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It's answer of "No" is predicated on two assumptions: that the lifeform is not colonial in nature and that time is not a localized phenomenon. While on the surf

It's answer of "No" is predicated on two assumptions: that the lifeform is not colonial in nature and that time is not a localized phenomenon. While on the surface that later assumption might sound absurd, our universe could very well be a Local Bubble of time. Time could even be a biological function of a higher dimensional being that is the size of the universe. There is also no way to disprove that without observing beyond the universe, which may get a bit dicey.

Swizec 9y ago
> There is also no way to disprove that without observing beyond the universe, which may get a bit dicey. My high school physics prof had the best answer to "What is beyond the universe?" --> "Surely if we ever find something outside of the universe, we will be smart enough to call that the universe too" He was referencing the idea that universe contains everything by definition.
- jfaucett 9y ago
  Thats a clever but not very mathematical answer. The general problem here is the conflation of universe i.e. "all of spacetime and everything we will ever discover" with the idea of a universal set, which doesn't have to include all elements and is rather arbitrary/relative.
- olegkikin 9y ago
  In terms of definitions, generally cosmos contains everything. Universe is our local observable space-time with the earliest event we can detect being the big bang.
  - Swizec 9y ago
    > Universe is our local observable space-time So if we observe something beyond what is currently observable, would that not become observable and thus part of the universe?
    - alansammarone 9y ago
      Yes, but it might also be the case that we don't observe something outside of it, but rather infer the existence of something outside of it through some other phenomenon (which is much more probable - observing something outside of the visible universe as we know it would violate relativity). In that sense, it would be there, but would never be visible.
      - Swizec 9y ago
        That's a really interesting question. If something is indirectly observable (you can observe/measure its effect), does that make it observable or not? Transitivit would say yes. If A implies B and B implies C then A implies C. That is, if you can observe A and that implies B, then you can observe B. Which makes it observable, no?
      - barrkel 9y ago
        All observations are inferences from indirect phenomena.
    - olegkikin 9y ago
      You're in a room. You give it label "room". Then you find a door, you go outside of the room, you don't call everything outside "room", you give new things new names. For now we're stuck in our universe, we know it's expanding (in something, potentially). So we preemptively give the name "cosmos" to EVERYTHING. It's entirely possible that cosmos is equal to universe. But it's also possible there are other universes out there, or something entirely different.
      - LambdaComplex 9y ago
        In your scenario, the door is a clear divider between "room" and "not room." What's the equivalent divider in the universe scenario?
    - cmiller1 9y ago
      The term observable when used in the context of the observable universe doesn't necessarily mean something we can actually measure or look at, but rather that which could theoretically have interacted with anything we could interact with based on the speed of light, the age of the universe, and cosmic expansion. Think of it as a bubble of time and everything outside of it hasn't happened yet.
eljimmy 9y ago
Thinking about what exists outside the universe always makes my brain feel weird. It seems impossible for your thoughts to imagine anything because your thoughts themselves are bound by the universe itself.
- komali2 9y ago
  Well even worse, our thoughts are bound by some maximum distance of comprehension. We can abstract the stellar scale but we can't understand it like we understand the distance across the street or whatever. I find this frustrating :(
  - ztjio 9y ago
    Well I think the implication that we can't understand/comprehend these things is itself frustrating and also wrong. Why does one assume that the scale of the universe and the scale of that street you refer to are any different? In both cases you are experiencing and considering an estimation of potentially infinite space at an almost metaphorical level as it relates to your experience, plans, and actions. Indeed, you can consider the universe as this thing which is maybe boundless and has so much stuff and might go on forever but for some reason you think it's any harder than realizing that the street may be infinite in space as well, by virtue of continuous subdivision. Before trying to dive in on any estimate of the smallest thing, do remember that smart people once thought atoms were the smallest thing, and then particles, and so on. And remember that the street itself, even just the stretch you're concerned about, is composed of a ludicrously large number of the "smallest" things we current are aware of. If we let go of this idea that at our own size, things are just some number of things that we can reason about (since that's clearly false, do you reason about the billions of living organisms in your own body right now? Could you?) then we can start to realize that smaller or bigger, we're merely consider a continuum at different scales and it's perfectly reasonable for the human mind to do so, it does so every day all the time.
    - komali2 9y ago
      I was thinking along the lines of evolutionary biology - I'm assuming my human brain is only capable of truly processing scales that realistically my ancestors would experience.
adrianratnapala 9y ago
If time were a different thing somewhere else, then physics in that somewhere else would very different, and our local concept of spatial size and even mass would not be applicable. So you still wouldn't have a life form "the size" of Galaxy. But you would still have something just as remarkable.
necessity 9y ago
Given no context I would have guessed that this comment was made on a Star Trek fan forum.
ztjio 9y ago
The position that time is not a localized phenomenon is preposterous. Given the observations of relativity and the effect that local gravitational force has on passage of time, and more recent experiment and theory about time actually arising as an effect of quantum entanglement (https://arxiv.org/abs/1310.4691 https://arxiv.org/abs/1310.4691), to presume in the context of such a big, extremely-theoretical idea that time is not local is plain nuts. It's not so hard to imagine that the rules of relativity are imposed and that outside of that imposition, they don't exist or are discontinuous to some degree. Indeed, it doesn't even take any imagination if one considers the theories and research related to what I linked above. So personally I'd dismiss the conclusion given its predication on this idea. To me, time not being local is the controversial position.
- coldtea 9y ago
  >It's not so hard to imagine that the rules of relativity are imposed and that outside of that imposition, they don't exist or are discontinuous to some degree. As if some not widely accepted recent papers without empirical verification are the ultimate source of truth in physics? All kinds of bizarro ideas are a dime a dozen in papers...
  - freshhawk 9y ago
    Time as an emergent phenomena is hardly a fringe idea.
- raattgift 9y ago
  > preposterous Well, specifically, proper-time intervals are path-local in General Relativity (GR). There is a unique coordinate-invariant proper-time interval between two points on a timelike worldline. I think that extending that to "time is a localized phenomenon" is harder than it seems, notably because worldlines depend on the full solution of the Einstein Field Equations. In a Big Bang cosmology (with a hyperbolization of the EFEs and ignoring constraints and diffeomorphism freedom), it's pretty brave to deny a relationship between the early boundary and the values of the fields at any point p on the manifold given that the causal cone at p of M contains the Big Bang. > effect that local gravitational force has on the passage of time It's the metric that leads to Lorentzian observables between observers at different points in the manifold. The metric near bodies like Earth closely approximates that of Schwarzschild spacetime in the way it generates geodesics including the null geodesics (among others) carrying information from one observer to another. Effects like gravitational redshift arise from the fact that in spacetime more-curved paths are shorter than less-curved paths (as opposed to how curved paths are longer than straight paths through Euclidean space). The metric's generation of geodesics is difficult to relate to a classical force or potential in general. Two objects in vacuum free-fall can be at different gravitational potential while feeling no force whatsoever; the one at higher potential ticks faster. It's a bit easier in near-Schwarzschild. Consider two atomic clocks falling from different altitudes[1] towards the same point on the (practically atmosphere-free) moon; almost all observers will agree that the higher clock runs faster than the lower clock until they are both smashed together on the surface. Yet if each clock is equipped with an vector accelerometer, both accelerometers will point nowhere in particular with a magnitude of zero from the start of their free-fall trajectory until collision with the moon's surface -- the first time force is reported by the accelerometers is when "lithobraking" starts. However, properly considering gravitational potential as a 4-vector generally requires some choices which eat the redundancies in the Einstein Field Equations. In General Relativity one has only the metric and Christoffel symbols and tedious arguments about which mathematical objects correspond to a Newtonian notion of a gravitational field (answer: "it depends" or "none of them"). Gauge-fixing lets one set a "depends" condition such that one can recover a vector potential field and a scalar field strength at each point; this approach is taken very seriously in Fedosin's covariant theory of gravitation for instance. > effect that local gravitational force has on passage of time Even if one takes steps to model some aspects of the gravitational interaction as a force, the proper time interval of an object doesn't change with the force acting on it. But the frequencies, lengths and related quantities of an object at some distance does depend on the force the object feels compared to the force the observer feels. (Moreover, if observers are in vacuum free-fall then they will feel no force at all, and can only infer the gravitational interaction from either a deviation from a straight-line track on a choice of coordinates, or by comparing the ticking rates of their own wristwatch with the wristwatch of several observer at some distance -- from [Synge 1960] this would take a minimum of five freely-falling wristwatches in total). Generally the complexities of setting down this kind of gauge-and-coordinate conditions leads relativists away from worrying about relating GR's mathematical objects and Newton's, and it's easier to say "gravitation is not a force" rather than "with some effort you can treat gravitation as a force in local coordinates and in a local gauge but you'll still find yourself returning to the Special Relativistic forms of physics equations because they genuinely are the simplest form and are always valid in the neighbourhood around a point on a geodesic". > if one considers the theories and research related to what I linked above General Relativity is in extremely precise accord with observation at many length scales and direct experiment within the solar system. Deviations from General Relativity that are different in the limit of the parameterized post-Newtonian formalism (which applies at solar system scales) are almost entirely ruled out. Although it is perfectly reasonable to consider General Relativity to be an emergent theory, the theory it emerges from is (a) unknown (b) unobvious and (c) extremely difficult to take guesses at. Indeed, your offer of 1310.4691 is wholly rooted in this: canonically quantized GR conflicts violently with observations and experiments, and the usual workaround is to do some condition-fixing (which your referenced paper does) and then to try to get around the pseudo-forces brought in to describe local physics (in models like Page-Wooter these pseudo-forces appear as constraints in the theory ([2], which your authors reference in their first sentence and several times thereafter). The paper you point to also notes that the proposed experiment cannot select among a number of theories including General Relativity (where the Hamiltonian itself is a constraint). > To me, time not being local is the controversial position. I dunno, we do appear to live in an observable universe which admits an obvious equatorial 3+1 slicing in which there are an awful lot of Eulerian and nearly-Eulerian observers. Is the hill to die on the alignment of one's "natural" choice of timelike axis with the metric expansion or the way you put down coordinates on that axis? And how do you square either of those choices with the initial value formalism? - -- [1] This is implicitly fixing a gauge wherein the surface of the moon is special; this is analogous to having a set of tunable air-pressure gauges at a point at sea level and setting it to 0 there, then using the readings of the tuned pressure gauges in helicopters riding above one another over the 0 point in order to say things about the state of each helicopter. In particular, one would use the reading of the pressure gauge as the basis of a coordinate axis (e.g. in marking coordinates on the radial axis in spherical coordinates on the 0-calibration point, or on the z axis in a choice of Cartesian coordinates on the 0-calibration point). [2] K. Kuchař, in G. Kunstatter, D. Vincent, and J. Williams (eds), Proceedings of the 4th Canadian Conference on General Relativity and Relativistic Astrophysics, (Singapore, World Scientific, 1992).

Swizec 9y ago

> There is also no way to disprove that without observing beyond the universe, which may get a bit dicey. My high school physics prof had the best answer to "What is beyond the universe?" --> "Surely if we ever find something outside of the universe, we will be smart enough to call that the universe too" He was referencing the idea that universe contains everything by definition.

jfaucett 9y ago
Thats a clever but not very mathematical answer. The general problem here is the conflation of universe i.e. "all of spacetime and everything we will ever discover" with the idea of a universal set, which doesn't have to include all elements and is rather arbitrary/relative.
olegkikin 9y ago
In terms of definitions, generally cosmos contains everything. Universe is our local observable space-time with the earliest event we can detect being the big bang.
- Swizec 9y ago
  > Universe is our local observable space-time So if we observe something beyond what is currently observable, would that not become observable and thus part of the universe?
  - alansammarone 9y ago
    Yes, but it might also be the case that we don't observe something outside of it, but rather infer the existence of something outside of it through some other phenomenon (which is much more probable - observing something outside of the visible universe as we know it would violate relativity). In that sense, it would be there, but would never be visible.
    - Swizec 9y ago
      That's a really interesting question. If something is indirectly observable (you can observe/measure its effect), does that make it observable or not? Transitivit would say yes. If A implies B and B implies C then A implies C. That is, if you can observe A and that implies B, then you can observe B. Which makes it observable, no?
    - barrkel 9y ago
      All observations are inferences from indirect phenomena.
  - olegkikin 9y ago
    You're in a room. You give it label "room". Then you find a door, you go outside of the room, you don't call everything outside "room", you give new things new names. For now we're stuck in our universe, we know it's expanding (in something, potentially). So we preemptively give the name "cosmos" to EVERYTHING. It's entirely possible that cosmos is equal to universe. But it's also possible there are other universes out there, or something entirely different.
    - LambdaComplex 9y ago
      In your scenario, the door is a clear divider between "room" and "not room." What's the equivalent divider in the universe scenario?
  - cmiller1 9y ago
    The term observable when used in the context of the observable universe doesn't necessarily mean something we can actually measure or look at, but rather that which could theoretically have interacted with anything we could interact with based on the speed of light, the age of the universe, and cosmic expansion. Think of it as a bubble of time and everything outside of it hasn't happened yet.

eljimmy 9y ago

Thinking about what exists outside the universe always makes my brain feel weird. It seems impossible for your thoughts to imagine anything because your thoughts themselves are bound by the universe itself.

komali2 9y ago
Well even worse, our thoughts are bound by some maximum distance of comprehension. We can abstract the stellar scale but we can't understand it like we understand the distance across the street or whatever. I find this frustrating :(
- ztjio 9y ago
  Well I think the implication that we can't understand/comprehend these things is itself frustrating and also wrong. Why does one assume that the scale of the universe and the scale of that street you refer to are any different? In both cases you are experiencing and considering an estimation of potentially infinite space at an almost metaphorical level as it relates to your experience, plans, and actions. Indeed, you can consider the universe as this thing which is maybe boundless and has so much stuff and might go on forever but for some reason you think it's any harder than realizing that the street may be infinite in space as well, by virtue of continuous subdivision. Before trying to dive in on any estimate of the smallest thing, do remember that smart people once thought atoms were the smallest thing, and then particles, and so on. And remember that the street itself, even just the stretch you're concerned about, is composed of a ludicrously large number of the "smallest" things we current are aware of. If we let go of this idea that at our own size, things are just some number of things that we can reason about (since that's clearly false, do you reason about the billions of living organisms in your own body right now? Could you?) then we can start to realize that smaller or bigger, we're merely consider a continuum at different scales and it's perfectly reasonable for the human mind to do so, it does so every day all the time.
  - komali2 9y ago
    I was thinking along the lines of evolutionary biology - I'm assuming my human brain is only capable of truly processing scales that realistically my ancestors would experience.

adrianratnapala 9y ago

If time were a different thing somewhere else, then physics in that somewhere else would very different, and our local concept of spatial size and even mass would not be applicable. So you still wouldn't have a life form "the size" of Galaxy. But you would still have something just as remarkable.

necessity 9y ago

Given no context I would have guessed that this comment was made on a Star Trek fan forum.

ztjio 9y ago

The position that time is not a localized phenomenon is preposterous. Given the observations of relativity and the effect that local gravitational force has on passage of time, and more recent experiment and theory about time actually arising as an effect of quantum entanglement (https://arxiv.org/abs/1310.4691 https://arxiv.org/abs/1310.4691), to presume in the context of such a big, extremely-theoretical idea that time is not local is plain nuts. It's not so hard to imagine that the rules of relativity are imposed and that outside of that imposition, they don't exist or are discontinuous to some degree. Indeed, it doesn't even take any imagination if one considers the theories and research related to what I linked above. So personally I'd dismiss the conclusion given its predication on this idea. To me, time not being local is the controversial position.

coldtea 9y ago
>It's not so hard to imagine that the rules of relativity are imposed and that outside of that imposition, they don't exist or are discontinuous to some degree. As if some not widely accepted recent papers without empirical verification are the ultimate source of truth in physics? All kinds of bizarro ideas are a dime a dozen in papers...
- freshhawk 9y ago
  Time as an emergent phenomena is hardly a fringe idea.
raattgift 9y ago
> preposterous Well, specifically, proper-time intervals are path-local in General Relativity (GR). There is a unique coordinate-invariant proper-time interval between two points on a timelike worldline. I think that extending that to "time is a localized phenomenon" is harder than it seems, notably because worldlines depend on the full solution of the Einstein Field Equations. In a Big Bang cosmology (with a hyperbolization of the EFEs and ignoring constraints and diffeomorphism freedom), it's pretty brave to deny a relationship between the early boundary and the values of the fields at any point p on the manifold given that the causal cone at p of M contains the Big Bang. > effect that local gravitational force has on the passage of time It's the metric that leads to Lorentzian observables between observers at different points in the manifold. The metric near bodies like Earth closely approximates that of Schwarzschild spacetime in the way it generates geodesics including the null geodesics (among others) carrying information from one observer to another. Effects like gravitational redshift arise from the fact that in spacetime more-curved paths are shorter than less-curved paths (as opposed to how curved paths are longer than straight paths through Euclidean space). The metric's generation of geodesics is difficult to relate to a classical force or potential in general. Two objects in vacuum free-fall can be at different gravitational potential while feeling no force whatsoever; the one at higher potential ticks faster. It's a bit easier in near-Schwarzschild. Consider two atomic clocks falling from different altitudes[1] towards the same point on the (practically atmosphere-free) moon; almost all observers will agree that the higher clock runs faster than the lower clock until they are both smashed together on the surface. Yet if each clock is equipped with an vector accelerometer, both accelerometers will point nowhere in particular with a magnitude of zero from the start of their free-fall trajectory until collision with the moon's surface -- the first time force is reported by the accelerometers is when "lithobraking" starts. However, properly considering gravitational potential as a 4-vector generally requires some choices which eat the redundancies in the Einstein Field Equations. In General Relativity one has only the metric and Christoffel symbols and tedious arguments about which mathematical objects correspond to a Newtonian notion of a gravitational field (answer: "it depends" or "none of them"). Gauge-fixing lets one set a "depends" condition such that one can recover a vector potential field and a scalar field strength at each point; this approach is taken very seriously in Fedosin's covariant theory of gravitation for instance. > effect that local gravitational force has on passage of time Even if one takes steps to model some aspects of the gravitational interaction as a force, the proper time interval of an object doesn't change with the force acting on it. But the frequencies, lengths and related quantities of an object at some distance does depend on the force the object feels compared to the force the observer feels. (Moreover, if observers are in vacuum free-fall then they will feel no force at all, and can only infer the gravitational interaction from either a deviation from a straight-line track on a choice of coordinates, or by comparing the ticking rates of their own wristwatch with the wristwatch of several observer at some distance -- from [Synge 1960] this would take a minimum of five freely-falling wristwatches in total). Generally the complexities of setting down this kind of gauge-and-coordinate conditions leads relativists away from worrying about relating GR's mathematical objects and Newton's, and it's easier to say "gravitation is not a force" rather than "with some effort you can treat gravitation as a force in local coordinates and in a local gauge but you'll still find yourself returning to the Special Relativistic forms of physics equations because they genuinely are the simplest form and are always valid in the neighbourhood around a point on a geodesic". > if one considers the theories and research related to what I linked above General Relativity is in extremely precise accord with observation at many length scales and direct experiment within the solar system. Deviations from General Relativity that are different in the limit of the parameterized post-Newtonian formalism (which applies at solar system scales) are almost entirely ruled out. Although it is perfectly reasonable to consider General Relativity to be an emergent theory, the theory it emerges from is (a) unknown (b) unobvious and (c) extremely difficult to take guesses at. Indeed, your offer of 1310.4691 is wholly rooted in this: canonically quantized GR conflicts violently with observations and experiments, and the usual workaround is to do some condition-fixing (which your referenced paper does) and then to try to get around the pseudo-forces brought in to describe local physics (in models like Page-Wooter these pseudo-forces appear as constraints in the theory ([2], which your authors reference in their first sentence and several times thereafter). The paper you point to also notes that the proposed experiment cannot select among a number of theories including General Relativity (where the Hamiltonian itself is a constraint). > To me, time not being local is the controversial position. I dunno, we do appear to live in an observable universe which admits an obvious equatorial 3+1 slicing in which there are an awful lot of Eulerian and nearly-Eulerian observers. Is the hill to die on the alignment of one's "natural" choice of timelike axis with the metric expansion or the way you put down coordinates on that axis? And how do you square either of those choices with the initial value formalism? - -- [1] This is implicitly fixing a gauge wherein the surface of the moon is special; this is analogous to having a set of tunable air-pressure gauges at a point at sea level and setting it to 0 there, then using the readings of the tuned pressure gauges in helicopters riding above one another over the 0 point in order to say things about the state of each helicopter. In particular, one would use the reading of the pressure gauge as the basis of a coordinate axis (e.g. in marking coordinates on the radial axis in spherical coordinates on the 0-calibration point, or on the z axis in a choice of Cartesian coordinates on the 0-calibration point). [2] K. Kuchař, in G. Kunstatter, D. Vincent, and J. Williams (eds), Proceedings of the 4th Canadian Conference on General Relativity and Relativistic Astrophysics, (Singapore, World Scientific, 1992).