If the universe is infinite, does that mean that everything exists somewhere?

[Richard87]

If the universe is infinite, does that mean that everything exists somewhere, besides obviously impossible things like a star that contains oxygen but doesn't contain oxygen or a 4-sided triangle?

 

[mgb_phys]

It would if it was but it isn't

 

[Chalnoth]

If the universe is infinite, does that mean that everything exists somewhere, besides obviously impossible things like a star that contains oxygen but doesn't contain oxygen or a 4-sided triangle?

Well, consider this by way of analogy.

The set of all even numbers is infinite. I can go on counting even numbers for ever and ever and never reach an end.

But clearly the set of all even numbers does not include all possible numbers. It doesn't include, for instance, the number pi.

So even if the universe is infinite (we don't know whether or not it is), then that doesn't necessarily mean that all possibilities are realized.

However, there may be other reasons to believe that all possibilities are realized, mainly stemming from quantum mechanics, where we find, for instance, that if there is the possibility of matter inhabiting a region of space, then particles of that sort of matter will necessarily pop in and out of the vacuum. Another way of saying this is that in quantum mechanics, there mere possibility of existence forces existence. So it is not unreasonable to suspect that perhaps all possibilities must actually be realized.

This doesn't mean that anything and everything we can imagine occurs, of course. We can imagine quite a lot of impossible things, as you mention above. But we can also imagine a great many things that are not obviously impossible, and yet may turn out to be upon deeper inspection.

 

[Entropee]

Well so far we think that the Universe is finite, but with no boundaries. I really hate the word infinity >.< It's so unbelievably unfathomable, and people just toss it around as if it's just a large number. Good thoughts on the subject though.

 

[Chalnoth]

Well so far we think that the Universe is finite, but with no boundaries.

I don't know who this "we" is, but so far as I am aware there is no consensus on this. Currently there just is insufficient evidence to say anything more than, "the universe is very, very big."

 

[JnWaco]

So there might not be another Earth where I'm dating Jennifer Aniston? Dang.

 

[Chalnoth]

So there might not be another Earth where I'm dating Jennifer Aniston? Dang.

Well, just because you can imagine it doesn't mean it's possible. Consider, for a moment, how many opportunities you have had to get to know a beautiful actress. Probably not very many.

If, in this parallel world, you were the sort of person that had a life where you were in at least occasional contact with beautiful actresses, would your life be so different that that person even count as being you in the first place?

 

[Entropee]

I don't know who this "we" is, but so far as I am aware there is no consensus on this. Currently there just is insufficient evidence to say anything more than, "the universe is very, very big."

Okay okay.. by "we" I mean Stephen Hawking haha

And if our anti particles formed anti people on an anti Earth we could have identical twins down to the last particle...maybe... ;P

 

[Chalnoth]

Okay okay.. by "we" I mean Stephen Hawking haha

I'm pretty sure if you asked him straight up he'd say basically the same thing I just did. He did, of course, present the no boundary proposal (where the universe has no boundary either in time or in space), but that doesn't mean he would go so far as to claim that he knows it's true. He may think it likely (it's his idea, after all), but I doubt he'd go that far.

And if our anti particles formed anti people on an anti Earth we could have identical twins down to the last particle...maybe... ;P

Well, we don't have anti-particles. That's one of the requirements of our cosmological observations: that early-on, there was a very small breaking of the symmetry between matter and antimatter.

 

[Entropee]

Well yes I agree with you that's why i said its what he "thinks" not knows, and would YOU go so far as to say that you "know" we don't have anti-particles? There may not be symmetry between matter and antimatter but It's still somewhere.

 

[Chalnoth]

Well yes I agree with you that's why i said its what he "thinks" not knows, and would YOU go so far as to say that you "know" we don't have anti-particles? There may not be symmetry between matter and antimatter but It's still somewhere.

Yes, because we've actually looked for them. They're not out there. Basically, if the matter and anti-matter were physically separated, then you'd occasionally get clumps of matter running into clumps of anti-matter, causing rather large explosions. We don't see any of that.

Furthermore there's the problem that around the time of the emission of the CMB, our universe was extremely uniform, so that there was no way that normal matter and anti-matter could have been out of contact with one another.

 

[Entropee]

Thats true, but why then was the early universe so hot?

Also an unrelated question maybe you can answer for me, if most of the universe is hydrogen, why didnt all the hydrogen undergo nuclear fusion when the universe was as big as a baseball? Was it because the particles were different at the time?

 

[Chalnoth]

Thats true, but why then was the early universe so hot?

It appears to be a result of the end of inflation. Basically, whatever it was that drove inflation had to have a whole lot of energy. When it decayed, it reheated our universe to a tremendous temperature.

Also an unrelated question maybe you can answer for me, if most of the universe is hydrogen, why didnt all the hydrogen undergo nuclear fusion when the universe was as big as a baseball? Was it because the particles were different at the time?

Right, if the expansion rate would have been slower then, it would have. It would have progressed all the way to producing iron and that'd be the most common element.

But this takes time. First the protons and neutrons condense out of the quark-gluon plasma, so you have hydrogen right away. Then you start to make helium from the hydrogen. Then you start to make heavier and heavier elements.

As it turns out, the expansion rate was such that the universe cooled to where the nuclear fusion basically stopped by the time there was only around 25% helium sitting around, and long before more than trace amounts of anything else formed. Incidentally, this is even faster than it sounds, because much of the helium stemmed from the neutrons that were around early-on (when you have nothing but protons around, fusion takes a heck of a lot of energy, as you have to convert protons to neutrons, and because they repel one another, but when you have lots of neutrons sitting around it's much easier).

 

[Entropee]

I thought we didnt have protons and neutrons in the early universe, wasn't there lots of particle decay so they would be different now?

 

[Chalnoth]

I thought we didnt have protons and neutrons in the early universe, wasn't there lots of particle decay so they would be different now?

Oh, well, in the very early universe there weren't any. But when the quark-gluon plasma cooled, well, protons and neutrons were the particles they condensed into: they're the lightest baryons. Heavier baryons are unstable and would have quickly decayed into protons and neutrons.

 

[Entropee]

About how long did it take for the quark-gluon plasma to cool?

 

[Chalnoth]

About how long did it take for the quark-gluon plasma to cool?

Well, either way I don't know off the top of my head and you might be able to find it yourself as quickly as I could off of Google, but what specifically do you mean by this?

That is, are you asking how long the process of nucleosynthesis took, from the time the protons/neutrons condensed out of the plasma to the time that fusion stopped? Or are you asking how long after the end of inflation that this occurred?

 

[Entropee]

How long after the end of inflation is more what i meant. But yeah i could google it lol.

 

[Chalnoth]

How long after the end of inflation is more what i meant. But yeah i could google it lol.

Hehe :) Yeah, I actually looked it up to. It's about three minutes ;)

 

[Entropee]

Wow nice haha, did you see my post on your profile?

 

[JnWaco]

Well, just because you can imagine it doesn't mean it's possible. Consider, for a moment, how many opportunities you have had to get to know a beautiful actress. Probably not very many.

If, in this parallel world, you were the sort of person that had a life where you were in at least occasional contact with beautiful actresses, would your life be so different that that person even count as being you in the first place?

lol, you sure know how to pour water on a nice thought!

just kidding

 

[Chalnoth]

lol, you sure know how to pour water on a nice thought!

just kidding

Haha, well, I think that it still can be extremely interesting.

Imagine, for a moment, just walking down the street. If we just take the part of your wave function that you know about today, and imagine all of the future parts (using the many worlds interpretation, of course), then those future parts will likely follow nearly the same but slightly different trajectories, for a while. I imagine it like a blurring of myself, some parts slightly ahead, some slightly behind. Some slightly to the left, some slightly to the right, etc. So the different parts of my wave function are slowly, very slowly dispersing. It might take many trips outside the house before anything interesting happens.

But then something interesting does happen: a car, going too fast, almost hits me. Well, it almost hits the "me" that I see, but there are other me's that were in slightly different places: some of them were just a little bit too close to the car, and got smacked. Suddenly, what were once very similar worlds become very different.

In another situation, something very similar is happening, but the event that causes the divergence is, say, I'm not paying attention to where I'm going, and I almost run into a pretty girl. I manage to apologize for the incident, strike up a conversation, and we start dating. Of course, that's just the "me" that I observe: some of the me's in other worlds either are far enough away that they don't almost run into her, or are close enough that they actually run into her and just end up pissing her off. In some others, the conversation takes a slightly different turn and we never see each other again. Etc. etc.

So there might well be people out there who, when I was a child, were still part of my wave function, the part that I remember, but who today have extremely different lives.

 

[Axuality]

If the universe is infinite, does that mean that everything exists somewhere, besides obviously impossible things like a star that contains oxygen but doesn't contain oxygen or a 4-sided triangle?

You must define the word 'infinite' before you can validly ask this question, and before anyone can validly answer it.

Does that make sense?

And if you're able to define it to your satisfaction, then you'll have answered your own question, I believe. :)

 

[Chalnoth]

You must define the word 'infinite' before you can validly ask this question, and before anyone can validly answer it.

That's easy: if the universe is infinite in space, then even if one could travel much faster than the speed of light, one could travel forever without ever crossing one's path.

Another way of saying it is that if you could write down coordinates for the entire universe, then you'd never reach a number in those coordinates that was "beyond" the universe.

 

[JnWaco]

Haha, well, I think that it still can be extremely interesting.

Imagine, for a moment, just walking down the street. If we just take the part of your wave function that you know about today, and imagine all of the future parts (using the many worlds interpretation, of course), then those future parts will likely follow nearly the same but slightly different trajectories, for a while. I imagine it like a blurring of myself, some parts slightly ahead, some slightly behind. Some slightly to the left, some slightly to the right, etc. So the different parts of my wave function are slowly, very slowly dispersing. It might take many trips outside the house before anything interesting happens.

But then something interesting does happen: a car, going too fast, almost hits me. Well, it almost hits the "me" that I see, but there are other me's that were in slightly different places: some of them were just a little bit too close to the car, and got smacked. Suddenly, what were once very similar worlds become very different.

In another situation, something very similar is happening, but the event that causes the divergence is, say, I'm not paying attention to where I'm going, and I almost run into a pretty girl. I manage to apologize for the incident, strike up a conversation, and we start dating. Of course, that's just the "me" that I observe: some of the me's in other worlds either are far enough away that they don't almost run into her, or are close enough that they actually run into her and just end up pissing her off. In some others, the conversation takes a slightly different turn and we never see each other again. Etc. etc.

So there might well be people out there who, when I was a child, were still part of my wave function, the part that I remember, but who today have extremely different lives.

I'm a layman, just getting into physics, but that makes sense. So are there infinite universes, or just one universe that is infinite. I saw a special on the Discovery channel where they said there were an infinite number of universes in the "multiverse".

How was that proven (or derived)?

 

[Axuality]

That's easy: if the universe is infinite in space, then even if one could travel much faster than the speed of light, one could travel forever without ever crossing one's path.

Another way of saying it is that if you could write down coordinates for the entire universe, then you'd never reach a number in those coordinates that was "beyond" the universe.

You're a smart guy/girl obviously, and thanks for your post.

But he didn't SAY 'infinite in space', like you did. He said just 'infinite'.

But despite that, no matter how fast you travel, you would never cross your own path in a FINITE universe, if the universe was constantly creating itself faster than you could get there.

And as to your second definition, you can't write down the coordinates for an entire infinite universe. And even if you tried, you might never reach a number outside the universe because the universe may be growing faster than you can chart it...- while still remaining currently finite.

So again, like the original poster, you can't really use the word infinite even in a phrase such as 'infinite in space', until you define the word infinite. As soon as you do, then you'll realize that infinite has but one definitive meaning. All others are derived for context.

Not to mention after all, that you gave descriptions of 'infinite in space', not a definition of 'infinite in space'.

So my proposal remains- You must define 'infinite' before you use the term.

 

[Axuality]

If the universe is infinite, does that mean that everything exists somewhere, besides obviously impossible things like a star that contains oxygen but doesn't contain oxygen or a 4-sided triangle?

Yes Richard87, if the universe is TRULY infinite, it means that it contains all things real.

And if you're wondering if you're dating Jennifer Aniston somewhere, I can tell you 'yes, you are', and tell you how to find that "part" of the universe, but don't ask please. :)

 

[Chalnoth]

You're a smart guy/girl obviously, and thanks for your post.

Guy, actually :)

But he didn't SAY 'infinite in space', like you did. He said just 'infinite'.

But despite that, no matter how fast you travel, you would never cross your own path in a FINITE universe, if the universe was constantly creating itself faster than you could get there.

True, but that's usually what people mean. And that's why I said, "even if you could move at arbitrary speed" :) Perhaps a better way of stating it is that if you could freeze the expansion, then you could travel forever without crossing your own path in an infinite universe.

And as to your second definition, you can't write down the coordinates for an entire infinite universe. And even if you tried, you might never reach a number outside the universe because the universe may be growing faster than you can chart it...- while still remaining currently finite.

Well, in general this is true, you can't. But in special cases it's entirely possible (because the real numbers are also infinite). A flat, uniformly-expanding universe would be one example, where simple co-moving coordinates work just fine. The infinite extent actually doesn't affect this.

Mathematically, infinity is quite well-defined. See the extended real number line here.

 

[JnWaco]

I was reading about infinity - and aren't there differing orders of infinity, and even sets of infinite numbers that still exclude other numbers?

Like the set of all even numbers is infinite. But it does not include the number 1, 3, 5, 7, etc. So even if the universe was infinite, there could still be an "everthing" that doesn't exist?

Perhaps this is more of a philosophical question.

 

[Chalnoth]

I was reading about infinity - and aren't there differing orders of infinity, and even sets of infinite numbers that still exclude other numbers?

Like the set of all even numbers is infinite. But it does not include the number 1, 3, 5, 7, etc. So even if the universe was infinite, there could still be an "everthing" that doesn't exist?

Perhaps this is more of a philosophical question.

Well, there could be an infinite number of possible things that still don't exist. However, I don't think that would count as "everything".

 

[JnWaco]

Well, there could be an infinite number of possible things that still don't exist. However, I don't think that would count as "everything".

Well, I was referring to the original poster's question - poor choice of words on my part- I just meant that an infinite universe could still not have everything exist, and in fact there could be an infinite number of things that wouldn't exist.

 

[SpaceTiger]

However, there may be other reasons to believe that all possibilities are realized, mainly stemming from quantum mechanics, where we find, for instance, that if there is the possibility of matter inhabiting a region of space, then particles of that sort of matter will necessarily pop in and out of the vacuum. Another way of saying this is that in quantum mechanics, there mere possibility of existence forces existence. So it is not unreasonable to suspect that perhaps all possibilities must actually be realized.

This has been my increasing feeling as well; that is, that there is no actual difference between possibility and actuality. It even negates the necessity for "meaning" or an "origin" -- things are simply because they can be. To my knowledge, however, it's still not the mainstream interpretation of quantum mechanics in the physics community (still Copenhagen?), though it's not clear how useful a "mainstream" stance on philosophy is.

Anyway, so that I don't venture too far off-topic, to address the original question... we still can't say whether the universe is infinite or finite and it's possible we'll never know. If the universe is finite, it's likely that our particle horizon back to inflation (the largest comoving distance we can possibly observe) is a good deal smaller than the full extent of the universe. If inflationary theory is correct, the rapid expansion of the scale factor in the early universe would have caused our effective horizon to contract from its pre-inflation size and render much of the universe unobservable.

 

[Chalnoth]

This has been my increasing feeling as well; that is, that there is no actual difference between possibility and actuality. It even negates the necessity for "meaning" or an "origin" -- things are simply because they can be. To my knowledge, however, it's still not the mainstream interpretation of quantum mechanics in the physics community (still Copenhagen?), though it's not clear how useful a "mainstream" stance on philosophy is.

So far as I am aware, among people that have actually thought about this in depth, the many-worlds interpretation is predominant. I think the Copenhagen interpretation is just a result of the "shut up and calculate" school of thought, where a large number of physicists just don't want to bother with these sorts of details, and would rather just get to work learning other things.

More recently, however, quantum computing research has forced many physicists to look in more detail at the specific nature of collapse, and so I expect that the "shut up and calculate" school won't last very long, as the Copenhagen interpretation doesn't actually say what happens at the boundary of collapse. It doesn't say when collapse happens, or how it happens.

There are also a few other schools of thought, but as far as I know they are strong minority views.

Anyway, if you're interested in reading a bit more on the "anything that can happen does happen" possibility, you may be interested in this paper by Max Tegmark:
http://arxiv.org/pdf/0704.0646

It's highly speculative, and would be extremely difficult to find any evidence in favor of it, but I find it quite the intriguing idea.

 

[SpaceTiger]

Anyway, if you're interested in reading a bit more on the "anything that can happen does happen" possibility, you may be interested in this paper by Max Tegmark:
http://arxiv.org/pdf/0704.0646

Thanks for the link. I knew that Max was vocal on these issues, but hadn't seen his paper.

 

[oldman]

If the universe is infinite, does that mean that everything exists somewhere

No, of course not.

Some infinities are bigger than others, and the infinity of distinguishable configurations of things is a factorial kind of infinity that is always much, much bigger than the infinity of the number of things.

Think of building a universe as a collection of things, starting with a just a few. As your universe grows the number of ways the things can be arranged differently grows very much faster than their number. So all possible configurations (everything) is something that can never be realized. You needn't even struggle with the impossibility of imagining infinity. And that old idea of monkeys typing Hamlet, given enough time, is nonsense for much the same kind of reason.

 

[Chalnoth]

And that old idea of monkeys typing Hamlet, given enough time, is nonsense for much the same kind of reason.

Not really, because that idea is based upon simple probability, and assumes that the monkeys are typing in a purely random fashion. If that's the case, then as time gets large enough, the probability that they successfully type hamlet will approach one. Of course, the time required to do that is unbelievably large.

 

[Freeman Dyson]

In an infinite universe, anything above zero probability happens an infinite amount of times. If the universe were infinite it would take an infinite amount of time to figure that out. The finite hides the infinite.

 

[Chronos]

About 3 minutes after the big bang the universe was cool enough for elementary particles [e.g., protons] to begin to form.

 

[ViewsofMars]

I'm going to play around with what you said Freeman. (I'm in one of those kind of moods today. I hope you don't mind. )

In an infinite universe [with dark energy], anything above zero probability happens an infinite amount of times [due to dark energy].

I've inserted within your thoughts my thoughts noted within the brackets.

If the universe were infinite it would take an infinite amount of time to figure that out. The finite hides the infinite.

Interesting. Two comments:

1. "However, the results of the WMAP mission and observations of distant supernova have suggested that the expansion of the universe is actually accelerating which implies the existence of a form of matter with a strong negative pressure, such as the cosmological constant. This strange form of matter is also sometimes referred to as the "dark energy". If dark energy in fact plays a significant role in the evolution of the universe, then in all likelihood the universe will continue to expand forever." (From NASA, Is the Universe Infinite?
http://map.gsfc.nasa.gov/universe/uni_shape.html)

2. "Since light travels at a finite speed, distant objects are seen as they existed in the past. We see the Sun not as it is now, but how it was eight minutes ago. (The Sun is eight light minutes away from the Earth). We see the nearby stars as they were several years ago. We see Andromeda, the nearest spiral galaxy as it was roughly 2.5 million years ago. Thus, the most distant objects that we see are the oldest objects that we can directly detect.

" Quasars are the most distant distinct objects that astronomers have been able to detect. In a region smaller than our solar system, a quasar emits more light than our entire Milky Way galaxy. Quasars are believed to be supermassive black holes, whose masses exceed that of a million Suns, and whose pull is swallowing gas and stars from their host galaxies. They shine brightly by converting the gravitational energy of the infalling material into light. The most distant quasars are seen at a time when the universe was one tenth its present age, roughly a billion years after the Big Bang." (From NASA- When Did the First Cosmic Structures Form?
http://map.gsfc.nasa.gov/universe/rel_firstobjs.html)

 

[Dmitry67]

No, of course not.

Some infinities are bigger than others, and the infinity of distinguishable configurations of things is a factorial kind of infinity that is always much, much bigger than the infinity of the number of things.

Think of building a universe as a collection of things, starting with a just a few. As your universe grows the number of ways the things can be arranged differently grows very much faster than their number. So all possible configurations (everything) is something that can never be realized. You needn't even struggle with the impossibility of imagining infinity. And that old idea of monkeys typing Hamlet, given enough time, is nonsense for much the same kind of reason.

Max Tegmark does not agree with you:

http://space.mit.edu/home/tegmark/multiverse.html

How many parallel universes are there?
Why must we have duplicates?

From Richard Reeves, valueprint@earthlink.net, April 18, 2003 14:23:31
Q: Given infinity, why isn't it equally plausible that the worlds within it would express infinite variety, rather than repetition
The answer is that there are only a finite number of possible states that a Hubble volume can have, according to quantum theory. Even classically, there are clearly only a finite number of perceptibly different ways it can be.

How rigorous is this?

From Bert Rackett, bertrckt@pacbell.net, Sat Apr 19 22:22:13 2003
Q: I very much enjoyed reading your Scientific American and Science and Uitimate Reality papers, but I am entirely befuddled about your estimates for likely distance of an identical environment. You claim that the volume may be completely defined by a (very long) list of binary values denoting the presence or absence of a proton, but this of course oversimplifies things.
A: Although classical physics allows an infinite number of possible states that a Hubble volume can be in, it's a profound and important fact that quantum physics allows only a finite number. The numbers I mentioned in the article, like 10^10^118 meters, were computed using the exact quantum-mecanical calculation, and the classical stuff about counting protons in a discrete lattice arrangement was merely thrown in as a pedagogical example to give a feel where the numbers come from, since that turns out to give the same answer.

Why must all regions have duplicates, not just one?
From Jeffery Winkler, jeffery_winkler@mail.com, Oct 13, 2003, at 0:58
Q: Just because something is infinite, does not mean that all possibilities are realized. The number pi is infinitely long, pi = 3.14159... and in that case, all combinations of digits are realized. However, the number 1/3, converted into a fraction, is also infinitely long, 1/3 = .33333... and in that case, all combinations of digits are not realized.
A: That's correct: infinite space alone guarantees only that SOME Hubble volume will have a duplicate, not that our own will. However, if (as in the current cosmological standard model) the cosmic density fluctuations originate from quantum fluctuations during inflation, their statistical properties DO guarantee that our (and indeed every) Hubble volume has a duplicate.
Is there a countable or uncountable infinity of universes?

Is it countable even with continuous wave functions?
From David Fotland, fotland@smart-games.com, August 3, 2003 21:09:49
You argued that the total number of possible states in a universe is finite, so if the total of all universes is infinite, then every possible universe must exist. I understand that quantum states have discrete vales, but the wave function is a continuous function. Can't the probabilities that give the possible locations of particles have any real value?
Interestingly, they can't: you can prove that in a finite volume, there's only a discrete number of allowed quantum wavefunctions. If the energy is finite, it's even a finite number.
But even a hydrogen atom has infinitely many states!
From Attila Csoto, csoto@matrix.elte.hu, Wed Mar 17 12:59:29 2004
Q: You say in your papers that the number of possible quantum states within the Hubble-volume is finite. I understand your argument, but there is a problem which puzzles me. If we single out one hydrogen atom in our Hubble volume, it has itself an infinite number of different bound states. So one could imagine a Hubble sphere next to ours which is the same as ours except that this hydrogen atom iis not in its ground state but in the next excited state, and in the next sphere in the next higher state, etc. These universes differ from each other by a tiny amount of energy but I don't think that this should matter. So, my question is: how can we have a finite number of possible quantum states in our sphere, if one hydrogen atom already has an infinite number of possible bound states?
A: There's infinitely many bound states if only space is truly infinite. There's in fact a beautiful old paper by Erwin Schrödinger deriving the exact solutions for a hydrogen atom in a closed finite Universe, showing that in this case, the number of bound states is finite.

 

[ViewsofMars]

Dmitry67, you have presented Max Tegmark whose last publication was from 2003, Richard Reeves (2003), Bert Rackett (2003), Jeffery Winkler (2003), David Fotland (2003), Attila Csoto (2004).

The year is 2009. We have come a long way since 2003-2004. You may wish to review the topic “offshoot from 'Theoretically how far can one see in the universe'” p.g. 3, and look at my contributions (msg’s 40 and 42) that have the most current evidence (2008 and 2009) that continues to support the Big Bang Theory, which is the standard model. I've provided the link below for you and others to explore.

I should also mention that Steven Weinberg on July 7, 2009 gave a lecture at CERN. He talked about inflation. Near the end of his presention he did say, "The world is really what we've always known, the standard model plus relativity." He wasn't trying to discourage string theorists yet he knows as a scientist that observations are essential if you are going to call it SCIENCE.

https://www.physicsforums.com/showthread.php?t=338032&page=3

 

[Dmitry67]

It appears that you are not familiar with the most important article: http://arxiv.org/abs/0704.0646 - really genious!
and year is 2007 - not 2003. Do you have any other arguments against his logic except the year of publication?

 

[ViewsofMars]

It appears that you are not familiar with the most important article: http://arxiv.org/abs/0704.0646 - really genious! and year is 2007 - not 2003.

Don't be curt or snippy with me. Dmitry67, I was going off the first link you gave when mentioning Max Tegmark. I didn't see this abstract you are now presenting on his website. The *abstract* by Max Tegmark is entitled, "The Mathematical Universe". As we know, math isn't science. Futhermore, it is a hypothesis of his.

Do you have any other arguments against his logic except the year of publication?

The year of publication is important as you will note with WAMP. I think it is important to see the current information. I've earlier provided you a link to another topic for you to review.

I know now that Max Tegmark's has a *hypothesis* that has been submitted to Cornell University. I'm sorry to disappoint you, but I'm not a fan of his "consciousness" and "parallel universes". I don't find his hypothesis in NASA. Also, hypothesis don't make it into internationally known peer-reviewed journals such as Science and Nature.

 

[Dmitry67]

At first, could you clarify what do you mean by "math isn't science"? Do you mean that we can't prove self-consistency of any axiomatic system, or something else?

 

[Chalnoth]

Dmitry67,

Yes, I've heard this argument about "copy universes" before. I don't think it necessarily holds.

Here is the problem, as I see it: quantum mechanics doesn't guarantee that absolutely everything happens. It just says that many things happen. For instance, let's say I take a simple harmonic oscillator, and prepare it in the following state:

\mid \psi \rangle = \frac{1}{\sqrt{2}} \mid E_1 \rangle + \frac{1}{\sqrt{2}} \mid E_2 \rangle

Here we have a system in a mixture of two states. If I take a measurement of the energy at t=0, I will obtain with 50% probability E_1, and E_2 with 50% probability.

Now step back and consider what I might be able to conclude if I didn't know how the state was prepared, but only am aware of my measurement of the state. For instance, if I measure E_2, what can I conclude about the original state? Can I conclude that E_3 was also represented? That some other "me" observed E_3 while I observed E_2? Certainly not! I do know that whatever state the system was in, it was in a specific state, and my measurement of E_2, while not ruling out the possibility of a component of the wavefunction inhabiting E_3, there is no reason to believe that E_3 was represented (or E_1, for that matter).

Therefore I claim that even with taking quantum fluctuations into account, I don't see why all possibilities need to be represented. Regions of the universe are still due to unitary evolution of a quantum mechanical wave function. They are still deterministically dependent upon the initial conditions. And so even though many things surely do happen, we can't say with confidence that all possible things do.

However, that said, I do think that it is entirely possible that all possible things do happen. I particularly like Tegmark's "mathiverse" idea, for instance. I just don't think we can conclude from what we know today that it's actually true that all things possible do happen.

 

[rasp]

If the universe is infinite, does that mean that everything exists somewhere, besides obviously impossible things like a star that contains oxygen but doesn't contain oxygen or a 4-sided triangle?

The answer to your question depends on what you mean by everything. If by everything you mean all that is, then everything fits into a finite Universe, an infinite Universe is not needed. If your definition of everything is what is existent and also on what doesn't exist but could exist, then an infinite universe doesn't help you, you need either a many world interpretation, or a Hilbert Space in QM.

 

[xantox]

Therefore I claim that even with taking quantum fluctuations into account, I don't see why all possibilities need to be represented.

Do you mean, by questioning the assumptions of ergodicity and equilibrium of the inflationary patches?

 

[Chalnoth]

Do you mean, by questioning the assumptions of ergodicity and equilibrium of the inflationary patches?

I'm pretty sure those are taken to be approximating assumptions.

 

[xantox]

I'm pretty sure those are taken to be approximating assumptions.

Yes, they are just assumptions – just making sure whether you agree that if they are true then "copy universes" would hold too, or if your argument was another one. Although those assumptions are supported by unitarity, quantum gravity effects such as backreaction on the metric could indeed subtly change the picture.

 

[Entropee]

I'm not sure anything in our universe at all can lead us to believe anything at all about a "different" universe. Just my opinion.