rate… that’s an interesting almost metaphysical question; if time slows down, so does everything; so time still passes at one second per second. But of course time is not constant, as Einstein showed us. Only the speed of light is constant, everything else is relative. Else there’d be no twin paradox. ---
**Author:** ![elucidator](https://avatars.discourse-cdn.com/v4/letter/e/8edcca/32.png) [@elucidator](https://boards.straightdope.com/u/elucidator)\ **Post date:** [November 4, 2001, 1:14am UTC](https://boards.straightdope.com/t/the-speed-of-time/91318/7 "2001-11-04T01:14:14Z")
This sort of reminds be about the 19th cent. thing about “ether”, one of the deceased theories. Ether was a supposed medium through which light, being a wave, travled, rather like water does for a ripple. Maybe our approach to time suffers from the same error. We seem to be trying to concieve some absolute background, time iself, as opposed to (all the stuff that happens). We measure time only by actions: tickings of clock, humming of electrons, motions of moon. Since we measure time only by relative motion, whats wrong with thinking that time itself does not exist as a dimension? Would this do any damage to the equations of physics? ---
**Author:** ![Imaginary](https://avatars.discourse-cdn.com/v4/letter/i/ecb155/32.png) [@Imaginary](https://boards.straightdope.com/u/Imaginary)\ **Post date:** [November 4, 2001, 5:51am UTC](https://boards.straightdope.com/t/the-speed-of-time/91318/8 "2001-11-04T05:51:00Z")
I believe that time is a 4th dimension. That its speed is dependent on the speed of light. The speed of light is dependent on the vacuum energy density. So if you get a drop in the speed of light you get an increase in the speed of time to compensate. And because the speed of time is relative to the vacuum energy density you can have two different points in the universe with different speeds of time. So you could probably measure time in the following units: v(t) = planck length/speed of light So the speed of time would currently be around: 3.3x10^-44 time units. Well that’s my theory anyway. ---
**Author:** ![SPOOFE](https://avatars.discourse-cdn.com/v4/letter/s/c5a1d2/32.png) [@SPOOFE](https://boards.straightdope.com/u/SPOOFE)\ **Post date:** [November 4, 2001, 6:19am UTC](https://boards.straightdope.com/t/the-speed-of-time/91318/9 "2001-11-04T06:19:47Z")
[/quote] Measuring time as a distance between two pointsmeasuring one second apart, what speed does that point travel alonf time? [/quote] [Wiseass answer] One second per second. [/Wiseass answer] ---
**Author:** ![Bill\_H](https://avatars.discourse-cdn.com/v4/letter/b/a5b964/32.png) [@Bill\_H](https://boards.straightdope.com/u/Bill_H)\ **Post date:** [November 4, 2001, 6:36am UTC](https://boards.straightdope.com/t/the-speed-of-time/91318/10 "2001-11-04T06:36:40Z")
From The Feynman Lectures on Physics I (an awesome book, if you’re into this kind of thing): > [@](#): > > c[sup]2[/sup]t’ [sup]2[/sup] - x’ [sup]2[/sup] - y’ [sup]2[/sup] - z’ [sup]2[/sup] = c[sup]2[/sup]t[sup]2[/sup] - x[sup]2[/sup] - y[sup]2[/sup] - z[sup]2[/sup] > > This quantity is therefore something which, like the distance is “real” in some sense; it is called the _interval_ between the two space-time points, one of which is, in this case, at the origin. (Actually, of course, it is the interval squared, just as x[sup]2[/sup] + y[sup]2[/sup] + z[sup]2[/sup] is the distance squared.) We give it a different name because it is in a different geometry, but the interesting thing is only that some signs are reversed and there is a _c_ in it. > > Let us get rid of the _c_; that is an absurdity if we are going to have a wonderful space with _x_’s and _y_’s that can be interchanged. One of the confusions that could be caused by someone with no experience would be to measure widths, say, by the angle subtended at the eye, and measure depth in a different way, like the strain on the muscles needed to focus them, so that the depths would be measured in feet and the widths in meters. Then one would get an enormously complicated mess of equations in making transformations, and would not be able to see the clarity and simplicity of the thing for a very simple technical reason, that the same thing is being measured in two different units. Now in [the equation above] nature is telling us that time and space are equivalent; time becomes space; _they should be measured in the same units_. What distance is a “second”? It is easy to figure out from [the equation above] what it is. It is 3 x 10[sup]8[/sup] meters, _the distance that light would go in one second_. In other words, if we were to measure all distances and times in the same units, seconds then our unit of distance would be 3 x 10[sup]8[/sup] meters, and the equations would be simpler. Or another way that we could make the units equal is to measure time in meters. What is a meter of time? A meter of time is the time it takes for light to go one meter, and is therefore 1/3 x 10[sup]-8[/sup] sec, or 3.3 billionths of a second! We would like, in other words to put all our equations in a system of units in which _c_ = 1. I’m not exactly sure what the OP is asking, but perhaps this helps. ---
**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:** [November 4, 2001, 10:35pm UTC](https://boards.straightdope.com/t/the-speed-of-time/91318/11 "2001-11-04T22:35:02Z")
> [@](#): > > \*Originally posted by Qadgop the Mercotan \* > \*\* > > > [@](#): > > > > \*Originally posted by Mangetout \* > > Now as to whether time passes at a constant rate… that’s an interesting almost metaphysical question; if time slows down, so does everything; so time still passes at one second per second. > > But of course time is not constant, as Einstein showed us. Only the speed of light is constant, everything else is relative. Else there’d be no twin paradox. \*\* Sure, but how do you measure the passage of time locally without using time?