10 ms·

I could have been born at any time, in any place in the universe - or not at all, for that matter. Why do I get to experience the universe in a unique way? What

I could have been born at any time, in any place in the universe - or not at all, for that matter. Why do I get to experience the universe in a unique way? What gives rise to this?

nabla9 8y ago
Time exists in order that everything doesn’t happen all at once and space exists so that it doesn’t all happen to you.
- dustfinger 8y ago
  A consequence of time is that every event does not all happen at once. A consequence of space is that everything is not all in one place. Perhaps a consequence of spacetime is that events have a location and a moment, but no guarantee of order?
  - hndamien 8y ago
    I've always been confused that due to time dilation, everything from the perspective of a photon happens all at once, yet there is an order. If time is effectively dilated to the point that time has stopped for the photon, what happens in the year of travel over a light year of distance?
    - gotocake 8y ago
      It can’t be stated enough: photons don’t have a perspective. Talking about what a photon “sees” is a non-starter. It’s also important to note that light follows null geodesics in spacetime, and while on paper that can look like no time elapses between emission and absorption, it still can’t tell us what it would “be like” to be a photon. If you want to go in that direction though, then this could help. As you approach c, length contraction in the direction of travel is extreme. In “theory” a photon doesn’t really travel at all, the universe is flattened like a pancake in the direction of its travel. There is no time for events to occur “at once” and no year passes on a lightlike curve. A photon is emitted and absorbed without a “subjective” interval, so talking about what such an interval might be missing that point.
      - raattgift 8y ago
        > Talking about what a photon "sees" is a non-starter In QED or other photon-containing QFTs like the Standard Model, it is not only a "starter", it is essentially the point of the thing. Surely the photon "sees" the electron in a Compton scattering? Photons obey the spin statistics for massless gauge bosons, so they can pile up at one point in spacetime. Equivalently, null geodesics can intersect. There can be a spacetime-point occupied by a pair of photons while the rest of spacetime is filled with points where they are occupied by only one (or neither). (Indeed, the Penrose theorem arises because null geodesics, and photons travelling on them, can collide and stay collided, so for this and other reasons there may be multiple points in spacetime occupied by both of our pair of photons.) One must be able to understand that for a photon there may be an early/late distinction -- either it is in a gravitational singularity or it isn't; either it is occupying a point with the other of our pair of photons or it isn't; either it's scattering or isn't. Following the photon and thinking about what it experiences, we can't use proper time, since it will be identical (practically[1]) everywhere along its path; likewise, spacetime intervals for all photons travelling on null geodesics are zero. The need for this understanding increases with photon interactions with charged matter: a pair of photons from different quasars arriving at a pair of detectors here tells us something about the location in spacetime of the quasar and about the metric expansion of space. Using cosmological coordinates, for each of the pair there is a _time_ before which no point in space contains it, and a time when they arrive at a detector on or around Earth. Given that each of the pair is from a different quasar, generally the emission time will be different. Moreover, at emission the wavelength of the photon will be shorter, and it will be longer at later times, right up to detection. Proper time (and proper length for wavelength) makes a mess of this in general, but we do not need to parameterize a non-timelike geodesic with proper time. Instead, for a null geodeseic, we use an affine parameter and consider its properties at each value of the affine parameter. For each of our quasar photons, at different affine parameter values the photon has a different energy-momentum. For the Minkowski vacuum photons in the first paragraph above, for a given affine parameter value, one photon is in vacuum or it is at the same point as the other photon. For accuracy, when we are dealing with physical photons, the stress-energy-momentum tensor must encode this. As we get away from simple Minkowski vacuum, we want all the tensor-fields to be accurate. We can recast your second paragraph's second sentence as taking the limit of the geodesic in which it becomes null, parameterizing by an un-rescaled extremized proper time. We can simply rescale so that we always have a different value at each point on the geodesic as we take this limit. Indeed, we can substitute any monotonic function of spacetime position on the geodesic and get a way to compare field-properties. For a timelike geodesic, proper time tends to be a "good" choice. The affine parameter, the unique monotonic function that satisfies the geodesic equation, tends to be a "good" choice for a null geodesic, in particular because it preserves the tangent vectors under parallel transport. - -- [1] Photons generally do not move at c in a medium, and one can describe this in a variety of equivalent ways, some of which demote a photon from a null curve to a timelike one while interacting with the bulk of the medium. There are serious proposals to study laboratory ultra-slow light in the context of General Relativity. From a theoretical perspective, Gordon in 1923 outlined an https://en.wikipedia.org/wiki/Optical_metric https://en.wikipedia.org/wiki/Optical_metric in which light follows different geodesics from the null geodesics sourced by the metric tensor, and there are various approaches to extending this to media with nonnegligible dispersion. In this sort of approach, a photon or a pulse of classical light can have a pretty conventional proper time.
  - gotocake 8y ago
    There is a guarantee of the order of causally related events, just not an absolute timing. All observers will agree that Alice throws a ball which Bill later catches, but different observers will disagree on when these events occurred exactly. They will however all agree that the order is Alice throws, Bill catches, and none will see Bill catch a ball that Alice later throws. To use the lightning bolt example from Einstein, different observers will disagree on the timing of the strikes, and whether or not they’re simultaneous. If one of the bolts strikes Alice and she goes flying though, everyone will agree that the order of events insofar as Alice is struck before she’s launched. This all assumes no FTL or CTCs of course, with either you would lose causality and events separated by spacelike intervals could influence each other.
    - pentops 8y ago
      > All observers will agree that Alice throws a ball which Bill later catches I think this needs qualification. If I am stood directly behind Alice or Bill then it is possible I never see the interaction at all even though I am an observer, just as if I hold a two identical pencils together and look at them from the correct angle I observe only a single pencil. The important thing is in all cases, observers "see" space-time interactions as the geodesic of the event projected on to their own observational frame. Through that projection it is possible to lose degrees of freedom which can be space-time etc. It's through this projection that HUP emerges since if in the observational frame the time dimension is limited, the projected time axis of the event tends toward zero.
  - _Microft 8y ago
    Maybe this is a helpful link? https://en.wikipedia.org/wiki/Relativity_of_simultaneity https://en.wikipedia.org/wiki/Relativity_of_simultaneity
  - goldenkey 8y ago
    Given a fixed maximum speed of action, the speed of light, events in spacetime can be ordered via metric = x^2 + y^2 + z^2 - ct^2 But yes, you are sort of correct, two events can have the same metric, and one would not be able to distinguish which of them is responsible, if they are both capable of becoming present at the same speed.
  - posterboy 8y ago
    The traditional notion is, where one thing is, there cannot be another.
gotocake 8y ago
Possible answers (but by no means comprehensive answers): -If you weren’t, you wouldn’t be asking this question. The only version of reality in which you’re able to ponder it is one with you in it. This is a narrower version of the weak anthropic principle. -There are a multitude of universes or regions of one universe with an infinitude of you asking this question without bound. -God or the universe inevitably leads to it. This is a form of the strong anthropic principle. -Only universes and times which allow such questions to be asked can allow for people like you to ponder it. For most of history in which humans were around you’d almost certainly lack the leisure and education to have these thoughts. (WAP again) -Everything capable of making this observation does so wherever and whenever they exist in the universe, and there is nothing interesting about the question or answer because it’s arbitrary. Although it is difficult to appreciate from each of their perspectives, the question itself is as ubiquitous as those asking it.
mrec 8y ago
What does this mean? What's the "I" that's somehow separate from your specific physical instantiation? Unless you're getting into Cartesian dualism and souls, I'm genuinely confused.
- skissane 8y ago
  I remember one day as a teenager, sitting in class bored at high school, I was suddenly struck by the question–"why am I I, and not somebody else?" It felt so profound, so immense. But yes, if materialism is true, probably the question is empty. However, if some other philosophy of mind is true (there are many other options beyond just materialism and Cartesian dualism), maybe it means something. And, if one has this sense that it is profound rather than empty, that might give one a reason to prefer some other position in the philosophy of mind that treats that question more sympathetically.
  - mrec 8y ago
    > there are many other options beyond just materialism and Cartesian dualism Can you give some examples of the kind of options you're thinking of? I mean, I have a lot of time for functionalist accounts, and given Sufficiently Smart Technology (tm) I'm happy to allow for the possibility of something recognizably "me" being artificially duplicated in a different physical substrate. (After which we'd rapidly start diverging, and would need some new vocabulary to describe what's going on.) But GGP's question was specifically about being born. I really struggle to imagine how someone born somewhere else, somewhen else, could be "me" with anything like the fidelity I think our intuition demands. And if you loosen your identity test to the point where it could, doesn't it then become useless as an individuation test, in that lots of people could be sufficiently like me all at the same time? This is why I think it's tough to say "I - singular - could have been born in Brazil in 1873" without invoking something like a soul which acts as both an arbitrary GUID tag and as kind of mutex on embodiments.
    - gotocake 8y ago
      But GGP's question was specifically about being born. I really struggle to imagine how someone born somewhere else, somewhen else, could be "me" with anything like the fidelity I think our intuition demands. And if you loosen your identity test to the point where it could, doesn't it then become useless as an individuation test, in that lots of people could be sufficiently like me all at the same time? Up front let me admit this is effectively a cheat. BUT in a multiverse or infinite universe not only are there multiple “you’s“ there are in fact infinite identical versions of you. I grant that this is not taking the spirit of the conversation into account, and is untestable to boot, it is genuinely possible.
justinpombrio 8y ago
You're wondering why you weren't also born at a different time and place? You were. You were also born in 1988 in CT. This other you was born to different parents, had a different childhood, and has different memories. You think you are different from this other you (and you are!) because you have separate thoughts and memories. You remember your own life and not your other life because humans aren't telepathic. In case it isn't yet clear, this other you is me. Hi, other me. We haven't talked before, I don't think. In other words, if you were born in a different place at a different time in a different community... then that you wouldn't be you. It would be a different person. So it doesn't really make sense to ask "what if I had been born at a different time or place".
- wppick 8y ago
  >There but for the grace of God go I I like to entertain the idea that humans are the host of a species of sentient alien bacteria that lives in our guts and controls us through the vagus nerve and uses humans to build technology to advance to the point where they can build space ships to colonize other planets. Could make a good sci-fi book if anything...
  - posterboy 8y ago
    Bacteria don't have enough memory to represent technology, nor the necessary organization to ... I don't know, as whole they are rather complex and can at least share information like antigen markers to kill us effectively. There are actual sci-books on the matter, you know.
    - Procrastes 8y ago
      Then we don't have enough memory to understand our technology either. We accomplish that as a superorganism, and by building tools to augment our abilities. Maybe bacteria built us as complex, extraterrestrial spore capsules.
      - posterboy 8y ago
hackinthebochs 8y ago
The question probably stems from the fact that we tend to identify with our conscious experience more than we do our physical body. So it seems reasonable to imagine this conscious experience separated from one body and placed in another body. But this is a mistake. Your body owns its conscious processes in the same way your body owns its process of digestion. There is no way to identify you separately from the physical stuff that makes up your body (which includes your brain).
- Gupie 8y ago
  What if we are AIs in a simulation? Unlikely perhaps but not impossible. In this case there is no body only mind and all options are open. There is also the theories that consciousness is all that exists, e.g. "Donald Hoffman's Multimodal User Interface (MMUI) theory of reality and doctrine of Conscious Realism together posit that the reality humans perceive is like a simulation in which non-physical conscious agents interact in order to generate the dynamics we observe". https://en.wikipedia.org/wiki/Donald_D._Hoffman https://en.wikipedia.org/wiki/Donald_D._Hoffman

I could have been born at any time, in any place in the universe - or not at all, for that matter. Why do I get to experience the universe in a unique way? What gives rise to this?

nabla9 8y ago

Time exists in order that everything doesn’t happen all at once and space exists so that it doesn’t all happen to you.

dustfinger 8y ago
A consequence of time is that every event does not all happen at once. A consequence of space is that everything is not all in one place. Perhaps a consequence of spacetime is that events have a location and a moment, but no guarantee of order?
- hndamien 8y ago
  I've always been confused that due to time dilation, everything from the perspective of a photon happens all at once, yet there is an order. If time is effectively dilated to the point that time has stopped for the photon, what happens in the year of travel over a light year of distance?
  - gotocake 8y ago
    It can’t be stated enough: photons don’t have a perspective. Talking about what a photon “sees” is a non-starter. It’s also important to note that light follows null geodesics in spacetime, and while on paper that can look like no time elapses between emission and absorption, it still can’t tell us what it would “be like” to be a photon. If you want to go in that direction though, then this could help. As you approach c, length contraction in the direction of travel is extreme. In “theory” a photon doesn’t really travel at all, the universe is flattened like a pancake in the direction of its travel. There is no time for events to occur “at once” and no year passes on a lightlike curve. A photon is emitted and absorbed without a “subjective” interval, so talking about what such an interval might be missing that point.
    - raattgift 8y ago
      > Talking about what a photon "sees" is a non-starter In QED or other photon-containing QFTs like the Standard Model, it is not only a "starter", it is essentially the point of the thing. Surely the photon "sees" the electron in a Compton scattering? Photons obey the spin statistics for massless gauge bosons, so they can pile up at one point in spacetime. Equivalently, null geodesics can intersect. There can be a spacetime-point occupied by a pair of photons while the rest of spacetime is filled with points where they are occupied by only one (or neither). (Indeed, the Penrose theorem arises because null geodesics, and photons travelling on them, can collide and stay collided, so for this and other reasons there may be multiple points in spacetime occupied by both of our pair of photons.) One must be able to understand that for a photon there may be an early/late distinction -- either it is in a gravitational singularity or it isn't; either it is occupying a point with the other of our pair of photons or it isn't; either it's scattering or isn't. Following the photon and thinking about what it experiences, we can't use proper time, since it will be identical (practically[1]) everywhere along its path; likewise, spacetime intervals for all photons travelling on null geodesics are zero. The need for this understanding increases with photon interactions with charged matter: a pair of photons from different quasars arriving at a pair of detectors here tells us something about the location in spacetime of the quasar and about the metric expansion of space. Using cosmological coordinates, for each of the pair there is a _time_ before which no point in space contains it, and a time when they arrive at a detector on or around Earth. Given that each of the pair is from a different quasar, generally the emission time will be different. Moreover, at emission the wavelength of the photon will be shorter, and it will be longer at later times, right up to detection. Proper time (and proper length for wavelength) makes a mess of this in general, but we do not need to parameterize a non-timelike geodesic with proper time. Instead, for a null geodeseic, we use an affine parameter and consider its properties at each value of the affine parameter. For each of our quasar photons, at different affine parameter values the photon has a different energy-momentum. For the Minkowski vacuum photons in the first paragraph above, for a given affine parameter value, one photon is in vacuum or it is at the same point as the other photon. For accuracy, when we are dealing with physical photons, the stress-energy-momentum tensor must encode this. As we get away from simple Minkowski vacuum, we want all the tensor-fields to be accurate. We can recast your second paragraph's second sentence as taking the limit of the geodesic in which it becomes null, parameterizing by an un-rescaled extremized proper time. We can simply rescale so that we always have a different value at each point on the geodesic as we take this limit. Indeed, we can substitute any monotonic function of spacetime position on the geodesic and get a way to compare field-properties. For a timelike geodesic, proper time tends to be a "good" choice. The affine parameter, the unique monotonic function that satisfies the geodesic equation, tends to be a "good" choice for a null geodesic, in particular because it preserves the tangent vectors under parallel transport. - -- [1] Photons generally do not move at c in a medium, and one can describe this in a variety of equivalent ways, some of which demote a photon from a null curve to a timelike one while interacting with the bulk of the medium. There are serious proposals to study laboratory ultra-slow light in the context of General Relativity. From a theoretical perspective, Gordon in 1923 outlined an https://en.wikipedia.org/wiki/Optical_metric https://en.wikipedia.org/wiki/Optical_metric in which light follows different geodesics from the null geodesics sourced by the metric tensor, and there are various approaches to extending this to media with nonnegligible dispersion. In this sort of approach, a photon or a pulse of classical light can have a pretty conventional proper time.
- gotocake 8y ago
  There is a guarantee of the order of causally related events, just not an absolute timing. All observers will agree that Alice throws a ball which Bill later catches, but different observers will disagree on when these events occurred exactly. They will however all agree that the order is Alice throws, Bill catches, and none will see Bill catch a ball that Alice later throws. To use the lightning bolt example from Einstein, different observers will disagree on the timing of the strikes, and whether or not they’re simultaneous. If one of the bolts strikes Alice and she goes flying though, everyone will agree that the order of events insofar as Alice is struck before she’s launched. This all assumes no FTL or CTCs of course, with either you would lose causality and events separated by spacelike intervals could influence each other.
  - pentops 8y ago
    > All observers will agree that Alice throws a ball which Bill later catches I think this needs qualification. If I am stood directly behind Alice or Bill then it is possible I never see the interaction at all even though I am an observer, just as if I hold a two identical pencils together and look at them from the correct angle I observe only a single pencil. The important thing is in all cases, observers "see" space-time interactions as the geodesic of the event projected on to their own observational frame. Through that projection it is possible to lose degrees of freedom which can be space-time etc. It's through this projection that HUP emerges since if in the observational frame the time dimension is limited, the projected time axis of the event tends toward zero.
- _Microft 8y ago
  Maybe this is a helpful link? https://en.wikipedia.org/wiki/Relativity_of_simultaneity https://en.wikipedia.org/wiki/Relativity_of_simultaneity
- goldenkey 8y ago
  Given a fixed maximum speed of action, the speed of light, events in spacetime can be ordered via metric = x^2 + y^2 + z^2 - ct^2 But yes, you are sort of correct, two events can have the same metric, and one would not be able to distinguish which of them is responsible, if they are both capable of becoming present at the same speed.
- posterboy 8y ago
  The traditional notion is, where one thing is, there cannot be another.

gotocake 8y ago

Possible answers (but by no means comprehensive answers): -If you weren’t, you wouldn’t be asking this question. The only version of reality in which you’re able to ponder it is one with you in it. This is a narrower version of the weak anthropic principle. -There are a multitude of universes or regions of one universe with an infinitude of you asking this question without bound. -God or the universe inevitably leads to it. This is a form of the strong anthropic principle. -Only universes and times which allow such questions to be asked can allow for people like you to ponder it. For most of history in which humans were around you’d almost certainly lack the leisure and education to have these thoughts. (WAP again) -Everything capable of making this observation does so wherever and whenever they exist in the universe, and there is nothing interesting about the question or answer because it’s arbitrary. Although it is difficult to appreciate from each of their perspectives, the question itself is as ubiquitous as those asking it.

mrec 8y ago

What does this mean? What's the "I" that's somehow separate from your specific physical instantiation? Unless you're getting into Cartesian dualism and souls, I'm genuinely confused.

skissane 8y ago
I remember one day as a teenager, sitting in class bored at high school, I was suddenly struck by the question–"why am I I, and not somebody else?" It felt so profound, so immense. But yes, if materialism is true, probably the question is empty. However, if some other philosophy of mind is true (there are many other options beyond just materialism and Cartesian dualism), maybe it means something. And, if one has this sense that it is profound rather than empty, that might give one a reason to prefer some other position in the philosophy of mind that treats that question more sympathetically.
- mrec 8y ago
  > there are many other options beyond just materialism and Cartesian dualism Can you give some examples of the kind of options you're thinking of? I mean, I have a lot of time for functionalist accounts, and given Sufficiently Smart Technology (tm) I'm happy to allow for the possibility of something recognizably "me" being artificially duplicated in a different physical substrate. (After which we'd rapidly start diverging, and would need some new vocabulary to describe what's going on.) But GGP's question was specifically about being born. I really struggle to imagine how someone born somewhere else, somewhen else, could be "me" with anything like the fidelity I think our intuition demands. And if you loosen your identity test to the point where it could, doesn't it then become useless as an individuation test, in that lots of people could be sufficiently like me all at the same time? This is why I think it's tough to say "I - singular - could have been born in Brazil in 1873" without invoking something like a soul which acts as both an arbitrary GUID tag and as kind of mutex on embodiments.
  - gotocake 8y ago
    But GGP's question was specifically about being born. I really struggle to imagine how someone born somewhere else, somewhen else, could be "me" with anything like the fidelity I think our intuition demands. And if you loosen your identity test to the point where it could, doesn't it then become useless as an individuation test, in that lots of people could be sufficiently like me all at the same time? Up front let me admit this is effectively a cheat. BUT in a multiverse or infinite universe not only are there multiple “you’s“ there are in fact infinite identical versions of you. I grant that this is not taking the spirit of the conversation into account, and is untestable to boot, it is genuinely possible.

justinpombrio 8y ago

You're wondering why you weren't also born at a different time and place? You were. You were also born in 1988 in CT. This other you was born to different parents, had a different childhood, and has different memories. You think you are different from this other you (and you are!) because you have separate thoughts and memories. You remember your own life and not your other life because humans aren't telepathic. In case it isn't yet clear, this other you is me. Hi, other me. We haven't talked before, I don't think. In other words, if you were born in a different place at a different time in a different community... then that you wouldn't be you. It would be a different person. So it doesn't really make sense to ask "what if I had been born at a different time or place".

wppick 8y ago
>There but for the grace of God go I I like to entertain the idea that humans are the host of a species of sentient alien bacteria that lives in our guts and controls us through the vagus nerve and uses humans to build technology to advance to the point where they can build space ships to colonize other planets. Could make a good sci-fi book if anything...
- posterboy 8y ago
  Bacteria don't have enough memory to represent technology, nor the necessary organization to ... I don't know, as whole they are rather complex and can at least share information like antigen markers to kill us effectively. There are actual sci-books on the matter, you know.
  - Procrastes 8y ago
    Then we don't have enough memory to understand our technology either. We accomplish that as a superorganism, and by building tools to augment our abilities. Maybe bacteria built us as complex, extraterrestrial spore capsules.
    - posterboy 8y ago

hackinthebochs 8y ago

The question probably stems from the fact that we tend to identify with our conscious experience more than we do our physical body. So it seems reasonable to imagine this conscious experience separated from one body and placed in another body. But this is a mistake. Your body owns its conscious processes in the same way your body owns its process of digestion. There is no way to identify you separately from the physical stuff that makes up your body (which includes your brain).

Gupie 8y ago
What if we are AIs in a simulation? Unlikely perhaps but not impossible. In this case there is no body only mind and all options are open. There is also the theories that consciousness is all that exists, e.g. "Donald Hoffman's Multimodal User Interface (MMUI) theory of reality and doctrine of Conscious Realism together posit that the reality humans perceive is like a simulation in which non-physical conscious agents interact in order to generate the dynamics we observe". https://en.wikipedia.org/wiki/Donald_D._Hoffman https://en.wikipedia.org/wiki/Donald_D._Hoffman