I have been reading Hugh Ross’ rather bad statistical guesswork on the probability of life occurring in the universe. Ross lists 154 parameters he says are required for intelligent life to exist in the universe. Then he assigns probabilities to them. Actually he assigns probabilities to 322 parameters (not 154), which is a little confusing. Anyway, he concludes there is less that a 1 in 10282 chance intelligent life would occur without a divine miracle. Poor odds! He doesn’t estimate the probability of a deity spontaneously poofing itself into existence so it is there to create the miracle he claims is necessary. Wouldn’t that probability be zero? If not, surely it must be turtles all the way down?
Ignoring that, where to start with Ross’ figures? The first obvious comment is that he doesn’t (as far as I can tell) say how he arrives at the probabilities of any of his 322 parameters – probabilities that range from 0.00001 to 0.7. In my view his conclusion is meaningless because we don’t have anything like enough information to complete such a task. That fact alone sinks his argument before we even begin.
His article is a variation on the finely tuned universe argument – the idea that since the universe's physical constants are within a small tolerance of what is necessary for life, it must have been designed that way. Usually far fewer variables are quoted, and I have to say I’m skeptical of the number of items Ross thinks are necessary, quite apart from the probabilities he claims he has calculated for each one. But the arguments against both positions are the same.
Fine tuning does not imply design
There are various arguments against the idea that fine tuning means design. First, design rests on the assumption that the only type of life possible is the carbon-based form we are used to here on earth. But there is no reason to suppose this is so: we are restricting ourselves here by our own lack of knowledge and imagination.
Second, and totally fatal to the design argument, is that current theories point to the existence of an infinite number of other universes, each possibly with different sets of physical constants and conditions. Certainly a multi-universe scenario can not be ruled out since no known principle requires that only one universe exists. In fact astrophysicist Victor Stenger states:
No new hypothesis is needed to consider multiple universes. In fact, it takes an added hypothesis to rule them out-- a super law of nature that says only one universe can exist. But we know of no such law, so we would violate Occam's razor to insist on only one universe.
The argument is that an infinite number of universes exist, this universe is the one randomly tuned for life, and so this is the one where we have evolved and where we are here to observe that the universe is fine tuned for life. What else would we expect to observe? This is known as the Weak Anthropic Principle.
A third argument is that a fundamental theory of everything might predict that only a very narrow range of physical constants or even no range at all, would even be possible anyway. In other words, right now we just don’t know what the odds would be.
Talk Reason has a good write-up on why The Anthropic Principle Does Not Support Supernaturalism. In this article they use probability theory to show that the fine tuned argument actually contradicts design. Ross is just wrong.
Little green men?
Scott at the As If blog had another angle on this. He looked at Ross’ site and says Ross’ arguments makes it highly unlikely there are other inhabited planets in the universe. Scott takes Ross’ 154 parameters and assigns 50% probability to each (higher than Ross) and concludes the probability of there being a planet with all of these factors is less than 1 in 2 x 1046. He concludes that not only does the existence of Earth demand an explanation beyond random chance; it is also evidence that we are alone in the universe. See his post What are the odds? for the details. Scott asked for my comments.
Of course, if Ross is right and life demands a divine miracle, then applying probabilities to see if we are alone is meaningless - if God created us against the odds he could have created other life too. That argument didn’t especially appeal to me though. There are enough other reasons to reject Ross’ figures as evidence we are alone.
First, several of Ross’ parameters are for things that he says are necessary for life anywhere in the universe. For example:
6. decay rate of cold dark matter particles
7. hypernovae eruptions
9. white dwarf binaries
10. proximity of solar nebula to a supernova eruption
11. timing of solar nebula formation relative to supernova eruption
86. density of giant galaxies in the early universe
109. decay rate of cold dark matter particles
135. level of supersonic turbulence in the infant universe
136. number density of the first metal-free stars to form in the universe
141. heavy element abundance in the intracluster medium for the early universe
142. heavy element abundance in the intracluster medium for the early universe
144. pressure of the intra-galaxy-cluster medium
I’m not sure but I think there are several more. These, according to Ross, are all necessary for life to form in the universe, and those 12 items according to Scott’s formula would have a combined probability of only 0.00024. But since we know life (ie us) did form in the universe, we know the probability for all of these occurring is actually 1. These parameters, and probably several others, should be removed from Scott’s calculation.
Rolling up probabilities
Another major problem with Ross’ calculations is that many of his parameters are dependent on other parameters, resulting in incorrect multiplying up of probabilities. For example, take these four:
112. rate of nearby gamma ray bursts
119. gamma-ray burst events
128. frequency of gamma ray bursts in galaxy
152. quantity and proximity of gamma-ray burst events relative to emerging solar nebula
All of which if “too many” or “too few” are said to be a problem for life. Scott essentially multiplied these four 0.5 probabilities together to make a probability of all four occurring to be 0.0625. But surely they are essentially different ways of saying the same thing? He is multiplying four probabilities when there should just be one – 0.5.
How about these three:
20. parent star age
21. parent star mass
23. parent star color
But aren’t the color, mass and age of a star interdependent? For example, massive hot blue stars burn more quickly and therefore have shorter lives.
Look at these:
71. Kuiper Belt of asteroids (beyond Neptune)
94. total mass of Kuiper Belt asteroids
I would be grateful if anyone could explain the difference between those two.
Then there are these three:
105. distance from nearest black hole
15. parent star distance from center of galaxy
132. parent star distance from galaxy’s corotation circle
… any of which if “too close” or “too far” are claimed to mean life could not exist. But aren’t these essentially the same thing, or at least very similar? But there’s more – the above three are also linked to:
8. supernovae eruptions
16. parent star distance from closest spiral arm
24. galactic tides
110. ratio of inner dark halo mass to stellar mass for galaxy
117. star formation rate in solar neighborhood during past 4 billion years
118. variation in star formation rate in solar neighborhood during past 4 billion years
The reason is that these nine parameters (and maybe others), are all related to what is known as the Galactic Habitable Zone (GHZ): an area of space with a safe environment and access to the chemical materials necessary for building Earthlike planets. Scott’s 0.5 probability for each of these nine would yield a combined probability of 0.00195 (0.2%). However, a paper published in the journal Science in January 2004 estimated as many as 10% of all stars in the Milky Way galaxy would be within the GHZ – over 50 times what Scott would calculate.
Here’s another problem. The following numbered parameters are all to do with plate tectonics: 14, 54, 92, 153 and 154. Combined, with a 0.5 probability of each, they suggest the probability of plate tectonics arising as 0.03125. But SETI state:
There is nothing miraculous about tectonic activity, and in fact there is some evidence that it has occurred on both Mars and Venus.
Plate tectonics are probably fairly common, possibly even the norm, despite the 3% probability suggested by Scott using Ross’ parameters.
There are so many others like this it would be tedious to list them all, but I think the point is made: Ross did not allow for interdependencies – he incorrectly multiplies interdependent probabilities.
More errors
Then there are some parameters are just wrong. For example:
23. parent star color
* if redder: photosynthetic response would be insufficient
* if bluer: photosynthetic response would be insufficient
But SETI states:
Indeed, even stars somewhat brighter than the Sun, which because of their heightened ultraviolet production might be thought dangerous, could be the loci of life. Jim Kasting has shown that the enhanced ultraviolet radiation from F-type stars would produce so much atmospheric ozone that planetary surfaces could be very well shielded.
Also, Astrobiology Magazine states:
Of course, the development of photosynthesis on Earth did not just rely on the sun's wavelengths. It also was dependent on various factors specific to our planet, such as cloud cover, atmospheric composition, amount of land, and the depth of the ocean. Since so many factors played a role in the evolution of photosynthesis on Earth, perhaps photosynthesis could evolve on other worlds orbiting less-than-ideal stars.
In addition, other planetary factors perhaps could speed up the rate of photosynthesis development. There does not seem to be a particular reason why photosynthesis must develop at the same pace as it did on Earth.
As long as planets have enough liquid water oceans and cloud cover to protect against UV radiation, say Wolstencroft and Raven, planets orbiting most stars should be able to develop photosynthesis. One key to finding such planets is to look in the star's habitable zone.
(My bold.)
Ross’ probabilities ignore the habitable zone phenomenon: Earth like temperatures can be found around most stars, but at different distances. In addition, many of Ross’ parameters refer to Jupiter or Neptune, or to other factors relating just to our solar system. Again, Ross assumes that the formation of life requires a solar system like ours. He ignores the possibility of differing evolutionary paths that could adapt to colder/ hotter stars and planets, more/fewer massive planets, and countless other differing environments where life could still evolve. Ross also assumes that the time it took for intelligent life to evolve on Earth is the time it will take in all cases. Making these conclusions based on a statistical sample of one planet is absurd, and yet that is precisely what many of his parameters assume.
There are so many dubious parameters in Ross’ list it would be tedious to list them all, but I think the point is made: Ross’ list is bogus. Talk Reason has a very critical evaluation of Ross, covering some of these points, and others.
The Drake equation
The more usually quoted calculation for this kind of thing is the Drake equation devised by Dr. Frank Drake in the 1960s. The Drake equation estimates N: the number of civilizations in our galaxy with which we might expect to be able to communicate. Historical estimates of N range from 0.05 to 5,000, depending on the assumptions. From the link it seems like the current thinking is N = 0.0000008316. If there are 200 billion galaxies, I think that would make the potential number of civilizations with intelligence in this universe to be around 166,000.
Is that a reasonable estimate? In my opinion it is also based on many assumptions that we cannot be sure of – in other words I don’t know. But I’m pretty sure it’s a better guess than using Ross.
(Note: Pictures are from NASA and the Hubble)
Man are these sources cluelessly lost in the assumption that an admission that we are not here by accident means that godidit.
I have a lot to do today, so for now, I'll only kill one of the vast number of false assumptions that have been made:
There are various arguments against the idea that fine tuning means design. First, design rests on the assumption that the only type of life possible is the carbon-based form we are used to here on earth. But there is no reason to suppose this is so: we are restricting ourselves here by our own lack of knowledge and imagination.
Yes, there is reason that we know that it is more likely that carbon based life is more probably the only kind of life.
1) Our observed universe is carbon molocules by a factor of 10:1 over the next nearest competitor, which would be silicon based life.
2) Earth is silicon rich yet carbon based life forms more readily.
So much for rationale that is *designed* by ideologically motivated sources to downplay the significance of science that creationists abuse.
We can't rule out Multiverses
LOL!!!... no that's false.
Who can tell me why?
Posted by: island | January 12, 2006 at 02:59 AM
We can't rule out Multiverses
LOL!!!... no that's false.
Who can tell me why?
It's my understanding that we can't rule them out for the same reason we can't rule out other life in the universe: The laws of physics and probability, as we know them, would render a single universe or a single inhabited planet in our universe as very, very unlikely.
It seems to me that, strangely enough, Occam's razor favors multiple universes in this case: a single universe hypothesis would have to presume the existence of a currrently unknown (meta-)law of physics biased against multiverses, or the existence of a particular unlikely outcome.
Of course, my current understanding of physics could be dead wrong.
Posted by: BronzeDog | January 12, 2006 at 06:23 AM
The existance (or lack of existance) of multiple universes is a topic I, myself, remain firmly agnostic about.
Although I have to wonder ... if there WERE an infinite quantity of universes, would some of them be able to be non-naturalistic?
Posted by: Sotek | January 12, 2006 at 07:12 AM
Define "non-naturalistic". ;)
Posted by: BronzeDog | January 12, 2006 at 07:59 AM
"We can't rule out Multiverses"
LOL!!!... no that's false.
Who can tell me why?
It's my understanding that we can't rule them out for the same reason we can't rule out other life in the universe: The laws of physics and probability, as we know them, would render a single universe or a single inhabited planet in our universe as very, very unlikely.
It seems to me that, strangely enough, Occam's razor favors multiple universes in this case: a single universe hypothesis would have to presume the existence of a currrently unknown (meta-)law of physics biased against multiverses, or the existence of a particular unlikely outcome.
Of course, my current understanding of physics could be dead wrong.
Be careful what you're arguing about here. In the case of "fine-tuning" and the anthropic principle, we can rule out multiverses as a argument againt it because the anthropic principle is a fact of the observed universe.
This all changes if the multiverse is by some miricle proven to exist, or if "multiverse reasoning" is proven to be necessary to the one true theory of everything. Until or unless that happens, facts of the observed universe take precedence of speculative theoretical projections about what *might* *maybe* would'a shoulda' could exist elsewhere, so no, multiverses are not a valid argument against the special implications of fine-tuning.
Sotek wrote:
Although I have to wonder ... if there WERE an infinite quantity of universes, would some of them be able to be non-naturalistic?
Every known occurrence has a natural cause, and "non-natural" occurrence isn't something that is observed to be real, so there is no valid reason to believe that non-natural anything is even possible.
Posted by: island | January 12, 2006 at 08:24 AM
Vic the .... wrote:
No new hypothesis is needed to consider multiple universes. In fact, it takes an added hypothesis to rule them out-- a super law of nature that says only one universe can exist. But we know of no such law, so we would violate Occam's razor to insist on only one universe.
Vic Stenger is a clueless moron.
Only one universe is observed, so it requires no additional hypothesis to "rule them out"... idiot.
I hate that guy!
Posted by: island | January 12, 2006 at 09:02 AM
The argument is that an infinite number of universes exist, this universe is the one randomly tuned for life, and so this is the one where we have evolved and where we are here to observe that the universe is fine tuned for life. What else would we expect to observe? This is known as the Weak Anthropic Principle.
No, that's not what the weak anthopic principle says... that's what antifanatics who want to downplay the implied significance say.
These are just a few of the real scientific interpretations:
http://nedwww.ipac.caltech.edu/level5/Peacock/Peacock3_5.html
http://zebu.uoregon.edu/~imamura/209/mar31/anthropic.html
http://www.jca.umbc.edu/~george/html/courses/glossary/cosmo_principle_copern.html
Anthropic interpretation of quantum theory (2004)
Brandon Carter; arxiv.org/abs/hep-th/0403008
The Physics Behind the Large Number Coincidences
Scott Funkhouser; arxiv.org/abs/physics/0502049
Posted by: island | January 12, 2006 at 09:06 AM
A third argument is that a fundamental theory of everything might predict that only a very narrow range of physical constants or even no range at all, would even be possible anyway. In other words, right now we just don’t know what the odds would be.
This is true... we only have evidence that they can be the way that they are, and we can't assume that our universe isn't the most-natual configuration that a universe can have, per the principle of least action.
A real scientist would look for some good physical reason why the special implications of the anthropic principle might be true before they race off into the fantasy-land fairy-tales and unproven theoretical specuation.
FYI... the anthropic principle isn't limited to the Earth... and readily extends to apply to every banded spiral galaxy that exists on the same evolutionary "plane" as we do.
Which makes for a valid testable prediction that SETI will prove or disprove.
Posted by: island | January 12, 2006 at 09:14 AM
Only one universe is observed, so it requires no additional hypothesis to "rule them out"... idiot.
Remember the fundamental principle of logic that states, "Absence of evidence is not evidence of absence."
So unless there is some reason to believe that we should observe such universes if they exist, or some proof that other universes cannot exist, we cannot base any conclusion on the assumption that they do not. Which knocks a huge hole any kind of "fine tuning" argument.
Posted by: trrll | January 12, 2006 at 03:27 PM
Regarding whether a multiverse violates Occam’s Razor, Cosmologist Max Tegmark wrote in Scientific American:
This is essentially the same as my Victor Stenger quote: “No new hypothesis is needed to consider multiple universes. In fact, it takes an added hypothesis to rule them out”.
Posted by: Skeptico | January 12, 2006 at 04:36 PM
Island:
Re: Yes, there is reason that we know that it is more likely that carbon based life is more probably the only kind of life.
1) Our observed universe is carbon molocules by a factor of 10:1 over the next nearest competitor, which would be silicon based life.
2) Earth is silicon rich yet carbon based life forms more readily.
In our observed universe that is true. The point was that a completely different universe it might be different – carbon might not exist, atoms as we know them might not exist, but something else could exist their place and a completely different form of life could exist.
Posted by: Skeptico | January 12, 2006 at 04:46 PM
Island:
Re: No, that's not what the weak anthopic principle says... that's what antifanatics who want to downplay the implied significance say.
These are just a few of the real scientific interpretations:
http://nedwww.ipac.caltech.edu/level5/Peacock/Peacock3_5.html
From your first link:
(My bold.)
How is that different from what I wrote:
Posted by: Skeptico | January 12, 2006 at 04:59 PM
Now this is much more interesting than ID biology!
ID biology was utter nonsense. ID physics is ... interesting. My Fermi Paradox page goes into some of what makes this such a fascinating topic. (http://www.faughnan.com/setifail.html)
The bit about the hundreds of parameters is probably junk, especially since I think they're not independent variables. Still, there are a lot of secular physicists who are at least a bit troubled by the extent to which we appear 'singular' and oddly 'balanced' in space and time. (Why should the universe change its inflationary parameters around now? It's a heuristic in physics that we're not special.)
Of course even if the universe were in some sense tuned (something which we might be able to do not long from now, create tuned universes that is), there's nothing to say it was tuned for us. Maybe our universe is just one in a series of millions of attempts to create a universe that optimizes dark matter distribution, and we're the equivalent of bacterial contamination of a discarded broth.
Anyway, I for one will be grateful to engage in a discussion on cosmologic design and the Fermi Paradox with evangelicals. At least it's not intrinsically stupid.
Posted by: John Faughnan | January 12, 2006 at 07:43 PM
"Only one universe is observed, so it requires no additional hypothesis to "rule them out"... idiot."
Remember the fundamental principle of logic that states, "Absence of evidence is not evidence of absence."
But it's not evidence "for", either, so you can't use it as such in lieu of evidence that does exist for only one universe.
The rule here is that one is proven UNTIL there is some reason not to believe it. What you're saying is like saying that god is an equally valid possiblity because there is no evidence that god doesn't exist.
You're wrong.
So unless there is some reason to believe that we should observe such universes if they exist, or some proof that other universes cannot exist, we cannot base any conclusion on the assumption that they do not. Which knocks a huge hole any kind of "fine tuning" argument.
Nope, empiricism always supercedes bullshit and unproven theoretical speculation.
I gave the criterion for which a multiverse is acceptable without direct proof.
You ignored it.
Posted by: island | January 13, 2006 at 03:00 AM
Skeptico... I suggest that you read what I wrote to tgibbs and if that doesn't work for you, then go here:
www.math.columbia.edu/~woit/wordpress
... tell these Loop Quantum Gravity theorists that the Earth has an infinite number of moons because it might be possible that we just can't see em.
Posted by: island | January 13, 2006 at 03:06 AM
John Faughnan wrote:
ID physics is ... interesting.
There is no such thing as "ID" physics even if we're not here by accident, because there is no evidence, nor any reason to conclude that there is an intelligent agent involved.
The bit about the hundreds of parameters is probably junk, especially since I think they're not independent variables. Still, there are a lot of secular physicists who are at least a bit troubled by the extent to which we appear 'singular' and oddly 'balanced' in space and time.
I agree that the parameters are not independent variables, but that means that they are all dependently tuned to derive hundreds of ecobalances that would all run extremely far away from conditions that are conducive to life if any one of them were to become permanently changed.
Of course even if the universe were in some sense tuned (something which we might be able to do not long from now, create tuned universes that is), there's nothing to say it was tuned for us. Maybe our universe is just one in a series of millions of attempts to create a universe that optimizes dark matter distribution, and we're the equivalent of bacterial contamination of a discarded broth.
There IS reason to say that the universe is tuned for intelligent life... and you damned near hit the nail on the head, but we're already directly affecting the symmetry of the universe... holding it flat, while driving expansion... uncoincidentally.
Anyway, I for one will be grateful to engage in a discussion on cosmologic design and the Fermi Paradox with evangelicals. At least it's not intrinsically stupid.
The only plausible ID theory is some lame alien intervention junk, where the distance to plausibility rules it out as serious scientific consideration without some very hard and direct proof.
Evidence for natural "design" does not constitute evidence for "intelligent" design witout proof.
Inherent thermodynamic structuring, however... is a different story... especially when a "biocentric" universe requires intelligent life as a practical means to an end.
Posted by: island | January 13, 2006 at 03:29 AM
Maybe our universe is just one in a series of millions of attempts to create a universe that optimizes dark matter distribution...
This is good... and VERY close.
There is a valid theory about this.
Think... perpetually driven toward absolute symmetry via an inherent asymmetry/imbalance in the energy that cannot be reconciled.
AKA... The Second Law owns it all.
Posted by: island | January 13, 2006 at 03:46 AM
Some more problems :
1. It doesn't matter how improbable life arising by natural means is, since the probability of divine creation is zero.
2. Fine-tuning is an argument AGAINST divine creation. Finely-tuned systems are fragile and inefficient. Who designs a system that stops functioning if you change one variable in its environemnt (like temperature) a tiny little bit ? That's insanity.
Posted by: Francois Tremblay | January 13, 2006 at 03:51 AM
Francois Tremblay made some very good points as they apply to "Devine Intervention", except for one point that could be misinterpreted if taken out of this context:
Finely-tuned systems are fragile and inefficient.
The anthropic balances are only unstable or "fragile" if they aren't fixed, which is what the anthropic cosmological principle is about. For example, the "anthropic flatness" of the universe is supposed to be the most natural configuration if inflationary theory is true, but this is also true without the need for inflationary theory if the universe has volume when a big bang occurs.
While it is true that the universe will runaway in the direction of expansion if the cosmological constant increases, this is not true if the universe is fixed to its flat configuration by the mechanism behind the anthropic principle.
As far a efficiency goes, intelligent life is by far the most energy-efficient means for increasing the entropy of our expanding universe that has an increasing negative pressure component... e.g., a growing need for systems that can do the job efficiently.
However, this good reason for us to be here also means that intelligent life will be as common in the universe as the grand scale thermodynamic need demands.
Maybe our eyes aren't perfect, which is what one might expect a supernatural power to produce, but they're good enough to get the job done, which is all that is needed to justify the imperfection that we've actually got.
Posted by: island | January 13, 2006 at 02:40 PM
But it's not evidence "for", either, so you can't use it as such in lieu of evidence that does exist for only one universe.
There is no evidence whatsoever for the "only" part, because absence of evidence is not evidence of absence. I am not trying to draw a conclusion based upon the number of universes, merely pointing out that no valid conclusion can be drawn based on any assumption regarding whether the universe is singular or multiple. All fine-tuning arguments are critically dependent upon the assumption of a singular universe. Obviously, if the number of universes is large enough, some will be suitable for life, and as a matter of simple logic, every living observer will observe a universe that is well-suited for its kind of life.
Ironically, many of the same people who will insist that the apparent fine-tuning of our universe cannot be taken as evidence for the existence of unobserved other universes will then turn around and argue that the apparent fine-tuning of our universe does constitute evidence for an unobserved designer.
The rule here is that one is proven UNTIL there is some reason not to believe it.
I agree that we have evidence for the existence of one universe. Because absence of evidence is not evidence of absence, the most that we can logically conclude from that observation is that there exists at least one.
Nope, empiricism always supercedes bullshit and unproven theoretical speculation.
Do you actually imagine that to be an argument? "Empiricism" does not supersede logic--and the principle that absence of evidence is not evidence of absence is not an "unproven theoretical speculation"--it is a fundamental rule of logic.
tell these Loop Quantum Gravity theorists that the Earth has an infinite number of moons because it might be possible that we just can't see em.
However, there are numerous reasons to believe that we should be able to detect other moons if they exist. So failure to observe other moons does constitute evidence that they either do not exist, or are very different from our moon in such a way as to make them undetectable by normal gravitational or optical methods. On the other hand, since there is no reason to believe that we should be able to observe other universes even if they exist, the fact that we have not observed them is not evidence either way.
Posted by: trrll | January 14, 2006 at 08:28 AM
There is no evidence whatsoever for the "only" part, because absence of evidence is not evidence of absence.
No, that's false... We observe only one universe, and there is absolutely no reason to believe that more can exist.
Posted by: island | January 14, 2006 at 10:21 AM
*yawn*
http://abyss.uoregon.edu/~js/ast123/lectures/lec19.html
Arguments Against the Multiverse Concept:
Its not science:
It is sometimes objected that because our observations are limited to a single universe (e.g. a Hubble volume) then the existence of other universes cannot be observed, and so their existence cannot be considered a proper scientific hypothesis. Even taking into account the fact that future observers will see a larger particle horizon, and so have access to a bigger volume of space, most regions of the multiverse (at least in the eternal inflation model) can never be observed, even in principle. While this may indeed preclude direct confirmation of the multiverse hypothesis, it does not rule out the possibility that it may be tested indirectly. Almost all scientists and philosophers accept the general principle that the prediction of unobservable entities is an acceptable scientific hypothesis if those entities stem from a theory that has other testable consequences.
There is only one possible universe:
It is occasionally argued that the observed universe is the unique possible universe, so that talk of `other' universes is ipso facto meaningless. Einstein raised this possibility when he said, in his typical poetic manner, that what really interested him was whether `God had any choice in the creation of the world'. To express this sentiment more neutrally, Einstein was asking whether the universe could have been otherwise (or nonexistent altogether). The hope is sometimes expressed that once a fully unified theory of physics is achieved, it will turn out to have a unique solution corresponding to the observed universe. It is too soon to say whether string/M theory will eventually yield a unique description (so far, the evidence is to the contrary), but the hypothesis of a unique reality would in any case seem to be easily dispatched. The job of the theoretical physicist is to construct mathematically consistent models of reality in the form of simplified, impoverished descriptions of the real world. For example, the so-called Thirring model describes a two spacetime dimensional world inhabited by self-interacting fermions. It is studied because it offers an exactly soluble model in quantum field theory. Nobody suggests the Thirring model is a description of the real world, but it is clearly a possible world. So unless some criterion can be found to eliminate all the simplified models of physics, including such familiar constructs as Newtonian mechanics, there would seem to be a strong prima facie case that the universe could indeed have been otherwise that `God did have a choice'.
The fake universe problem:
The multiverse theory forces us to confront head-on the contentious issue of what is meant by physical reality. Is it meaningful to assign equal ontological status to our own, observed, universe and universes that are never observed by any sentient being? This old philosophical conundrum is exacerbated when account is taken of the nature of observation. In most discussions of multiverse theory, an observer is simply taken to mean a complex biological organism. But this is too restricted. Most scientists are prepared to entertain the possibility of conscious machines, and some artificial intelligence (AI) advocates even claim we are not far from producing conscious computers. In most multiverse theories, although habitable universes may form only a sparse subset, there is still a stupendous number of them, and in many cases an infinite number. (That is the case with Boltmann's original model, and eternal inflation, for example.) It is therefore all but inevitable that some finite fraction of habitable universes in this vast, possibly infinite, set, will contain communities of organisms that evolve to the point of creating artificial intelligence or simulated consciousness. It is then but a small step to the point where the engineered conscious beings inhabit a simulated world. For such beings, their `fake' universe will appear indistinguishable from reality. So should we include these simulated universes in the ensemble that constitutes the multiverse?
Why stop there?:
A final objection to the existing multiverse theories is a challenge to the criteria for defining universes. In most multiverse theories, universes are labeled by laws of physics and initial conditions. Even in extreme multiverse scheme, the chosen criterion is mathematical consistency. It might be objected that these terms are narrow and chauvinistic - indeed, just the sort of criteria to be expected from mathematical physicists. Other ways of categorizing universes are conceivable, and could lead to even larger concepts of multiverse. Examples might be the set of all possible artistic structures, or morally good systems, or mental states. There may be criteria for categorization that lie completely beyond the scope of human comprehension. To suppose that the ultimate nature of reality is founded in twenty-first century human physics seems remarkably hubristic.
Posted by: island | January 14, 2006 at 11:03 AM
No, that's false... We observe only one universe, and there is absolutely no reason to believe that more can exist.
Actually, that is not true--there are some models of the universe in which multiple universes necessarily arise. Since these models have not been excluded experimentally, there is indeed reason to believe that more can exist (whether they do exist is of course another matter). There is definitely no reason to believe that more cannot exist. Since we would not expect to observe them easily (or at all, depending upon the model) even if they did exist, the fact that we don't observe them is not evidence either way--it is only evidence for the existence of this universe.
Posted by: trrll | January 14, 2006 at 02:35 PM
Yeah, but... my point all along has been that "some models" don't mean anything against impications that fall from the directly observed model until "some models" are proven to be more than a presumption about what might be possible.
Another way to put this is that the observed universe is the necessarily preferred cosmological model, unless the more complex model can produce more accurate answers, since it can't do it in less steps.
That's a common definition for the preferred theory, aka., the most conservative mainstream approach.
Then there's that whole argument for falsifiability, that string theorists want to get around by redefining how science is done... kinda like Kansas... is this an ID theory?
Posted by: island | January 14, 2006 at 04:59 PM
Yeah, but... my point all along has been that "some models" don't mean anything against impications that fall from the directly observed model until "some models" are proven to be more than a presumption about what might be possible.
Rather, it is the other way around--the possibility of multiple universes cannot be excluded unless all models in which multiple universes are possible are definitively excluded. Failing that, the notion that the universe is singular is mere speculation, and no definitive conclusions can be drawn based upon that assumption.
Another way to put this is that the observed universe is the necessarily preferred cosmological model, unless the more complex model can produce more accurate answers, since it can't do it in less steps.
However, it is by no means clear that a cosmological model in which the universe is singular is in fact simpler. In many models, some additional mechanism would be required to prohibit the universe from being multiple. After all, the rule in physics is that if something can exist once, then it can exist multiple times. So some strong basis is required for making the universe an exception. Moreover, multiple universes are simpler in the scientific sense of having a smaller number of free parameters--this is, after all, the fundamental issue of "fine tuning"--the fact that there are a number of free cosmological parameters that appear to be arbitrarily set, apparently coincidentally, to values that are conducive to the existence of organized matter, and therefore life. If universes are multiple, this problem disappears. No value needs to be assumed or explained, because these parameters take all possible values in different universes, and only those universes suitable for life happen to have observers.
Finally, you seem to have the misconception that conclusions can be drawn based upon Occam's Razor. This is false. There is no logical reason why the simplest hypothesis is best, and indeed, the historical trend in science is for simple hypotheses to be found to be wrong, and to be replaced by more complex ones. So no real conclusions can be drawn based upon which hypothesis is simpler. In other words, even though a multiplicity of universes is in fact the simpler hypothesis, we are still prohibited from drawing conclusions based upon that assumption. Occam's Razor is not a guide to truth--it is an empirical rule of thumb for efficiently ordering hypotheses for experimental investigation. Hypotheses with fewer free parameters tend to be more restrictive, and thus are more easily tested and, if they are wrong, excluded. So the more efficient way to proceed is to start with the simplest hypotheses and work toward more complex.
Then there's that whole argument for falsifiability, that string theorists want to get around by redefining how science is done
Again, falsifiability is not a guide to truth or a basis for drawing conclusions--it is a criterion for constructing hypotheses that are amenable to scientific investigation. So far, nobody has figured out how to falsify the hypothesis that there are other universes, just as nobody has figured out how to falsify the hypothesis that there are not. However, many of the theories that entail multiple universes are still being explored theoretically, so these models may yet generate testable predictions that would bear upon the question of the singularity or multiplicity of universes. Until such time, we can draw no conclusion that is dependent upon the assumption either that there are, or are not, multiple universes.
Posted by: trrll | January 14, 2006 at 07:36 PM
Island:
Re: ... tell these Loop Quantum Gravity theorists that the Earth has an infinite number of moons because it might be possible that we just can't see em.
I would say that’s a false analogy: if the Earth had any additional moons we would be able to detect them. A more valid analogy would be to say that we expect planets orbiting other stars to have moons, even though we cannot detect them, since there is no reason to suppose they could not exist.
As tgibbs wrote, there are models that predict multiple universes. This means that we have a reason to suppose they might exist, which makes the multiverse a different proposition from God (no reason to suppose God exists), and which is why this idea is different from intelligent design. IOW, multiple universes are worthy of consideration. Also, in some models, additional assumptions are required to prohibit multiple universes, which is why some say Occam’s Razor favors multiple universes.
I accept your point that multiple universes are currently unfalsifiable and so not (yet) supported by evidence, but that does not means they can be ruled out. Absence of evidence is not evidence of absence unless qualified experimenters have looked for evidence and they would have been expected to find such evidence if it exists. I don’t believe you can say this yet for multiple universes.
Whether or not the multiverse is really the more parsimonious explanation is clearly disputed by different scientists, so perhaps I should have said we currently cannot decide either way.
Posted by: Skeptico | January 15, 2006 at 05:14 PM
My response posted at:
http://www.swanigan.squarespace.com/display/ShowJournal?moduleId=226309¤tPage=2
Posted by: Scott | January 16, 2006 at 07:24 AM
Whether or not other universes exist is something that will probably never be known.
The fine-tuning argument, however, seems to rely on an a priori assumption of a negative: That there are no other universes. From this negative premise (among others), it draws a positive conclusion that the universe was fine-tuned. Drawing positive conclusions from negative premises is a no-no.
Once again, I'm reminded of Candide, where they assume, a priori, that this is the only possible world, therefore it is the best of all possible worlds, and everything happens for the best of all possible reasons.
Posted by: BronzeDog | January 16, 2006 at 07:38 AM