# Time In a Time-less Physics. **URL:** \ **Category:** Factual Questions\ **Created:** [December 3, 2009, 3:32am UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804 "2009-12-03T03:32:50Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [December 3, 2009, 7:33pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/21 "2009-12-03T19:33:17Z")
> [@panache45](#): > > If anyone has seriously proposed a universe without time, has anyone proposed a universe without space? Well, the [holographic principle](http://en.wikipedia.org/wiki/Holographic_principle) gets rid of space as we know it, replacing it with a fluctuating two-dimensional information structure. ---
**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:** [December 3, 2009, 7:36pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/22 "2009-12-03T19:36:38Z")
> [@c\_goat](#): > > So things like time travel (going to arbitrary points in the past/future) aren’t possible for that reason. But I can go to arbitrary points in the future – give me a powerful enough rocket, and I’ll return to this here spot in the year 30,000, having aged nary a day. ---
**Author:** ![c\_goat](https://avatars.discourse-cdn.com/v4/letter/c/f4b2a3/32.png) [@c\_goat](https://boards.straightdope.com/u/c_goat)\ **Post date:** [December 3, 2009, 7:44pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/23 "2009-12-03T19:44:50Z")
> [@Half\_Man\_Half\_Wit](#): > > But I can go to arbitrary points in the future – give me a powerful enough rocket, and I’ll return to this here spot in the year 30,000, having aged nary a day. OK not trying to have a debate here but this wasn’t what I meant. I’m talking more about the instantaneous jump / time machine thing. I’m not saying the above would work or not, just that to me, even if it works, it doesn’t prove that time exists. It just proves that going really really fast will have an effect on you. ---
**Author:** ![ivan\_astikov](https://avatars.discourse-cdn.com/v4/letter/i/58f4c7/32.png) [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)\ **Post date:** [December 3, 2009, 7:45pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/24 "2009-12-03T19:45:14Z")
Without a consciousness willing to apply measurements to existence, there wouldn’t be any ‘time’, would there? All our measurements are based upon the revolution of our planet at a point when some creature can experience and register them. ---
**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:** [December 3, 2009, 7:57pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/25 "2009-12-03T19:57:49Z")
> [@](#): > > To the physicists: does General Relativity impose a stronger “arrow” on time than the Second Law of Thermodynamics? > > After all, matter can fall into a black hole, but can never leave. That’s definite. On the other hand, a tepid cup of tea can always turn into a hot cup of tea with a floating ice cube. It’s astronomically unlikely to happen in any reasonable time frame, but not strictly forbidden. We don’t understand quite _how_, but it’s clear that black holes follow the same laws of thermodynamics as everything else. The entropy of a black hole is, as you might imagine, very large, and is proportional to the area of the event horizon. Thus, while it’s pretty straightforward to come up with processes that increase the area of the event horizon (like dropping something in), it’s much harder to decrease the area of the event horizon, and requires that you have something to dump the entropy into (like Hawking radiation). A ship falling into a black hole increases the entropy of the system, and a ship emerging from a black hole decreases the entropy, so the “black hole arrow of time” is really just the same old thermodynamic arrow of time. There are only three arrows of time known in all of the laws of physics. First is the thermodynamic arrow of time (the past has lower entropy than the future), and almost every possible other arrow of time you can think of ultimately comes back to that one. Then there’s the cosmological arrow of time (the Universe was smaller in the past than in the future), which doesn’t really seem to have any inherent significance, and could presumably reverse without making any difference to anything on a smaller scale. Finally, there’s the particle physics arrow of time, which is so subtle that it only shows up at all in oscillations of second or third generation mesons, only indirectly even in those cases, and only at about one part in a thousand, and is not known to have any physical significance whatsoever outside of those limited circumstances (though it might ultimately be related to the reason why we don’t have just as much antimatter as matter in the Universe). ---
**Author:** ![Tom\_Tildrum](https://avatars.discourse-cdn.com/v4/letter/t/e95f7d/32.png) [@Tom\_Tildrum](https://boards.straightdope.com/u/Tom_Tildrum)\ **Post date:** [December 3, 2009, 8:59pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/26 "2009-12-03T20:59:41Z")
Stephen Hawking postulated the concept of “imaginary time,” but damned if I know what the hell he thought that actually meant. ---
**Author:** ![Bytegeist](https://avatars.discourse-cdn.com/v4/letter/b/9dc877/32.png) [@Bytegeist](https://boards.straightdope.com/u/Bytegeist)\ **Post date:** [December 3, 2009, 9:57pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/27 "2009-12-03T21:57:42Z")
> [@Spatial\_Rift\_47](#): > > Congratulations, you just discovered the problem Stephen Hawking (and many other physicists) have spent their careers on. _Woo hoo!_ > [@Spatial Rift 47](#): > > For example, one idea is that the informational essence of everything that falls in is (roughly speaking) smeared across the event horizon. This would take your “rocket ship exits black hole, film at 11” scenario and reduce it to the same thermodynamic analysis as the tepid cup of tea suddenly becoming piping hot. > [@Chronos](#): > > We don’t understand quite _how_, but it’s clear that black holes follow the same laws of thermodynamics as everything else. […] while it’s pretty straightforward to come up with processes that increase the area of the event horizon (like dropping something in), it’s much harder to decrease the area of the event horizon, and requires that you have something to dump the entropy into (like Hawking radiation). A ship falling into a black hole increases the entropy of the system, and a ship emerging from a black hole decreases the entropy, so the “black hole arrow of time” is really just the same old thermodynamic arrow of time. Thanks for these explanations, particularly the green bits. I think I’m still a little unclear though. Return to the escaping spaceship for a moment, but instead make it a more modest escaping _electron_. Suppose there’s a fast-moving electron that just a moment ago (in its reference frame) edged past the event horizon of a black hole. If there were now a big enough emimssion of Hawking radiation (which, being a set of quantum events, is at least possible, if incredibly unlikely?), could the electron now find itself back on the outside of the horizon? In orbit, and unable to escape without more energy, but at least no longer doomed? If this can’t happen, is it because GR strictly disallows it (no matter by what mechanism the black hole’s entropy might decrease). Or is it impossible because I’m not understanding yet how all this works? (That’s where I’d lay my money.) Or is it merely an _improbable_ event, technically possible but unlikely to happen in anything less than a googolplex years? ---
**Author:** ![Bytegeist](https://avatars.discourse-cdn.com/v4/letter/b/9dc877/32.png) [@Bytegeist](https://boards.straightdope.com/u/Bytegeist)\ **Post date:** [December 3, 2009, 10:14pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/28 "2009-12-03T22:14:53Z")
> [@Tom\_Tildrum](#): > > Stephen Hawking postulated the concept of “imaginary time,” but damned if I know what the hell he thought that actually meant. I’ve sometimes wondered if the dimensions or coordinates of space and time would not be better modeled with complex numbers instead of reals. Not that I have any particular reason to think it would be helpful. I just wonder if anyone has ever tried it. If “complex spacetime” turned out to be a successful model, with newer and better explanatory power, that would be mighty weird all right, but maybe no weirder than Quantum Mechanics is. ---
**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:** [December 3, 2009, 10:16pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/29 "2009-12-03T22:16:42Z")
> [@c\_goat](#): > > OK not trying to have a debate here but this wasn’t what I meant. I’m talking more about the instantaneous jump / time machine thing. But you don’t have a ‘space machine’, either – i.e. you can’t just bridge arbitrary distances instantaneously. Does that mean space doesn’t exist, too? And besides, what does ‘instantaneously’ mean in this context, exactly? > [@](#): > > I’m not saying the above would work or not, just that to me, even if it works, it doesn’t prove that time exists. It just proves that going really really fast will have an effect on you. What would prove time’s existence to you? > [@ivan\_astikov](#): > > Without a consciousness willing to apply measurements to existence, there wouldn’t be any ‘time’, would there? Seems to me that the same point could be made in reverse – that without time, there wouldn’t be any consciousness to measure it, since conscious measurement implies a change in knowledge over time. ---
**Author:** ![Spatial\_Rift\_47](https://avatars.discourse-cdn.com/v4/letter/s/a8b319/32.png) [@Spatial\_Rift\_47](https://boards.straightdope.com/u/Spatial_Rift_47)\ **Post date:** [December 3, 2009, 11:50pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/30 "2009-12-03T23:50:25Z")
> [@Bytegeist](#): > > Return to the escaping spaceship for a moment, but instead make it a more modest escaping _electron_. Suppose there’s a fast-moving electron that just a moment ago (in its reference frame) edged past the event horizon of a black hole. If there were now a big enough emimssion of Hawking radiation (which, being a set of quantum events, is at least possible, if incredibly unlikely?), could the electron now find itself back on the outside of the horizon? In orbit, and unable to escape without more energy, but at least no longer doomed? > > If this can’t happen, is it because GR strictly disallows it (no matter by what mechanism the black hole’s entropy might decrease). Or is it impossible because I’m not understanding yet how all this works? (That’s where I’d lay my money.) Or is it merely an _improbable_ event, technically possible but unlikely to happen in anything less than a googolplex years? It almost sounds like you’re trying to use quantum tunneling to extract the electron from the black hole. That dog won’t hunt - quantum tunneling is reserved for finite barriers only, and even then it has to be rather on the thin side. Once an electron crosses the event horizon, it does not come out again. It can no more exit the horizon than it could go back to last Saturday - because, as it happens, time and space coordinates trade places inside a black hole. The singularity isn’t a place, it’s a time. GR strictly disallows the scenario you propose. What physicists are currently investigating is if (and if so how), by observing the black hole, you can deduce that an electron did go in, and that it had X amount of energy when it did. This is where Hawking radiation may play a role. If it is not strictly thermal, but instead modulated by some quantum process, it may in fact be encoding the black hole’s conquests, like some cosmic receipt. ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [December 4, 2009, 12:23am UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/31 "2009-12-04T00:23:09Z")
> [@Bytegeist](#): > > I’ve sometimes wondered if the dimensions or coordinates of space and time would not be better modeled with complex numbers instead of reals. Not that I have any particular reason to think it would be helpful. I just wonder if anyone has ever tried it. > > If “complex spacetime” turned out to be a successful model, with newer and better explanatory power, that would be mighty weird all right, but maybe no weirder than Quantum Mechanics is. It is modeled this way in a sense in relativity. The spatial distance between two points 1 and 2 is (x[sub]1[/sub]-x[sub]2[/sub])[sup]2[/sup] + (y[sub]1[/sub]-y[sub]2[/sub])[sup]2[/sup] + (z[sub]1[/sub]-z[sub]2[/sub])[sup]2[/sup]. In space time it is this minus c[sup]2/sup[sup]2[/sup]. c can be made equal to 1 by the right change of units so then the distance in space time is the sum of the squares of the difference in x y and z and the imaginary difference in t. Related perhaps but much removed: I read in some book, that physical space-times on N dimensions only make sense if there is one or N-1 time-like dimensions. ---
**Author:** ![Jim\_B](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jim_b/32/4338_2.png) [@Jim\_B](https://boards.straightdope.com/u/Jim_B)\ **Post date:** [December 4, 2009, 4:06am UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/32 "2009-12-04T04:06:12Z")
> [@CalMeacham](#): > > Exactly how long ago did you see this show? > > How long was it? (Never mind. It’s a joke, I get it.:)) ---
**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:** [December 4, 2009, 4:55am UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/33 "2009-12-04T04:55:19Z")
> [@](#): > > Return to the escaping spaceship for a moment, but instead make it a more modest escaping electron. Suppose there’s a fast-moving electron that just a moment ago (in its reference frame) edged past the event horizon of a black hole. If there were now a big enough emimssion of Hawking radiation (which, being a set of quantum events, is at least possible, if incredibly unlikely?), could the electron now find itself back on the outside of the horizon? In orbit, and unable to escape without more energy, but at least no longer doomed? Basically, what that comes down to is saying that quantum mechanics should make the precise location of the event horizon, like the precise location of anything, somewhat uncertain. We can deal with that to some extent, which is what gives us things like Hawking radiation to begin with, but to really deal with things properly, you’d need quantum gravity. Looking at it another way, though, the question is flawed by definition. An event horizon is defined globally, not locally: If the situation ever changes in such a way that the electron can get out, then, by definition, it never actually crossed the event horizon, no matter what it may have seemed like at that moment. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [December 4, 2009, 6:45am UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/34 "2009-12-04T06:45:31Z")
**Jim B.** said: > [@](#): > > I was afraid someone would ask for a link. Well, if you insist I could offer this one from my last thread. As you can see, if you scroll up a little, **Jihi** says: I think you misunderstand **Jihi** in that thread. **Jihi** is contrasting time with matter. Matter is _stuff_. Time is not _stuff_. However, in the same context, Space is not stuff either. Space is dimensions - length, width, height. It has no tangible context, just the ability for matter to have tangible context. Time is like space. It has no tangible context, but allows matter to have tangible context. So **Jihi** does not appear to be claiming that time does not exist, only that time is not physical stuff, it is expanse of the framework that allows stuff. **c\_goat** said: > [@](#): > > “Time doesn’t exist” is really just saying there is no physical manifestation of time. So things like time travel (going to arbitrary points in the past/future) aren’t possible for that reason. Things move, and time is the concept we came up with to describe that motion. Once something moves, it’s no longer where it was, and that’s that. Basically, I reject the concept of space-time. Yes, I realize there’s a lot of people smarter than me who don’t. I say there’s only space. So how does any change occur? How can an acorn grow to a tree? How can ice melt? How can something move? How can anything ever be different? Location in space is defined by three coordinates. Shape in space is defined by three coordinates. But in order for any change to occur, there has to be a framework, a context, a _dimension_ in which to occur. That _dimension_ for change is called time. Time is not an object, any more than length is an object. Length is a description of an object, a property that an object has, defined by two points along one linear dimension. Similarly, age is a measurement of the length of two points in temporal dimension. > [@](#): > > For me, they’re not the same thing. I think a 4th dimension is possible and might exist. If it does exist, it’s not time. I _think_ your hung up on what the word “dimension” means. Dimension is a characteristic or property of extent. The three common and familiar ones are length, width, and height. These are easy to conceptualize and are the same kind of thing (whatever that thing is), so the pattern is to look for a fourth one of those. But there is a different kind of extent than directional extent - that is temporal extent. That is what time is. I think the issue is perceiving Space as a physical something. We have to be careful to differentiate the Space of “where things exist” from the space that is the scattering of things outside of Earth’s atmosphere. That space occurs _in_ Space, but does not directly constitute Space. That is why physicists talk about the fabric of spacetime. They have proposed/framed the expanse of the three directional extents into the overarching concept of Space (in which objects and matter and energy occur). And they have discovered that time behaves similarly to the dimensions of space, that it is a measure of extent of a slightly different kind but still a measure of extent, and so they have incorporated it into 1 whole concept that works together. That is what _spacetime_ is - the framework of extents. > [@](#): > > For me the problem is that you can’t test time dilation without using a physical clock of some kind. The change in motion means different forces acting on the clock, which makes it behave differently. It doesn’t prove time exists, it just proves that motion has an effect on the properties of the clock. But different types of clocks can be used - a mechanical (pendulum) clock, a radioactive decay clock, a “clock” based upon some other form of well understood and regulated chemical reaction (i.e. constant or mathematically consistent). And each of these different clocks are affected the same way. How can motion affect each of these clocks , clocks that mark time in very different ways and have different features and different susceptibilities to accelerations, in exactly the same way? You need to supply the mechanism. Physicists say the mechanism is the one mechanism each of these “clocks” has in common - time. **Half Man Half Wit** said: > [@](#): > > But I can go to arbitrary points in the future – give me a powerful enough rocket, and I’ll return to this here spot in the year 30,000, having aged nary a day. **c\_goat** said: > [@](#): > > OK not trying to have a debate here but this wasn’t what I meant. I’m talking more about the instantaneous jump / time machine thing. But nobody has devised an instantaneous jump / time machine thing. Sure, they have been conceptualized, but nobody has worked out how they could work. So that is really a cop out. Whereas **Half Man Half Wit** is talking exactly about Relativity, about using velocity and acceleration to reduce the time he passes through compared to the time Earth passes through. That is how he gets to the future. Getting to the past would be a bit trickier for him. Oh, is that what you’re trying to distinguish? His ability to travel to some point in our past, not necessarily to travel to some point in our future by going really fast? Okay. All I can do is reiterate that no one has developed a credible means for achieving time travel to the past. All they can currently propose is reaching a point in the future at a different rate than the rest of us get there. But guess what - that requires Time to exist, and exist as a dimension of extent. **ivan astikov** said: > [@](#): > > Without a consciousness willing to apply measurements to existence, there wouldn’t be any ‘time’, would there? All our measurements are based upon the revolution of our planet at a point when some creature can experience and register them. Just because we conscious entities have become aware of time and chosen some arbitrary method of measuring that time, that does not mean we control the existence of time. Time is the extent of duration, the thing that allows change to occur. If there were just one instant, everything would be identical and never become different. Chemical reactions occur. They have duration. That duration is the passage of time. One thing having duration that has a cyclical nature is the rotation of our planet. That cyclical nature gives us an easy way to perceive change in consistent increments. But that is just a convenience for making consistent units of measure. The universe rolled on for a very long time before there were any puny humans around to start measuring it. ---
**Author:** ![c\_goat](https://avatars.discourse-cdn.com/v4/letter/c/f4b2a3/32.png) [@c\_goat](https://boards.straightdope.com/u/c_goat)\ **Post date:** [December 4, 2009, 2:35pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/35 "2009-12-04T14:35:56Z")
> [@Half\_Man\_Half\_Wit](#): > > But you don’t have a ‘space machine’, either – i.e. you can’t just bridge arbitrary distances instantaneously. Does that mean space doesn’t exist, too? And besides, what does ‘instantaneously’ mean in this context, exactly? > > What would prove time’s existence to you? You’re right, the instantaneous thing was a bad example, that’s obviously just a fictional construct. What I mean by time travel is more like being able to visit the future and then come back, or to view the past or future. Time dilation is only a one way trip, and only allows for travel in one direction. That wasn’t the kind of time travel I meant. As for what would prove time’s existence, I’m not really sure. I suppose if it could be shown that something from the future had an effect on the past that would do it. Time dilation makes me think it doesn’t exist, because if it existed it should be possible to measure it reliably. ---
**Author:** ![Bytegeist](https://avatars.discourse-cdn.com/v4/letter/b/9dc877/32.png) [@Bytegeist](https://boards.straightdope.com/u/Bytegeist)\ **Post date:** [December 4, 2009, 2:57pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/36 "2009-12-04T14:57:24Z")
> [@c\_goat](#): > > As for what would prove time’s existence, I’m not really sure. I suppose if it could be shown that something from the future had an effect on the past that would do it. Why doesn’t normal causation (events in the past affect the present and future) demonstrate the existence of time? > [@](#): > > Time dilation makes me think it doesn’t exist, because if it existed it should be possible to measure it reliably. Measurements of space are also affected by relative speeds. Distances and lengths shrink according to a moving observer, along the direction of his motion. So then, I guess that would mean space doesn’t exist either, since it can’t be measured “reliably”. Also, the frequency of emitted light (or other EM radiation) changes as a function of the relative speed of the emitter and the observer. Therefore, color doesn’t exist. ---
**Author:** ![c\_goat](https://avatars.discourse-cdn.com/v4/letter/c/f4b2a3/32.png) [@c\_goat](https://boards.straightdope.com/u/c_goat)\ **Post date:** [December 4, 2009, 3:28pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/37 "2009-12-04T15:28:16Z")
> [@Irishman](#): > > So how does any change occur? How can an acorn grow to a tree? How can ice melt? How can something move? How can anything ever be different? Location in space is defined by three coordinates. Shape in space is defined by three coordinates. But in order for any change to occur, there has to be a framework, a context, a _dimension_ in which to occur. That _dimension_ for change is called time. This is where things get philosophical. It sounds like you’re saying change exists, therefore so does time. I’m saying that’s not necessarily the case, time only “exists” as something we use to measure or describe change. > [@](#): > > I _think_ your hung up on what the word “dimension” means. > … > I think the issue is perceiving Space as a physical something. We have to be careful to differentiate the Space of “where things exist” from the space that is the scattering of things outside of Earth’s atmosphere. That space occurs _in_ Space, but does not directly constitute Space. Probably… I can’t say I really know what it means. When I spoke of Space, I meant the “where things exist” kind. I do think of it as a physical something. The 4th dimension in that context would be “where Space exists”. I understand how time is used as a 4th dimension of measurement, and I don’t have a problem with that. > [@](#): > > That is why physicists talk about the fabric of spacetime. They have proposed/framed the expanse of the three directional extents into the overarching concept of Space (in which objects and matter and energy occur). And they have discovered that time behaves similarly to the dimensions of space, that it is a measure of extent of a slightly different kind but still a measure of extent, and so they have incorporated it into 1 whole concept that works together. That is what _spacetime_ is - the framework of extents. My problem with spacetime is when it gets to the idea that all of spacetime actually exists simultaneously, and the possibility to bridge points along that system. As a concept for measuring/recording things, I’m OK with using 4 points to describe an event or object or whatever. > [@](#): > > But different types of clocks can be used - a mechanical (pendulum) clock, a radioactive decay clock, a “clock” based upon some other form of well understood and regulated chemical reaction (i.e. constant or mathematically consistent). And each of these different clocks are affected the same way. How can motion affect each of these clocks , clocks that mark time in very different ways and have different features and different susceptibilities to accelerations, in exactly the same way? I’m skeptical that they’re all actually affected the same way. We’re only capable of a tiny fragment of light speed for our experimentation. I don’t think that’s enough where a truly significant measurement can be made. Maybe at .75c a pendulum clock would be off by a month whereas the chemical one would be off by a year and a human along for the ride would look as though they aged 10 years. Also, has anyone ever done an experiment with multiple types of clocks at the same time? From what I read on Wikipedia it doesn’t appear to have been done. That would be interesting to me. > [@](#): > > Oh, is that what you’re trying to distinguish? His ability to travel to some point in our past, not necessarily to travel to some point in our future by going really fast? Yeah basically, my response above expands on that. ---
**Author:** ![c\_goat](https://avatars.discourse-cdn.com/v4/letter/c/f4b2a3/32.png) [@c\_goat](https://boards.straightdope.com/u/c_goat)\ **Post date:** [December 4, 2009, 3:46pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/38 "2009-12-04T15:46:46Z")
> [@Bytegeist](#): > > Why doesn’t normal causation (events in the past affect the present and future) demonstrate the existence of time? I don’t really know how to explain it. I guess because it’s “normal” for it to work that way. If time was real, it seems like it should work in any direction. > [@](#): > > Measurements of space are also affected by relative speeds. Distances and lengths shrink according to a moving observer, along the direction of his motion. So then, I guess that would mean space doesn’t exist either, since it can’t be measured “reliably”. I guess the thing here is that it’s not changing the actual distance/length, just the observers perception of it. With time, it’s supposed to be changing the actual amount of time. I suppose saying it can’t be measured reliably was the wrong choice of words. It doesn’t appear to have any kind of actual constancy is more like it. > [@](#): > > Also, the frequency of emitted light (or other EM radiation) changes as a function of the relative speed of the emitter and the observer. Therefore, color doesn’t exist. “Color” is just a classification of different frequencies of light. The emitted light still exists, and thus color still does too. ---
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [December 4, 2009, 3:51pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/39 "2009-12-04T15:51:54Z")
What you are describing is the death of the Universe-nothing happens-no movement-no velocity, acceleration or jerk. One moment is like the next, because all action has ceased. This period will end, when a bearded genleman proclaims “Let there be light” ---
**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:** [December 4, 2009, 4:32pm UTC](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804/40 "2009-12-04T16:32:03Z")
> [@c\_goat](#): > > I’m skeptical that they’re all actually affected the same way. We’re only capable of a tiny fragment of light speed for our experimentation. I don’t think that’s enough where a truly significant measurement can be made. Maybe at .75c a pendulum clock would be off by a month whereas the chemical one would be off by a year and a human along for the ride would look as though they aged 10 years. But the prediction made by special relativity is completely independent of the kind of clock mechanism used, and the reality is that we’re observing exactly the amount of time dilation theory predicts, so if it only held for certain kinds of clocks, then we’d have to have gotten enormously lucky to test just those kinds; and in a sense, yes, there have been different clocks used to test this: the well-known test is the two atomic clocks in jets flying in opposite directions around the world, but actually particle physicists confirm the prediction of time dilation to a much greater degree of accuracy all the time – the muon, sort of a slightly heavyset brother to the electron, has a lifetime of about 2.2 micro seconds. Now, these cats are routinely produced in the upper atmosphere by incident cosmic rays, and then detected on the ground. The problem is that even going at the speed of light, in 2.2 micro seconds, you’re only going to get about 660 metres far, which isn’t nearly enough to bridge the distance between the upper atmosphere and the surface. Only the time dilation predicted by special relativity can account for them getting here after all, and does so with high precision. The same goes for all other particles at relativistic speeds – and in the end, clocks are just large collections of particles, too. And yes, all those measurements do, in fact, agree with theoretical predictions. [Previous page](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804.md?page=1) [Next page](https://boards.straightdope.com/t/time-in-a-time-less-physics/519804.md?page=3)