6 ms·

The Quantum Mechanics of Fate (2014)

66 points by jeremynixon 12y ago

amelius 12y ago
Why don't we just define time such that no communication to the past is possible.
- ChrisClark 12y ago
  Isn't that just the same thing as covering our ears and saying, "Na na nana na, I can't hear you!" If some causal effects might be travelling back in time, we should investigate it instead of just saying, "I don't like it, so let's just define it the way we want."
  - amelius 12y ago
    No it is not the same thing. It provides a different way of looking at the same problem. Because if we force the direction of time to be always forward, we would have to modify our understanding of physics to make that assumption hold, leading to a different view of the same results, which could be extremely useful.
Fjolsvith 12y ago
This is the scientific explanation of how occult magical systems work.
- Desloges 12y ago
  I'm currently reading Cosmic Trigger (1977!) with an open skeptical mind and this was the first thing I thought.
lisper 12y ago
> the universe as a whole is skewed in the forward direction, because its past endpoint was highly ordered, and its future endpoint is highly disordered. This is highly misleading. The arrow of time is not thermodynamic, it's quantum. It's defined by increased entanglement, not increased entropy. http://blog.rongarret.info/2014/10/parallel-universes-and-arrow-of-time.html http://blog.rongarret.info/2014/10/parallel-universes-and-ar...
- rndn 12y ago
  Does increasing entanglement explain the second law of thermodynamics?
  - lisper 12y ago
    AFAIK this is an open question. My guess would be that yes, it does. I'm also guessing that the first person who actually does the math to prove it will win the Nobel prize in physics.
- dnetesn 12y ago
  This is another Nautilus article, by Julian Barbour, on the arrow of time. http://nautil.us/issue/9/time/the-mystery-of-times-arrow http://nautil.us/issue/9/time/the-mystery-of-times-arrow
  - dnetesn 12y ago
    and this from Paul Davies on the flow of time. http://nautil.us/blog/where-did-time-come-from-and-why-does-it-seem-to-flow http://nautil.us/blog/where-did-time-come-from-and-why-does-...
- kordless 12y ago
  I was reading about computation the other day and stumbled upon a concept where something can't be computable if it requires more operations than there is energy in the universe to do the operations. While reading the post you linked to, it struck me that the speed of light is a similar barrier to us. We can't travel the speed of light. We always like to talk about it and what we would 'observe', but it's theoretically impossible for us to do.
- tbrownaw 12y ago
  This is highly misleading. The arrow of time is not thermodynamic, it's quantum. It's defined by increased entanglement, not increased entropy. That's not at all what I remember from physics class when I was at university, and would seem to imply (incorrectly) that non-QM models can't produce an arrow of time.
lordnacho 12y ago
>To think about this problem, consider the most prosaic of objects: a popsicle stick. The stick will bend or buckle, depending on the pressure you apply to both ends. Now imagine a popsicle stick whose ends are separated in time, rather than in space. I have to admit I don't know what that means. Anyone got a way to describe this?
- Terr_ 12y ago
  I'd just focus on the stuff around it, I'm not entirely sure how the metaphor adds to that.
- weinzierl 12y ago
  "to buckle" probably is meant in its technical sense referring to Eulers formula where the boundary conditions play an important role. https://en.wikipedia.org/wiki/Buckling https://en.wikipedia.org/wiki/Buckling In short: If a structure fails by buckling only depends on the following properties: load on the structure, modulus of elasticity, moment of inertia, length of the structure and a factor, whose value depends on the conditions of end support of the structure. The factor is a number between 0.5 and 2 depending only on the condition of both ends. For example if both ends are free to rotate it is 1.0, if both are fixed, it is 0.50, and so on.
- lyall 12y ago
  It's just comparing time and space by analogy. Instead of two related events separated in time, we have the two ends of the popsicle stick separated in space. Obviously if an event A causes an event B to happen, then changing A will have an effect on B. In the same way, pushing on end A of the popsicle stick will affect end B. But with the Popsicle stick things also work the other way around; pushing on end B affects end A too. The jump is made here: if pushing on end B of the popsicle stick affects end A, then couldn't we imagine changing event B to have an effect on event A (even though A occurs before B)?
increment_i 12y ago
Wouldn't messages passing from the future to the past imply that the future can then influence the past? Which of course introduces a slew of paradoxes. I realize the concept is concerned with single particles, but could there exist a series of messages that alters the original particles so much so as to introduce a paradox? (e.g. in the vein of "the grandfather paradox" in human time travel to the past, where a man kills his own grandfather.) edit: clarity.
- spiritplumber 12y ago
  Outside of physics, the future influences the past all the time, though. Imagine that you are in Stalinist Russia and win a minor scientific prize for a paper you wrote. There is a purge, and while you manage to not get deported to Siberia, the prize is reassigned to a less brilliant but more politically orthodox colleague, to the point that he is listed as first author of your paper. He goes on to have a better career because of this paper, and by the end of the affair, nobody remembers that you wrote the paper to begin with. If all observable effects of an events have been retconned, can that event be said to have occured? Can a similar situation happen in physics, and if so, does it "count" if only macroscopic effects are reversed? (To keep with the analogy, in this case, everything but your memory has been changed, but your memory hasn't been - although it might over time, due to you wanting to avoid cognitive dissonance).
- givan 12y ago
  > An atom that normally emits light will cease emitting when its surroundings become incapable of absorbing that light. Thus one event (emission) depends on something that does or doesn’t happen in the future (absorption). “That’s one of the examples of a particle probing the future and seeing what’s there, and then making a decision based on it, and just not decaying Using the above analogy the message sent from the future (the man exists) to the past will prevent the grandfather to be killed just like the decaying atom, maybe the messages send back and forth from the future rewrites the events to prevent the paradox, something like backtracking until it works.
- DennisP 12y ago
  Time travel doesn't necessarily introduce paradox. Imagine you have a billiard table, on which there's a wormhole. If you roll a billiard ball into the wormhole on the right trajectory, it will emerge three seconds prior to entering the wormhole, hit its earlier self a solid blow, and its earlier self will never enter the wormhole, creating a paradox. But when you try, it emerges from the wormhole on an altered trajectory, and strikes itself only a glancing blow. And why did it emerge with an altered trajectory? Because it was struck a glancing blow. This is the Novikov self-consistency principle [1]. Physicists have been unable to find initial conditions that don't allow a consistent solution. On the other hand, nobody has proven that consistent solutions always exist. And sometimes there are lots of consistent solutions. (I wonder whether that's why quantum physics isn't deterministic, but I'm no physicist.) [1] http://en.wikipedia.org/wiki/Novikov_self-consistency_principle http://en.wikipedia.org/wiki/Novikov_self-consistency_princi...
chakademus 12y ago
"The standard interpretation of entanglement is that there is some kind of instant communication happening between the two particles." This is flat-out not true. The standard interpretation is that the entangled objects are part of a single quantum state. Measurement/observation of the state collapses the wave-function, and does not necessarily imply communication between the constituent parts.
- cma 12y ago
  Sort of depends on your view of the reality of the wave function, in light of its maybe-interpreted-as faster than light collapse.
- semi-extrinsic 12y ago
  Agreed. This[1] xkcd comic applies to almost every Nautilus article I've ever seen. [1] http://xkcd.com/1240/ http://xkcd.com/1240/
- mahranch 12y ago
  > This is flat-out not true. The standard interpretation is Unrelated Query: How can something be "flat out not true" if it's only an interpretation? Seems to be that what you're describing is a consensus or popular view opposed to a hard fact or universal truth.
  - JadeNB 12y ago
    > How can something be "flat out not true" if it's only an interpretation? I think that chakademus meant that it is flat-out not true that "the standard interpretation … is that there is some kind of instant communication happening between the two particles" (notice the scope of the quotation marks); that is, that this is not the standard interpretation, not that this interpretation is 'wrong' (whatever that means).
- deciplex 12y ago
  I read that to be more like "the naive interpretation of entanglement". The author even spends the remainder of the paragraph reminding (or educating) the reader that faster-than-light communication is not possible, and then the rest of the article is exploring retrocausality as another mechanism to explain entanglement with violating FTL restrictions.
mjrpes 12y ago
"An atom that normally emits light will cease emitting when its surroundings become incapable of absorbing that light. Thus one event (emission) depends on something that does or doesn't happen in the future (absorption)." What role does relativity play in this discussion? From the point of view of a photon, there is no lapse in time between emission and absorption. Emission and absorption happens instantaneously, since time never "ticks" for the photon as it traverses space. So, at least from the photon's point of view, there is no need to evoke the past/future causality in this situation.
timinman 12y ago
If the future or present influence the past, it undermines scientific study, including, ironically, the hypothesis of the article, because disruption from the future would be an unknown variable in every experiment. It's pretty hard to understand what can happen outside the dimensions we are constrained by. If the past is malleable, we could keep using the scientific method, but with humility, like: "The experiment's data support my claim so long as there was not unknown interference from actors unbound by linear time, space, and matter." That sentiment is not too far from the attitude of many of us, rational people, who believe that in addition to humanly measurable causes, there are also supernatural or spiritual realities to consider.

66 points by jeremynixon 12y ago

amelius 12y ago

Why don't we just define time such that no communication to the past is possible.

ChrisClark 12y ago
Isn't that just the same thing as covering our ears and saying, "Na na nana na, I can't hear you!" If some causal effects might be travelling back in time, we should investigate it instead of just saying, "I don't like it, so let's just define it the way we want."
- amelius 12y ago
  No it is not the same thing. It provides a different way of looking at the same problem. Because if we force the direction of time to be always forward, we would have to modify our understanding of physics to make that assumption hold, leading to a different view of the same results, which could be extremely useful.

Fjolsvith 12y ago

This is the scientific explanation of how occult magical systems work.

Desloges 12y ago
I'm currently reading Cosmic Trigger (1977!) with an open skeptical mind and this was the first thing I thought.

lisper 12y ago

> the universe as a whole is skewed in the forward direction, because its past endpoint was highly ordered, and its future endpoint is highly disordered. This is highly misleading. The arrow of time is not thermodynamic, it's quantum. It's defined by increased entanglement, not increased entropy. http://blog.rongarret.info/2014/10/parallel-universes-and-arrow-of-time.html http://blog.rongarret.info/2014/10/parallel-universes-and-ar...

rndn 12y ago
Does increasing entanglement explain the second law of thermodynamics?
- lisper 12y ago
  AFAIK this is an open question. My guess would be that yes, it does. I'm also guessing that the first person who actually does the math to prove it will win the Nobel prize in physics.
dnetesn 12y ago
This is another Nautilus article, by Julian Barbour, on the arrow of time. http://nautil.us/issue/9/time/the-mystery-of-times-arrow http://nautil.us/issue/9/time/the-mystery-of-times-arrow
- dnetesn 12y ago
  and this from Paul Davies on the flow of time. http://nautil.us/blog/where-did-time-come-from-and-why-does-it-seem-to-flow http://nautil.us/blog/where-did-time-come-from-and-why-does-...
kordless 12y ago
I was reading about computation the other day and stumbled upon a concept where something can't be computable if it requires more operations than there is energy in the universe to do the operations. While reading the post you linked to, it struck me that the speed of light is a similar barrier to us. We can't travel the speed of light. We always like to talk about it and what we would 'observe', but it's theoretically impossible for us to do.
tbrownaw 12y ago
This is highly misleading. The arrow of time is not thermodynamic, it's quantum. It's defined by increased entanglement, not increased entropy. That's not at all what I remember from physics class when I was at university, and would seem to imply (incorrectly) that non-QM models can't produce an arrow of time.

lordnacho 12y ago

>To think about this problem, consider the most prosaic of objects: a popsicle stick. The stick will bend or buckle, depending on the pressure you apply to both ends. Now imagine a popsicle stick whose ends are separated in time, rather than in space. I have to admit I don't know what that means. Anyone got a way to describe this?

Terr_ 12y ago
I'd just focus on the stuff around it, I'm not entirely sure how the metaphor adds to that.
weinzierl 12y ago
"to buckle" probably is meant in its technical sense referring to Eulers formula where the boundary conditions play an important role. https://en.wikipedia.org/wiki/Buckling https://en.wikipedia.org/wiki/Buckling In short: If a structure fails by buckling only depends on the following properties: load on the structure, modulus of elasticity, moment of inertia, length of the structure and a factor, whose value depends on the conditions of end support of the structure. The factor is a number between 0.5 and 2 depending only on the condition of both ends. For example if both ends are free to rotate it is 1.0, if both are fixed, it is 0.50, and so on.
lyall 12y ago
It's just comparing time and space by analogy. Instead of two related events separated in time, we have the two ends of the popsicle stick separated in space. Obviously if an event A causes an event B to happen, then changing A will have an effect on B. In the same way, pushing on end A of the popsicle stick will affect end B. But with the Popsicle stick things also work the other way around; pushing on end B affects end A too. The jump is made here: if pushing on end B of the popsicle stick affects end A, then couldn't we imagine changing event B to have an effect on event A (even though A occurs before B)?

increment_i 12y ago

Wouldn't messages passing from the future to the past imply that the future can then influence the past? Which of course introduces a slew of paradoxes. I realize the concept is concerned with single particles, but could there exist a series of messages that alters the original particles so much so as to introduce a paradox? (e.g. in the vein of "the grandfather paradox" in human time travel to the past, where a man kills his own grandfather.) edit: clarity.

spiritplumber 12y ago
Outside of physics, the future influences the past all the time, though. Imagine that you are in Stalinist Russia and win a minor scientific prize for a paper you wrote. There is a purge, and while you manage to not get deported to Siberia, the prize is reassigned to a less brilliant but more politically orthodox colleague, to the point that he is listed as first author of your paper. He goes on to have a better career because of this paper, and by the end of the affair, nobody remembers that you wrote the paper to begin with. If all observable effects of an events have been retconned, can that event be said to have occured? Can a similar situation happen in physics, and if so, does it "count" if only macroscopic effects are reversed? (To keep with the analogy, in this case, everything but your memory has been changed, but your memory hasn't been - although it might over time, due to you wanting to avoid cognitive dissonance).
givan 12y ago
> An atom that normally emits light will cease emitting when its surroundings become incapable of absorbing that light. Thus one event (emission) depends on something that does or doesn’t happen in the future (absorption). “That’s one of the examples of a particle probing the future and seeing what’s there, and then making a decision based on it, and just not decaying Using the above analogy the message sent from the future (the man exists) to the past will prevent the grandfather to be killed just like the decaying atom, maybe the messages send back and forth from the future rewrites the events to prevent the paradox, something like backtracking until it works.
DennisP 12y ago
Time travel doesn't necessarily introduce paradox. Imagine you have a billiard table, on which there's a wormhole. If you roll a billiard ball into the wormhole on the right trajectory, it will emerge three seconds prior to entering the wormhole, hit its earlier self a solid blow, and its earlier self will never enter the wormhole, creating a paradox. But when you try, it emerges from the wormhole on an altered trajectory, and strikes itself only a glancing blow. And why did it emerge with an altered trajectory? Because it was struck a glancing blow. This is the Novikov self-consistency principle [1]. Physicists have been unable to find initial conditions that don't allow a consistent solution. On the other hand, nobody has proven that consistent solutions always exist. And sometimes there are lots of consistent solutions. (I wonder whether that's why quantum physics isn't deterministic, but I'm no physicist.) [1] http://en.wikipedia.org/wiki/Novikov_self-consistency_principle http://en.wikipedia.org/wiki/Novikov_self-consistency_princi...

chakademus 12y ago

"The standard interpretation of entanglement is that there is some kind of instant communication happening between the two particles." This is flat-out not true. The standard interpretation is that the entangled objects are part of a single quantum state. Measurement/observation of the state collapses the wave-function, and does not necessarily imply communication between the constituent parts.

cma 12y ago
Sort of depends on your view of the reality of the wave function, in light of its maybe-interpreted-as faster than light collapse.
semi-extrinsic 12y ago
Agreed. This[1] xkcd comic applies to almost every Nautilus article I've ever seen. [1] http://xkcd.com/1240/ http://xkcd.com/1240/
mahranch 12y ago
> This is flat-out not true. The standard interpretation is Unrelated Query: How can something be "flat out not true" if it's only an interpretation? Seems to be that what you're describing is a consensus or popular view opposed to a hard fact or universal truth.
- JadeNB 12y ago
  > How can something be "flat out not true" if it's only an interpretation? I think that chakademus meant that it is flat-out not true that "the standard interpretation … is that there is some kind of instant communication happening between the two particles" (notice the scope of the quotation marks); that is, that this is not the standard interpretation, not that this interpretation is 'wrong' (whatever that means).
deciplex 12y ago
I read that to be more like "the naive interpretation of entanglement". The author even spends the remainder of the paragraph reminding (or educating) the reader that faster-than-light communication is not possible, and then the rest of the article is exploring retrocausality as another mechanism to explain entanglement with violating FTL restrictions.

mjrpes 12y ago

"An atom that normally emits light will cease emitting when its surroundings become incapable of absorbing that light. Thus one event (emission) depends on something that does or doesn't happen in the future (absorption)." What role does relativity play in this discussion? From the point of view of a photon, there is no lapse in time between emission and absorption. Emission and absorption happens instantaneously, since time never "ticks" for the photon as it traverses space. So, at least from the photon's point of view, there is no need to evoke the past/future causality in this situation.

timinman 12y ago

If the future or present influence the past, it undermines scientific study, including, ironically, the hypothesis of the article, because disruption from the future would be an unknown variable in every experiment. It's pretty hard to understand what can happen outside the dimensions we are constrained by. If the past is malleable, we could keep using the scientific method, but with humility, like: "The experiment's data support my claim so long as there was not unknown interference from actors unbound by linear time, space, and matter." That sentiment is not too far from the attitude of many of us, rational people, who believe that in addition to humanly measurable causes, there are also supernatural or spiritual realities to consider.