If it can happen, it does happen?

[rrw4rusty]

Hi,

 

In quantum mechanics there is a... what?... I don't know so I'm hoping someone can help me... I'll say theory for now though this might be wrong. It says something like this 'If there is a probability that something can happen then, it does happen but in parallel universes.'

 

I hope I've gotten that close enough to correct for someone to know what I'm talking about -- it's been 20 years since I really dug into quantum mechanics.

 

First is this a prediction? a theory? or what?

 

Second, does it have a name?

 

Third has anything about this changed in the last 20 years?

 

How likely is it that this really exists?

 

Finally... gulp, does string theory have any impact on this?

 

Anything you know are any of the questions you can answer would be greatly appreciated! I'm using this in my sci-fi book to (don't laugh too hard) explain Dark Energy. If this were to really exist can you imagine how incredable its expansion over time would be!

 

Rusty

[Sisyphus]

http://en.wikipedia.org/wiki/Many-worlds_interpretation

 

It's an "interpretation."

[swansont]

There's a particle physics maxim, "that which is not prohibited is mandatory," which means that (especially at the particle physics level) because you keep sampling the system, many, many times, even something with a small probability will end up occurring.

 

Of course, this is balanced somewhat by Rabi's famous quote, "Who ordered that?" after getting news of the discovery of the muon.

[ajb]

There's a particle physics maxim, "that which is not prohibited is mandatory," which means that (especially at the particle physics level) because you keep sampling the system, many, many times, even something with a small probability will end up occurring.

 

Related to this is the idea that "if it is consistent with the symmetries, then it must be included in the action ".

[rrw4rusty]

So... in some universe I've already done the dishes?

 

rusty

[Severian]

Even if that interpretation were true, in what sense would it be you who already did the dishes? And for that matter, the dishes in your universe would still be unwashed. Indeed, if you lay claim to the action of washing the dishes in that other universe, I am sorry to tell you that you have infinitely many dishes still to wash in the others.

[toastywombel]

I think you are referring to Richard Feynman's Sum Over Histories.

A system gets from "state A" to "state B" by every possible path or history.

 

Its also known as Path Integral Formulation or Sum over Paths, and it is a description of quantum theory. A sound description too, it is accepted by many physicists and mathematicians, including Stephen Hawking. Here are some links:

http://en.wikipedia.org/wiki/Path_integral_formulation

http://en.wikipedia.org/wiki/Path_integral_formulation

http://www.aei.mpg.de/einsteinOnline/en/spotlights/path_integrals/index.html

 

From wikipedia:

"Feynman's approach is often used to explain in words the seemingly bizarre conclusions derived by mathematics and experimental results, in particular the famous double slit experiment, which was a starting point for the investigation of quantum mechanics (and is often a starting point for students of physics)."

 

Hope this helps

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more information from the third link I posted above:

 

This refers to a proof for the Feynman Interpretation. This interpretation is essential to quantum mechanics as we know it.

 

"There's even an exact proof, found by two mathematical physicists, Konrad Osterwalder from Switzerland and the German Robert Schrader: They proved a theorem showing that the properties of a quantum theory formulated in the space-time of special relativity can indeed be reconstructed exactly by using the Feynman recipe on an imaginary-time version of that same space-time."

Edited October 28, 2009 by toastywombel

[Severian]

Sorry toastywombel, but I don't think that is true at all. Feynman's Path Integral formulation of QFT is not suggesting alternate realities. It is deeper reasoning for the principle of least action. I think the OP is talking about the Many-Worlds interpretation of Quantum Mechanics.

[toastywombel]

what specifically in my post is not true at all? tell me.

Rusty said:

"'If there is a probability that something can happen then, it does happen but in parallel universes.'"

 

up until the "but" part has to do with Feynman's Sum Over Histories. The parallel universes part has to do with many worlds.

 

Furthermore the many worlds interpretation is in-part based of Feynman's Sum Over Histories.

 

I did not say anything in-accurate in my post.

Edited October 28, 2009 by toastywombel

[Severian]

what specifically in my post is not true at all? tell me.

 

I don't think the statement "I think you are referring to Richard Feynman's Sum Over Histories" is true at all, since he isn't.

[toastywombel]

I don't think the statement "I think you are referring to Richard Feynman's Sum Over Histories" is true at all, since he isn't.

 

Well to say that its not true is rather ridiculous. I said "I think you are referring to Richard Feynman's Sum Over Histories". To imply that that statement is not true at all is to imply that you know what I think. You could argue that you don't think that, that was what Rusty was referring to but to imply that my statement is dishonest is rather insulting.

 

Plus when he said "if it can happen, it does happen, but in parallel universes" the part up until but has much to do with Feynman's Postulate.

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Furthermore, you said, "Feynman's Path Integral formulation of QFT is not suggesting alternate realities. It is deeper reasoning for the principle of least action."

 

That is true but just because that is true does not discount my argument. Although Feynman's Sum Over Histories does not suggest alternate realities, the Many Worlds Interpretation is an interpretation of the implications of Feynman's Postulate.

 

Feynman's Sum Over Histories said that State A reaches State B by every possible path or history and because of that the amplitude of a specific set of events is the product of the amplitudes of all possible events.

 

Rusty: "If it can happen, it does happen."

Feynman: "State A reaches State B by every possible path or history"

 

Now compare those two statements how can you say that I am completely wrong?

 

I would conclude that we are both right to a degree, both Feynman's Postulate and the Many Worlds Interpretation have to do with what Rusty was talking about.

Edited October 29, 2009 by toastywombel
Consecutive posts merged.

[Severian]

Well to say that its not true is rather ridiculous. I said "I think you are referring to Richard Feynman's Sum Over Histories". To imply that that statement is not true at all is to imply that you know what I think. You could argue that you don't think that, that was what Rusty was referring to but to imply that my statement is dishonest is rather insulting.

 

Get a grip. I never suggested you were being dishonest. I was simply saying that I thought rusty was asking something different from your interpretation. My statement was "Sorry toastywombel, but I don't think that is true at all", so I was merely stating my opinion as to what he was meaning. To know for sure we would really need rusty to tell us himself.

[toastywombel]

Get a grip. I never suggested you were being dishonest. I was simply saying that I thought rusty was asking something different from your interpretation. My statement was "Sorry toastywombel, but I don't think that is true at all", so I was merely stating my opinion as to what he was meaning. To know for sure we would really need rusty to tell us himself.

 

Lol, fair point, you were just stating your opinion in opposition to mine. We'll I concur, I guess we will have to wait for Rusty to tell us. My argument though is that both of our responses are correct to a degree. I apologize for getting so upset.

[rrw4rusty]

http://en.wikipedia.org/wiki/Many-worlds_interpretation

 

It's an "interpretation."

 

Yes! This is it. Thanks!

Rusty

[Bob_for_short]

The Swansont first paragraph is the most exact answer. Referring to parallel universes is a weakness of some physicists. Give sufficient number of trials and even a low-probable event will occur. As simple as that.

[toastywombel]

The Swansont first paragraph is the most exact answer. Referring to parallel universes is a weakness of some physicists. Give sufficient number of trials and even a low-probable event will occur. As simple as that.

 

What do you mean it was the most correct answer. Many Worlds is an interpretation of quantum physics partly based on Feynman's Sum of Histories (lol gotta defend my viewpoint). But. . .

 

If you look at the original post Rusty was asking about what theory referred to parallel universes because he is mentioning it in his book. The answer he wanted was obviously the Many Worlds Interpretation. No one was trying to answer which interpretation is more accurate.

 

And who are you to decide the Many Worlds Interpretation is a weakness of some physicists? Are you not aware of the three interpretations of quantum physics. There are three schools of thought on the subject and although Multi-Worlds is not the most accepted (Copenhagen most likely is), it seems from reading your previous posts about "virtual particles" that you are really trying to stir-up trouble with your somewhat out-dated views on quantum mechanics.

 

Read the original post before replying.

Edited October 30, 2009 by toastywombel

[Bob_for_short]

...And who are you to decide the Many Worlds Interpretation is a weakness of some physicists?

I am somebody who has his own opinion based on his own experience (practice).

 

Referring to other worlds without any possibility to verify where they are and what happens there is not science. It's telling stories.

 

Everybody in life cares about this world. This is the human practice. And science is a systematisation of facts of this practice.

[ajb]

I have two related questions.

 

How does this relate to Borel's law of large numbers?

 

How low would a probability need to be so that the chance of the even having happened in our observable universe (given the finite age and size of our universe) is so small, we can say that it has almost certainly never occurred?

[Severian]

Referring to other worlds without any possibility to verify where they are and what happens there is not science. It's telling stories.

 

While I agree with that (i.e. which QM interpretation you chose is not science, but opinion or belief), I don't think the many-worlds interpretation is any scientifically less reasonable than the Copenhagen interpretation. Scientists should feel free to have opinions and world-views, as long as they don't infringe on scientific observations. Since you cannot make an experiment to tell the difference between these interpretations, they are equally valid world-views and no scientist should be derided for beliefs that do not contradict observation.

[Bob_for_short]

While I agree with that (i.e. which QM interpretation you chose is not science, but opinion or belief), I don't think the many-worlds interpretation is any scientifically less reasonable than the Copenhagen interpretation.

I did not tell that the MWI is the only wrong one. There are many of them. Still, we all in our daily practice think of this world solely. This is sufficient, fortunately.

[Severian]

I did not tell that the MWI is the only wrong one. There are many of them.

 

Can you prove that statement?

[Bob_for_short]

Prove what? That there are no other worlds? That people, insted of accepting the complexity of this world, invent deterministic pictures furnished with hidden parameters or other interpretations? The fact that there are many of them and they are different proves already what you ask.

[ajb]

Prove what? That there are no other worlds? That people, insted of accepting the complexity of this world, invent deterministic pictures furnished with hidden parameters or other interpretations? The fact that there are many of them and they are different proves already what you ask.

 

I think the point being raised is that one cannot prove an interpretation to be right or wrong.

 

An interpretation is just a "retelling" of a calculation or mathematical construction using words and physical ideas.

 

As such, it is not obvious how one could say that many-worlds exist* or not.

 

________________

* what ever exists means in this context.

[Bob_for_short]

...An interpretation is just a "retelling" of a calculation or mathematical construction using words...

Yes, whatever the words mean, as soon as you use words, it is already an interpretation, and nobody can blame you for that.

[ajb]

Yes, whatever the words mean, as soon as you use words, it is already an interpretation, and nobody can blame you for that.

 

So if we accept that many-world is an interpretation rather than a statement about the formulation of quantum mechanics, then it is difficult to understand what is meant by many-worlds existing or not.

 

Meaning, that we are free to use this interpretation (bound by the limits of an interpretation) and any other interpretation we find desirable.

 

There is nothing to prove or disprove.

 

However, if many worlds in not an interpretation but a reformulation of quantum mechanics without wave-function collapse, then maybe there is an experiment to show it to be correct. I don't know.

Edited October 30, 2009 by ajb