#### hbi99

If we assume that multiverse exists; it means that scientists goal are to prove this theory...but they are not successful in our universe. That means that there infinite universes where they have succeeded to prove it. Than scientist from one of those infinite universes, should be able to enter our universe and thereby prove our existence - at the same time - we would get proof of their existence...consequently proof of multiverse.

Since no other scientists from parallell universes has "knocked" on our door, it is proof that multiverse doesn't exist.

Related Beyond the Standard Model News on Phys.org

#### jedishrfu

Mentor
If we assume that multiverse exists; it means that scientists goal are to prove this theory...but they are not successful in our universe. That means that there infinite universes where they have succeeded to prove it. Than scientist from one of those infinite universes, should be able to enter our universe and thereby prove our existence - at the same time - we would get proof of their existence...consequently proof of multiverse.

Since no other scientists from parallell universes has "knocked" on our door, it is proof that multiverse doesn't exist.
Welcome to PF!

Nice logic but flawed:

OPTION 1: Consider the statement: Everything I say is a lie.

That can never be proved true or false in any universe.

OPTION 2: It takes 15 billion years to be smart enough to make the knocker, hence no one has knocked yet.

OPTION 3: Remember the joke about the guy who refused to leave his home when the police warned him of an imminent flood saying God will protect me.

When the flood waters rose he climbed up on his roof and a police boat came by and he said God will protect me.

Finally when the helicopter came to the rescue, he refused and said God will protect me.

After being swept away by the waters and arriving in Heaven, he complains to God why didn't you save me and God says what do you mean, I sent a warning, a boat and helicopter what more do you want?

For this case, what would a knock sound like? Maybe we've heard it already.

#### hbi99

Since there are infinite of universes, the "knock" would be of all kind...as well as physical entering to our universe from theirs. Perhaps we've "heard" knocking and "ignored" but we should witness their appearance as well.

#### phinds

Gold Member
Since there are infinite of universes, the "knock" would be of all kind...as well as physical entering to our universe from theirs. Perhaps we've "heard" knocking and "ignored" but we should witness their appearance as well.
No, there is absolutely no evidence of any kind for more than one universe. If you believe there is, you need to cite it. Not a THEORY that there might be or has to be put proof that there is. You will not find any such.

#### hbi99

I definitely don't believe in multiverse. I guess my question is;
If the theoretical physicists accepts and/or argues for such possibility, how can they disregard that we haven't gotten visitors from another enlightened universe?

#### phinds

Gold Member
I definitely don't believe in multiverse. I guess my question is;
If the theoretical physicists accepts and/or argues for such possibility, how can they disregard that we haven't gotten visitors from another enlightened universe?
No idea. You'd have to ask them. I'm sure they have a perfectly reasonable rationale since otherwise they would have to give up on their belief in a multiverse.

My point is that you seem to think that the lack of any such explanation IS evidence of the multiverse. If you don't believe in the multiverse, why worry about irrelevant issues?

#### DennisN

Hi hbi99!
I do agree with what phinds said above, but I also want to point out another flaw in your logic:

(A) That means that there infinite universes where they have succeeded to prove it. (B) Than scientist from one of those infinite universes, should be able to enter our universe [...] (bolding and "A" and "B" added by me)
How does A imply B? Having evidence that something exists does not automatically imply that it can be visited.

#### haushofer

It can, if they try it on "anything can happen-thursday".

#### Chronos

Gold Member
Maybe they already visited here and reported back - "No intelligent life forms detected."

#### hbi99

Hi hbi99!
How does A imply B? Having evidence that something exists does not automatically imply that it can be visited.
Infinite possibilities means that A implies B...that implies C...and it even implies Z. If infinite is used as an argument in a theory, than it can be used in the opposing argument, hence disaffirming the initial argument by following a logic containing "infinite".

#### phinds

Gold Member
Infinite possibilities means that A implies B...that implies C...and it even implies Z. If infinite is used as an argument in a theory, than it can be used in the opposing argument, hence disaffirming the initial argument by following a logic containing "infinite".
This is nonsense. Infinity has no impact on logic. Either A implies B or it does not.

Gold Member

#### hbi99

This is nonsense. Infinity has no impact on logic. Either A implies B or it does not.
Can you paste in a link where it is proven that infinity has no impact on logic?

@ChrisVer - thanks for the links

#### micromass

Can you paste in a link where it is proven that infinity has no impact on logic?
You misunderstand infinity. You seem to think that when something is infinite, then "everything will happen". This is a very common misunderstanding. The relevant theory is that of the Infinite Monkey Theorem which says that if a monkey is given an infinite amount of time, then he will produce a work by Shakespeare. The point that many miss is that there are many assumptions in the Infinite Monkey Theorem which needs to be satisfied. If you miss those assumptions, then the Monkey will not produce Shakespeare even when given an infinite amount of time.

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

In short, just because something is infinite, does not mean that everything will happen. For example, the following string is infinite:

$$010101010101010101...$$

and yet the number $2$ will not appear. The interval $[0,1]$ is infinite, and still it will not contain negative numbers. And a physical example: you can never break the physical laws even if the universe exists for an infinite amount of time.

#### phinds

Gold Member
Can you paste in a link where it is proven that infinity has no impact on logic?
In addition to misunderstanding infinity, as micromass has pointed out, you misunderstand this forum. The way it works here is that if you make a definitive statement (such as "Infinite possibilities means that A implies B") YOU are responsible for providing the link to its validity.

If this seems unreasonable to you, stop and think about this: why would science or math journals devote space to DISproving nonsense? It just doesn't work that way.

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#### ChrisVer

Gold Member
Another example about infinity...the energy states of the infinite well are : $E_{n}= n^2 \epsilon$, and they are infinite... so are their eigenstates $|n>$.
Although the eigenstates are infinte, the $<m|n>= \delta_{mn}$ or , for illustrating what I want to say better, $<m|n>=0$ for $m \ne n$ holds for all of them. So you have infinite eigenstates, but their projection on each other (but themselves) is always zero.

If I understand the thing about the string vacua, if you have several vacua $|0_{i}>$, then their projection on each other will give you zero if they are not the same... $<0_{j}|0_{i}>=0$.
Or even if they were to be somehow communicating between each other, then their difference (or better said the potential you would use) would have to be such that they wouldn't be able to decay on to each other for as long as the universe time is ... That is also used in other theories (GUTs) where you can have several vacua and somehow they can decay on to each other.... if that's true, then the universe can exist in a metastable state.

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#### flowerdave

Can you paste in a link where it is proven that infinity has no impact on logic?

@ChrisVer - thanks for the links
No, I will not post a link, sorry. But I will say this: in mathematics infinity has a definite meaning and a referent.

In other areas "infinity" lacks a referent and is meaningless and therefore has no impact on an argument. See: Logical Positivism.

note: I oversimplify for the sake of brevity

#### mal4mac

If we assume that multiverse exists; it means that scientists goal are to prove this theory...but they are not successful in our universe. That means that there infinite universes where they have succeeded to prove it. Than scientist from one of those infinite universes, should be able to enter our universe...
Maybe the existence of other universes isn't something we can prove by experiment (the ultimate standard of proof in physics!) Even if other universes can be shown to exist by experiment, maybe it would still not be possible to enter another universe.

#### Chronos

Gold Member
The infinite multiverse concept invokes logical paradoxes. I like the Fermi comment - 'where are they?'. In other words, where are all the 'visitors' from this infinite number of parallel universes? Are they garden gnomes we are unable to perceive, or just nonsense?

#### hbi99

Maybe the existence of other universes isn't something we can prove by experiment (the ultimate standard of proof in physics!) Even if other universes can be shown to exist by experiment, maybe it would still not be possible to enter another universe.
Doesn't "impossible" contradict "infinite possibilities/universes"? Don't get me wrong...I accept that it might not be possible but in that scenario, "infinite" should be removed from the equation since there is at least one impossible universe. In a infinite number of universes, everything should be possible.

#### craigi

The infinite multiverse concept invokes logical paradoxes. I like the Fermi comment - 'where are they?'. In other words, where are all the 'visitors' from this infinite number of parallel universes? Are they garden gnomes we are unable to perceive, or just nonsense?
The simple conclusion is that either the number of universes in which you or someone like you would be aware that you had been visited is likely to be lower than those where there is no such awareness, or there is some observation selection bias which means you're not a representative sample of that set.

There are many ways that this can be true. To scetch out a few:

* Some physical mechanism means that it's not possible.
* You or someone like you are of little interest to those with such advanced technology.
* Intelligent races are rare or short lived and rarely reach sufficient technical capabilities.
* Technology is more likely to result in self destruction than advanced exploration.
* Races with such advanced technology have ethical reasons not to visit you or somone like you.

etc...

The whole concept of observation selection bias as an intrinsinc property of the universe is very challenging for physics, since the scientific tradition has involved removing it at all costs.

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#### julcab12

...I have little concern on infinity. I'm more skeptic about the solution and dynamic involved; "Ok, Lets provide a multiple solution to that huge space in (string landscape). Let's play along, predict and break apart it's properties in advance with levels. And after awhile infinity again."

Is there a room of doubt in which that huge space can have a different approach to it?

#### tzimie

Going all the way to TOE (probably leading to Multiverse/boiling superdense vacuum giving birth to baby Universes) should we abandon falsifiability at some point?

#### craigi

Going all the way to TOE (probably leading to Multiverse/boiling superdense vacuum giving birth to baby Universes) should we abandon falsifiability at some point?
The problem with falsifiability as a test is that it is frequently misunderstood or disagreed upon what it is that should be subject to falsifiability.

Occam's Razor should be used as the basis for falsifiability but again it is often disagreed upon which of competing explanations is the simplest.

It is frequently misunderstood that a multiverse is postulated as a solution to a problem and as such should be subject to falsifiability. Instead, a mulitverse emerges in different aspects of physics as a consequence of a minimal assumption theory and an extra assumption is required to remove it. Nevertheless there are still disagreements about the correct application of Occam's Razor.

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#### tzimie

Instead, a mulitverse emerges in different aspects of physics as a consequence of a minimal assumption theory and an extra assumption is required to remove it.
So the logic is the same as with alternative worlds in MWI.
I mean, people can have different points of view, but logic should be self-consistent: one can't accept the existence of baby universes because "extra assumption is required to remove" baby universes and at the same time deny MWI, right? Alternatively, if one denies MWI for "having extra undetectable stuff", that person should also deny the existence of the Multiverse, right?

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