7 ms·

Can We Escape from Time?

76 points by Hooke 10y ago

gwern 10y ago
"What would be good, though, would be for someone to call us back when the thinking leads to something, anything, that we can see or feel or sense or even understand—because all this astonishingly brilliant thought and science and learning and history, all these amazing stories, as far as I can tell, have no consequences at all. Our commonsense subjective understanding of time is as telling, as tyrannical, as it ever was. A century-plus of fervent speculation and analysis of time and time travel have led to exactly no outcomes. We are as stuck in the present, as irrevocably exiled from both past and future, as ever." Einstein's time dilation has practical consequences: aside from being able to observe the slowdown in atomic clocks taken up in airplanes and the many consequences in astronomy, we also have GPS, which would not work without taking relativity into account. If GPS doesn't count as a 'consequence' or 'outcome' due to a non-traditional understanding of time, nothing does!
- dom0 10y ago
  This is a relatively common misconception. The location calculation in GPS is independent of any time dilation between the GPS receiver and the satellites (as long as the satellites have roughly equal dilation), because the receiver clock is derived from the satellites' signals. This is also the reason why you need at least four satellites for a 3D fix, and three for a 2D fix - you are always deriving an additional unknown variable, time. (And this is also the reason why a GPS time receiver works with only one satellite: the position is locked when they are set up, after that they can work with 1+ satellites. More satellites will reduce errors, though.) The time dilation is therefore only compensated so that you can use a GPS receiver as a very accurate, absolute clock.
  - WJW 10y ago
    Technically the fourth variable that a receiver solves for is the clock error in the receiver, not the actual time (though that then follows easily enough). The system of equations is only solvable because it is assumed that the clock error of the satellietes relative to each other is zero. I'm not convinced though that time dilation is the same for all the satellites, since they are not all in the same orbit. Since the system works by determining signal delay between the satellite and the receiver and the signals move at (rougly) the speed of light, even an nanosecond error in time is already a 30 cm error in position. According to [0] the clock drift due to relativistic effects would be over 45000 nanoseconds per day. So keeping the clocks synchronized for all the satellites is crucial and relativistic corrections are super important for accurate positioning. [0]: http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps....
    - dom0 10y ago
      > According to [0] the clock drift due to relativistic effects would be over 45000 nanoseconds per day. Between an uncorrected satellite and the receiver. This error is already removed through the fourth variable, only the average error of the satellites used for this remains (assuming perfect receiver etc.). So even if the satellites where not corrected the positioning error would not be "XY kilometers per day and climbing", the much smaller difference in time dilation between satellites would remain though.
      - jayisbatman 10y ago
        The location calculation is completely dependent upon relativistic time dilation. The Navistar satellites have an orbital speed of 8,750 MPH (more than 2 miles per second, relative to our earth surface frame), they are subject to a relativistic time dilation adjustment of -7201ns (slower than our earth surface frame). The location calculation cannot ignore that. The GPS signal (radio) takes on average 1 foot per nanosecond (perhaps a slightly bit more, but this is electromag radiation in a non-vacuum). If your receiver didn't account for this you would be more than a mile from your actual location. Relativity and its time dilation are required for any satellite based location system -- unless your satellites are at altitude of zero.
brianberns 10y ago
"'There is no difference between Time and any of the three dimensions of Space except that our consciousness moves along it,' says the Traveller. That turned out, amazingly and counterintuitively, to be true. 'In surprisingly short order this notion would become part of the orthodoxy of theoretical physics,' says Gleick." What? Spacetime does contain four dimensions, but the whole reason that time travel is fiction, rather than fact, is because the time dimension is different from the space dimensions.
- Razengan 10y ago
  I wonder. If the universe is deterministic, and nothing is random, then Time could be thought of as a vector whose values encompass all the properties of everything in existence and the direction of changes in each of them. If we knew all the "rules" that govern those changes and could make a simulation that captured the current state of everything, we could traverse back and forth along that vector (but probably not beyond the instant when that simulation was turned on, because then it would have to simulate itself...)
  - scardine 10y ago
    We can calculate things like if the moon is ever going to leave Earth's orbit and we can tell it was much closer to Earth in prehistoric times. We can predict the future and recall the past, just not in a scale that is practical for our mundane lives. Personally, I think this is a humility lesson: in the grand scheme of things, the entire span of a human life is less than a tiny drop in the ocean of time.
  - baytrailcat 10y ago
    This was a prevalent idea in physics till quantum mechanics burst into the scene. I don't remember where I saw it, this the most convincing argument I heard regarding simulating future: Our universe is actually the most efficient computer that can simulate the future with our physical laws. Meaning, at any given time, it is not actually executing a pre-determined program, it is busy computing the future.
    - 10y ago
imchillyb 10y ago
Picture Time as the surface of a pond. Events are a stone being dropped into or skipped along the surface of that pond. The waves produced by the event are viewable from all angles. The actual event -the stone drop- occurs only once. The event is immutable, even though the ripples persist and are measurable. We may eventually be able to view the ripples in more detail, and see past or future events. The events themselves though, are immutable. They've already occurred or have not occurred yet. The stone does not change. The interaction between stone and surface does not change. What changes is our ability to decipher data from that event, not the event itself.
- deleted 10y ago
  [deleted]
- flatline 10y ago
  You could argue there is no event per se: it's all just ripples.
dschiptsov 10y ago
Sure. Time is a mere environmentaly conditioned mental conception. No such phenomena exist. Only environmental and social conditioning. It could only be derived by an intelligent observer. No observer - no time. For a photon there is no time. BTW, conversation laws are hinting to an illusory nature of time. Change of compound structures do exist and it is in everything we are able to observe. But the whole is unchanged, no matter what fancy theories or simulations would say.
- camerintinbun 10y ago
  But for a photon, it doesn't experience time for the reason that it travels at the speed of light. It is a slightly different phenomenon.
bitL 10y ago
Are we capable of existing outside time? Imagine instead of living in an [array of time-frames], moving in one direction, i.e. time, in a single frame only, like a snapshot (even with the possibility to observe the whole [array of time-frames] at once). Would you have any words to describe it? I think all our mental models would just collapse.
- seanp2k2 10y ago
  Considering you wouldn't be able to move or take in any new light, sound, etc it sounds pretty boring. Dark stillness.
- NumberCruncher 10y ago
  Some people say time is just an illusion we use to process reallity as an [array of time-frames]. I think what you are looking for is a kind of enlightening which in this case would mean stepping out of the illusion of time. Some people reported to achieve this with meditation and/or psychodelics.
- yarou 10y ago
  The closest existence I can think of is being trapped in a singularity. An observer would obviously see your body obliterated in mere seconds, but time would exponentially slow down on your end.
to3m 10y ago
A pretty substantial flaw in the piece, almost enough to sink it, is the suggestion that Looper is somehow more worthy of calling out than Primer. Tsk... somebody sack the fact checkers... Primer: http://www.imdb.com/title/tt0390384/ http://www.imdb.com/title/tt0390384/ (Interesting not least because its budget was about 50p)
- lomnakkus 10y ago
  It's a REALLY confusing film, but absolutely brilliant in the way that it shows just how confusing a world with time travel would be[1]. The way everything escalates in the latter half of the film is insane. For a "simple" explanation of the plot, see [2]. Since this analysis was done by a third party, it's obviously hard to be sure that this is fully correct, but it at least seems very close. [1] For anyone able to observe the multiple time lines, obviously. :) [2] https://i0.wp.com/media2.slashfilm.com/slashfilm/wp/wp-content/images/primer-chart.jpg https://i0.wp.com/media2.slashfilm.com/slashfilm/wp/wp-conte... (massive SPOILERS, obviously)
  - FeepingCreature 10y ago
    Also recommended: Primer commentary track. Run it beside the movie, and it'll drop in to explain things as they happen. https://qntm.org/commentary https://qntm.org/commentary
    - lomnakkus 10y ago
      Hadn't heard of this before -- I am sooo going to try this. Thanks for the link!
lisper 10y ago
The reason we can't go back in time is that time and information (and hence consciousness, which is made of information) are inextricably linked by quantum physics: http://blog.rongarret.info/2014/10/parallel-universes-and-arrow-of-time.html http://blog.rongarret.info/2014/10/parallel-universes-and-ar...
- cousin_it 10y ago
  Your post explains why going back in time along the same path is pointless because you lose the information. But maybe we could take a different path (closed timelike curve) and keep the information.
  - lisper 10y ago
    > going back in time along the same path is pointless because you lose the information No, it's much deeper than that: the accumulation of information is what creates time. > closed timelike curve This is at the limits of scientific knowledge so there's nothing definitive one could say about it at this point. But you might want to read this: https://www.scientificamerican.com/article/time-travel-simulation-resolves-grandfather-paradox/ https://www.scientificamerican.com/article/time-travel-simul...
nol13 10y ago
The basics for time travel start at CERN in about a year and end in 2034 with the first "time machine" built by GE. Too bad we can't post pictures or I'd show it to you.
- agumonkey 10y ago
  Just leave a note to yourself.
- heydenberk 10y ago
  To still be in this timeline, we need to retcon Titor's 2015 nuclear war.
- ChuckMcM 10y ago
  I realize that time travel is not invented in my lifetime, if it had been I would have traveled back to tell myself to get out of tech stocks in 1999 :-)
johndoez 10y ago
Read my Lips, Time is Real. And no new taxes.
blacksqr 10y ago
Not at the moment.
- ExpiredLink 10y ago
  Not for a moment.

76 points by Hooke 10y ago

gwern 10y ago

"What would be good, though, would be for someone to call us back when the thinking leads to something, anything, that we can see or feel or sense or even understand—because all this astonishingly brilliant thought and science and learning and history, all these amazing stories, as far as I can tell, have no consequences at all. Our commonsense subjective understanding of time is as telling, as tyrannical, as it ever was. A century-plus of fervent speculation and analysis of time and time travel have led to exactly no outcomes. We are as stuck in the present, as irrevocably exiled from both past and future, as ever." Einstein's time dilation has practical consequences: aside from being able to observe the slowdown in atomic clocks taken up in airplanes and the many consequences in astronomy, we also have GPS, which would not work without taking relativity into account. If GPS doesn't count as a 'consequence' or 'outcome' due to a non-traditional understanding of time, nothing does!

dom0 10y ago
This is a relatively common misconception. The location calculation in GPS is independent of any time dilation between the GPS receiver and the satellites (as long as the satellites have roughly equal dilation), because the receiver clock is derived from the satellites' signals. This is also the reason why you need at least four satellites for a 3D fix, and three for a 2D fix - you are always deriving an additional unknown variable, time. (And this is also the reason why a GPS time receiver works with only one satellite: the position is locked when they are set up, after that they can work with 1+ satellites. More satellites will reduce errors, though.) The time dilation is therefore only compensated so that you can use a GPS receiver as a very accurate, absolute clock.
- WJW 10y ago
  Technically the fourth variable that a receiver solves for is the clock error in the receiver, not the actual time (though that then follows easily enough). The system of equations is only solvable because it is assumed that the clock error of the satellietes relative to each other is zero. I'm not convinced though that time dilation is the same for all the satellites, since they are not all in the same orbit. Since the system works by determining signal delay between the satellite and the receiver and the signals move at (rougly) the speed of light, even an nanosecond error in time is already a 30 cm error in position. According to [0] the clock drift due to relativistic effects would be over 45000 nanoseconds per day. So keeping the clocks synchronized for all the satellites is crucial and relativistic corrections are super important for accurate positioning. [0]: http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps....
  - dom0 10y ago
    > According to [0] the clock drift due to relativistic effects would be over 45000 nanoseconds per day. Between an uncorrected satellite and the receiver. This error is already removed through the fourth variable, only the average error of the satellites used for this remains (assuming perfect receiver etc.). So even if the satellites where not corrected the positioning error would not be "XY kilometers per day and climbing", the much smaller difference in time dilation between satellites would remain though.
    - jayisbatman 10y ago
      The location calculation is completely dependent upon relativistic time dilation. The Navistar satellites have an orbital speed of 8,750 MPH (more than 2 miles per second, relative to our earth surface frame), they are subject to a relativistic time dilation adjustment of -7201ns (slower than our earth surface frame). The location calculation cannot ignore that. The GPS signal (radio) takes on average 1 foot per nanosecond (perhaps a slightly bit more, but this is electromag radiation in a non-vacuum). If your receiver didn't account for this you would be more than a mile from your actual location. Relativity and its time dilation are required for any satellite based location system -- unless your satellites are at altitude of zero.

brianberns 10y ago

"'There is no difference between Time and any of the three dimensions of Space except that our consciousness moves along it,' says the Traveller. That turned out, amazingly and counterintuitively, to be true. 'In surprisingly short order this notion would become part of the orthodoxy of theoretical physics,' says Gleick." What? Spacetime does contain four dimensions, but the whole reason that time travel is fiction, rather than fact, is because the time dimension is different from the space dimensions.

Razengan 10y ago
I wonder. If the universe is deterministic, and nothing is random, then Time could be thought of as a vector whose values encompass all the properties of everything in existence and the direction of changes in each of them. If we knew all the "rules" that govern those changes and could make a simulation that captured the current state of everything, we could traverse back and forth along that vector (but probably not beyond the instant when that simulation was turned on, because then it would have to simulate itself...)
- scardine 10y ago
  We can calculate things like if the moon is ever going to leave Earth's orbit and we can tell it was much closer to Earth in prehistoric times. We can predict the future and recall the past, just not in a scale that is practical for our mundane lives. Personally, I think this is a humility lesson: in the grand scheme of things, the entire span of a human life is less than a tiny drop in the ocean of time.
- baytrailcat 10y ago
  This was a prevalent idea in physics till quantum mechanics burst into the scene. I don't remember where I saw it, this the most convincing argument I heard regarding simulating future: Our universe is actually the most efficient computer that can simulate the future with our physical laws. Meaning, at any given time, it is not actually executing a pre-determined program, it is busy computing the future.
  - 10y ago

imchillyb 10y ago

Picture Time as the surface of a pond. Events are a stone being dropped into or skipped along the surface of that pond. The waves produced by the event are viewable from all angles. The actual event -the stone drop- occurs only once. The event is immutable, even though the ripples persist and are measurable. We may eventually be able to view the ripples in more detail, and see past or future events. The events themselves though, are immutable. They've already occurred or have not occurred yet. The stone does not change. The interaction between stone and surface does not change. What changes is our ability to decipher data from that event, not the event itself.

deleted 10y ago
[deleted]
flatline 10y ago
You could argue there is no event per se: it's all just ripples.

dschiptsov 10y ago

Sure. Time is a mere environmentaly conditioned mental conception. No such phenomena exist. Only environmental and social conditioning. It could only be derived by an intelligent observer. No observer - no time. For a photon there is no time. BTW, conversation laws are hinting to an illusory nature of time. Change of compound structures do exist and it is in everything we are able to observe. But the whole is unchanged, no matter what fancy theories or simulations would say.

camerintinbun 10y ago
But for a photon, it doesn't experience time for the reason that it travels at the speed of light. It is a slightly different phenomenon.

bitL 10y ago

Are we capable of existing outside time? Imagine instead of living in an [array of time-frames], moving in one direction, i.e. time, in a single frame only, like a snapshot (even with the possibility to observe the whole [array of time-frames] at once). Would you have any words to describe it? I think all our mental models would just collapse.

seanp2k2 10y ago
Considering you wouldn't be able to move or take in any new light, sound, etc it sounds pretty boring. Dark stillness.
NumberCruncher 10y ago
Some people say time is just an illusion we use to process reallity as an [array of time-frames]. I think what you are looking for is a kind of enlightening which in this case would mean stepping out of the illusion of time. Some people reported to achieve this with meditation and/or psychodelics.
yarou 10y ago
The closest existence I can think of is being trapped in a singularity. An observer would obviously see your body obliterated in mere seconds, but time would exponentially slow down on your end.

to3m 10y ago

A pretty substantial flaw in the piece, almost enough to sink it, is the suggestion that Looper is somehow more worthy of calling out than Primer. Tsk... somebody sack the fact checkers... Primer: http://www.imdb.com/title/tt0390384/ http://www.imdb.com/title/tt0390384/ (Interesting not least because its budget was about 50p)

lomnakkus 10y ago
It's a REALLY confusing film, but absolutely brilliant in the way that it shows just how confusing a world with time travel would be[1]. The way everything escalates in the latter half of the film is insane. For a "simple" explanation of the plot, see [2]. Since this analysis was done by a third party, it's obviously hard to be sure that this is fully correct, but it at least seems very close. [1] For anyone able to observe the multiple time lines, obviously. :) [2] https://i0.wp.com/media2.slashfilm.com/slashfilm/wp/wp-content/images/primer-chart.jpg https://i0.wp.com/media2.slashfilm.com/slashfilm/wp/wp-conte... (massive SPOILERS, obviously)
- FeepingCreature 10y ago
  Also recommended: Primer commentary track. Run it beside the movie, and it'll drop in to explain things as they happen. https://qntm.org/commentary https://qntm.org/commentary
  - lomnakkus 10y ago
    Hadn't heard of this before -- I am sooo going to try this. Thanks for the link!

lisper 10y ago

The reason we can't go back in time is that time and information (and hence consciousness, which is made of information) are inextricably linked by quantum physics: http://blog.rongarret.info/2014/10/parallel-universes-and-arrow-of-time.html http://blog.rongarret.info/2014/10/parallel-universes-and-ar...

cousin_it 10y ago
Your post explains why going back in time along the same path is pointless because you lose the information. But maybe we could take a different path (closed timelike curve) and keep the information.
- lisper 10y ago
  > going back in time along the same path is pointless because you lose the information No, it's much deeper than that: the accumulation of information is what creates time. > closed timelike curve This is at the limits of scientific knowledge so there's nothing definitive one could say about it at this point. But you might want to read this: https://www.scientificamerican.com/article/time-travel-simulation-resolves-grandfather-paradox/ https://www.scientificamerican.com/article/time-travel-simul...

nol13 10y ago

The basics for time travel start at CERN in about a year and end in 2034 with the first "time machine" built by GE. Too bad we can't post pictures or I'd show it to you.

agumonkey 10y ago
Just leave a note to yourself.
heydenberk 10y ago
To still be in this timeline, we need to retcon Titor's 2015 nuclear war.
ChuckMcM 10y ago
I realize that time travel is not invented in my lifetime, if it had been I would have traveled back to tell myself to get out of tech stocks in 1999 :-)

johndoez 10y ago

Read my Lips, Time is Real. And no new taxes.

blacksqr 10y ago

Not at the moment.

ExpiredLink 10y ago
Not for a moment.