I was wondering what people think of the following loose definition of time.

Each "slice" of time is an output from the input of the state of the universe in the prior "slice". What we experience as time is due to the changes that go on in our minds during each slice of time. Basically, the universe would just be a big input-output program with the position and velocites of all particles being both the input and output and the laws of nature being the function that transforms the input to the output. Of course there would be some randomness in the function due to QM and I don't know how to account for the inability to have exact position and velocity of a particle.

So is this idea totally wacky? Should I drop it now or does it have any scientific validity? I have a feeling it contradicts what GR and SR have to say about time because the above theory would require an absolute measure of time so to speak.

Hum,
Are you suggesting it’s a bit like driving a car on a road....
The way (you perceive?) the road under the car has somehow has a bearing on the direction of the road ahead....?

A sort of deterministic route?

Hum,
Are you suggesting it’s a bit like driving a car on a road....
The way (you perceive?) the road under the car has somehow has a bearing on the direction of the road ahead....?

A sort of deterministic route?

No. I see Cephas1012's statements quite consistant with my own views.

Due infact to QM it is not deterministic. But once an event occurs (which requires a flow or change of state of energy) it becomes part of a Dynamic Present along with all other conditions in the universe at the simultaneous ordinent point spatially.

That is each Dynamic Present is different with events which constitute such a slice in time and are shifted by simultaneity as a function or orientation to all events in the universe.

Hence our Dynamic Present consists of nothing but "Past" events. Our consciesness creates the illusion of time flow and suggests a "Future".

To move (change ordinate points) shifts which events which constitute a Dynamic Present and in relation to all other such ordinate points consists of "Past" and "Future" events relative to other such Dynamic Presents.

I'm sure you could condense that description/analogy quite a lot though, something along the lines of; Time is a measure of change in the other three dimensions. Maybe, except look in a thesaurus and find a more technical word for measure or try a dictionary for a more appropriate one, whatever that's jsut semantics and now i'm waffling, i'll leave it with you...not to you, jsut with you, christ i have to disambigufy my own sentences. I'll stop equivocating, wow this thesuarus thing is fun.

i think i could agree that there is something to your definition of time. i don't see how it would contradict GR or anything. what we percieve as time may be different from what you define as time. let's say that there is a mechanism that just goes from one step to the next like you say, that could result in a world that has time as we currently perceive it. time could just be another effect of the computation of the step function of the universe, yet independent of it, and quite different.

Due infact to QM it is not deterministic. But once an event occurs (which requires a flow or change of state of energy) it becomes part of a Dynamic Present along with all other conditions in the universe at the simultaneous ordinent point spatially.

This makes absolutely no sense; what has quantum mechanics to do with this ? Or did you just think it would sound fancy ?

This makes absolutely no sense; what has quantum mechanics to do with this ? Or did you just think it would sound fancy ?

Well I would have to challenge your comment. It seems obvious that the "Uncertainity" principle is in opposition to a concept of "Determainistic" results.

Is it really though? Or is that just the Copenhagen interpretation?

*just thought I'd spice things up!*

Well I would have to challenge your comment. It seems obvious that the "Uncertainity" principle is in opposition to a concept of "Determainistic" results.

Unfortunately incorrect. You are confusing "determinism" with "predictability". Quantum mechanics is a deterministic theory, but it does not predict measurement results, only probabilities for a certain result.

When you do perform the measurement, you get some result (which one exactly is not predictable). The range of possible results that you could have gotten is governed by the uncertainty principle (which says something about the variance of the probability distribution of a variable). However, this variance ("uncertainty") is completely determineable at any given time through the Schrödinger equation, and so are the allowed possible outcomes.

Hence: QM is deterministic. But don't worry, that is a common mistake, even amongst physicists...

But actually I was refering to other parts of the sentence which made even less sense...

Is it really though? Or is that just the Copenhagen interpretation?

*just thought I'd spice things up!*

I don't understand what you are trying to say here ?

Unfortunately incorrect. You are confusing "determinism" with "predictability". Quantum mechanics is a deterministic theory, but it does not predict measurement results, only probabilities for a certain result.

When you do perform the measurement, you get some result (which one exactly is not predictable). The range of possible results that you could have gotten is governed by the uncertainty principle (which says something about the variance of the probability distribution of a variable). However, this variance ("uncertainty") is completely determineable at any given time through the Schrödinger equation, and so are the allowed possible outcomes.

Hence: QM is deterministic. But don't worry, that is a common mistake, even amongst physicists...

But actually I was refering to other parts of the sentence which made even less sense...

Your are correct in that I was thinking of deterministic more in the form of meaning predestined or the old classical idea that a current state is a direct consequence of some former state where there can be no variable outcomes.

Your are correct in that I was thinking of deterministic more in the form of meaning predestined or the old classical idea that a current state is a direct consequence of some former state where there can be no variable outcomes.

... which is also true for quantum mechanics; a solution to the Schrodinger equation is unique (meaning that a former state uniquely determines a future state), and so are the probabilities of outcomes that you predict with it.

... which is also true for quantum mechanics; a solution to the Schrodinger equation is unique (meaning that a former state uniquely determines a future state), and so are the probabilities of outcomes that you predict with it.

I would point out the radical alternate outcomes that come with probabilitiy vs predestination. The QM version can be seen more in the likeness of "Evolution" in biology. A long series of repeated functions with an occasional difference. It is that difference that has allowed life to form and flourish creating millions of different life forms.

I don't understand what you are trying to say here ?

IMO quantum theory says that we cannot predict measurements below a certain level of accuracy. Copenhagen says that the reason behind that is that there's an inherent randomness to the universe. Correct?

Crisp, I believe it depends on precisely what you mean be determinism. While you may have something specific in mind I think that QM definitely voids what most people would consider to be a deterministic Universe:


"Physicists have sometimes used the term "determinism" in a special way that people such as Karl Popper and Stephen Hawking have called scientific determinism.

In his book, A Brief History of Time, Hawking says that predictability is required for "scientific determinism" (start of chapter 4). He defines "scientific determinism" as meaning: something that will happen in the future can be predicted.

Karl Popper's book The Open Universe: An Argument For Indeterminism argues that in its strongest version, scientific determinism makes a very strong assertion, that "all events are in principle predictable". The qualifier "in principle" can lead to persistent arguments.

Since many limitations on predictability are now known (for a partial list see: Quantum indeterminacy), most people who argue for determinism do not argue in favor of a strong version of scientific determinism. For example, a weaker type of determinism is one that only implies a unique, mechanical course for the universe with future events being caused by past events.

Hawking admits that even the uncertainty principle does not absolutely rule-out a kind of determinism "in principle", and says that quantum mechanics may very well allow the universe to be deterministic. He wrote:

"These quantum theories are deterministic in the sense that they give laws for the evolution of the wave with time. Thus if one knows the wave at one time, one can calculate it at any other time. The unpredictable, random element comes in only when we try to interpret the wave in terms of the positions and velocities of particles. But maybe this is our mistake: maybe there are no positions and velocities, but only waves. It is just that we try to fit the waves to our preconceived ideas of positions and velocities. The resulting mismatch is the cause of the apparent unpredictability." (conclusions section of A Brief History Of Time)"

http://encyclopedia.thefreedictionary.com/Scientific%20determinism

~Raithere

I would point out the radical alternate outcomes that come with probabilitiy vs predestination. The QM version can be seen more in the likeness of "Evolution" in biology. A long series of repeated functions with an occasional difference. It is that difference that has allowed life to form and flourish creating millions of different life forms.

You are really, really, really stretching the working field of quantum theory too far here.

IMO quantum theory says that we cannot predict measurements below a certain level of accuracy. Copenhagen says that the reason behind that is that there's an inherent randomness to the universe. Correct?

It depends what you mean by a certain level of accuracy. You see, when you put quantum mechanics to practice in "regular labs" (i.e. no particle accelerators or femto/pico-scale experiments) then you hardly notice anything about the "lack" of accuracy because quantum theory only predicts probabilities for outcomes. In most experimental situations, it will be such that one outcome simply has an overwhelming probability. Even the particle in the box will be nearly completely trackable, and it will not suddenly tunnel or collapse to a position in alpha centauri.

The problem you are really refering to is the interpretation of quantum mechanics (where there is no experimental way to rule out one). The Copenhagen interpretation is the most "common" interpretation but it also has its own problems. Since it is only an interpretation, you can only take it seriously up to a given point. As Hawking said, as quoted by Raithere here, "perhaps there are just waves". As a scientist, I have an opinion, but no scientific evidence ofcourse (it lies beyond the realm of science).

Having said that, you can argue whether there is "inherent randomness" in the universe. It depends on what interpretation you want to follow. The Copenhagen interpretation (with the collapse of the wavefunction) indeed associates some randomness to the world. The many-worlds interpretation or Bohmean mechanics do not do this (they don't have a measurement collapse procedure, which is the stochastic part of the Copenhagen/von Neumann interpretation).

Bye!

Crisp

I believe it depends on precisely what you mean be determinism. While you may have something specific in mind I think that QM definitely voids what most people would consider to be a deterministic Universe

Yes, the idea of determinism has also evolved over time. The idea of "scientific" determinism started with Descartes I think, but it has indeed weakened over the course of time.

I agree that it voids what most people see as "deterministic", which is the oldest and most extreme interpretation of determinism: every event is predictable (the universe as a machine). However, I believe that in that interpretation of the word, determinism and predictability are intertwined just to get one "determinism". I think it is better, in the new light shed by quantum mechanics and the philosophical theories around it, to seperate the two. This weakens the idea of the strict determinism to "being able to predict all elements of the scientific theory" (the wavefunction), where predictability refers to the interpretation of the theory. Note that for non-quantum theories, and for other interpretations than the Copenhagen/Born interpretation, the strict determinism is recovered.

Hawking admits that even the uncertainty principle does not absolutely rule-out a kind of determinism "in principle", and says that quantum mechanics may very well allow the universe to be deterministic. He wrote:

"These quantum theories are deterministic in the sense that they give laws for the evolution of the wave with time. Thus if one knows the wave at one time, one can calculate it at any other time. ..."

Which is precisely what I tried to point out ;). Quantum mechanics is indeed deterministic in that sense. The measurement collapse procedure (present in "conventional" quantum mechanics) seems to be a problem as it is stochastic in nature, but strictly speaking it is not an element of quantum mechanics, but rather an element of the interpretation of it. This is also what Hawking refers to when he says that "... it might just be waves".

Excellent post btw.

Bye!

Crisp

Crisp,

Thanks. I'm not really a fan of the Copenhagen interpretation either. But these other interpretations have their own odd ramifications. What, IYO, would be the effect of these 'non-collapsing' interpretations upon such concepts as particles/objects and locality for instance?

~Raithere

Thanks. I'm not really a fan of the Copenhagen interpretation either. But these other interpretations have their own odd ramifications. What, IYO, would be the effect of these 'non-collapsing' interpretations upon such concepts as particles/objects and locality for instance?

Well, this is quite difficult. The problem of interpretations has its source in the problem of the measurement. You can do a few things in order to avoid the collapse of the wavefunction ("non"-determinism to use a huge word):

- You cannot measure at all and say that each possible outcome is simply a branch to an "alternate" universe (many-worlds interpretation). This seems a bit unsatisfactory because here, measurements do not really have results since measurements do not really take place. The fact that I see a particular result in my experiment is merely a coincidence that I branched to that particular alternate universe. It gets complicated when two people measure the same thing at the same time... what universe do we branch to ? ;)

- Or you can say that quantum mechanics is not complete, and that "more" is needed to describe the outcomes of experiment. This is the Bohmian mechanics way, which adds another equation (which describes the particle in a classical way) to quantum mechanics. There are ways to argue how the equation comes in, but it is really some sort of a deus ex machina for "conventional" quantum mechanics.

Whether you want to follow "other" interpretations of quantum mechanics really comes down to how serious you want to take the collapse in the quantum process. I tend to think more like von Neumann in this issue, who said that the collapse should be looked at as some sort of "effective" description of the measurement proces; that you should use the Schrodinger equation on both the measurement device and the system to calculate that the result of the measurement corresponds to some form of "collapse" on the system itself.

That option is inbetween the conventional interpretation of quantum mechanics (with measurements, i would call this the copenhagen interpretation), and the born statistical interpretation of the wave function.

Bye!

Crisp

Crisp after all that, lets get back to what I was saying.

MacM stated that uncertainty principle is in direct opposition to determinism.

I am saying it is not by the above. Do u understand now why I said it?

Crisp after all that, lets get back to what I was saying. MacM stated that uncertainty principle is in direct opposition to determinism. I am saying it is not by the above. Do u understand now why I said it?

Yes. I agree with you. I also now understand what you meant (which is due to me being a non-native english speaker, so no worries ;)).

Crisp,

Ditto on language interpretation. I believe I have clarified what I took the "determinisim" to mean, that as being "pre-destination". I don't challenge members here clarifying the meaning in scientific circles as applied.