Time travel - an idea
Discussion
I was working with a bit of software recently that simulates water. You can set up a 3D world, give the water object a starting point then run a simulation that calculates how that water reacts to the 3D environment. Once this is done, I can move back and forward along the timeline. Clever stuff.
I started thinking about where this could go and figured there isn't really a limit - it's just a matter of computing power.
We know the universe consistently abides by a series of laws. We may not fully understand them all yet but it seems inevitable we will one day.
If you can disregard free will, it's possible that state the universe at any one point in time is merely the culmination of a vast number of events, processes, reactions etc.
If we could somehow record that state - say, take a snapshot of the state of every atom at one or several points in time - then (with enough computing power) we could calculate out how they arrive at that state by reverse engineering all those events.
This effectively gives us a computed simulation of the universe that would allow you to move back and forward through time. The grandfather paradox isn't an issue because you're only viewing, not interacting.
Given computing power has advanced something like ten million percent in my lifetime, that side of things is probably achievable. It's just the small matter of capturing the state of the universe but I'm sure somebody can figure that out
What do you reckon, sciency folk. Any sense in the theory?
I started thinking about where this could go and figured there isn't really a limit - it's just a matter of computing power.
We know the universe consistently abides by a series of laws. We may not fully understand them all yet but it seems inevitable we will one day.
If you can disregard free will, it's possible that state the universe at any one point in time is merely the culmination of a vast number of events, processes, reactions etc.
If we could somehow record that state - say, take a snapshot of the state of every atom at one or several points in time - then (with enough computing power) we could calculate out how they arrive at that state by reverse engineering all those events.
This effectively gives us a computed simulation of the universe that would allow you to move back and forward through time. The grandfather paradox isn't an issue because you're only viewing, not interacting.
Given computing power has advanced something like ten million percent in my lifetime, that side of things is probably achievable. It's just the small matter of capturing the state of the universe but I'm sure somebody can figure that out
What do you reckon, sciency folk. Any sense in the theory?
PineBarren said:
By observing, you influence the outcome.
This is true but isn't Heisenberg's uncertainty principle.PineBarren said:
This is.The simulation will only use the data you give it. You cannot know who stepped on a butterfly in 1634, or whether they stepped over it.
I had a similar idea whereby you could trace every action by examining the microshopic marks left by two surfaces when they touch, and in this way reconstruct where everything had been in previous time. (There is probably an equation for it but my maths stopped at trigonometry...)
I had a similar idea whereby you could trace every action by examining the microshopic marks left by two surfaces when they touch, and in this way reconstruct where everything had been in previous time. (There is probably an equation for it but my maths stopped at trigonometry...)
Simpo Two said:
The simulation will only use the data you give it. You cannot know who stepped on a butterfly in 1634, or whether they stepped over it.
Absolutely but that's not quite what I'm suggesting.On a more sensible scale, let's say this game of Boules is our data point:
From the data we have - the displacement of gravel where they hit the ground, their weight and friction values - couldn't we calculate the trajectory they must have taken to arrive there, therefore simluating the events preceding that moment?
durbster said:
From the data we have - the displacement of gravel where they hit the ground, their weight and friction values - couldn't we calculate the trajectory they must have taken to arrive there, therefore simluating the events preceding that moment?
For Boules yes, for atoms no.You have two, related, problems. The first is that many natural processes are chaotic in that small perturbations in initial conditions lead to large differences later on. These means that with a finite amount of information beyond a certain time event would cease to be predictable. The second problem is that the Heisenberg uncertainty principle guarantees a certain amount of uncertainty in your variables regardless of how good your measurement techniques get.
Durbster,
You have taaken on a superhuman task! You may have heard of the "Three Body Problem", in which the movements of three planets or moons are to be predicted. It was shown before the end of the 19th century that there is no solution to this problem, because of the complexities of the interactions of just three gravitational fields, and that's without Heisenberg or Quantum, because they hadn't been thought of then!
That's just three items, three variables. Even in your boule example, your simulation would need to deal with many, many more variables. As a counter example, and one that removes many of the variables in boule, including the gravel plus wind and temperature, consider snooker. That starts from exactly the same place every time, yet have you ever seen two snooker games played the same?
JOhn
You have taaken on a superhuman task! You may have heard of the "Three Body Problem", in which the movements of three planets or moons are to be predicted. It was shown before the end of the 19th century that there is no solution to this problem, because of the complexities of the interactions of just three gravitational fields, and that's without Heisenberg or Quantum, because they hadn't been thought of then!
That's just three items, three variables. Even in your boule example, your simulation would need to deal with many, many more variables. As a counter example, and one that removes many of the variables in boule, including the gravel plus wind and temperature, consider snooker. That starts from exactly the same place every time, yet have you ever seen two snooker games played the same?
JOhn
Yes, but regardless of whether we know how to solve the 3-body problem, there is a solution, it's just that we don't know how to calculate it analytically.
(Calculating it computationally is certainly feasible eg. on a lattice).
Classically speaking (i.e. not quantum) it is possible to observe and know the positions and velocities of all the atoms in the universe at a particular point in time. It is then philosophically possible to write down equations of motion for all the universe. Though no one could be so clever as to solve them, a solution MUST EXIST and therefore the future is knowable.
Not being clever enough to work out the solution to a set of equations of motion doesn't mean that there is no valid solution!
ETA: If you read Arcadia by Tom Stoppard, the characters Septimus and Thomasina have a discussion on exactly this topic.
(Calculating it computationally is certainly feasible eg. on a lattice).
Classically speaking (i.e. not quantum) it is possible to observe and know the positions and velocities of all the atoms in the universe at a particular point in time. It is then philosophically possible to write down equations of motion for all the universe. Though no one could be so clever as to solve them, a solution MUST EXIST and therefore the future is knowable.
Not being clever enough to work out the solution to a set of equations of motion doesn't mean that there is no valid solution!
ETA: If you read Arcadia by Tom Stoppard, the characters Septimus and Thomasina have a discussion on exactly this topic.
First of all, thanks for humouring me. 
I've never heard of the uncertainty principle and the majority of the wiki page went over my head but I think I understand enough to see why it's a problem. It does sound a bit like infinity - i.e. the name given to something we haven't really grasped yet.
Am I right in thinking that's only an issue if you're taking data from a single point in time? So if you could get data from multiple points in time you could calculate both the position and the momentum?
I was thinking about weather forecasts today because they seem to be a real life example of this idea. Granted they use up enormous computing power and are still a bit rubbish but as technology improves, so does the simulation. Is it really too much to imagine that if computing power advances at, what, ten million percent over the next 50 years as it has the last, this kind of simulation could go deeper and deeper into the natural world?
I've never heard of the uncertainty principle and the majority of the wiki page went over my head but I think I understand enough to see why it's a problem. It does sound a bit like infinity - i.e. the name given to something we haven't really grasped yet.
Am I right in thinking that's only an issue if you're taking data from a single point in time? So if you could get data from multiple points in time you could calculate both the position and the momentum?
I was thinking about weather forecasts today because they seem to be a real life example of this idea. Granted they use up enormous computing power and are still a bit rubbish but as technology improves, so does the simulation. Is it really too much to imagine that if computing power advances at, what, ten million percent over the next 50 years as it has the last, this kind of simulation could go deeper and deeper into the natural world?
Edited by durbster on Friday 14th June 20:27
The point about the uncertainty principle is that it isn't just a measurement problem. It genuinely seems to be that the particle isn't anywhere in particular. Look up the double slit experiment where a particle seems to go through 2 slits at the same time.
One interpretation is that there is a range of places it could be, and observing it pins it down.
Another is the observer finding the particle is choosing to be in the universe where is it in one place rather than the universe where it is somewhere else. Before that the observer could be in both universes at the same time and if they didn't start investigating quantum particles they wouldn't notice anything odd going on.
One interpretation is that there is a range of places it could be, and observing it pins it down.
Another is the observer finding the particle is choosing to be in the universe where is it in one place rather than the universe where it is somewhere else. Before that the observer could be in both universes at the same time and if they didn't start investigating quantum particles they wouldn't notice anything odd going on.
tapkaJohnD said:
Durbster,
You have taaken on a superhuman task! You may have heard of the "Three Body Problem", in which the movements of three planets or moons are to be predicted. It was shown before the end of the 19th century that there is no solution to this problem, because of the complexities of the interactions of just three gravitational fields, and that's without Heisenberg or Quantum, because they hadn't been thought of then!
That's just three items, three variables. Even in your boule example, your simulation would need to deal with many, many more variables. As a counter example, and one that removes many of the variables in boule, including the gravel plus wind and temperature, consider snooker. That starts from exactly the same place every time, yet have you ever seen two snooker games played the same?
JOhn
Thing about the snooker game, at the end all the balls are in the pockets; I'd say it was impossible to extrapolate from there back to any time after the first player breaks off.You have taaken on a superhuman task! You may have heard of the "Three Body Problem", in which the movements of three planets or moons are to be predicted. It was shown before the end of the 19th century that there is no solution to this problem, because of the complexities of the interactions of just three gravitational fields, and that's without Heisenberg or Quantum, because they hadn't been thought of then!
That's just three items, three variables. Even in your boule example, your simulation would need to deal with many, many more variables. As a counter example, and one that removes many of the variables in boule, including the gravel plus wind and temperature, consider snooker. That starts from exactly the same place every time, yet have you ever seen two snooker games played the same?
JOhn
durbster said:
Absolutely but that's not quite what I'm suggesting.
On a more sensible scale, let's say this game of Boules is our data point:
From the data we have - the displacement of gravel where they hit the ground, their weight and friction values - couldn't we calculate the trajectory they must have taken to arrive there, therefore simluating the events preceding that moment?
You're assuming that there's only one unique path between the start of the Universe and the state that you want to "work back" from.On a more sensible scale, let's say this game of Boules is our data point:
From the data we have - the displacement of gravel where they hit the ground, their weight and friction values - couldn't we calculate the trajectory they must have taken to arrive there, therefore simluating the events preceding that moment?
Also on a practical level it would be impossible to record everything about the universe. Think about it, you need to record the position and speed of every part of every atom. Where will you store that data? On a memory chip? But then you have to record the state of every part of every atom on the chip. Where will you store that?
Plus, as someone else has mentioned, you can't know both i) where a particle is, and ii) how fast it's going.
There's also the practicality of making an observation of everything at once. You'd need a "camera" of somekind to record everything. But how do you record the state of the cameras? (See memory problem.)
You're also ignoring the speed of light. The universe is pretty big, so how would you take a simultaneous snapshot of it all? How would you sync your cameras up?
A complete non starter as far as I can tell.
BUT what's interesting, is that maybe it would be possible for an outside observer. (Bear with me.) You water simulation is being run from "outside" the system. It would be impossible for a man on a boat in your simulation to take all the measurements, but as the person operating the simulation you're outside and not bound by the same rules. So you have access to measurement and storage devices which are OUTSIDE the system you're monitoring.
So if there is a place which is outside of our Universe, then maybe entities there COULD run such a simulation as you refer to.
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