The Physics Quote that changed my life

[FoxCommander]

This quote that i found in the book Super Force by Paul Davies, once read, litterally summed up all the thoughts that I have had since I could remember about how the universe works. tell me if you also think its true

"An intelligence knowing, at any given instant of time, all forces acting in nature, as well as momentary positions of all things of which the universe consists, would be able to comprehend the motions of the largest bodies of the world and those of the smalles atoms in one single formula, provided it were sufficently powerful to subject all data to analysis; to it, nothing would be uncertain, both future and past would be present before its eyes." -Pierre Laplace

 

[sylas]

This quote that i found in the book Super Force by Paul Davies, once read, litterally summed up all the thoughts that I have had since I could remember about how the universe works. tell me if you also think its true

"An intelligence knowing, at any given instant of time, all forces acting in nature, as well as momentary positions of all things of which the universe consists, would be able to comprehend the motions of the largest bodies of the world and those of the smalles atoms in one single formula, provided it were sufficently powerful to subject all data to analysis; to it, nothing would be uncertain, both future and past would be present before its eyes." -Pierre Laplace

It is now usually thought not to be true. One way to think of the distinction between classical physics and non-classical modern physics is whether or not this statement is true.

This is approaching deep waters; but a simple example can show of a specific case in which the statement is thought to be false.

The decay of an unstable atom is not predictable, not even in principle. In modern quantum physics, this is thought to be an event which is undetermined. All that you can obtain, given hypothetically complete information about the prior state, is a probability that the atom will decay. Many other similar examples exist: photon emission from an excited atom, identifying where an individual photon will end up in the double slit experiment, and so on.

In other words, the universe is inherently unpredictable, or non-deterministic.

There are some interesting proposals for ways to recover some level of determinism in physics; treating the universe as continually branching into alternate histories, all equally real (Everett's many worlds model for quantum mechanics) or some kind of "hidden variable" extension of physics (usually thought to be disproved; but some physicists are still looking for ways to manage it).

But pragmatically, it does seem that the statement is false; given the radioactive decay example. It just is not predictable; existing quantum mechanical physics suggests that there is no information, no hidden variable, which could be used to tell in advance when a decay will occur.

Cheers -- sylas

PS. There's another thread currently giving more detail on this: [thread=355056]Wave function collapse and the statistical nature of quantum states [/thread].

 

[FoxCommander]

Thanks, and yes I guess when I think about this quote I forget that quantum is never predictable no matter the amount of info. But I remembered distinctly thinking about this since I was very little and it just struck me as so amazing that someone put it into words so beautifully.
Thanks again for your insights and i will definitely check out that thread
Sincerely FC

 

[Archosaur]

The Heisenberg uncertainty principal: Biggest buzz-kill in the history of man.

 

[FoxCommander]

true that man, true that

 

[sganesh88]

I always compare this idea with that of life. We just don't know how an individual will act in a particular situation. But as a whole, the society will behave in a deterministic way. Is that a sensible analogy? Of course the difficulty in predicting the individual's behavior is perhaps due to the complexity of the interactions while in the quantum world, uncertainty is inherent.

 

[FoxCommander]

I always compare this idea with that of life. We just don't know how an individual will act in a particular situation. But as a whole, the society will behave in a deterministic way. Is that a sensible analogy? Of course the difficulty in predicting the individual's behavior is perhaps due to the complexity of the interactions while in the quantum world, uncertainty is inherent.

Yes I always thought that, but then that's saying like if you were to go out and study people. In the quote it is talking about someone who knows EVERYTHING, like God. This person would know all the things that affect the person and the postion of all their chemicals in their brain, so knowing that couldn't you then predict what would occur? since it is all chemical reactions and such. But then I wouldn't know how big of a differenct it would make once Quantum levels are also put into play, since those are as you said inherently uncertain

 

[sganesh88]

Personally i don't like the claim of chemical interactions explaining all the beautiful intricacies of life. :) Ok. Maybe I'm violating some PF rules here. *Shut up Ganesh*

 

[FoxCommander]

Personally i don't like the claim of chemical interactions explaining all the beautiful intricacies of life. :) Ok. Maybe I'm violating some PF rules here. *Shut up Ganesh*

pssssttt... me either :), just don't tell anyone and we won't get in trouble ha ha

 

[lightarrow]

This quote that i found in the book Super Force by Paul Davies, once read, litterally summed up all the thoughts that I have had since I could remember about how the universe works. tell me if you also think its true
...

Do you come from the 19° century?
Things changed a lot since then...

 

[Archosaur]

Do you come from the 19° century?
Things changed a lot since then...

I like to think we're beyond harassment here.

Besides, everyone who understands why the quote isn't true thought that is was at some point. You. Me. Hell, Einstein.

 

[FoxCommander]

yes as i said, I have had this idea in my mind for a while. But Quantum kinda ruined it for me... BOOO QUANTUM!

But don't you sometimes wish it were true? Like archosaur said, everyone did at one point

Dont know thought you guys would have some cool insights, Thanks everyone :D

 

[Redbelly98]

I'm trying to remember something I read about 25 years ago. The idea of the universe being deterministic was used in a Mark Twain short story The Mysterious Stranger. Written in between the LaPlace quote and the development of quantum mechanics, it's about a stranger who arrives in town and knows what will happen in the future.

I always compare this idea with that of life. We just don't know how an individual will act in a particular situation. But as a whole, the society will behave in a deterministic way. Is that a sensible analogy? Of course the difficulty in predicting the individual's behavior is perhaps due to the complexity of the interactions while in the quantum world, uncertainty is inherent.

This post brings to mind Asimov's novel Foundation (or was it a trilogy?). The premise was that we had learned to predict the future evolution of sociey hundreds of years in advance, without knowing what actual individuals will be doing, much as the weather is predicted today. (Vastly different time scale though.)

 

[mikeph]

I always compare this idea with that of life. We just don't know how an individual will act in a particular situation. But as a whole, the society will behave in a deterministic way.

I disagree.. the mechanisms behind social interaction may be chaotic. If one person decides to buy a newspaper, that might mean a manager reaches his sales target and buys a Porsche. If you have a particularly fun physics teacher at school, you might do a PhD and discover something new!

I think these sorts of multipliers mean than an individual is much more predictable than a country- look at how disastrous economic management is compared to psychological treatment.

 

[sganesh88]

If one person decides to buy a newspaper, that might mean a manager reaches his sales target and buys a Porsche.

A lot of time i have behaved like Forrest Gump in my life.
"I just felt like running"
"So... you just ran?"
"well... yeah!"
:)

 

[Phrak]

This post brings to mind Asimov's novel Foundation (or was it a trilogy?). The premise was that we had learned to predict the future evolution of sociey hundreds of years in advance, without knowing what actual individuals will be doing, much as the weather is predicted today. (Vastly different time scale though.)

You remember correctly. Asimov's psychohsitory.

http://en.wikipedia.org/wiki/Psychohistory_(fictional)"

I must have read it more than 30 years ago.

 

[Phrak]

I like to think we're beyond harassment here.

Besides, everyone who understands why the quote isn't true thought that is was at some point. You. Me. Hell, Einstein.

Every interpretation of quantum mechanics, that I know of, attempts to find it true.

To date, there must be hundreds of threads on PF involved in arguments to establish, or insist on some particular way over another way, that determinism is a property of quantum mechanics.

 

[FoxCommander]

I disagree.. the mechanisms behind social interaction may be chaotic. If one person decides to buy a newspaper, that might mean a manager reaches his sales target and buys a Porsche. If you have a particularly fun physics teacher at school, you might do a PhD and discover something new!

I think these sorts of multipliers mean than an individual is much more predictable than a country- look at how disastrous economic management is compared to psychological treatment.

Ah but now you must see at what caused this person to buy the magazine. If you were to somehow view this situation in a movie like scene where you could not interact with it, you will see that the simulation will run along the same path because the factors haven't changed. Say i have a ball and i put it on a certain spot on a hill, at the bottom of a hill is some dominos, I can put it in the same spot over and over again and it will still hit the dominos the same way everytime. Therefore since everything has a cause you could take all the information you could possibly imagine and put it in a computer and run simulation after simulation and as long as you don't change anything and all your information is correct you could in fact possibly predict the future. Quantum how ever is uncertain so you could either be slightly off or disasterously wrong. Who knows but Does quantum being of such unimaginably small proportions be that much of a factor?

 

[bjacoby]

Therefore since everything has a cause you could take all the information you could possibly imagine and put it in a computer and run simulation after simulation and as long as you don't change anything and all your information is correct you could in fact possibly predict the future. Quantum how ever is uncertain so you could either be slightly off or disasterously wrong. Who knows but Does quantum being of such unimaginably small proportions be that much of a factor?

Well this is the essence of the situation, is it not? The basic question is whether causality is a natural law in the earth? Does every action have a cause? Generally speaking causality is a natural law in the earth. Note that the quantum mechanical arguments of radioactive decay really prove nothing. One cannot substitute ignorance for action.

Case in point. Are coin flips truly random? No they are not. There is only our ignorance of the detailed forces, inertia, moments of inertia and aerodynamic actions that prevent our predicting the outcome of each and every coin toss HAD we the information needed to calculate it. Similarly, while we know we can't predict when an atom will decay and eject a particle, we certainly have no way of knowing (quantum mechanical claims to the contrary not withstanding) just what determines such an ejection. And we do not know that IF we understood the exact mechanisms that we might not be able to exactly predict particle ejection. Ignorance is not a substitute for knowledge.

All this leads us right back to our fundamental question. Is the universe causal or random? In other words does all physical phenomena have a cause. Or are certain things acausal? Do radioactive particles simply fly out of atoms at random without any cause initiating that? We do know that in classical physics causality is considered a natural law. One can define causality by saying that no two actions can happen at the same time. This means that IF one is going to look for acausal actions in quantum mechanics the proof is going to be in the old 19th century concept of "action at a distance" which is now termed "non-local" to cover up what it really is.

And surprisingly such non-local actions have apparently been observed. The whole area needs much further study and even worse quickly progresses into the fringe as such actions quickly lead to transluminal communications and other "forbidden" areas. So in terms of physics this is clearly an area in need of serious investigation, but at the same time, quickly leading AWAY from physics and into philosophy. All of which makes this, like cosmology, a very speculative and difficult area of exploration.

 

[vanesch]

At this point I usually like to remind people what they actually mean by determinism, and to point out that the concept isn't so easy.

Determinism is usually understood to be the principle by which "if we know everything about the current state of the universe, and we know the correct laws of physics, then we can determine uniquely what will be the future state of the universe".

In fact, of a given theory, it is pretty simple to find out whether it is deterministic or not: does the theory in question allow you to calculate what is the future state of a universe that follows exactly the theory, if you know whatever is to be (according to the theory) the current state, and the laws the theory stands for ?

Typically, Newton's mechanics is considered to be deterministic, up to one caveat: the fact that the "current state of the universe" in Newtonian mechanics is given by real numbers (positions and momenta), and that we don't know how to even write down the vast majority of real numbers (let alone "measure" it). This caveat is what gives rise to the field of "deterministic chaos". But apart from that, it is deterministic in that knowing current positions and momenta of all matter points and the correct force laws, allows you to know in principle the positions and momenta of those matter points in the future.
So there is already a caveat in Newton's mechanics itself (deterministic chaos), but moreover, the universe described by Newton's laws looks only approximately to the "real" universe.

The same can be said about classical electromagnetism (Maxwell's laws) and about classical relativity.

As others pointed out, quantum theory killed the idea. Now, there are interpretations of quantum theory which would make nature appear again as "deterministic", but where there is some property of nature which is part of the theory itself which doesn't allow any being of KNOWING the precise state of the universe at a certain moment (I'm thinking of Bohmian mechanics here). This means that even though nature might "be" deterministic, we cannot "exploit" that property because of some principle, which will forbid us to "know" the current state beyond a probabilistic description, and this probabilistic description will then propagate to the end result, only allowing for probabilistic predictions - as does standard quantum theory.

But I always like to throw in the following. When we talk about "laws of nature", usually we think about relatively succinct mathematical formulations: relatively "simple" mathematical structures that generalize easily to the situation at hand. But this doesn't need to be so. You could think of another kind of law of nature, one in which all past and future events are simply summed up in some kind of table. Call it "the Book". Now, we don't have "initial conditions" and a rather simple calculation rule on how to deduce future events, we simply have the full list of all events in the universe, as a "law of nature". There's of course no way to DISCOVER this "law of nature", but it is conceivable as law of nature. In fact, it is rather more amazing that extreme simplifications are possible, which reduce to just a few simple mathematical structures, applicable to a vast array of conditions.

So, in Newton's world, instead of giving you a simple differential equation from which we can DEDUCE all positions of matter points as a function of time, where this differential equation is the "law of nature", the law of nature in "the Book" would then simply be the functions of time which give us the positions of the matter points themselves. These functions are of course way more involved than just the differential equation to which they appear to be a solution, but that's just a matter of complexity of the laws of nature. What is amazing in physics, is that there are such immense "short cuts", such as a differential equation.

But let us for a moment imagine that the "true" laws of nature are just the "list of all events" (the Book). Now, is that "deterministic" or not ? On one hand, of course it is! If ever you had the Book, you could just READ what's going to happen, the future events are specified without any ambiguity. So it is of course deterministic. But there doesn't need to be a "law" that allows you from just the slice of "now" events to deduce the next slice of events. There may be only a statistical correlation if you insist on a "simple" mathematical law (a kind of correlation that's given by a theory like quantum theory for instance).

Or we could have a totally "random" universe, with no correlation between different slices of events. No causality at all, not even a probabilistic causality. This would be a very weird place to live in and certainly it is not our universe. But it is conceivable and it is even conceivable to have such a totally random universe, described by a very precise "Book", one in which every event is listed, but in which there are no obvious "simple" correlations between events in different time slices.

 

[trini]

Quite simply, quantum has not been around very long, the fact that it can't explain everything due to uncertainty principles et al may just be due to the lack of understanding of the field. Think about how long after Newton that Einstein formulated relativity.

A more precise statement should be, present understanding of quantum mechanics cannot predict all events. Consider also that we have not necessarily (and i really don't think we have) discovered all the forces in nature. In fact, the forces we are missing may simply be occurring on such a massive scale that we don't even realize they are independent forces at all. It's like the statement, a fish cannot fully grasp the concept of water, because he has never experienced anything else.

 

[the_awesome]

It sounds like a case of hard determinism vs a libertarian position (include compatibilism if you want to). Of course a libertarian position can either take the route of a supernatural soul (something which I believe), or of course, quantum mechanics.

 

[FoxCommander]

Wow, these are some good responces... Thanks everyone!

They have all helped me understand a little bit more. I guess this quote "changed" my life because it made me realize that everything can be explained using the laws of physics, Why we see color or a rainbow, why the Earth goes round the sun and the moon around the earth, why i feel pain, why i hear. And all this got me thinking. If we could explain it that means we know what causes it. I think that eventually once we understand Quantum, maybe there will be something else to explain, or maybe Quantum will be the last straw. but we will be that much closer to being able to comprehend it all, and even predict the future.
So i guess what I am askin now is what else other than Quantum is still left to be explained fully?

 

[vanesch]

Quite simply, quantum has not been around very long, the fact that it can't explain everything due to uncertainty principles et al may just be due to the lack of understanding of the field. Think about how long after Newton that Einstein formulated relativity.

Might be, but quantum mechanics is now with us for more than about 80 years...

A more precise statement should be, present understanding of quantum mechanics cannot predict all events.

It is hard to imagine that one would "understand better" quantum mechanics and "find out" how to go beyond the uncertainty principle (except by some improved version of Bohmian mechanics), because in quantum mechanics, this uncertainty is not an "not knowing" but rather a "not making sense". It is not that there is something that tells you "thou shall not know", but rather that for instance a single momentum state *is made up* of different position states, so there's no meaning attached in quantum mechanics to "a precise momentum AND a precise position", not any more as there would be a precise frequency attached to a step function (which has a spectral decomposition in several frequencies).

So if "precise position and precise momentum" would make sense again, quantum mechanics as we know it would be largely out of the window - not just "better understood".

 

[mikeph]

Ah but now you must see at what caused this person to buy the magazine. If you were to somehow view this situation in a movie like scene where you could not interact with it, you will see that the simulation will run along the same path because the factors haven't changed. Say i have a ball and i put it on a certain spot on a hill, at the bottom of a hill is some dominos, I can put it in the same spot over and over again and it will still hit the dominos the same way everytime. Therefore since everything has a cause you could take all the information you could possibly imagine and put it in a computer and run simulation after simulation and as long as you don't change anything and all your information is correct you could in fact possibly predict the future. Quantum how ever is uncertain so you could either be slightly off or disasterously wrong. Who knows but Does quantum being of such unimaginably small proportions be that much of a factor?

Yes, determinism with a set of known initial conditions leads to a predictable future, but the chaotic element comes from a slight deviation from these initial conditions. So I am suggesting if the person does not buy a newspaper, then the manager does not buy a Porsche, and we have arbitrarily small changes at t=0 leading to large changes in the world after sufficiently long times. I do think life itself is chaotic, even without the need to invoke probability of QM.
vanesch I think your post above (#20) was very good!

 

[the_awesome]

Yes, determinism with a set of known initial conditions leads to a predictable future, but the chaotic element comes from a slight deviation from these initial conditions. So I am suggesting if the person does not buy a newspaper, then the manager does not buy a Porsche, and we have arbitrarily small changes at t=0 leading to large changes in the world after sufficiently long times. I do think life itself is chaotic, even without the need to invoke probability of QM.

vanesch I think your post above (#20) was very good!

Hm...just thinking about this. If everything was deterministic, then wouldn't that help to prove the butterfly effect?

 

[vanesch]

Hm...just thinking about this. If everything was deterministic, then wouldn't that help to prove the butterfly effect?

The butterfly effect is an allegoric way to talk about deterministic chaos. It is a consequence of what I talked about earlier in this thread: that even our "deterministic" theories (like Newtonian mechanics) have a fundamental problem, namely the fact that the "state" of nature is described by real numbers. In fact, the butterfly effect is even possible in any kind of theory where the state is described by a dense set. The reason is that it is always possible to conceive a dynamics where allowed trajectories by the (deterministic) dynamics diverge from one another, and if you do this in a dense set, then it is always possible to have two states that are *arbitrarily close* one to another evolve away from one another to a given "distance", in a finite (and sometimes even short) time. It is only if the state set doesn't have accumulation points that this is impossible.

In fact, we are extremely lucky that many of our interesting systems do NOT have systematically this behaviour - otherwise dynamics would be totally useless even though on paper "deterministic". But there are systems around that do have this "divergence" property, and that means that no matter how precise we can determine the initial conditions, this precision will of course be finite, and after sufficient time, different trajectories starting within this "blob" of initial conditions will diverge. That's deterministic chaos and that's what is described by the "butterfly effect". The butterfly effect doesn't mean that if we kill all butterflies, there won't be any storms anymore

 

[mikeph]

However you can have determinism without chaos, eg. a pendulum. Nothing is chaotic in that system, so determinism by itself does not cause chaos. I would guess it arises from there not being an analytic solution to the equations describing a system, which describe it fully.

This is something I am trying to get to grips with: how can a system be totally described by an equation, and its motion cannot be written in closed form? Eg. the three body problem (I always talk about this as it is what I did my dissertation on!), the equations are so easy to write down from Newton's law of gravity, but there is no analytic expression for the paths of these objects in terms of their initial conditions (6 vectors of position and momentum). Can any algorithm converge on the correct path for arbitrarily long time? How can it if the motion is chaotic? But nature seems to know one that works for real life. That boggles my mind...

 

[FoxCommander]

All these seem to end at one theory, The butterfly effect. To me this "effect" is cool to think about and stuff but what it requires is that something must be changed.

Lets take that example of the Newspaper stand. Initially we had a man buy the last one needed to make the quota so the manager can buy a new porsche, don't ask me how he got the money just go with it. Now if you CHANGE the initial conditions, you have essentially changed the equation of the problem. Take the equation for the trajectory or a ball thrown at an angle, if you throw it at the same velocity and height, it will always hit the ground at the same time, assuming we are neglecting anything other than gravity. But if you CHANGE the velocity you will change the equaition used to determine the path of the ball, Hence a new reality. Think about determining the path of Earth around the sun, I am sure we have a computer somewhere that can determine it with almost 99% correctness(not a word I am guessing) but of course if we knew the very EXACT numbers and correct equations we would then determine it 100%.

The fact that we can't predict it one hundred percent doesn't mean that its chaotic, it just means we have information missing. Like weather, of course what we predict it to do is always changing because we don't have all the correct information. Now let's go back to the ball. Let's say we had the velocity to be 1% off from what it actually was, at first we would see no difference in the paths using the same equations, but eventually they would deviate enough for us to notice, This is partly the basis of the butterfly effect. We can never really predict the future because we are not perfect.

My question still stands though: Could some intelligence, not human, something godly and all-knowing(In other words "perfect"), knowing all the information, not just the ones that we humans understand or know about but EVERYTHING that could possibly be measured, and having all the exact equations, including all of quantum and the rest of the unknown sciences out there. And if this intelligence had sufficient capacity to analyze all the data and equations... THEN can it know both what has happened and what will happen? (past and future)

 

[the_awesome]

My question still stands though: Could some intelligence, not human, something godly and all-knowing(In other words "perfect"), knowing all the information, not just the ones that we humans understand or know about but EVERYTHING that could possibly be measured, and having all the exact equations, including all of quantum and the rest of the unknown sciences out there. And if this intelligence had sufficient capacity to analyze all the data and equations... THEN can it know both what has happened and what will happen? (past and future)

Yes I believe so

 

[trini]

well, if something is all knowing then it must know what's going to happen without calculation

 

[mikeph]

if you CHANGE the initial conditions, you have essentially changed the equation of the problem... if you CHANGE the velocity you will change the equaition used to determine the path of the ball, Hence a new reality.

I think you should place more emphasis on the difference between a governing equation and an initial condition. If you change the velocity, you will NOT change the equation used to determine the path of the ball. That equation is Newton's law for gravity, and is independent of initial conditions. All you do is get a different path, as different constants of integration.

Initial conditions ---> [Governing equations] ---> future state

That is the process, and if the governing equations can be used to find a general solution in terms of the initial conditions then the system is not chaotic. The governing equations are based on reality, and do not change.You cannot know the "EXACT" initial conditions, these are in some sort of real space (for example, real^6 to describe the initial 3-position and 3-velocity of a particle), and since any two distinct numbers in real space has infinitely many numbers between them, you come up with the problem that you can only approximate the initial conditions. For example, if you observe a particle to have x-coordinate of position 3.104, that is always just an approximation to the real value it has, which is going to be an infinitely long string of decimal places - essentially the probability of you picking a random real number and it being an integer is zero, due to the weight of non-integers compared to integers in real space. And the chaotic nature of some systems means that any two arbitrarily close initial conditions will eventually deviate; so even in the absence of probability we get a system which we cannot predict.

 

[vanesch]

However you can have determinism without chaos, eg. a pendulum. Nothing is chaotic in that system, so determinism by itself does not cause chaos. I would guess it arises from there not being an analytic solution to the equations describing a system, which describe it fully.

In fact, the double pendulum IS chaotic Look at the double pendulum here
http://en.wikipedia.org/wiki/Double_pendulum

This is something I am trying to get to grips with: how can a system be totally described by an equation, and its motion cannot be written in closed form?

The set of continuous functions is way way larger than the set of "closed form" solutions when you take a rather small set of "generating" functions (say, all classical functions of Abramowitz and Stegun for instance). Differential equations make up a set of solution functions in the space of continuous (and n times differentiable) functions, but this subset doesn't have anything to do in most cases with that meager subset of "closed form" functions.

Eg. the three body problem (I always talk about this as it is what I did my dissertation on!), the equations are so easy to write down from Newton's law of gravity, but there is no analytic expression for the paths of these objects in terms of their initial conditions (6 vectors of position and momentum). Can any algorithm converge on the correct path for arbitrarily long time? How can it if the motion is chaotic? But nature seems to know one that works for real life. That boggles my mind...

Yes, that's puzzling indeed. But maybe not for the reason you think. You seem to say: how does nature do to "solve this differential equation better than my best computer can". But the real puzzling thing is that there is a differential equation that can be written down in the first place, of which the solution (even though we can't compute it exactly) is what nature is doing!

 

[vanesch]

Think about determining the path of Earth around the sun, I am sure we have a computer somewhere that can determine it with almost 99% correctness(not a word I am guessing) but of course if we knew the very EXACT numbers and correct equations we would then determine it 100%.

Point is, we can't know it. Heck, we can't even *write down* most real numbers. There is only a subset of measure zero of the real numbers that we can write down, and by this I even mean all kinds of "notation" like square root, "solution{}" etc...

The fact that we can't predict it one hundred percent doesn't mean that its chaotic, it just means we have information missing. Like weather, of course what we predict it to do is always changing because we don't have all the correct information. Now let's go back to the ball. Let's say we had the velocity to be 1% off from what it actually was, at first we would see no difference in the paths using the same equations, but eventually they would deviate enough for us to notice, This is partly the basis of the butterfly effect. We can never really predict the future because we are not perfect.

But that was already build in from the moment we postulated that positions were going to be triples of real numbers...

My question still stands though: Could some intelligence, not human, something godly and all-knowing(In other words "perfect"), knowing all the information, not just the ones that we humans understand or know about but EVERYTHING that could possibly be measured, and having all the exact equations, including all of quantum and the rest of the unknown sciences out there. And if this intelligence had sufficient capacity to analyze all the data and equations... THEN can it know both what has happened and what will happen? (past and future)

Well, as I said before, you could simply consider the "law of nature" to be the Book, the entire list of all events in spacetime. A "being" that knew this book, wouldn't even have to "calculate", it would simply "look up" what is happening where at what time slice.

As practical scientific theory it is utterly useless, but it is conceivable as a theory, no ?

As I said before, what is truly amazing is that we can find "simpler" forms of scientific theory that DO give us relationships between events in different time slices. It didn't need to be that way (although probably it did, if there was any form of intelligent life to emerge - so probably no intelligent life form can ever live in a universe where there is not the slightest bit of "causal relation" - that is, simple relations between events in different time slices).

 

[pgardn]

To me events automatically imply time. So we automatically assume events interact with each other because this notion has existed when evolution produced our want to go forward brains. Life that actually contemplates the future based on present and past is bound to come up with causality.

We are very strange animals. Maxed out control freaks we are. Personally I am having fun with this struggle. For some reason it is satisfying. Maybe if it was not satisfying in some way we would not be here. (This is not a religious notion)

 

[FoxCommander]

I think you should place more emphasis on the difference between a governing equation and an initial condition. If you change the velocity, you will NOT change the equation used to determine the path of the ball. That equation is Newton's law for gravity, and is independent of initial conditions. All you do is get a different path, as different constants of integration.

Initial conditions ---> [Governing equations] ---> future state

Im talking about the equation of the motion not the equaitons used to find these motions. Take a ball thrown at an angle, the graph would look like a parabola, if you change the speed or direction of the ball you will change the path it takes and one equation of motion could not possibly determine them all

x²=y doesn't look like 2x²+2x+1=y Therefore you will need different equations of MOTION, however you will still use the same equations of gravity to determine this path

 

[FoxCommander]

Point is, we can't know it. Heck, we can't even *write down* most real numbers. There is only a subset of measure zero of the real numbers that we can write down, and by this I even mean all kinds of "notation" like square root, "solution{}" etc...



But that was already build in from the moment we postulated that positions were going to be triples of real numbers...

This is exactly what I am trying to say, Everyone keeps thinking i mean if some Human was to try and figure out all these numbers. We can not possibly know the exact value of them due to the infinite decimal places factor you guys/girls keep bringing up

I am talking about some Super intelligence, not neccessarily all-knowing, knew all the values of everything and then knew all the exact equations, then could it compute the future and past... To me I don't see how it could not... And no this person is not all knowing so he/she would have to actually work out the equations and figure it out him/her self.

Is there anything stopping this Being from finding the truth?

 

[diazona]

Im talking about the equation of the motion not the equaitons used to find these motions. Take a ball thrown at an angle, the graph would look like a parabola, if you change the speed or direction of the ball you will change the path it takes and one equation of motion could not possibly determine them all

x²=y doesn't look like 2x²+2x+1=y Therefore you will need different equations of MOTION, however you will still use the same equations of gravity to determine this path

This path is what we call a solution to the equation of motion. The equation of motion itself is something more general, something like F = ma or i\hbar \partial \psi/\partial t = H \psi (depends on which theory you're using). Probably what you're thinking of as "equation of gravity" corresponds to the equation of motion.

This is exactly what I am trying to say, Everyone keeps thinking i mean if some Human was to try and figure out all these numbers. We can not possibly know the exact value of them due to the infinite decimal places factor you guys/girls keep bringing up

I am talking about some Super intelligence, not neccessarily all-knowing, knew all the values of everything and then knew all the exact equations, then could it compute the future and past... To me I don't see how it could not... And no this person is not all knowing so he/she would have to actually work out the equations and figure it out him/her self.

Is there anything stopping this Being from finding the truth?

Maybe. That's kind of the definition of determinism - if the universe is deterministic, then this super-intelligent being would be able to compute the future; if not, then even a super-intelligent being, knowing everything there is to know about the universe at a single moment in time to infinite precision, would not be able to compute what would happen in the future. I believe the majority opinion right now is that physics is not deterministic (which is what quantum mechanics suggests).

 

[vanesch]

I am talking about some Super intelligence, not neccessarily all-knowing, knew all the values of everything and then knew all the exact equations, then could it compute the future and past... To me I don't see how it could not... And no this person is not all knowing so he/she would have to actually work out the equations and figure it out him/her self.

Is there anything stopping this Being from finding the truth?

Yes, but you are missing my point. What tells you that the "exact laws of nature" are of the evolutionary kind, that is "starting conditions + evolution equations" ? This is the way we like to build our theories which try to describe nature, but what tells you that this is the "right" way to describe nature ? What if the "true laws of nature" are simply the Book (the list of all events in the universe) - and that we can only find approximate theories with "evolution equations" which do in fact nothing else but describe approximate correlations between events in different time slices ?

For sure, this is the way physics has worked since its beginnings and the paradigm "starting conditions + evolution equations" is pretty successful. In fact, it is probably the only *practical* way of doing physics. The fact that it seems to work doesn't necessarily mean that this is the way the "machinery of nature" works, but for sure it describes strong correlations between events in different, successive time slices. We seem to think of these correlations as "causal relationships", and if they are univocal, we call them "deterministic". I also argued that such correlations are necessary - up to a point - in order for some form of intelligent life to emerge: if there are NO correlations between events at a certain time, and the next set of events, then it is hard to imagine how you can "start to understand" this world, and it is hard to imagine how you could have intelligent life (or even life for short - as there can be no "actions with a purpose" given that nothing you do "now" will determine whatever in "now + epsilon seconds"). So in any case, any universe in which there is "some mechanism with a purpose" (like life, and certainly, intelligent life) needs to have correlations between events in different time slices, and finding out these correlations will give rise to theories which have {initial conditions + evolution equations}, which are nothing else but means to describe these correlations.

But again, nature doesn't have to "work" that way although, based upon our theories, we can mentally *picture* it that way. If spacetime is nothing but a bag of events, in between, as we saw, there are correlations between events in different time slices, then so be it. How it "came to be" that way (which is then nothing else but the question of "how the machinery of nature works") is an entirely different question (and most probably unanswerable) than the question of "what the correlations are" (our scientific theories), even though the mental picture we might associate with a given scientific theory is of course a *possible* way of telling us how "it came to be that way".

Think of a good fiction book, or a cartoon. Here too, we have correlations between the different "time slices" (Coyote running after Roadrunner) and we could think of "laws of coyote-physics", but how the successive events in the cartoon *came to be* (on the drawing table of the cartoonist in this case) has nothing to do with the correlations between the time slices in the movie which constituted our coyote-physics. Even though you might have found differential equations describing the motion of the queue of Roadrunner, and you might wonder how the movie projector "worked this out real-time during the projection of the motion picture while your super-duper computer couldn't converge to a solution in one hour", this is simply because that's not "how the movie works". It works by projecting different slices of "the Book" (here, the motion picture) on the screen.
This is a poor analogy of course, but I try to make you think about the concepts of "laws of nature" in the form of {initial conditions + evolution equations), causality and determinism in a broader frame.

The paradigm {initial conditions + evolution equations} is probably the only *practical way* to find out laws of nature, and they indicate correlations between events in successive time frames. They suggest causal relationships. Whether nature works that way, through genuinly causal mechanisms, or not, is a totally different question. In order to "understand" (that is, get some intuition) the theory with the evolution equations, it is very useful to set up a mental picture of a universe where nature DOES work that way. But that doesn't mean actual nature is working that way. Maybe it does, maybe it doesn't. Your mental picture is then just a conceptual construction based upon the theory at hand.

 

[mikeph]

That "book" would be almost as displeasing than the "multiverse" theory used to explain fine-tuning of constants..

But you are right, who knows whether the local area of spacetime we experiment in corresponds to a few pages which have a remarkable correlation. Why does anything have to be like it is at 391.49 bn years after the big bang? Who knows if there was a big bang, maybe the book is infinitely long and at current time the pages contain a "trace" that would make us believe there is a big bang.

Seems to be bordering metaphysics! I think we need to assume governing laws exist in order to make any progress.

 

[vanesch]

Seems to be bordering metaphysics! I think we need to assume governing laws exist in order to make any progress.

That's because concepts such as causality and determinism are metaphysical concepts (they say something ABOUT physics and physical theories). As well as "exist", btw. So no wonder we're talking metaphysics when dealing with them.

I don't know if it is necessary to assume that governing laws "exist" (of course they exist,as an idea, in a Platonian sense!) to make progress although I can see its utility. However, even if it is a good idea to take on certain working hypotheses, I also think it is very useful to be aware of what assumptions we've been making and what could have been different - even though for practical purposes we prefer to think it isn't.

 

[mikeph]

In any case it has given me a new perspective!

 

[FoxCommander]

OHHHH I get it now vanesch, That makes good sense. I thought when you said Book you meant just like a list of information or something, not like an actual book.

You have given me a new way of looking at this whole thing, which is cool. Thanks!

Well Thank you guys very very much for all of your opinions, I loved an appreciated them all.
This was actually my first Thread post and you guys have made it very successful
Also, Happy Thanksgiving(for those in America)


FoxCommander