Is Paul Steinhardt's Statement "Rather Pathetic"? Why?

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In summary, Paul Steinhardt, a prominent physicist at Princeton University, has spoken out strongly against the idea of a multiverse and the use of the anthropic principle in explaining the properties of our universe. He believes that our universe is not accidental and that the current failure of string theory to find a unique universe is a sign of our immature understanding or potential error in the theory. Despite objections from others, Steinhardt stands firm in his belief and sees the current enthusiasm for string theory as natural and expected to decrease as the Large Hadron Collider becomes more prominent.
  • #1
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Universe not accidental: Is this Steinhardt statement "rather pathetic"? If so, why?

I think the heyday of string multiverse talk probably came somewhere in 2003-2006. Except for popularizations we hear little about it these days compared with 5 or 6 years ago. Paul Steinhardt (Albert Einstein Professor of Physics at Princeton) deserves substantial credit for this as one who led off in January 2005 with a strong statement in opposition.
http://edge.org/response-detail/805/what-do-you-believe-is-true-even-though-you-cannot-prove-it
Interestingly, when I gave this link in another thread, Chalnoth replied in a way that begs for explanation/discussion.
Chalnoth said:
I've always found that response to anthropic arguments to be rather pathetic.

Steinhardt was supported by influential members of the string community such as David Gross and to some extent also by his Princeton colleague Edward Witten. Multiverse papers were excluded from the "Strings 2008" conference at CERN and have made little or no showing at subsequent Strings XXXX. The anthropic bandwagon started by Leonard Susskind with his 2003 "Anthropic String Landscape" paper, which certainly affected planning of Strings 2005, lost a much of its momentum and Steinhardt took the lead in speaking out on this issue.

This statement was published around January 1, 2005 by the Edge online magazine in response to their annual queston, which in 2005 was "WHAT DO YOU BELIEVE IS TRUE EVEN THOUGH YOU CANNOT PROVE IT?"

==quote Edge 2005 annual question==

Paul Steinhardt:

I believe that our universe is not accidental, but I cannot prove it.

Historically, most physicists have shared this point-of-view. For centuries, most of us have believed that the universe is governed by a simple set of physical laws that are the same everywhere and that these laws derive from a simple unified theory.

However, in the last few years, an increasing number of my most respected colleagues have become enamored with the anthropic principle—the idea that there is an enormous multiplicity of universes with widely different physical properties and the properties of our particular observable universe arise from pure accident. The only special feature of our universe is that its properties are compatible with the evolution of intelligent life. The change in attitude is motivated, in part, by the failure to date to find a unified theory that predicts our universe as the unique possibility. According to some recent calculations, the current best hope for a unified theory—superstring theory—allows an exponentially large number of different universes, most of which look nothing like our own. String theorists have turned to the anthropic principle for salvation.

Frankly, I view this as an act of desperation. I don't have much patience for the anthropic principle. I think the concept is, at heart, non-scientific. A proper scientific theory is based on testable assumptions and is judged by its predictive power. The anthropic principle makes an enormous number of assumptions—regarding the existence of multiple universes, a random creation process, probability distributions that determine the likelihood of different features, etc.—none of which are testable because they entail hypothetical regions of spacetime that are forever beyond the reach of observation. As for predictions, there are very few, if any. In the case of string theory, the principle is invoked only to explain known observations, not to predict new ones. (In other versions of the anthropic principle where predictions are made, the predictions have proven to be wrong. Some physicists cite the recent evidence for a cosmological constant as having anticipated by anthropic argument; however, the observed value does not agree with the anthropically predicted value.)

I find the desperation especially unwarranted since I see no evidence that our universe arose by a random process. Quite the contrary, recent observations and experiments suggest that our universe is extremely simple. The distribution of matter and energy is remarkably uniform. The hierarchy of complex structures ranging from galaxy clusters to subnuclear particles can all be described in terms of a few dozen elementary constituents and less than a handful of forces, all related by simple symmetries. A simple universe demands a simple explanation. Why do we need to postulate an infinite number of universes with all sorts of different properties just to explain our one?

Of course, my colleagues and I are anxious for further reductionism. But I view the current failure of string theory to find a unique universe simply as a sign that our understanding of string theory is still immature (or perhaps that string theory is wrong). Decades from now, I hope that physicists will be pursuing once again their dreams of a truly scientific "final theory" and will look back at the current anthropic craze as millennial madness.

==endquote==
 
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  • #2


Yes, I am aware that many people object to the multiverse ideas. I still find the objections pathetic. Specifically, I object to this statement:

"The anthropic principle makes an enormous number of assumptions"

Except that in reality, it requires more assumptions to assume a unique universe than it does to assume a prolific universe-generation process: you still need a universe-generation process, except now it can only ever occur once. And forcing that universe-generation process to only occur once requires additional and completely unreasonable assumptions.

If these people were only objecting to the way in which the multiverse ideas were used, I would have no problem. There are surely many very bad ways to make use of multiverse ideas, as there are bad ways to use a great many theoretical ideas. But the objections to the multiverse ideas as a matter of principle are pathetic and irrational. Physicists really should know better, and it is utterly sad that they don't.

But by the way, I don't expect any reduction in overall enthusiasm for string theory, but a reduction in string theory work is natural and expected as the LHC started to turn on. Scientists in general are going to tend to be more interested in real data than in pie-in-the-sky ideas that we don't yet know how to connect to experiment. When the LHC becomes mature, I'm sure that we will see a dramatic uptick in string theory again, barring the emergency of any more compelling alternatives.
 
  • #3


Chalnoth said:
Yes, I am aware that many people object to the multiverse ideas. I still find the objections pathetic. Specifically, I object to this statement:

"The anthropic principle makes an enormous number of assumptions"

.
Is not the force of Steinhardt's objection the next part of his sentence:
—regarding the existence of multiple universes, a random creation process, probability distributions that determine the likelihood of different features, etc.— none of which are testable because they entail hypothetical regions of spacetime that are forever beyond the reach of observation.

Of course it depends on what you mean by the Anthropic Principle; Steinhardt seems to identify it with the multiverse concept.

The multiverse is only one of the hypotheses that 'explains' the propitious coincidences.

I always stick with Stephen Hawking's definition: "The universe is as it is because we are."

Garth
 
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  • #4


Garth said:
Is not the force of Steinhardt's objection the next part of his sentence:


Of course it depends on what you mean by the Anthropic Principle; Steinhardt seems to identify it with the multiverse concept.

The multiverse is only one of the hypotheses that 'explains' the propitious coincidences.

I always stick with Stephen Hawking's definition: "The universe is as it is because we are."

Garth
That's not a valid objection either, because a unique universe is also not testable, due to the inability to verify that uniqueness. Furthermore, there is no requirement that the universe accept our demands that it be testable.

Like I said, you can object to the specific ways in which multiverse ideas are applied. I see no problem with that. These ideas can certainly be applied very poorly in certain cases. But it is still, by far, most likely the case that we live in some sort of multiverse.
 
  • #5


Well this definition of Hawking is blatantly circular.

I mean the universe is the way it is because we are, then it begs the question what came first sentient beings or the stuff that they are made from?

Cause you you can ask why are we the way we are? and you get the answer, because the universe is that way.

:rolleyes:
 
  • #6


And I haven't read in depth what the idea of multiverse means.

But if you take the universe as everything that exists, it doesn't matter how do you call it, multiverse, cosmos, etc.
 
  • #7


Im curious , is the position of the Earth in the solar system considered to be an accidennt/anthropically selected or is there some underlying theory that allows us to predict where the Earth should be based on the known laws of physics?
If the former is true why can't the laws/constants of nature be the same ? I am not saying they are, but why rule it our a priori?
 
  • #8


MathematicalPhysicist said:
And I haven't read in depth what the idea of multiverse means.
Well, there are multiple ideas. Max Tegmark has suggested a three-level hierarchy:

Level I: Inflation predicts that you'll get many Hubble volumes with all possible realizations of the various initial conditions. This can basically be understood as the statement that the universe is much larger than the part of it we can observe.
Level II: Our current knowledge of theoretical physics seems to indicate that the same fundamental laws of physics can potentially lead to very different low-energy laws of physics due to accidents in our past. Combine this with the Level I multiverse and you get that some of these disconnected regions not only have different galaxies, but different low-energy laws of physics altogether.
Level III: Quantum mechanics unambiguously predicts that the part of the wavefunction we observe is not the only part. This really doesn't add anything on top of the previous two multiverse ideas, but it does suggest that the entire multiverse can actually exist as different components of the wavefunction of the universe within our Hubble horizon.

Tegmark has also suggested a fourth level, that of different fundamental laws. I do think his idea here is interesting, but it's really difficult to say anything beyond that.
 
  • #9


Chalnoth said:
That's not a valid objection either, because a unique universe is also not testable, due to the inability to verify that uniqueness. Furthermore, there is no requirement that the universe accept our demands that it be testable.

Like I said, you can object to the specific ways in which multiverse ideas are applied. I see no problem with that. These ideas can certainly be applied very poorly in certain cases. But it is still, by far, most likely the case that we live in some sort of multiverse.

Why is it more likely?
 
  • #10


In Brian Greene's 2011 book, Hidden Reality, nine different parallel universe proposals are explained: Quilted, Inflationary, Brane, Cyclic, Landscape,Quantum, Holographic, Simulated, ans Ultimate. In the first chapter he states " I want you to get a sense of how modern scientific investigations... naturally suggest this astounding possibility" of many universes. The book presents strong arguements for concluding that our universe is not the only one.
 
  • #11


Fuzzy Logic said:
Why is it more likely?
For two main reasons:
1. In general, a unique universe requires more assumptions than a prolific one.
2. Discoveries in high energy physics point to the existence of spontaneous symmetry breaking, which would lead to different regions of space-time realizing different low-energy laws of physics (spontaneous symmetry breaking is an essential component of the standard model: no string theory required, though naturally string theory suggests a much greater degree of flexibility).
 
  • #12


Garth said:
I always stick with Stephen Hawking's definition: "The universe is as it is because we are."
Garth
MathematicalPhysicist
Well this definition of Hawking is blatantly circular.
I mean the universe is the way it is because we are, then it begs the question what came first sentient beings or the stuff that they are made from?
Cause you you can ask why are we the way we are? and you get the answer, because the universe is that way.
Stephen Hawking's definition is succinct, it simply means that if the laws and constants of the universe were not propitious for life then we would not be here. As we are here "the universe is as it is".

garth
 
  • #13


skydivephil said:
Im curious , is the position of the Earth in the solar system considered to be an accidennt/anthropically selected or is there some underlying theory that allows us to predict where the Earth should be based on the known laws of physics?
If the former is true why can't the laws/constants of nature be the same ? I am not saying they are, but why rule it our a priori?
That's precisely the anthropic argument -- the position and characteristics of the Earth do not arise from some fundamental theory. We live here on Earth simply because we can. Now, in this analogy the Earth is identified with the Universe. Since the Earth exists in a larger space with widely ranging conditions (there are many other, different kinds of planets orbiting many other, different kinds of stars) the analogy necessitates the existence of a multiverse: our Universe among many different kinds. The postulation of the multiverse is what some people find objectionable.
 
  • #14


bapowell said:
That's precisely the anthropic argument -- the position and characteristics of the Earth do not arise from some fundamental theory. We live here on Earth simply because we can. Now, in this analogy the Earth is identified with the Universe. Since the Earth exists in a larger space with widely ranging conditions (there are many other, different kinds of planets orbiting many other, different kinds of stars) the analogy necessitates the existence of a multiverse: our Universe among many different kinds. The postulation of the multiverse is what some people find objectionable.

So would you agree that either (a) the above idea on the position of the Earth is unscientific or (b) we can't reject anthropic reasoning a priori on the grounds that it's unscientific?
I can't see a third alternative, but maybe someone else can?
 
  • #15


skydivephil said:
So would you agree that either (a) the above idea on the position of the Earth is unscientific or (b) we can't reject anthropic reasoning a priori on the grounds that it's unscientific?
I can't see a third alternative, but maybe someone else can?
No, the main difference is that we have access to the rest of the universe -- we can observe other planets outside of the Earth. This enables us to confirm that there is indeed a rich assortment of possible conditions. We have no such empirical access to other universes. The anthropic principle, as applied to the universe, is therefore non-scientific.
 
  • #16


bapowell said:
No, the main difference is that we have access to the rest of the universe -- we can observe other planets outside of the Earth. This enables us to confirm that there is indeed a rich assortment of possible conditions. We have no such empirical access to other universes. The anthropic principle, as applied to the universe, is therefore non-scientific.
Except for the simple fact that there are other ways to demonstrate this. As I noted above, spontaneous symmetry breaking events would, unambiguously, lead to different regions of the universe with different low-energy physics. And we can detect the impact of such events through our investigation of high-energy physics.
 
  • #18


Chalnoth said:
Except for the simple fact that there are other ways to demonstrate this. As I noted above, spontaneous symmetry breaking events would, unambiguously, lead to different regions of the universe with different low-energy physics. And we can detect the impact of such events through our investigation of high-energy physics.
Yeah, but that doesn't constitute observational evidence since you are referring to domains outside the causal Hubble patch. In particular, you are assuming that a sufficiently large universe exists in which the order parameter can take on sufficiently many values to give enough variation on which to base an anthropic argument. This may be true, but it is not, nor ever will be, an empirical argument. But agreed -- it is certainly suggestive.
 
  • #19


skydivephil said:
Before the 1990's we could not observe other planets, so would you have said it was unscinetific then? And what do you say to the many claims that multiverse might be observable , see here:
http://arxiv.org/abs/1109.3473
or:
http://blogs.discovermagazine.com/cosmicvariance/2010/12/22/observing-the-multiverse-guest-post/
or
Look, the idea is that we can observe the universe outside the Earth. We know that a larger space exists with other places in it that we could have lived. That alone breaks the analogy. The problem with the multiverse is that it is almost by definition unobservable.
 
  • #20


bapowell said:
Yeah, but that doesn't constitute observational evidence since you are referring to domains outside the causal Hubble patch. In particular, you are assuming that a sufficiently large universe exists in which the order parameter can take on sufficiently many values to give enough variation on which to base an anthropic argument. This may be true, but it is not, nor ever will be, an empirical argument. But agreed -- it is certainly suggestive.
That's not even necessary, though, as the nature of quantum mechanics guarantees that all of these different symmetry breaking events are realized right here as different branches of the wavefunction.
 
  • #21


Chalnoth said:
That's not even necessary, though, as the nature of quantum mechanics guarantees that all of these different symmetry breaking events are realized right here as different branches of the wavefunction.
Oh, and you can observe these other branches? They are epistemologically objective?
 
  • #22


bapowell said:
Look, the idea is that we can observe the universe outside the Earth. We know that a larger space exists with other places in it that we could have lived. That alone breaks the analogy. The problem with the multiverse is that it is almost by definition unobservable.


Yes we know that now, but we did not have any evidence of other planets before the 1990's, so what would have been your view then on the position of the Earth?
Also you didnt reposnd to the claims that it is possible to obtain evidence of the mulitverse. I don't know whether to believe these claims or not. But what I can say is that I do see more papers offering what they claim is an observational signal to the multiverse than papers claiming an observable singature of a final theory mentioned by Steinhardt.
 
  • #23


skydivephil said:
Yes we know that now, but we did not have any evidence of other planets before the 1990's, so what would have been your view then on the position of the Earth?
I believe I answered this above. I don't think that it matters whether other planets are observed. What matters is that there are other regions of space where we could have existed. We can observe the rest of the universe, and we can conclude that there are indeed many places where we can't likely exist -- like on Mercury or Pluto (and yes, these count!). We can conclude then that there is nothing fundamental about Earth's properties -- we live here simply because we can. We can't say the same about the Universe because we have no evidence for the existence of, and no knowledge about the characteristics of, the multiverse. We don't know whether it exists let alone whether there are vast regions that do not support universes like our own (this is the measure problem that was referred to by someone earlier -- we don't even have the theoretical tools to understand an infinite multiverse). That said...

Also you didnt reposnd to the claims that it is possible to obtain evidence of the mulitverse. I don't know whether to believe these claims or not. But what I can say is that I do see more papers offering what they claim is an observational signal to the multiverse than papers claiming an observable singature of a final theory mentioned by Steinhardt.
Sorry, I didn't even see these! Yes, it's certainly true that some models that postulate the existence of other universes might have observationally distinct signatures. And observing these would be suggestive. Of course, it would be necessary to rule out all other degenerate explanations, and of course, the evidence would need to be strong, given what they say about extraordinary claims and all that...
 
  • #24


Yes I agree with that, extraordinary claims require extraordinary evidence and we would have to rule all out other less prosaic explanation if such a bubble collision was claimed as observed. It would be easy to fool ourselves thinking we had seen such a pattern becuase we want to . But I believe the authors of the afromentioned papers went to great lengths to exclude such effects, they seemed to be doing science to me.
They may be on a fools errand and chasing something that doenst exist or that does exist but we can never detect, but maybe they will get lucky and make a definitive detection.
I think we should wait and see rather than have a priori assumpotions.
 
  • #25


skydivephil said:
I think we should wait and see rather than have a priori assumpotions.
Absolutely agreed. I don't mean to suggest that I have an a priori assumption that multiple universes don't exist. I simply don't know, and welcome any evidence that supports their existence. My point was simply that the anthropic principle -- which depends on the existence of a multiverse -- is not a scientific proposal simply because we currently lack evidence of this existence.
 
  • #26


bapowell said:
Absolutely agreed. I don't mean to suggest that I have an a priori assumption that multiple universes don't exist. I simply don't know, and welcome any evidence that supports their existence. My point was simply that the anthropic principle -- which depends on the existence of a multiverse -- is not a scientific proposal simply because we currently lack evidence of this existence.

I think that is quite a reasonable position to take and that Steinhardt could agree with you!
He opposes making unscientific assumptions. But he does not, himself, assume that patches of the universe with other values of what we call physical constants do NOT exist. He does not need that assumption.

Just an undirected comment: the reductionist program (call it Baconian if you like, in honor of the Elizabethan gentleman sometimes accused of writing Shakespeare's plays) has never been to explain why existence exists---only why it works the way it does.

To find the simplest natural explanations for as much as you can, for the time being, proposing no theory unless it can be tested, assuming nothing for which there is no evidence. And when that is done, look for the explanation behind THAT explanation.

Skydive, try looking back at the closing paragraphs of Steinhardt's statement and see if they are inconsistent with what Brian Powell just said. :biggrin:

I don't think they are inconsistent! In either case it is the open minded reductionist faith: you don't have to give up asking why, and you don't have to make stuff up.

The world is not accidental. At every step, there are reasons. You may not be able to answer all the questions at once, or why existence exists, but there is always one further deeper explanation of how it works. We are not yet ready to give up on the reductionist program. There is no evidence that we need to give up yet. I think that's Steinhardt's message.
 
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  • #27


bapowell said:
Absolutely agreed. I don't mean to suggest that I have an a priori assumption that multiple universes don't exist. I simply don't know, and welcome any evidence that supports their existence. My point was simply that the anthropic principle -- which depends on the existence of a multiverse -- is not a scientific proposal simply because we currently lack evidence of this existence.

Yes but surely the point of doing sciencve is to try and find that evidence. What the point in just cofnirming what we already know? Well ok we should always keep testing our theories to destruction, but no one won a Nobel prize for ther next decimal place confirmatrion of an existing theory.

I agree we currently do not have sufficient evidence to claim the multiverse exist and i think those that say its the only option are wrong. However there seems to be hint of a multiverse in our current scientific picture.
I see this in that
1) inflation has good evidence in favour of it.
2) inflation as descirbed by both its main supporters: Guth, Linde, Vilenkin etc and itsdmain detractors Steinhardt, Turok etc is eternal and hence implies a multiverse.

Now as Marcus has pointed out before, inflation may not be eternal. Furthermore maybe inflaiton will faill at the final hurdle (detection of B mdoe/primordial gravitational waves) and turn out ot be a failed theory. But with the evidence so far in favour of it (inflation) it seems to me that whilst we shouldn't accept the mutliverse as true, we shouldn't equate it to pseudo science as some people have done. It seems to me that in the classification of what's science and what isn't there is a grey area here.
 
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  • #28


bapowell said:
Oh, and you can observe these other branches? They are epistemologically objective?
They are an unambiguous consequence of the nature of quantum mechanics. You can get rid of them, of course, if you assume by fiat that they do not exist. But there is no reason whatsoever to make that assumption.

And the model in which these other branches occur, by the way, makes some very specific predictions about the nature of wave function collapse, predictions that have been tested:
http://vigo.ime.unicamp.br/~jc/p4887_1.pdf

Basically, requesting that we can only test a model in certain, specific ways is irrational and itself extremely unscientific. Any decent model makes a wide variety of predictions, and it is not in any way required that all of those predictions be testable. Demanding that one specific prediction be testable, when there are other tests that can be done instead, is simply refusing to engage in a critical examination of the idea.
 
  • #29


skydivephil said:
I see this in that
1) inflation has good evidence in favour of it.
2) inflation as descirbed by both its main supporters: Guth, Linde, Vilenkin etc and itsdmain detractors Steinhardt, Turok etc is eternal and hence implies a multiverse.
Sure, these are good candidates (notwithstanding Marcus' reasonable objection that inflation might not be eternal). As is quantum mechanics which Chalnoth mentioned earlier. But we can't observe these other regions of the universe. In order for anthropic reasoning to be successful, we must observe them, and we must learn about the distribution of these spaces -- what their properties are and so forth. Until we do this, all we have are suppositions. These might be based on well-tested theories, and these theories might even require the existence of a multiverse in order to be consistent. This would constitute a strong prediction for the existence of a multiverse. But a prediction requires evidence for its validation. My contention is with this latter point: we don't at present have any evidence for it, and so anthropic arguments are, at present, fundamentally non-scientific.
 
  • #30


Chalnoth said:
Any decent model makes a wide variety of predictions, and it is not in any way required that all of those predictions be testable. Demanding that one specific prediction be testable, when there are other tests that can be done instead, is simply refusing to engage in a critical examination of the idea.
But we're not trying to establish the correctness of a given model, like quantum mechanics. We are trying to understand the nature of one of its predictions. Until you empirically verify the existence of other universes, I'm sorry, they do not correspond to any objective reality. Of course QM makes other predictions, and of course these are sufficient to support the validity of the theory. It sounds like we are arguing two different points. All I'm saying is that it is unscientific to construct a principle based on the details of unobserved phenomena. I'm surprised you won't concede this.
 
  • #31


bapowell said:
But we're not trying to establish the correctness of a given model, like quantum mechanics. We are trying to understand the nature of one of its predictions. Until you empirically verify the existence of other universes, I'm sorry, they do not correspond to any objective reality.
This attitude of yours is fundamentally anti-science. It is exactly like the creationists complaining that we don't have transitional fossils because we don't have a continuous line of fossils of every lineage. Or that evolution isn't science because it can't be repeated.

Models do not exist in a vacuum. Refusing to believe in a definitive prediction of a model, even though that model has been thoroughly vetted through other means, and even though this other prediction is a natural consequence of the parts of the model that has been vetted, is just plain anti-science.
 
  • #32


Chalnoth said:
Refusing to believe in a definitive prediction of a model, even though that model has been thoroughly vetted through other means, and even though this other prediction is a natural consequence of the parts of the model that has been vetted, is just plain anti-science.
It's not a matter of belief (who sounds like the creationist?) I've stated above (which you didn't read because you were too busy planning your rebuttal) that I am agnostic to the existence of the multiverse because it has not been observed. Once evidence accumulates in favor of it, I will accept it as part of objective reality. <---- THAT is science. To do otherwise is to merely have faith in its existence. Which is precisely what you are doing whether or not you choose to accept it.

Another important point you missed, is that my argument is not so much about the purported existence of the multiverse, but of its character. The anthropic principle presupposes not just its existence, but makes assumptions about its character. Such assumptions I refuse to accept without evidence.

There's a little thing called inductive reasoning. You should google it.
 
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  • #33


bapowell said:
It's not a matter of belief (who sounds like the creationist?)
No, it's a matter of evidence. And refusing to take evidence at face value is the problem here.
 
  • #34


Chalnoth said:
No, it's a matter of evidence. And refusing to take evidence at face value is the problem here.
OK. What evidence, taken at face value or otherwise, can you provide for the existence of mutliple universes?
 
  • #35


Chalnoth said:
Is not the force of Steinhardt's objection the next part of his sentence:
—regarding the existence of multiple universes, a random creation process, probability distributions that determine the likelihood of different features, etc.— none of which are testable because they entail hypothetical regions of spacetime that are forever beyond the reach of observation.

Garth
That's not a valid objection either, because a unique universe is also not testable, due to the inability to verify that uniqueness. Furthermore, there is no requirement that the universe accept our demands that it be testable.

Like I said, you can object to the specific ways in which multiverse ideas are applied. I see no problem with that. These ideas can certainly be applied very poorly in certain cases. But it is still, by far, most likely the case that we live in some sort of multiverse.
Let's get this quite clear.
In this argument no-one is trying to assert or prove that our universe is unique or to prove that other universes don't exist.

It is not the uniqueness of our universe that is to be tested but its existence, and I think that we have enough evidence to assert that it actually does exist in a scientifically verifiable way. (Fans of the Matrix not withstanding!)

Other universes may well exist, in fact as a theologian I might argue that if the total density parameter [itex] \Omega [/itex] is just greater than unity, as some results suggest, so that this universe is bounded and finite, and if the creative power of God is infinite, then there has to be many (an infinite number?) such universes!

It is as a scientist that I have a problem. It is not the possibility of these other universes that is the question but their verification, or falsification, by scientific observation and testing. Garth
 
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<h2>1. What did Paul Steinhardt say that was considered "rather pathetic"?</h2><p>Paul Steinhardt made a statement criticizing the theory of cosmic inflation, which suggests that the universe underwent a rapid expansion in its early stages.</p><h2>2. Why was Paul Steinhardt's statement controversial?</h2><p>Paul Steinhardt's statement was controversial because it went against the widely accepted theory of cosmic inflation, which has been supported by numerous observations and experiments.</p><h2>3. What evidence does Paul Steinhardt provide to support his statement?</h2><p>Paul Steinhardt argues that there is no concrete evidence to support the theory of cosmic inflation and that it is based on assumptions and mathematical models rather than observational data.</p><h2>4. How have other scientists responded to Paul Steinhardt's statement?</h2><p>Other scientists have responded with criticism, arguing that there is significant evidence to support the theory of cosmic inflation and that it has been a successful framework for understanding the early universe.</p><h2>5. What impact could Paul Steinhardt's statement have on the field of cosmology?</h2><p>Paul Steinhardt's statement has sparked a debate within the field of cosmology and could potentially lead to further research and exploration of alternative theories to explain the origins of the universe.</p>

1. What did Paul Steinhardt say that was considered "rather pathetic"?

Paul Steinhardt made a statement criticizing the theory of cosmic inflation, which suggests that the universe underwent a rapid expansion in its early stages.

2. Why was Paul Steinhardt's statement controversial?

Paul Steinhardt's statement was controversial because it went against the widely accepted theory of cosmic inflation, which has been supported by numerous observations and experiments.

3. What evidence does Paul Steinhardt provide to support his statement?

Paul Steinhardt argues that there is no concrete evidence to support the theory of cosmic inflation and that it is based on assumptions and mathematical models rather than observational data.

4. How have other scientists responded to Paul Steinhardt's statement?

Other scientists have responded with criticism, arguing that there is significant evidence to support the theory of cosmic inflation and that it has been a successful framework for understanding the early universe.

5. What impact could Paul Steinhardt's statement have on the field of cosmology?

Paul Steinhardt's statement has sparked a debate within the field of cosmology and could potentially lead to further research and exploration of alternative theories to explain the origins of the universe.

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