Is the Multiverse Theory Changing Our Understanding of Cosmology?

[skydivephil]

Just to clarify what I said was :

"In this sense the mutliverse is not a theory its a proposed consequecne of a theory: inflation. I would highly reccomend this article:
http://arxiv.org/abs/hep-th/0702178
or reading Guths book for a historical account of how the theory came about .
https://www.amazon.com/dp/0201328402/?tag=pfamazon01-20

I also said eternal inflation arises from normal inflation. I didnt mean to imply this was the only the logical cosequence of inflation and if I gave that impression I apologise. Thast why I like the phrase "a proposed consequecne of a theory". What I meant was the idea of a mutlvierse arises from a certain approach to analysing what inflation implies. Its not something that was simply invented to get rid of fine tuning problems which was what was being claimed. That approach is outlined by Guth in the links above. Whether he's right, I have no opinion.

As fas as LQC being incompatible with eternal inflation. I didnt find any papers on this. I did write to Martin Bojowald (for those that don't know, he wrote one of the first papers on the LQC bounce and the popular article that made the front cover of Scientific American )about it and you may find his reply ineteresting.
He said "LQC is consistent with eternal infaltion...combining eternal inflation with LQC has not been done in detail yet becuase it is technically complicated, but conceptually you would get a picture in which there is a bounce leading from collapse to expansion, followed by several phases of inflation in the expanding branch".

Of course that's just one man's opinion. So if you could link to anything that opposes that view, I would welcome any material you may have.

 

[marcus]

Phil, I have trouble with some of the language. So I will quote some of the language in your post and try to sort out and respond.

Just to clarify what I said was :

"In this sense the mutliverse is not a theory its a proposed consequecne of a theory: inflation...
I also said eternal inflation arises from normal inflation. I didnt mean to imply this was the only the logical cosequence of inflation ...What I meant was the idea of a mutlvierse arises from a certain approach to analysing what inflation implies...

As fas as LQC being incompatible with eternal inflation. ...
He said "LQC is consistent with eternal infaltion...
...

I hope you realize I did not say LQC was incompatible with some inflation scenario.

We have to distinguish carefully between being consistent with and implying.

If the LQC bounce implies some X as a consequence then if have the bounce then you have to have X.

If LQC bounce is merely consistent with some Z it merely means it doesn't rule out the possi bility. If you have the bounce it doesn't prevent the possibility that, under whatever additional assumptions are necessary, Z might happen. In other words it is not incompatible with Z. That does not mean that LQC implies Z.

 

[George Jones]

Please keep religious discussion, either pro or con, out of all posts in this thread, and out of all posts in the science forums at Physics Forums.

 

[Tanelorn]

Please keep religious discussion, either pro or con, out of all posts in this thread, and out of all posts in the science forums at Physics Forums.

George, sorry I will comply with the rules. In haste I was trying to recall Hawking's arguments with reference to reasons why a Multiverse might be a possibility.
Just to be clear does this also include terms like "creator"? etc.

I think you might have to delete a lot more posts though - about 118!
https://www.physicsforums.com/search.php?searchid=2986718

 

[skydivephil]

Phil, I have trouble with some of the language. So I will quote some of the language in your post and try to sort out and respond.


I hope you realize I did not say LQC was incompatible with some inflation scenario.

We have to distinguish carefully between being consistent with and implying."
-----------
Yes that's make a lot of sense. I relaise that being compatible with and implying are not the same, very good point as always.
My personal worry would be that if eternal inflation and LQC are both true, and I recognise this is a big if, that might remove the bounce from detectability. Do you agree this is correct or have I misunderstood?

 

[marcus]

...
My personal worry would be that if eternal inflation and LQC are both true, and I recognise this is a big if, that might remove the bounce from detectability. Do you agree this is correct or have I misunderstood?

I think you are right about that. Can't speak with much confidence about the such inflation scenarios so I have to emphasize that I just suspect that's right, without feeling sure.

In practical research community terms the main issue is what was the immediate cause of the big bang or as I prefer to say the immediate cause of the start of expansion.

Regarding that question "a random quantum fluctuation in some unknown physics" and "LQG bounce" are two competing answers. In a practical, immediate problem sense, I mean.

LQG is comparatively mundane unexotic and I expect in the near/medium term they'll be looking for signs of it having happened. If they see signs then research time and money will go more into studying that, with less interest in eternal inflation.

On the other hand if they don't see signs of bounce having happened then I would expect interest in Loop cosmology and perhaps LQG as a whole to wane. With more active interest in some random quantum fluctuation as a trigger for expansion.

 

[marcus]

If you accept what Ashtekar says about the enhanced liklihood of sufficient ordinary inflation in the Loop case then the usual support for "Eternal Inflation" is flawed. There is much less reason to be interested in it, beyond inherent fantasy-appeal of the the grandiose vision.

Specifically, sufficient means 60 e-folds--to produce the observed uniformity. The usual argument is basically one of desperation: "we can't think of any normal physics mechanism for inflation to get started, and then continue 60 e-folds, and then stop!" But Ashtekar can. (Loop is comparatively mundane, you quantize and go with established cosmology. I might say it is no more than a "hop" of faith.)

Once you posit some exotic leap-of-faith mechanisms you see stuff happening like eternal inflation. Support for eternal inflation depends on not being able to think of any other way that an adequate inflation episode could have started and then turned off.

It looks to me like some of these guys with exotic brane-clash and multiverse ideas have vested interest in ignoring simple answers--which threaten the raison d'être for some unnecessarily elaborate pet constructs.

You saw what happened at the end of Neil Turok's talk---we discussed this earlier. I'll get the link in case anyone else wants to check it out. It was the opening talk at a Perimeter conference he and some other people organized on "Challenges for Early Universe Cosmology"
http://pirsa.org/11070044/
Overview of the Challenges
Neil Turok
12/07/2011 - 9:00 am

The video lasts 1 hour 10 minutes and Elena's comment about the Ashtekar Sloan work starts right about 1 hour 7 minutes. You can of course drag the button to just hear the last 3 minutes. But the talk is interesting overall--especially the comments from the audience---Leonard Susskind, Sean Carroll etc etc. IIRC this starts around minute 55.

At this point Turok has his summary slide up. The challenges he identifies are:
Singularity
Tuning [in particular to get inflation which continues long enough and then turns off]
Reliance on anthropics
Measure
Several audience comments stressed challenges related to entropy: "2nd law" paradoxes.

I'm not suggesting one should take this talk as actually authoritative/representative about early universe cosmology. Neil, Lenny, Sean, Lindei, Vilenkin...etc are vocal but they are not currently writing a lot of papers or getting cited very much. I think it is a subcommunity which may be feeling a bit on the defensive at present. The interesting part is to see what arguments they have organized to justify this collection of ideas.

 

[eloheim]

Aren't there some Anthropic Principle-related suggestions for the Multiverse? Like one would expect the values of any natural "constants" vital to intelligent life to be only barely deviant from typical. Basically, assuming that a universe fit for life will need to be more picky about them than otherwise, finding we live in a "1-in-a-trillion" universe when there are a "million-in-a-trillion" other ways (universes) that allow for life would make our theories on such things seem very unlikely to be true.

Does anyone have a good understanding of if we have any indications on this for our values (universe), or even any notions of what kind of values we should be looking at?

 

[Deuterium2H]

Please keep religious discussion, either pro or con, out of all posts in this thread, and out of all posts in the science forums at Physics Forums.

Hi George,

Not saying you don't...but I hope you are just as strong in your advice when it comes to the opposite scenario. For example, Hawking's fervent insistence that our Universe does not need or require a "Creator", is just as much a metaphysical and philosophical position (and as such, is outside the bounds of "Science) as those who posit some sort of Intelligent Creator behind it all.

In either case, we are stepping outside "Science", and what can be tested and potentially falsified. If Religion has no place in the discussion of the origin of the Universe, neither does the speculative metaphysics of a "cyclic" universe, or even a "multiverse" for that matter, IMHO.

 

[jdm1001]

Sorry everyone, I had not intention to create a discussion on determining the what the un-caused, cause is. It is absolutely imperative that faith in science must be supported by observations and known facts. All I wanted to do is show how the study of the un-caused cause and the study of the unknown are rapidly merging into the one in the same.

 

[juanrga]

I really know nothing whatsoever about cosmology although I find it very interesting. It seems that a lot of physicists nowadays reckon there's a multiverse. I don't particularly want there to be a multiverse. WHAT DO YOU FOLKS THINK. Also, if there was a multiverse, would the laws of physics be the same for all of the universes? And would every single possibility be actually occurring in some universe out there? Like, in one universe am I being cut into bits from the toes up without anaesthetic and then having my body regenerated by some piece of advanced technology and then being cut up again OVER AND OVER FOREVER? All the while having faeces smeared in my face?

Multiverse is a non-scientific hypothesis.

 

[Chalnoth]

Multiverse is a non-scientific hypothesis.

Completely and utterly false. Try again.

 

[juanrga]

Completely and utterly false. Try again.

Multiverse is a non-scientific hypothesis

http://en.wikipedia.org/wiki/Multiverse#Criticisms

 

[Chalnoth]

Multiverse is a non-scientific hypothesis

http://en.wikipedia.org/wiki/Multiverse#Criticisms

Noting that some people say that doesn't actually make it true. Back in here in reality, it is very much a scientific hypothesis. For example:
http://arxiv.org/abs/0901.0007

 

[juanrga]

Noting that some people say that doesn't actually make it true. Back in here in reality, it is very much a scientific hypothesis. For example:
http://arxiv.org/abs/0901.0007

My original statement remains unchanged

 

[otherme]

Hi, I'm new here and don't pretend to understand very much of what's being said but physics fascinates me. Multiverse theory fascinates me. And, as with all sciences, don't you start with a postulate then go about proving or disproving that postulate. Something like multverse and M theory would be, I would imagine, very difficult to prove one way or the other. From my understanding, universes are close to, connected and sometimes intertwine each other - or so the theory goes. I should say - a theory goes, as there are so many. Like I said, I don't understand much but find it all fascinating. I feel there is something more than what we see with our eyes.

 

[rbj]

I agree with a Multiverse of observable universes if that is the right word. I have trouble with them having different laws of Physics,

i think the idea is that they might have different fundamental constants than our universe.

in my opinion, the concept of the Multiverse was cooked up so that the (weak) Anthropic principle would be able to explain away any teleological argument about the existence of God. if there are many, many other universes, some might be life friendly and some not. and it's an example of selection bias that we find ourselves in a universe that is life friendly.

 

[rbj]

Completely and utterly false. Try again.

So when you show me an experiment that will test and falsify the existence of some other universe, I'll show you an experiment that will do the same regarding God. Wanna see my God-measuring device?

Chalnoth, your belief, and that is all it is, is unscientific.

 

[Chalnoth]

i think the idea is that they might have different fundamental constants than our universe.

in my opinion, the concept of the Multiverse was cooked up so that the (weak) Anthropic principle would be able to explain away any teleological argument about the existence of God. if there are many, many other universes, some might be life friendly and some not. and it's an example of selection bias that we find ourselves in a universe that is life friendly.

The only way you could possibly come to this conclusion would be through complete and utter ignorance of the scientific discussion surrounding the multiverse. Put simply, no god ever has or ever will come into it, because no scientist worth their salt considers a god as a reasonable hypothesis, or has done so for quite a long time. There are strong epistemological reasons for this which I won't go into, but suffice it to say that it is fundamentally impossible to make forward progress in science by using a god hypothesis (no matter which god you're talking about).

Instead, the argument has always been between two camps within the theoretical physics community. On the one side, we have physicists who think that the natural laws we observe must be derivable from some fundamental theory. This has, for much of the history of physics, been the majority view. However, recent work in developing grand-unified theories has put doubt on this view, to the point that high-energy theorists are becoming increasingly convinced that it is just not feasible. And so physicists are increasingly moving away from the idea of a fundamental theory from which everything we observe inevitably follows and towards a fundamental theory which is prolific. A prolific fundamental theory explains everything we observe by stating that many things happen, and life occurs where it can occur, with most of the universe being uninhabitable.

None of this has ever referenced any sort of god, either before or after.

 

[Chronos]

Science seeks a causal relationship between properties and evolution of the universe. God is a first principle proposition and neither science or mathematics is the right tool for dealing with first principles.

 

[skydivephil]

i think the idea is that they might have different fundamental constants than our universe.

in my opinion, the concept of the Multiverse was cooked up so that the (weak) Anthropic principle would be able to explain away any teleological argument about the existence of God. if there are many, many other universes, some might be life friendly and some not. and it's an example of selection bias that we find ourselves in a universe that is life friendly.

The history of science is not really a question of your opinion. It is possible to go and look up things and see where certain ideas came from.
There are different definitions of the multiverse. I would sugggest the two most popular ideas are the many worlds interpretation of Qm and the inflationary multiverse.
The first was invented to deal with the problems of the Copenhagen interpretation of QM, nothing to do with anthropics. The second came from inflation. Inflation was desgined to solve one problem and one problem only, that's the magnetic monopole problem, again nothing to do with anthropics. Later it was realized it solved other problems and as the theory was developed it was argued the inevtiable consequence of inflation was a multiverse. If you would like to read about this I suggest reading Alan Guths book "The Inflationary Universe", there is also a new biography of Hugh Everett which woudl enable you to understand the motivation of the first type. They were not invented as a way of dealing with arguments for god, that just not histroically accurate at all.

 

[pebbleanrock]

Science seeks a causal relationship between properties and evolution of the universe. God is a first principle proposition and neither science or mathematics is the right tool for dealing with first principles.

I read a book explaining the creation of the universe. It said the universe started its journey as a tiny empty space surrounded by a sea of energy at absolute zero. The energy was in the form of straight strings before it had decayed into the circular stringed form of the particles of this universe. In describing the space /matter or energy relationship of the centre of a black hole, Einstein said it was infinity + infinity + infinity and was accused of a mistake. While a black hole has not reached this state, it does describe the sea of energy or the state the black hole energy is trying to entropize to. This is best envisaged as a super BEC [ Bohr Einstein Condensate ] where an almost infinite quanta of straight string fits into the same space. The energy, under pressure has arced into the tiny empty space and raised the temperature of the nearby sea. As this almost infinitely deep straight string area decays into circular string quantum they have their own piece of space. Part of the residue of each matter/antimatter annihilation would be 2 quanta of new space. A multitude of waves is moving through the energy sea. These differing waves of straight string then decay into different energy amounts thus producing the vast array of different particles. As well as the annihilation, other particles combine to form hydrogen and helium. The book is the Bible and seems to have been incorrectly read for thousands of years. My full essay can be found at <pebbleanrock.org>. comment?

 

[cephron]

I read a book explaining the creation of the universe. ... The book is the Bible and seems to have been incorrectly read for thousands of years. My full essay can be found at <pebbleanrock.org>. comment?

The bible is simply not a scientific textbook. The important points made in Genesis are about who God is and what his relationship is to man and creation, not the details of the mechanistic process by which it all happened. To try to turn the Bible into a science textbook is worse than useless.

I think Chronos had it right. Science makes models to explain objective, repeatable observations. Science simply does not make any claims about God, because God doesn't interact with the world in an objective, repeatable basis.

 

[pebbleanrock]

The bible is simply not a scientific textbook. The important points made in Genesis are about who God is and what his relationship is to man and creation, not the details of the mechanistic process by which it all happened. To try to turn the Bible into a science textbook is worse than useless.

I think Chronos had it right. Science makes models to explain objective, repeatable observations. Science simply does not make any claims about God, because God doesn't interact with the world in an objective, repeatable basis.

You do not know this . You have been told by somebody. 'circle of the earth' THEN they thought "its round." hang the Earth on nothing"then they thought we're just floating there" "Write on tablet of your heart" heart transplant scientists find in 1990's that heart nerves support memory. Entropy,"the heavens will wear out like a garment" all these written 3500 years ago. Now its opened up again.

 

[cephron]

You do not know this . You have been told by somebody.

Which part? That God doesn't interact with the world in an objective, repeatable basis?

Technically, you're right--perhaps in the future someone will identify an objective, repeatable observation that somehow can only be explained by God existing. But such a thing has not yet been discovered--if it had, it would be trivial to objectively prove that God exists. If you can do that, I'm all ears (although you'd have to find a different forum to do it, this one is about science). But anyway, until that happens, science has nothing to say about God.

Edit: Exegesis wars are fun, but this forum is not the place for them. The fundamental problem with using the bible as a science textbook, though, is that you'll only be able to selectively interpret (and sometimes horrendously stretch) the bible to match what science has already told us. Good luck using the bible to make any scientific predictions that science hasn't already made...

Edit 2: Sorry for sounding harsh, but there won't be much sympathy here for using the bible for "science". I wanted to at least explain why it doesn't work, but this is actually off-topic from the thread. If you want to continue this discussion, you should start a new thread. Probably not in the cosmology section, though.

 

[Chronos]

Science tells you as much about God as eating meat loaf tells you about the chef. Theism is deliberately excluded from science because it has zero utility in modeling the universe. Worse yet, it tempts us to concede the match before we even comprehend the rules of the game - which is, at best, unconstructive.

 

[cephron]

Well, to be fair, it's playing an entirely different game altogether. Its goals are different from science's; its definition of "constructive" as well. You can't really get an objective definition of "constructive" (in this context) without dipping into philosophy or something. But I would agree that it has no scientific utility. I like your meatloaf analogy. ;)

 

[Chalnoth]

Its goals are different from science's;

In a way. But only in that the goal of science is to discover the true nature of reality, while the goal of religion, where it interacts with science, is to convince people that the religion offers the secrets to the true nature of reality.

 

[rbj]

Science tells you as much about God as eating meat loaf tells you about the chef. Theism is deliberately excluded from science because it has zero utility in modeling the universe. Worse yet, it tempts us to concede the match before we even comprehend the rules of the game - which is, at best, unconstructive.

everything you say here is agreeable to me, Chronos.

i see that they deleted some of the personal attack posts, but not all:

The only way you could possibly come to this conclusion would be through complete and utter ignorance of the scientific discussion surrounding the multiverse.

i didn't suggest to delete any posts, particularly my response to Chalnoth's arrogant attack post, only that they lock the thread. oh well, who's to judge the judgment of the admins.

so Chalnoth is allowed to point to others and accuse them of "complete and utter ignorance of the scientific discussion surrounding the multiverse" when, in fact, he/she has no idea what the other's level of ignorance is.

so, i'll ask again, is the hypothesis of other universes a testable, falsifiable hypothesis? if Chalnoth says it is, i'll continue to ask him to define such an experiment or something that would be measured or experienced differently if other universes existed than if they did not.

it's a very similar challenge made by respectable skeptics like Michael Shermer: "Here's the deal, there is no conflict between science and religion as long as the God you believe in doesn't do anything."

i agree with Shermer on this. i just want to hold the same standard of falsifiability to the belief in other universes.

some time is allowed between the development of a theory and when its falsifiability is tested. the aether was proposed long before the Michaelson-Morley experiment (which shown that, if the aether existed, it didn't seem to have any effect on anything, including when we would have expected it to have some effect). GR was proposed a few years before Eddington traveled south to measure the shift in the perihelion precession of Mercury (which seemed to support the prediction from GR).

string theory and M-theory are nice little theories. one elegant explanation for the source and existence of other universes is that they result from other solutions to the same brane equations (that i will certainly admit i do not understand in any depth). these different solutions can result in different universes that may have different fundamental constants (and i mean the dimensionless ones, like those that John Baez has enumerated), some sets of fundamental constants will result in matter forming and stars living long enough for life to evolve enough to ask the question "how is it that we are here?" some combinations of these constants will not, and those universes will go by utterly unbeheld.

it's nice and elegant, but it's not a falsifiable theory. we can't test it. it's about the same as Michael Shermer's concept of God.

now, if Chalnoth might choose to be a little more humble about this (maybe take after the example of Chronos), i would be interested in what he/she has to say. but if his/answer is a sweeping and arrogant "Completely and utterly false. Try again." or "The only way you could possibly come to this conclusion would be through complete and utter ignorance ...", then i am less interested in whatever he/she has to say.

and i would like it if the sysops here would be more even handed in deleting or retaining contentious posts.

 

[Chalnoth]

rbj, when you come into a thread and launch into a series of baseless accusations that have nothing whatsoever to do with any of the actual scientific discussion on the topic, you should expect people to get a little annoyed at you.

And yes, I stand by my statement that you are horribly ignorant of the scientific discussion on this matter, because the epithets you have thrown out have nothing whatsoever to do with the actual scientific discussion. An accusation of ignorance, by the way, does not necessarily impinge upon your character. We are all ignorant of a great many things. What's wrong with you is you feel the need to pontificate about things which you know nothing about. Such hubris is not going to make people happy with you.