On Mon, 6 Oct 2003, Ioan Oprea wrote:

The point I was trying to make is that the anthropic principle is not
something that results from the theory (neither string theory nor any
other one). And the fact that we have to use it reflects rather an
inability of our theory than its success.

I totally agree. Every time physicists (and one might even say "pure
scientists") face some truly difficult problems, some of them start to
give up and accept not-quite-scientific explanations - especially the
anthropic principle - as the last chance. The appearance of the anthopic
principle is therefore a symptom of the fact that the physicists have a
problem to explain a known fact scientifically.

In the case of the recent popularity of the anthropic principle among some
string theorists, the truly difficult problem was the cosmological
constant problem. The problem "doubled" once the astrophysical
observations showed that not only that Lambda is much much smaller than
any reasonable scale that one can imagine to emerge from a high energy
theory, but it is - despite its tiny value - nonzero. We - I mean all
theoretical and particle physicists - just don't have a natural
explanation of this fact, and therefore physicists - inspired by Bousso
and Polchinski - started to propose scenarios meant to generate a huge
number of metastable vacua in the theory which has the virtue that one of
them is more likely to have the right, minuscule value of the cosmological
constant. Some people started to like these highly-degenerate vacua so
much that they declared that string theory must certainly predict this
huge number of vacua, and therefore the anthropic considerations will be
always necessary in string theory.

In my opinion, this whole direction of research might be, and it's quite
likely, on a wrong track. We should still try to find a formalism that
allows to compute the cosmological constant and other SUSY-breaking
effects reliably and scientifically, and the small value will emerge as a
consequence of a pretty general, rigid and rather unique small set of
vacua - such as the heterotic strings on Calabi-Yau 3-folds. This will
make these huge, artificially created multiverses of stringy vacua
irrelevant for physics, and once we understand the theory really well, we
might be able to prove that there's something wrong with this "huge
landscape".

For example, you could ask that the solution
describe a universe with a certain amount of Fe atoms (I dont't know
the proportion of Fe in our universe, but you could adjust the
percentage in order to include our universe among the selected
solutions). Why not use this to select the right solution?

Right! This is very similar to my favorite example. Before physicists
understood Schrodinger's equation (that's responsible for the properties
of all the atoms), they could have argued that the world has hundreds of
elementary particles (the atoms or - at least - their nuclei) whose
properties (masses, spectral lines etc.) must be chosen exactly as they
are observed, otherwise the world would not admit life. Well, today we can
calculate all the properties of these atoms from a handful or parameters,
and therefore we know that such an anthropic proposal would have been
silly. Unfortunately we can't calculate the cosmological constant after
SUSY breaking reliably today, and therefore I can't show whether/that the
case of the cosmological constant is analogous. Yes, I think it may be,
and a physicist who wants to continue to try to make nontrivial progress
in this direction *should* believe that these two examples are analogous.

The choice of the constraint on the solutions is (almost) completely
random. And I might be missing something here, but this doesn't look
like a TOE, but resembles more a creation myth. Each theorist could
have his own favourite criterion of selecting the right solutions, the
only requirement being that our universe is included.

Exactly. This is not real science. Some advocates of the anthropic
principle in string theory argue that string theory could still explain
the quantum properties of black holes. Which black holes? should we ask.
The properties of the observed black holes? Why should we believe that the
theoretical ones have anything to do with the observed ones, unless we can
calculate and compare at least one number? Once we admit that we don't
know physics at higher energies (the particle spectrum etc.), we can't
claim anything specific about quantum gravity either. If we were satisfied
with the claims that string theory describes the black hole entropy
consistently and this is why string theory is better, theoretical physics
- and string theory in particular - would become a religion.

The internal mathematical consistency is what makes string theory
attractive, probable and promising - but it does not prove it!

The only real reason why some people are happy to accept such a scenario
is that we have not quite understood one number - the cosmological
constant. In the light of string theory's shocking ability to give us -
naturally - all the required ingredients for particle physics and gravity,
such a surrender does not look reasonable to me, especially because it
leads us to look at complicated vacua that don't explain the observed
facts too naturally. The old-fashioned vacua - like heterotic strings on
Calabi-Yau's - and some newer ones predict (very naturally) the particle
spectrum; the gauge groups etc. We don't quite know how to calculate
quantities after SUSY breaking, and Lambda is no exception. Why should we
suddenly transfer our belief to some other models that don't give too
convincing picture of reality and that look artificially, just because of
the single number?

__________________________________________________ ____________________________
E-mail: fax: +1-617/496-0110 Web: http://lumo.matfyz.cz/
phone: work: +1-617/496-8199 home: +1-617/868-4487
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Superstring/M-theory is the language in which God wrote the world.

Let me try to understand the Anthropic Principle. Suppose I want to
explain from fundamental principles why humans have ten fingers.
I say, suppose humans would normally have 12 fingers. Then I would
most likely have 12 fingers, too. But in the world I live, I have only 10.
Thus, according to Anthropic Principle, humans must have 10 fingers.
This is not an accident, but has a Fundamental Scientific Reason.

The logic seems flawless, but unimpressive. What counts as fundamental
explanations is a vague notion. The grounds for explaining X should be
simpler than X itself. Thus, my understanding is that invoking the
existence of complex creatures is a (simple and thus) valid application
of Anthropic Principle. Yet, assuming these creatures have any specific
similarity to us (e.g., being build from particles rather than from
karma units :-) is not. Please correct my naivete. Thanks! -Leonid.

(Levin) wrote in message ...
Let me try to understand the Anthropic Principle. Suppose I want to
explain from fundamental principles why humans have ten fingers.
I say, suppose humans would normally have 12 fingers. Then I would
most likely have 12 fingers, too. But in the world I live, I have only 10.
Thus, according to Anthropic Principle, humans must have 10 fingers.
This is not an accident, but has a Fundamental Scientific Reason.

I think it's even worse than that. Suppose you have a theory that
predicts all sorts of values for the number of fingers. But what you
actually see is that humans have 10 fingers. So if you were to use the
AP, then you'd say that humans have 10 fingers because otherwise they
wouldn't be fit to be here in this world, so you couldn't see them.


You could explain all sorts of things using this kind of argument. No
one will be able to prove you wrong. And even if , say, you find
another (more realistic) explanation for the number of fingers, that
won't automatically discard the AP.

i.o.

Lubos Motl wrote:


In the case of the recent popularity of the anthropic principle among some
string theorists, the truly difficult problem was the cosmological
constant problem. The problem "doubled" once the astrophysical
observations showed that not only that Lambda is much much smaller than
any reasonable scale that one can imagine to emerge from a high energy
theory, but it is - despite its tiny value - nonzero. We - I mean all
theoretical and particle physicists - just don't have a natural
explanation of this fact, and therefore physicists - inspired by Bousso
and Polchinski - started to propose scenarios meant to generate a huge
number of metastable vacua in the theory which has the virtue that one of
them is more likely to have the right, minuscule value of the cosmological
constant. Some people started to like these highly-degenerate vacua so
much that they declared that string theory must certainly predict this
huge number of vacua, and therefore the anthropic considerations will be
always necessary in string theory.

Dear Lubos,

Thanks for this account - although it makes my submission of yesterday on the
same thread, partially obsolete. As I understand it now, using the anthropic
principle is analogous - in fact the same thing - as divinatory arts; let me
at once add that there is more to divinatory arts than what meets the standard
rationalist's ear, at least in my version of the exercize.

The scenario goes thus : you start with a non-trivial formal object that
stands out for some arbitrary reason, and that as such you can't interpret
effectively as you would. You then use the fiction that the formal object is a
-speech act- by a supernatural and friendly Intelligence, in a -language- that
you don't know except for that representative speech act. This means that the
Intelligence had access to a paradigm of slight variations of the formal
object along some possible axes of variation, while being constrained on
others, and has picked that particular object among those it was free to
chose, as most promising for the function of telling you a bit of Truth, provided

(1) you assume that It is familiar with your situation and knows exactly the
problem of interpretation It leaves you with; and that It has made it as easy
as It could, given that Its control is very limited.

(2) It can count on your intelligence to lead your interpretation process
towards the intelligent suggestion It meant to make, rather than arbitrary
absurdities.

Provision (2) brings reason to the process, by making the intervention of the
Intelligence superfluous to some independent justification of the result, that
one has to find by oneself. In the case you describe, this corresponds to the
expectation that after having generalized string theory to admit these many
vacua and then selecting one or a few by a parsimonious anthropic constraint,
the resulting variant(s) will provide successful experimental predictions
(further than satisfying the constraint).

BTW, I am a bit surprised that none of the comments I could read in the thread
mentioned as a -feature- in favor of applying AP (all other things being
equal) that the selected vacua would -still- have to find a justification by
successful experimental tests. Maybe it is obvious, but all I read was
consistent with the pathological notion that it was worse than irrelevant.

Provision (1) is what makes applying AP isomorphic to divinatory arts, since
it invites you to abstract with parsimony outstanding atomic features of your
situation [that the Intelligence can most easily assume you can identify as
evident to It] which can serve [as common ground between It and you] to [help
It allude and] lead you to independent positive content.

Curiously enough, I had this parsimonious process of divinatory arts,
illustrated in a nutshell in a spr thread a few years back, having to do with
the first outstanding features of string theories to shine at the "fuzzy
focus" limit : the strange values they predicted for the dimensionalities of
space-time.

http://www.google.ch/groups?threadm=...pravda.ucr.edu

This would seem to show that meeting AP is in the destiny of string theories.

If I were you, I would reconsider my .sig; God is by definition the One that
can't be outsmarted

Cheers, Boris Borcic
--
"L'anthropie met un terme aux dynamiques"

(Ioan Oprea) wrote in message
. com...

(Levin) wrote in message ...

Let me try to understand the Anthropic Principle. Suppose I want
to explain from fundamental principles why humans have ten
fingers. I say, suppose humans would normally have 12
fingers. Then I would most likely have 12 fingers, too. But in the
world I live, I have only 10. Thus, according to Anthropic
Principle, humans must have 10 fingers. This is not an accident,
but has a Fundamental Scientific Reason.

I think it's even worse than that. Suppose you have a theory that
predicts all sorts of values for the number of fingers. But what you
actually see is that humans have 10 fingers. So if you were to use the
AP, then you'd say that humans have 10 fingers because otherwise they
wouldn't be fit to be here in this world, so you couldn't see them.


No, this is not what the anthropic principle says. You could only use
the anthropic principle to explain ten fingers if there was some
reason why people would be more likely to have ten fingers. Without
that, you can't use the anthropic principle, and the proponents are
not claiming that. You set up a straw man where you ridicule not the
anthropic principle, but your mischaracterization of it.

Jeffery Winkler

"Ioan Oprea" wrote in message
om...
(Levin) wrote in message
...
Let me try to understand the Anthropic Principle. Suppose I want to
explain from fundamental principles why humans have ten fingers.
I say, suppose humans would normally have 12 fingers. Then I would
most likely have 12 fingers, too. But in the world I live, I have only
10.
Thus, according to Anthropic Principle, humans must have 10 fingers.
This is not an accident, but has a Fundamental Scientific Reason.

I think it's even worse than that. Suppose you have a theory that
predicts all sorts of values for the number of fingers. But what you
actually see is that humans have 10 fingers. So if you were to use the
AP, then you'd say that humans have 10 fingers because otherwise they
wouldn't be fit to be here in this world, so you couldn't see them.



But that may actually be the case!

--
Dirk

The Consensus:-
The political party for the new millennium
http://www.theconsensus.org

Thanks to all who responded but I evidently failed to explain what
puzzles me. So I am still in the dark. Le me try again, slowly.

Any theory that contradicts the Anthropic Principle (AP) would also
contradict observations and so could be rejected without any Principle.
So, AP cannot help with selection of theories or predicting unknown
facts. It could only help to gain self-satisfaction of "explaining"
known facts. Self-satisfaction is a feeling notorious for often being
cheap, so one should be extra careful and extra clear with it.

Typically, AP explains observed phenomena X (e.g., values of some
parameters) by noting that they are necessary for existence of "life".
"Life" here is defined in many ways with confusing variance.
I saw it specified in generic terms, e.g., any processes that can
implement generic computations. A more vague, general concept was
"any sort of life that can fit our imagination". (I can only note
that our imagination is too feeble and hardly adequate for the task.)
I saw more restricted references to fermion-based life, barionic life,
carbon-based life, water-based planetary life, intelligent life.
To put it to extreme (and better match with the name of the Principle)
I stated my question with reference to 10-fingered Anthropic life.

My first question was which observed conditions Y are eligible here to be
used as (or instead of) a definition of life and which are not and why.
The second question was if there are any restrictions on the observed
phenomenon X (besides being clearly necessary for Y) required for
claiming that AP "explains" X. For instance, if Y is "carbon-based
life", could X be "existence of carbon"? Somehow, explanation that
"carbon must exist because it exists" does not seem very satisfying to me.

Please explain where the boundary lies, in such a way that I would
feel free to try to see if I can fit a ridiculous example within this
boundary. Failing to fit it is what brings a real satisfaction.

Thanks and sorry for perhaps missing something obvious, -Leonid Levin.

Thanks to all who responded but I evidently failed to explain what
puzzles me. So I am still in the dark. Let me try again, slowly.

Any theory that contradicts the Anthropic Principle (AP) would also
contradict observations and so could be rejected without any
Principle. So, AP cannot help with selection of theories or
predicting unknown facts. It could only help to gain self-satisfaction
of "explaining" known facts. Self-satisfaction is a feeling notorious
for often being cheap, so one should be extra careful and extra clear
with it.

Typically, AP explains observed phenomena X (e.g., values of some
parameters) by noting that they are necessary for existence of "life".
"Life" here is defined in many ways with confusing variance. I saw it
specified in generic terms, e.g., any processes that can implement
generic computations. A more vague, general concept was "any sort of
life that can fit our imagination". (I can only note that our
imagination is too feeble and hardly adequate for the task.) I saw
more restricted references to fermion-based life, barionic life,
carbon-based life, water-based planetary life, intelligent life. To
put it to extreme (and better match with the name of the Principle) I
stated my question with reference to 10-fingered Anthropic life.

My first question was which observed conditions Y are eligible here to be
used as (or instead of) a definition of life and which are not and why.
The second question was if there are any restrictions on the observed
phenomenon X (besides being clearly necessary for Y) required for
claiming that AP "explains" X. For instance, if Y is "carbon-based
life", could X be "existence of carbon"? Somehow, explanation that
"carbon must exist because it exists" does not seem very satisfying to
me.

Please explain where the boundary lies, in such a way that I would
feel free to try to see if I can fit a ridiculous example within this
boundary. Failing to fit it is what brings a real satisfaction.

Thanks and sorry for perhaps missing something obvious, -Leonid Levin.

(Leonid Levin) wrote in message ...

My first question was which observed conditions Y are eligible here to be
used as (or instead of) a definition of life and which are not and why.
The second question was if there are any restrictions on the observed
phenomenon X (besides being clearly necessary for Y) required for
claiming that AP "explains" X. For instance, if Y is "carbon-based
life", could X be "existence of carbon"? Somehow, explanation that
"carbon must exist because it exists" does not seem very satisfying to me.


What I meant was that since we are carbon-based lifeforms, our
existence means that we must have come into existence after the first
generation of stars created carbon, which puts a lower bound on the
age of universe, since there had to be enough time for stars to go
through our life cycle, and explains why we're in the present epoch
instead of earlier.

Jeffery Winkler

http://www.geocities.com/jefferywinkler

(Jeffery) wrote in message . com...
(Ioan Oprea) wrote in message
. com...

(Levin) wrote in message ...

Let me try to understand the Anthropic Principle. Suppose I want
to explain from fundamental principles why humans have ten
fingers. I say, suppose humans would normally have 12
fingers. Then I would most likely have 12 fingers, too. But in the
world I live, I have only 10. Thus, according to Anthropic
Principle, humans must have 10 fingers. This is not an accident,
but has a Fundamental Scientific Reason.

I think it's even worse than that. Suppose you have a theory that
predicts all sorts of values for the number of fingers. But what you
actually see is that humans have 10 fingers. So if you were to use the
AP, then you'd say that humans have 10 fingers because otherwise they
wouldn't be fit to be here in this world, so you couldn't see them.


No, this is not what the anthropic principle says. You could only use
the anthropic principle to explain ten fingers if there was some
reason why people would be more likely to have ten fingers. Without
that, you can't use the anthropic principle, and the proponents are
not claiming that. You set up a straw man where you ridicule not the
anthropic principle, but your mischaracterization of it.

Jeffery Winkler

Let's say you observe X. If life is more likely to exist if you have
X, then that explains why you observe X, since we're here to observe
it. Your problem is that you seem to think that we can say "life is
more likely to exist if you have X" for no other reason than the fact
we observe X, which leads to circular reasoning. However, in the
correct use of the anthropic principle, the sentence "life is more
likely to exist if you have X" is premised on something other than the
fact that we observe X. You have to have an actual reason why life
would be more likely if you have X.

Throughout biology, some variation of the anthropic principle works,
because life evolved to have the characteristics does, because
individuals with those characteristics were more likely to survive.
There are exceptions of course, such as the ten fingers. There is no
reason I can think of why ten fingers would be better than twelve
fingers, so you can't use the anthropic principle to explain it. We
have ten fingers because we happened to evolve from fish that had ten
bones in their fins.

Jeffery Winkler

http://www.geocities.com/jefferywinkler