Exploring the Grand Design: The Multiverse & Buckyball Experiment

[Lazernugget]

Wow, I just became flooded in thought...


Anyway, I recently read a Stephen Hawking book called the Grand Design, and I learned a lot! The book includes talk of multiple universes, and the buckyball experiment. I understood well but I have a question:

I understand the theory that particles travel every route possible, and that shows particles can effect themselves like waves, and that shows that it is possible other universes exist, the difference being the state of the route of the subatomic particle, but would these small infinite amount of routes for every single particle make the other universes actually consist of matter and other ACTUAL histories, leading to things like instead of drinking lemonade I drank apple juice today?

Oh, and another thing, how come OUR universe seems so perfect, even though the probability of subatomic particles RANDOMLY flying away to the moon for no reason seems so high when you read the theories?

(Correct me on any of this)

-LN

 

[Lazernugget]

(Bump)

 

[StevieTNZ]

Are you Varon by any chance?

 

[Lazernugget]

I don't...know? (Not sure what Varon means so...) ((I'm only 11, people))

 

[Varon]

Are you Varon by any chance?

Why, do I sound like a 11 year old? lol

to the original thread poster... always think of quantum field theory where particles are just momentum and energy of the field.. this means there are really no particles.. it's just fields... here there are no measurement problem... the fields got splitted by the slits and the they just trigger one of the existing millions of electrons in the detector which we mistakenly thought is the point where the original particle (or molecule) hit the detector when it fact the buckyball molecue just got smeared in the detector... this is according to the new von Neumann of the 21st century.

 

[Fyzix]

If you are 11 years old, I think you would find it better to ask these questions on a less "advanced" forum and more "layman" friendly.

There are also great tutorials explaining these sort of things, even for youngsters like yourself.
Just google around until you find the answer your looking for.

 

[Lazernugget]

If you are 11 years old, I think you would find it better to ask these questions on a less "advanced" forum and more "layman" friendly.

Nah... I understand many complicated things like this for my age, I ask questions related to things that I understand and in my range of understanding.


My basic question is if the alternate history theory states ACTUAL other histories exist or not, (Where things really exist)

 

[Drakkith]

Nah... I understand many complicated things like this for my age, I ask questions related to things that I understand and in my range of understanding.


My basic question is if the alternate history theory states ACTUAL other histories exist or not, (Where things really exist)

There is no evidence that alternate universes exist, so unfortunantly we cannot say anything on their possible histories. The idea that there are multiple universes and histories where every possible outcome happens is a popular one, but is NOT within the current means of science to observe. Whether the theory claims that this actually happens or not, I do not know.

If I may give you a little piece of advice: Don't get wrapped up in the near philosophical concepts of some theories. And remember and understand the key word in your earlier statement: Possible. Is it possible multiple universes exist? Yes, but only in the sense that we don't know if they are out there or not. This is a different meaning than me asking if it is possible that an asteroid will hit the earth. It IS 100% physically possible for an asteroid to hit the earth. We don't know if it is possible for alternate universe to exist using that meaning of possible.

 

[haael]

By the way, isn't the "summing over histories" a strong hint that MWI is true? It's not a proof of course, but the fact that "summing over histories" works implies strongly that the alternate histories must exist somewhere. Otherwise, we would have to admit that the sheer possibility of something being able to happen affects our world.

What do other interpretations have to say about "summing over histories"?

 

[Drakkith]

Otherwise, we would have to admit that the sheer possibility of something being able to happen affects our world.

What do you mean by this?

 

[haael]

What do you mean by this?

You know, let's say for now that the world is classical, or take the most classical interpretation of QM You can imagine.

Now let's consider some experiment with quantum effects, say double slit experiment. From the classical point of view, an electron passes through one of the slits. Now we see a nonclassical outcome, the interference pattern. The electron did pass through one of the slits, but it could pass through the other, and this possibility affected the real world.
What is worse, if there was an obstacle on that possible path, the pattern would change. The sheer possibility of something being able to happen (or not) changes the world.

What I want to say: the information of alternate paths must be encoded somewhere. The electron has passed through one of the slits, OK but the information of it possibly passing through the other must be written somewhere in our world. That's why I believe the wavefunction is objective, that is the first thing.

But the situation is quite simple when we have flat spacetime. One can employ deBB interpretation, the pilot wave function goes through slits, diffracts on them and so on. But what happens when we analyze the quantum evolution of the whole Universe, like Hawking?

Howking does "summing over histories" of the whole Universe. According to his theory, our current (our) universe state is a result of interference of all possible pasts, we are the brightest spot on the interference pattern. So OK, the known past of our universe is one of the paths. But there are plenty of other paths that the wavefunction of the Universe had travelled. My question: where is the information of these alternate paths encoded?

In the double slit experiment there are 2 concepts: the electron and the experiment apparatus with slits. Electron has a wavefunction that diffracts on the apparatus.

With the whole Universe we must have similar concepts. We have the Universe that has wavefunction. Our universe (our past) is one of the paths that the Universe wavefunction had travelled. But we must also have some environment where all this happens, some meta-Universe which fulfills similar role to the slit apparatus. Other universes hold the information of other possible pasts. That is the multi-world interpretation.

If someone doesn't believe in MWI then my question is: where is the information of these all possible pasts encoded? If the answer is "nowhere", then do You admit that the possibility of something being able to happen in the past could affect our present world?

Of course one possible answer is to not believe in "summing over histories" at all. I do not have an oppinion in this matter, to be honest.

 

[Drakkith]

If someone doesn't believe in MWI then my question is: where is the information of these all possible pasts encoded? If the answer is "nowhere", then do You admit that the possibility of something being able to happen in the past could affect our present world?

Encoded? I don't understand. A possibility is a chance of something occurring in the future. Events in the past don't have possibilities, they happened exactly as they happened.

The sheer possibility of something being able to happen (or not) changes the world.

Changes it from what to what? If something cannot happen then there isn't anything to change to. Just because it is possible for something to happen doesn't mean that it causes a change in our universe. It is when something does happen that causes changes. A radioactive particle has a chance of decaying every second. But the fact that it has that chance doesn't change anything, it is only when it actually decays that it changes something.

Our universe (our past) is one of the paths that the Universe wavefunction had travelled. But we must also have some environment where all this happens, some meta-Universe which fulfills similar role to the slit apparatus. Other universes hold the information of other possible pasts. That is the multi-world interpretation.

If that is the MWI, then I don't agree. It seems like inferred nonsense to me.

 

[haael]

If that is the MWI, then I don't agree. It seems like inferred nonsense to me.

It's not MWI per se, but it's "summing over histories" which strongly supports MWI in my opinion. Yes, it may be nonsense, or my understanding of it may be a nonsense, but Stephen Hawking is doing it, and when someone like him says something like this we should at least stop and think.

Hawking took an approach of using path integral to the whole Universe. I don't have an oppinion if it has any sense, much less if it gives good results. But he did.

Now my concern: if we assume that "summing over histories" do work, don't we also have to believe in MWI? I mean: different QM interpretations should give different results when considering "summing over histories", so it may be a means of distinguishing various interpretations.

 

[Polyrhythmic]

The electron did pass through one of the slits, but it could pass through the other, and this possibility affected the real world.

According to Quantum Mechanics, this is just not true. The electron didn't pass through either the first or the second slit. Its wave function carries a probability for both outcomes, and unless somebody measured explicitly, you cannot claim that it took one of those paths.

Also, what do you mean by "summing over histories"? Do you refer to the Feynman path integral?