# Why does special relativity predict the future already exists? **URL:** \ **Category:** Factual Questions\ **Created:** [January 31, 2017, 6:19pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677 "2017-01-31T18:19:04Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![KidCharlemagne](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@KidCharlemagne](https://boards.straightdope.com/u/KidCharlemagne)\ **Post date:** [February 1, 2017, 6:10am UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/21 "2017-02-01T06:10:44Z")
> [@rat\_avatar](#): > > The most simple answer, the future always exists for the same reason that “up” always exists. > > While there are some exceptions related to causality time is just one of the 4 dimensions that make up “spacetime” > > In spacetime your “world line” (if we ignore the fact that what is “you” gradually changes over time) is you, for your entire existence. > > Now there is a question about free will here that I cannot address without math but the fact that your worldline exists does not necessarily mean that things are pre-determaned in a way that you would think of as fate. > > Really the main implication is that the only thing that you can make sure observers can agree on is the spacetime interval. These observers may or may not agree on the timing of events, simultaneous of events, order of events etc… but they will always agree on the space time interval. (if they can observe the event) > > There is speculation and implications about free will in GR, but those tend to be either speculation on yet to be settled science or are conflating conflating the human construct of “spacetime” as an intuitive map of all time. > > If anyone else can point me at an tested theories on a predetermined future I would appropriate it but I doubt if it will ever be testable due to Hawking’s speech I saw back in the 80s > > “Not only does God play dice, but… he sometimes throws them where they cannot be seen.” > > But really even if you could know the state of the entire universe at one time this may likely not hold up once they find a way to merge GR and QM. > > That said, the world-line in spacetime is very useful but it does not to my knowledge strictly allow you to predict the future without knowing everything about the entire universe at one time. Which may be true but will never be possible (and only if you ignore the unsolved quantum issues) I’d love to see anything that indicates there’s a possibility for free will. As far as our brain is concerned, atoms might as well be billiard balls and any quantum effects are random, no? I might not believe in absolute determinism but my layman’ head can’t see any way around causal determinism. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [February 1, 2017, 7:00am UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/22 "2017-02-01T07:00:20Z")
> [@KidCharlemagne](#): > > I’d love to see anything that indicates there’s a possibility for free will. As far as our brain is concerned, atoms might as well be billiard balls and any quantum effects are random, no? I might not believe in absolute determinism but my layman’ head can’t see any way around causal determinism. Yes, most of these prediction ideas are the results of spherical cows. I do not have enough information around non GR but the small number of studies I have read recently seem to indicate that our “conscious” mind lives in the past. So I was being obtuse there. It is good to remember that it is highly unlikely that any of us will ever be able to intuitively think in 4 dimensional non-euclidian spacetime in an intuitive fashion. We just didn’t evolve with that as a core requirement for survival. The implications of this is that concepts and problem sets are reduced to thought experiments. But those thought experiments typically are very simplified. People need to think creatively but that doesn’t mean that those ideas are correct. The twin paradox as mentioned in the OP is more about time dilation and the relative effects. Some of the hardest concepts to grasp when you start out in GR is that there is no universal time, and that there is no arbitrary way to measure even distance between points in an objective way. This is why the twin paradox is a paradox. If one twin stays on earth and the other heads to some random point at the speed of light they are both going to think that the other is traveling away at the speed of light and each would see the other twins clock stop. The paradox was about which was actually aging slower. The answer is that the one in the space ship will have to turn around, and thus will be accelerating and it is that acceleration on return that makes the space travelers clock run slower. This is also the basic reason for length contraction, redshift etc… In a more real tangible example from your perspective a photon doesn’t experience time, as it is traveling at the speed of light, but from it’s perspective it does experience time but it’s lifetime is instant. This has been experimentally observed in several cases, like Muon that are created in the ionosphere that shouldn’t be able to reach the surface if it were not due to length contraction due to GR. There is no universal reference time, there is no universal reference frame, it is all relative. This can get very complicated very fast if you don’t simplify, as an example even basic entropy experiments start to break down if you want to consider gravity. As gravitational red shift which will cause “upward” traveling photons from heat to “blue shift” and have less energy while downward ones will red shift and will have more energy. (or the other way round as I may be mistaken) It is an insanely fun area of science but it does take a while to start to understand but I encourage anyone who finds it fun to learn things that will be beyond your intuitive mind to dig into it. It is fun to know that when you throw a baseball it is actually traveling at close to it’s straightest path through space time while you are being accelerated away from yours. ---
**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:** [February 1, 2017, 7:46am UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/23 "2017-02-01T07:46:17Z")
What does ‘already exists’ mean? The future doesn’t exist _now_, any more than ‘that place over there’ exists ‘right here’. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [February 1, 2017, 8:34am UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/24 "2017-02-01T08:34:44Z")
Special relativity is irrelevant. If we ignore free will discussions the universe either contains true randomness or is inherently predetermined. If it contains true randomness then the future does not exist by any sensible definition, if it’s inherently predetermined it does, for some definitions, but not by the pragmatic one just presented by Mangetout. Regardless of special relativity my future will be influenced by events already knowable at other points in space. Someone might have sent me a letter yesterday. Does that mean that my letter-reading future exists? No, because something might prevent it. The light of spectacular stellar phenomena I might be enjoying in my future are on their way right now, and someone closer to the phenomenon who were also aware of my existence could predict when that phenomenon will occur in my approximate location, but they are prevented from making accurate predictions since they can’t know exactly where I am, or what events may occur to prevent or delay me observing them. ---
**Author:** ![KidCharlemagne](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@KidCharlemagne](https://boards.straightdope.com/u/KidCharlemagne)\ **Post date:** [February 1, 2017, 1:28pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/25 "2017-02-01T13:28:41Z")
> [@Mangetout](#): > > What does ‘already exists’ mean? > > The future doesn’t exist _now_, any more than ‘that place over there’ exists ‘right here’. A lot of physicists believe that a 4th dimensional being could see your death today. That the entire past, present, and future have ‘already happened’ (or always existed) and time is just an illusion that we sense because evolution required we sense a chain of causality. If you put a two-dimensional being on the surface of a sphere and move that sphere through space, the space already exists. A three-dimensional being may move through a 4th dimension that already exists. ---
**Author:** ![FlikTheBlue](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fliktheblue/32/10972_2.png) [@FlikTheBlue](https://boards.straightdope.com/u/FlikTheBlue)\ **Post date:** [February 1, 2017, 1:42pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/26 "2017-02-01T13:42:15Z")
One scenario I play out in my head when contemplating this deterministic universe is the random nature of nuclear decay. Let’s say I have an atom of carbon 14 or hydrogen 3 or some other radioactive element in my body. It could randomly decay at such a moment that it will cause a mutation in one of my cells that will cause me to get cancer. Or it could randomly decay at a different time when it has been eliminated from my body and cause no damage to me. Obviously my future and the future of everyone I interact with will change due to this truly random event. Given that radioactive decay is random how can we say the future exists in some determined way? ---
**Author:** ![KidCharlemagne](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@KidCharlemagne](https://boards.straightdope.com/u/KidCharlemagne)\ **Post date:** [February 1, 2017, 2:03pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/27 "2017-02-01T14:03:02Z")
> [@FlikTheBlue](#): > > One scenario I play out in my head when contemplating this deterministic universe is the random nature of nuclear decay. Let’s say I have an atom of carbon 14 or hydrogen 3 or some other radioactive element in my body. It could randomly decay at such a moment that it will cause a mutation in one of my cells that will cause me to get cancer. Or it could randomly decay at a different time when it has been eliminated from my body and cause no damage to me. Obviously my future and the future of everyone I interact with will change due to this truly random event. Given that radioactive decay is random how can we say the future exists in some determined way? Because that radioactive decay might only appear random to us. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [February 1, 2017, 2:06pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/28 "2017-02-01T14:06:15Z")
> [@KidCharlemagne](#): > > A lot of physicists believe that a 4th dimensional being could see your death today. That the entire past, present, and future have ‘already happened’ (or always existed) and time is just an illusion that we sense because evolution required we sense a chain of causality. If you put a two-dimensional being on the surface of a sphere and move that sphere through space, the space already exists. A three-dimensional being may move through a 4th dimension that already exists. But that’s not a consequence of special relativity, it’s just using the imagery of special relativity, four-dimensional space-time, to illustrate determinism. And “evolution required we sense a chain of causality” as an explanation seems rather bizarre since the premise is that all of evolution is a predetermined path through a 4-D space where time isn’t “actually” special. ---
**Author:** ![KidCharlemagne](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@KidCharlemagne](https://boards.straightdope.com/u/KidCharlemagne)\ **Post date:** [February 1, 2017, 2:08pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/29 "2017-02-01T14:08:19Z")
> [@Whack-a-Mole](#): > > Try [this video.](https://youtu.be/MO_Q_f1WgQI?t=173) Watch for seven minutes and I think you will get it. Much better than the other ones. Mind exploding stuff. Ok I think I finally figured out what he’s talking about and, if so, he gives the concept a huge disservice like so many science popularizers who make the double-slit experiment look spookier than it is. The alien isn’t seeing our future when he bicycles towards us, he just sees a more recent version of our ancient past. I think. Someone correct me if I’m wrong. ---
**Author:** ![KidCharlemagne](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@KidCharlemagne](https://boards.straightdope.com/u/KidCharlemagne)\ **Post date:** [February 1, 2017, 2:11pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/30 "2017-02-01T14:11:54Z")
> [@naita](#): > > But that’s not a consequence of special relativity, it’s just using the imagery of special relativity, four-dimensional space-time, to illustrate determinism. > > And “evolution required we sense a chain of causality” as an explanation seems rather bizarre since the premise is that all of evolution is a predetermined path through a 4-D space where time isn’t “actually” special. Well the most bizarre aspect of minkowski space-time, if it’s true, would be the explanation for why we experience a sense of now. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [February 1, 2017, 2:53pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/31 "2017-02-01T14:53:54Z")
\ Does existence precede essence … or does essence precede existence? To wit … the past does not exist … we have only the memory of the past and these memories only exist in the here-and-now … we have only predictions of the future and these predictions only exist (again) in the here-and-now … only the present has essence, only the present has meaning, only the present has existence … all else is imagination … \ I now return you to your normal time/space … ---
**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:** [February 1, 2017, 4:07pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/32 "2017-02-01T16:07:18Z")
> [@KidCharlemagne](#): > > A lot of physicists believe that a 4th dimensional being could see your death today. That the entire past, present, and future have ‘already happened’ (or always existed) and time is just an illusion that we sense because evolution required we sense a chain of causality. If you put a two-dimensional being on the surface of a sphere and move that sphere through space, the space already exists. A three-dimensional being may move through a 4th dimension that already exists. Not ‘today’. A 4th-dimensional being might be able to see it all (and I’m not even going to say ‘all at once’), but ‘ **see all of time today** ’ is analogous to ‘ **be everywhere in the same place** ’. ---
**Author:** ![KidCharlemagne](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@KidCharlemagne](https://boards.straightdope.com/u/KidCharlemagne)\ **Post date:** [February 1, 2017, 4:15pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/33 "2017-02-01T16:15:38Z")
> [@Mangetout](#): > > Not ‘today’. > > A 4th-dimensional being might be able to see it all (and I’m not even going to say ‘all at once’), but ‘ **see all of time today** ’ is analogous to ‘ **be everywhere in the same place** ’. Yes it would have to be a 4th dimensional being’s version of “today.” ---
**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:** [February 1, 2017, 4:28pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/34 "2017-02-01T16:28:11Z")
> [@KidCharlemagne](#): > > Yes it would have to be a 4th dimensional being’s version of “today.” No. ‘today’ is a thing that happens to beings who do not have freedom of movement in the 4th dimension. A 4th-dimensional being would experience time _as a dimension_ - not ‘all bunched up in one place’. ‘Wednesday’ would be a traversible point on the dimension of ‘everywhen’ - in the same way as ‘here’ is a traversible point within spatial 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:** [February 1, 2017, 5:12pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/35 "2017-02-01T17:12:40Z")
The reason why some believe that special relativity implies a block universe (‘eternalism’) is basically the [Rietdijk-Putnam argument](https://en.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argument): two observers, which may at one point be in the same location, have, if they are relatively moving, different planes of simultaneity—i.e. different notions of which events they call ‘now’. One observer’s ‘now’ may include events to the future of events of the other observer’s ‘now’. For instance, if you’re standing still in the street, then to you, on your plane of simultaneity, a group of aliens in the Andromeda Galaxy may be contemplating whether to attack the Milky Way; while, if I pass you in my car, then, on my plane of simultaneity, the aliens have already started their conquest. The catch is that both you and me are simultaneous, while the alien’s debating is simultaneous to you, and their leaving for our galaxy is simultaneous to me. Hence, or so the argument goes, there can be no actual question of whether the aliens decide to invade, or not: their future is fixed, and by extension, so are all events in the future. There are ways around this, however. One possibility would be to subscribe to a [Lorentzian interpretation](https://en.wikipedia.org/wiki/Lorentz_ether_theory) of special relativity: since there, the phenomena of relativity are not due to space-time (which can be treated as Newtonian), there will be no problem with simultaneity. And indeed, one can argue that subscribing to the Minkowskian interpretation that places space-time at the center of special relativity already commits one to a kind of determinism: for what could it mean if one believes that the spacetime manifold is real, there are some future events that only come into existence? In what time should they come into existence? > [@Sage\_Rat](#): > > But remember that Special Relativity and Quantum Mechanics haven’t yet been joined together. They have: that’s called quantum field theory. The problems are with the general theory of relativity. ---
**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:** [February 1, 2017, 5:27pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/36 "2017-02-01T17:27:39Z")
> [@Mangetout](#): > > No. ‘today’ is a thing that happens to beings who do not have freedom of movement in the 4th dimension. A 4th-dimensional being would experience time _as a dimension_ - not ‘all bunched up in one place’. ‘Wednesday’ would be a traversible point on the dimension of ‘everywhen’ - in the same way as ‘here’ is a traversible point within spatial dimensions. Put another way, even for three-dimensional beings such as ourselves, but equipped with a time machine, when Doc sends Einstein one minute into the future, it’s not valid to say "He’s in the future now’. Because he’s in the future. ---
**Author:** ![KidCharlemagne](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@KidCharlemagne](https://boards.straightdope.com/u/KidCharlemagne)\ **Post date:** [February 1, 2017, 6:36pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/37 "2017-02-01T18:36:53Z")
> [@Mangetout](#): > > No. ‘today’ is a thing that happens to beings who do not have freedom of movement in the 4th dimension. A 4th-dimensional being would experience time _as a dimension_ - not ‘all bunched up in one place’. ‘Wednesday’ would be a traversible point on the dimension of ‘everywhen’ - in the same way as ‘here’ is a traversible point within spatial dimensions. I actually meant to clarify that but my edit was too late. I agree. ---
**Author:** ![KidCharlemagne](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@KidCharlemagne](https://boards.straightdope.com/u/KidCharlemagne)\ **Post date:** [February 1, 2017, 6:56pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/38 "2017-02-01T18:56:24Z")
> [@Half\_Man\_Half\_Wit](#): > > The catch is that both you and me are simultaneous, while the alien’s debating is simultaneous to you, and their leaving for our galaxy is simultaneous to me. Hence, or so the argument goes, there can be no actual question of whether the aliens decide to invade, or not: their future is fixed, and by extension, so are all events in the future. Well to me that isn’t the future described by eternalism. The aliens leaving their planet has already happened on the alien planet. To me, the guy in the car is just seeing a more recent version of the alien’s past. Is that right or am I missing something? ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [February 1, 2017, 7:29pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/39 "2017-02-01T19:29:57Z")
> [@KidCharlemagne](#): > > Well to me that isn’t the future described by eternalism. The aliens leaving their planet has already happened on the alien planet. To me, the guy in the car is just seeing a more recent version of the alien’s past. Is that right or am I missing something? Eternalism is a philosophical concept that says all points in time are “real”, vs that only right now is “real” That is a very very different concept from GR where there is no universal objective time at all. There are possible solutions to GR like closed timelike curves where time may not be causally connected to neighbors and it may even loop back on itself. The math works out but these are not proven but it would be possible for an object to move around this loop and return to the same place and time that it started. The difficult to accept idea that you are missing is that there is no “more recent version of the alien’s past” Because there is no objective universal clock. Do not try and bend the spoon. … Instead… only try to realize the truth. … there is no spoon. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [February 1, 2017, 7:47pm UTC](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677/40 "2017-02-01T19:47:08Z")
To further expand on this, think about how a straight line is the shortest path between two points but only with two dimensions. In 3+ dimensions you have a “geodesic” which the shortest possible line between two points. The Earth orbiting the Sun is following the geodesic, it is going “straight” and at a constant speed but as spacetime is curved it ends up orbiting the sun. The same thing can apply to the time dimension as well due to the curvature of spacetime. In this context “gravity” is a “fictional force” just like “centrifugal force” that doesn’t mean that it is not an observable force but that it is one that is due to your frame of reference. You can think of gravity as the ground running into you and pushing you away from your geodesic and making you take a longer path to get to the same destination in the time dimension. When you drop a penny off of a skyscraper or toss a baseball it’s curved path is actually going through time faster because it is following a path closer to the geodesic. These concepts are very difficult to accept but they have passed every test devised so far. Spacetime is non-euclidean and those concepts do not map to the “flat” geometry of everyday intuition. It is not just that the manifold of spacetime is curved, but the lines that would make up the X&Y divisions in euclidian geometry are not straight, equal spaced nor are they necessarily parallel. Worse yet due to effects like frame dragging objects moving through the manifold actually effect the global topology. It is a mad mad world. [Previous page](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677.md?page=1) [Next page](https://boards.straightdope.com/t/why-does-special-relativity-predict-the-future-already-exists/778677.md?page=3)