It might be occupying the same place. — Sir2u

How could it occupy the same place?

As I also mentioned in the other thread, there is no evidence for this cosmological multiverse, yet it is the one most people are quite willing to accept. On the other hand, there is overwhelming evidence for the quantum multiverse, yet this is supposed to be controversial. I find the psychology of this situation utterly bizarre. To add to the irony, if the cosmological multiverse exists, the quantum multiverse adds zero complexity to our view of reality. Very odd situation! — tom

It is my understanding neither multiverse is accepted by the physics community. As far as I can tell, the only justification for belief in the cosmological multiiverse is as a solution to problems caused by the so-called strong anthropic principle. Those problems have always seemed to me to reflect a misunderstanding of probability. It certainly isn't true that the quantum multiverse is uncontroversial. The way it is typically formulated, it is neither true nor untrue, since the other universes aren't even theoretically detectable. Are the other universes in the cosmological universe theoretically detectible? If not, then the theory doesn't mean anything.

What are the odds that out of all of the 3 pound hunks of matter out there in the vast universe or maybe even infinite multiverse, most of them lacking biology, you just happen to find yourself being a human in this special place and time? Did you win the cosmic lottery a hundred times over or something? Shouldn't you find it a bit surprising that you find yourself occupying such a privileged vantage point on the world? After all, it seems, you might have been a mouse instead, or a bacterium, or a cloud of dust or a rock in outer space. — oysteroid

What you are describing in your post is the strong anthropic principle scaled down from the universe to personal identify. Your argument in this paragraph and in the entire post represents just the misunderstanding of probability I discussed in a previous post.

It seems clear to me, although I won't be surprised if you disagree, that my identify is related to my physical nature. If I didn't have the body I have, I wouldn't be the person I am. I am not claiming mind/brain equivalence. You have already agreed that someone who has exactly the physical makeup I have is me. If that's true, we have moved the mystery of me being me from a psychological one to a physical one. I'm no different from a rock or bacteria or planet or electron.

Suppose we have a big bucket filled with a trillion marbles, one of which is gold, the rest of which are blue. We blindfold you and have you dig around and withdraw a marble. Then we ask you whether or not you should expect to take off the blindfold and find yourself holding a gold marble. Of course, the answer is no. With a random sample, you should expect to have a typical sample. If you do end up finding yourself with the one in a trillion golden marble, shouldn't you find this surprising? — oysteroid

Again, this is the fundamental misunderstanding associated with the anthropic principle. You may be surprised if you get a gold marble, but you had to get something. Let's set the problem up a little differently. Instead of marbles, let's say we have a deck of cards with 4 trillion cards, each in one of our standard four suits. Each suit has 999,999,999,997 numbered cards (including the ace as 1) and 12 face cards. So, I pick a card from the well shuffled deck. It's the a 2 of clubs. That's amazing!!! the odds of getting that are one in 4 trillion!!! Well... not so much. It would be truly amazing if it weren't one of the 4 trillion possibilities. Any particular card, say an ace of spades (or in your case, a gold marble) is only special based on some human judgment. The universe doesn't care at all.

Consider further what a strange idea it is that you can be something, some arbitrarily extended, but limited, collection of physical particles. People sometimes ask what it must be like, if it is like anything at all, to be a rock. Notice what they are doing! Is there some magical boundary around a rock other than the one we impose when we see a rock and identify it as such, mentally separating it from its surroundings? If a rock, which is a collection of many smaller things, why stop the collection at that point? Why not a pile of rocks? Why not the mountain? Why not the planet? Why not the whole universe? — oysteroid

The separation of the universe into people, marbles, planets, mountains, etc, what Lao Tsu called "the 10,000 things, is a human convention, although I assume it is one we follow based on the structure of our brains and minds.

There is one substance and it experiences all of its modifications and relations and is everywhere present to itself. And if you want to know what it is like to be it, just ask yourself. You're it. You're everything. — oysteroid

Finally, something I don't have to disagree with.

It is my understanding neither multiverse is accepted by the physics community. — T Clark

The cosmological multiverse is accepted by all those who accept our best theory of how our universe began, including Hawking and the other luminaries.

As far as I can tell, the only justification for belief in the cosmological multiiverse is as a solution to problems caused by the so-called strong anthropic principle. — T Clark

No, it is an inescapable consequence of our best theory of how the universe began.

Those problems have always seemed to me to reflect a misunderstanding of probability. — T Clark

What is that misunderstanding, and how does it apply to a deterministic multiverse?

It certainly isn't true that the quantum multiverse is uncontroversial. The way it is typically formulated, it is neither true nor untrue, since the other universes aren't even theoretically detectable. — T Clark

That is simply false. We routinely interact with the quantum multiverse.

Are the other universes in the cosmological universe theoretically detectible? If not, then the theory doesn't mean anything. — T Clark

You could have asked the same question of gravitational waves for 100 years.

best theory of how our universe began, — tom

Which theory is that?

What is that misunderstanding, and how does it apply to a deterministic multiverse? — tom

See my response to another of your posts.

That is simply false. We routinely interact with the quantum multiverse. — tom

If I understand you correctly, the interaction you describe is the quantum behavior of subatomic particles. As I indicated previously, that "interaction" is a consequence of one particular, controversial, interpretation of quantum mechanics. It is my understanding that that interpretation is not even theoretically differentiable from all the other interpretations. As I said, that makes it meaningless. If it turns out one interpretation can be verified, that judgment would change.

You could have asked the same question of gravitational waves for 100 years. — tom

Did a consensus of physicists consider gravitational waves theoretically undetectable? As I said, if it turns out the theories are differentiable, you may be right.

I mentioned the anthropic principle in both my previous posts. You haven't mentioned it. Does that mean you don't base any of your judgments on it?

Suppose that there are an infinite amount of universes and that everything that can happen does happen in some universe. So there's a universe just like ours with a planet identical to earth (lets call it earth-2), and everything on earth-2 is identical to earth to the last atom. So there's a Purple Pond user just like me typing this thought experiment. I'm atom for atom identical to the Purple Pond on this different universe. The question is: even though I'm separated from by an unimaginable distance, and we belong to different universes, am I the same person? — Purple Pond

Depends on what you mean by "person". The self is difficult to define, but for the most part (regardless of which way you choose to define who "you" are whether biologically, psychologically, historically, etc.), you are qualitatively identical to the person who is in that other universe, but not numerically so. We can talk about two apples set beside, that are the same in every respect with regards to their internal features, but that does not mean there is only one apple in front of us. Your counterpart is located somewhere else. He may operate exactly as you do, but you're currently here, and he's currently there in a parallel universe.

How could it occupy the same place? — Marchesk

If it is in a different dimension why would there be a problem with it being in the same place.

If it is in a different dimension why would there be a problem with it being in the same place. — Sir2u

Because it's in a different dimension. Are you in the same place as me when I'm in Times Square and you're 10 miles above?

Are you in the same place as me when I'm in Times Square and you're 10 miles above? — Marchesk

Obviously no. That is kind of silly.
We are different people and would never been in the same place in this dimension.
I am 10 miles away so I am in a different position in this dimension.

Would different dimensions, if they exist, be a part of this universe?
If you say yes, then they have to occupy the same space.
If you say no, then you have to go onto another idea called multiverse theory.

By definition, i.e., that they're separate necessarily means they're experiences are not the exactly the same. Even if it were possible to put you in a replicating machine and produce two biologically identical copies, immediately after such an event the experiences of both would necessarily make them different.

The question is: even though I'm separated from by an unimaginable distance, and we belong to different universes, am I the same person? — Purple Pond

It is my understanding that all electrons are exactly the same. Does that mean that all the electrons in the universe are the same electron? Actually, when I checked, there are ways of looking at the universe as though that's true - there is only one electron that moves forward and backward in time.

According to this article the idea is complete nonsense. It fails experimentally.

According to this article the idea is complete nonsense. It fails experimentally. — Purple Pond

But still, if we agree that a person in two different multiverses who is exactly the same is the same person, then, by that same logic, all the electrons in the universe are the same electron.

Good point. I agree.

But still, if we agree that a person in two different multiverses who is exactly the same is the same person, then, by that same logic, all the electrons in the universe are the same electron. — T Clark

What logic?

No two electrons in the universe can be in the same quantum state - they are fermions, remember.

No two electrons in the universe can be in the same quantum state - they are fermions, remember. — tom

In my extremely limited understanding of this subject, the fact that two electrons are in different quantum states does not mean they are not identical.

No two electrons in the universe can be in the same quantum state - they are fermions, remember. — tom

If they are entangled, do you think you can say which one is which? Is that A over there, and B over here, or vice versa?

Of course MWI "solves the problem" as ever. :-}

If they are entangled, do you think you can say which one is which? Is that A over there, and B over here, or vice versa? — apokrisis

The electrons will be in different locations, with non-overlapping wavefunctions, so you can label them as you wish. Usually they are labeled after the scientists who perform the measurements at the different locations: Alice and Bob.

Of course MWI "solves the problem" as ever. — apokrisis

Some people don't like solutions.

In my extremely limited understanding of this subject, the fact that two electrons are in different quantum states does not mean they are not identical. — T Clark

Identical and distinguishable, particularly if they are separated by a few Bohr radii.

Ah, so if they are entangled, we wait until they are disentangled? Eventually there is the one Bob measured and the one Alice measured? Except now we don’t know which Bob and which Alice in which world branch as we have just duplicated them under MWI.

Sounds legit.

Ah, so if they are entangled, we wait until they are disentangled? Eventually there is the one Bob measured and the one Alice measured? Except now we don’t know which Bob and which Alice in which world branch as we have just duplicated them under MWI. — apokrisis

If you are about to measure the spin of a particle, what difference does it make if the particle is entangled with another or not? Alice still measures the particle in her apparatus, not the one in Bob's apparatus.

The only way to discover if the particles are entangled is to compare records.

Suppose that there are an infinite amount of universes and that everything that can happen does happen in some universe. So there's a universe just like ours with a planet identical to earth (lets call it earth-2), and everything on earth-2 is identical to earth to the last atom. So there's a Purple Pond user just like me typing this thought experiment. I'm atom for atom identical to the Purple Pond on this different universe. The question is: even though I'm separated from by an unimaginable distance, and we belong to different universes, am I the same person? — Purple Pond

It depends on what kind of an other world you're talking about.

Here are two possibilities:

1. Physically-Related Places:

If you're talking about a physically-related "universe" that's really just a different region of this universe, or just a different sub-universe of which our Big-Bang Universe is a sub-universe, then of course that place is really physically there, and your duplicate is really physically there, as we mean physical reality for things in our universe. (even if we can't actually know or detect his existence).

Then of course you aren't he. You experience your own life, from your point of view, not from that of someone many trillions of lightyears away, or in a different physically-related universe.

Just as, if someone in a different town built a robot that's a perfect copy of you, You don't experience from its point of view. If it stubs its toe, you don't feel that.

2.

Different possibility-world

If it isn't a physically-related place, but is, instead, a different possibility-world, then it isn't meaningful to speak of it, because, if it's identical to this world, then it's the same possibility-world. There's no meaningful difference. That world isn't a different one. It isn't located at a different place in this universe or physically-related multiverse (which would make it spatially different and separate).

-------------------------

So, possibility #1 is the only meaningful one to speak of.

Max Tegmark estimated that, if this universe is infinite, or really huge, and if its physics is the same out to a great enough distance, and if it's density isn't systematically different, then the most likely distance, in meters, to a Hubble-volume that's identical to the Hubble-volume we're at the center of, is about 10 to the power of (10 to the 118th power).

If you're willing to settle for an identical hundred-light-year radius sphere, then it's probably only ten to the power of (10 the 92nd power)

If you'll settle for just an identical you, then the likely distance is only 10 to the power of (10 to the 28th power).

Michael Ossipoff

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