"Jeffery" wrote in message
m...
Interstellar travel is impossible since it would take centuries or
millennia to reach other stars. Aliens are not going to spend 1000
years traveling to our star,

That only means that they shouldn't travel slowly. The effects of time
dilation imply that an alien can make a trip across the Milky Way Galaxy
(~100,000 light years in diameter) in an an arbitrarily small amouint of
time according to their onboard clock (including their bioligical "clocks")
if they travel close enough to the speed of light.

Also there are things like wormholes (if its possible to create one) and
warp drives (which may be theortically possible) that are now appearing in
the mainstream physics literature.

One needs to "think out of the box" for such travel.

There are two relevent journal articles that pertain to this

"Wormholes in spacetime and their use for interstellar travel: A tool for
teaching general relativity," Michael S. Morris and Kip S. Thorne, Am. J.
Phys. 56, 395 (1988)
****************************
Rapid interstellar travel by means of spacetime wormholes is described in a
way that is useful for teaching elementary general relativity. The
description touches base with Carl Sagan's novel Contact, which, unlike most
science fiction novels, treats such travel in a manner that accords with the
best 1986 knowledge of the laws of physics. Many objections are given
against the use of black holes or Schwarzschild wormholes for rapid
interstellar travel. A new class of solutions of the Einstein field
equations is presented, which describe wormholes that, in principle, could
be traversed by human beings. It is essential in these solutions that the
wormhole possess a throat at which there is no horizon; and this property,
together with the Einstein field equations, places an extreme constraint on
the material that generates the wormhole's spacetime curvatu In the
wormhole's throat that material must possess a radial tension 0 with the
enormous magnitude 0 ~ (pressure at the center of the most massive of
neutron stars) × (20 km)2/(circumference of throat)2. Moreover, this tension
must exceed the material's density of mass-energy, rho_o*c^2. No known
material has this T_o rho_o*c^2 property, and such material would violate
all the ``energy conditions'' that underlie some deeply cherished theorems
in general relativity. However, it is not possible today to rule out firmly
the existence of such material; and quantum field theory gives tantalizing
hints that such material might, in fact, be possible.
****************************
(Note: Thorne now thinks that such wormhole travel seems impossible)

"The interstellar traveler," C. Lagoute and E. Davoust, Am. J. Phys. 63, 221
(1995)
****************************
Abstract - We investigate the physics of an interstellar journey on board a
spaceship with a constant acceleration, in the framework of special
relativity. It is in principle possible to cross the Galaxy within a human
lifetime. The aspect of the sky seen from the spaceship is severely
distorted by relativistic aberration; most of the visible sky shrinks to a
small region of strongly enhanced luminance in the direction of motion,
leaving the rest of the celestial sphere almost entirely dark. The invisible
universe becomes perceptible by the traveler, as the infrared and radio
radiations are Doppler-shifted to visible frequencies in the direction of
motion. Navigational problems posed by these relativistic effects are
examined.
****************************

This is the proof of the nonexistence of UFOs. To claim otherwise is the
same as believing
in UFOs.

I have no opinion on that at this moment. But if I did believe in it then it
doesn't make me a bad person does it? :-)

However ... there was one time in 1980 when I was driving through the desert
in New Mexico ... but I have no idea what that was. But it was weird!

No matter what our technology, we'll never travel to other
stars except maybe nearby stars like Alpha Centauri which you could
reach in a few decades. Otherwise the distances are just too vast. You
just have no comprehension of interstellar distances.

Gee. I always thought I did!

If you claim
that aliens can travel to other inhabited worlds, then why not say
that an alien space craft crashed in Roswell, New Mexico in 1947?

Because a thing is possible does not mean that it happened. Back in 1980 it
was possible to wipe out almost all life on Earth. That of course didn't
mean that it happened. Perhaps we're not interesting enough or that nobody
has seen us since we became smart monkey's. That is a very short period of
time in the grand scheme of things. Perhaps aliens thought they'd check out
Earth 100,000 years ago and found nothing of interesting beyond the typical
wildlife which they see on all life sustaining planets


Pmb

Stephen Harris wrote:

"Borcis" wrote in message
...

Radi Khrapko wrote:

An answer to the Fermi's question, `Where are they?', is
presented.


How do you get at the notion that fine-tuning the universe for an unique
civilization should be less "extreme" than fine-tuning it for many
civilizations ? It seems you imply an appeal to an interestingly
pathological version of the principle of parsimony


There is no _purpose_ involved in what you call fine-tuning or evolution.


Please note that I was borrowing the vocabulary of Radi Khrapko. As for
the matter of "purpose" that you introduce, I don't see a difference
between postulating "purposes" and postulating "objective" prior
probability distributions where we can't sample. In all these cases we
are dreaming up, to our emergent observations, invisible backstages that
we find plausible (according to our respective tastes).

Probability theory is just one manner to systematize and force
consistency in similar reasoning, and anthropic issues mark the point
where probability theory language becomes no better than a fig leaf (if
only) because there isn't enough data for it to meaningfully apply.

I was just trying to point out in Radi Khrapko's abstract, a core idea
that's at once most particular and debatable, namely the idea that among
initial conditions to the Universe, ones such that only a single
intelligent civilization emerges should be easier to come by, than ones
such that many intelligent civilizations emerge. The abstract implied it
was obvious, and I was questioning why should one consider this obvious.

Taking your reaction as a data point (= assuming it to be somehow
relevant), suggests that one should consider this obvious because "there
is no Purpose". This provides a model to my notion of "an appeal to an
interestingly pathological version of the principle of parsimony".

"The Teleological Argument explains nothing and is fundamentally flawed
in its logic. In order for life to exist, the universe must havecertain
necessary properties, but it does not follow that the universe has
those properties for the purpose of creating life. "

To me even this debunking of "The Teological Argument" is flawed in its
logic by discussing purpose without defining it. Ascription of purpose
belongs to sociology, and in order to deny the soundness of its
transposition to cosmology (or evolution theory, for that matter) one
needs to first fix the shape of the transposition. IOW, I don't know
what "the purpose of creating life" is supposed to mean, and this being
given I can't agree on the assertion that it doesn't follow.


It is more accurate to call it a comparison of random events repeating
themselves in similar environments. Suppose there are only a trillion
random events which have to repeat identically to evolve life and lead
to a civilization. The odds of that sting of events repeating in this or
a billion universes like this one is vanishingly remote. There are a lot
of unknown variables in the Drake equation. You would have to
assume that only like 50 random events had to repeat in a suitable
environment in the universe to roughly duplicate our history.


As a matter of fact I don't think your usage of "random" is
enlightening. I looks to me like standard litterature jargon to say
exactly what I said - when I said that the assumption we are alone,
promotes to significance what we would otherwise tend to dismiss as
probable idiosyncrasies of our particular past - because it would
promote these conditions to plausible conditions of possibility, not
just of ourselves, but of intelligent life in general.

I don't like the
term fine-tuning


Once again, not mine.

because it suggests an intentional manipulation
of an anthropic nature to a culminating event composed actually
of random happenings along the way which produced the
potential for an observing civilization of a pre-existing process.


I see what you mean, but (according to the generally acknowledged causal
picture) of course the "random happenings" are themselves the
consequence of the initial state, as much as anything else that
"randomly" happens.

And - what allows you to distinguish what you call "random happenings",
is precisely that you view them not as random but as related to our
existence as observers, by a link of functional necessity.

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

"Torquemada" wrote in message . com...
This argument, and some more radical conclusions, are in Chapter 9 of Barrow
and Tipler's "The Anthropic Cosmological Principle". In fact, it's now
called the Barrow-Tipler argument.

Dear Torquemada,
I have no this book. I would be grateful if you could let me know
where else I can read this argument, and some more radical
conclusions, and who and where called it the Barrow-Tipler argument.
Note, the argument was not discussed at the conference entitled
{Anthropic Arguments in Fundamental Physics and Cosmology}, which was
held in Cambridge from 30 August to 1 September 2001.
Radi

(Radi Khrapko) wrote in message . com...
An answer to the Fermi's question, `Where are they?', is
presented. The answer is: we are alone because our Universe
is bad for a civilization. The combination of physical constants
does not need to be more fine tuned than is necessary to permit
one civilization and, since extreme fine tuning of the constants
is a very unlikely event, it is most likely that our Universe is
just good enough to permit development of only one
civilization. The alternative anthropic principle can be
formulated as follows: `It is most likely to observe a universe
in which civilized life is an extremely rare phenomenon.'

Astronomical and Astrophysical Transactions 22 (2003) 847-850

Radi Khrapko

It does not sound as a "new Anthropic Principle", it sounds as a
particular version of it. It is perfectly possible that probability
threshold is too low to meet another instance of life (as we perceive
it). However our perception of life is very limited by our
understanding of reality itself. Multiverse construct gives us way to
see enormously more complex picture of nature.

George

----- Original Message -----
From: "island"
Newsgroups: sci.physics.research
Sent: Saturday, December 27, 2003 1:48 AM
Subject: A New Anthropic Principle


Stephen Harris wrote:

There is no _purpose_ involved in what you call fine-tuning or
evolution.

Okay, I tried to keep my fingers quiet, but this has just gotten to be
too much!

A "new" Anthropic principle goes as follows, and please note that the
primary entropic inclination of every object in a big bang induced
expanding universe says that you cannot make an unfounded faith-like
philosophical leap outside of this primary inclination of natu


I've already show this group the physics of the entropic evolutionary
process by which the universe and humans commonly evolve, and yet they
continue as if nothing at all got said, even though I openly challenged
the group to "agree" that this is important... whatever... Whatever is
right!... Whatever happened to the good ole' days when John Baez, Matt,
Oz, Charles and others would be all over this for the neat and plausible
thing that it represents? I don't understand what's happend to this
place?


I don't see that your new version of the anthropic principle has much to do
with the new one presented by Radi Khrapko. Yours seems much like the
theory developed by biologists into self-organization/complexity.

Some people may not have been able to see what you were driving at
so here is a post which explains it a bit more clearly:

Guy Hoelzer of sci.bio.evolution
"I, too, think it is correct to say that there is a purpose to life for
the same reason that it is correct to say that there is a purpose to
the existence of any physical process in the universe. I think that
all of them ultimately serve to dissipate energy or matter across
spatial gradients of change, which is driven by the 2nd law of
thermodynamics (or a similar universal physical law that has yet to be
perfectly articulated). Life certainly does this. The only way that
life could stop doing this would be to cease as a process altogether
(total extinction)." end of quote

Guy also made a statement close to: The purpose of life is to extend or
improve the 2nd Law of Thermodynamics ability to dissipate energy
in a controlled manner. IOW, plantlife evolved because it could soak
up the sun's energy and then release it over an extended period.

Now before you can have a planet with a molten surface which will
cool down so that plantlife can evolve, you need a sun. Our sun could
not have happened early in the life of the universe because we have
carbon which is necessary for life.

There is a process by which helium and hydrogen stars eventually
go supernova and produce carbon which is necessary for our type
of life. It is just as logical to say that this process was directed by,
or given purpose by the 2nd Law of Thermodynamics because it
led to evolution and creation of life-supporting stars and planets
which then developed plantlife also to further the domain and
sovereignty of the 2nd Law of Thermodynamics. The argument
is a good deal less than compelling.

island wrote: Whatever is
right!... Whatever happened to the good ole' days when John Baez, Matt,
Oz, Charles and others would be all over this for the neat and plausible
thing that it represents? I don't understand what's happend to this
place?


SH: Your argument is hardly new. There are a lot of valid topics available
that deserve attention which takes time so responses have to be prioritized.
It is not all difficult to perceive your argument as handwaving from the
fringe.

I think there are causal processes and then processes which are concurrent
and caused by a common parent energy/force. It is a logical fallacy to
assign
causality between two observations when instead they are concurrent. Your
argument does not establish the 2nd law of thermodynamics or entropy as
the original cause of the Big Bang theory though they are both consequences
in the observed universe. It isn't known if all the forces were unified at
the
moment of the Big Bang and perhaps gravity is an exception. This idea of a
preferred direction comes up more often in biology, natural selection and
chance.

Regards,
Stephen

"Pmb" wrote


"Wormholes in spacetime and their use for interstellar travel: A tool
for teaching general relativity," Michael S. Morris and Kip S. Thorne,
Am. J. Phys. 56, 395 (1988)
[...........]
(Note: Thorne now thinks that such wormhole travel seems impossible)


Do you have a link to where Thorne talks about his new position?

Cheers,
Michael C Price
----------------------------------------
http://mcp.longevity-report.com
http://www.hedweb.com/manworld.htm

Thomas Palm wrote:
(Radi Khrapko) wrote in
om:


An answer to the Fermi's question, `Where are they?', is
presented. The answer is: we are alone because our Universe
is bad for a civilization. The combination of physical constants
does not need to be more fine tuned than is necessary to permit
one civilization and, since extreme fine tuning of the constants
is a very unlikely event, it is most likely that our Universe is
just good enough to permit development of only one
civilization. The alternative anthropic principle can be
formulated as follows: `It is most likely to observe a universe
in which civilized life is an extremely rare phenomenon.'

Astronomical and Astrophysical Transactions 22 (2003) 847-850


This is an interesting idea, but the answer is far from obvious. Assume
that there are 100 universes where intelligent life is so unlikely to occur
that it only happens on one place and 1 universe where it is a bit more
likely so it exist on 900 planets. Then there is 90% probability that we
live in the last one, even if most of the universes where life can occur
are more hostile.

By observing how common life is we may then draw some conclusion about
exactly how sensitive the parameters are that control the likelyhood of
life in the universe, although obviously statistics based on a single
sample is chancy.
Chancy is the word, because it is indeed a statistical argument. But why
is probability walking around in the disguise of a principle?

"Radi Khrapko" wrote in message
m...
"Torquemada" wrote in message
. com...
This argument, and some more radical conclusions, are in Chapter 9 of
Barrow
and Tipler's "The Anthropic Cosmological Principle". In fact, it's now
called the Barrow-Tipler argument.

Dear Torquemada,
I have no this book. I would be grateful if you could let me know
where else I can read this argument, and some more radical
conclusions, and who and where called it the Barrow-Tipler argument.
Note, the argument was not discussed at the conference entitled
{Anthropic Arguments in Fundamental Physics and Cosmology}, which was
held in Cambridge from 30 August to 1 September 2001.
Radi

groups.google.com is a widely used search engine. Also at xxx.lanl.gov
one can use keywords to search for papers.

http://nedwww.ipac.caltech.edu/level...eacock3_5.html
"Suppose we imagine some process that produces an ensemble of a large number
of universes with widely varying properties or even physical laws. What the
weak anthropic principle points out is that only those members of the
ensemble that are constructed so as to admit the production of intelligent
life at some stage in their evolution will ever be the subject of
cosmological enquiry. The fact that we are observers means that, if the
production of life is at all a rare event, any universe that we can see is
virtually guaranteed to display bizarre and apparently improbable
coincidences.

THE STRONG ANTHROPIC PRINCIPLE The ultimate form of anthropic reasoning is
to assert that the coincidences we have remarked on are more than that: that
the universe must be such as to admit the production of intelligent life at
some time. This idea is known as the strong anthropic principle. Is such an
idea a part of testable science? The whole basis of the weak anthropic
principle is the argument that life-free universes cannot be observed, and
observations of these counter-examples would be required in order to falsify
the strong anthropic principle. However, this extension of anthropic ideas
does have some attractions. Much weak anthropic reasoning invokes the
generation of an ensemble of universes, but we have no idea whether such a
concept is valid. It does apply to certain forms of inflationary cosmology,
but it is equally possible that there is only one universe. In this case of
a unique event, the arguments of statistical selection effects that lie at
the core of weak anthropic reasoning are less satisfying; was it inevitable
that life should arise on the one occasion that it has a chance? A possible
position here is that the universe was designed for life, but this does not
constitute a mechanism within the bounds of physics for enforcing a strong
anthropic principle. It is consistent with the facts, but is in no way a
proof for the existence of a creator. More profitable ideas are to be found
in the area of the interpretation of quantum mechanics, which is a topic
discussed to some extent in chapter 6 (chapter 7 of Barrow & Tipler 1986
gives a full discussion of the relation between quantum and anthropic
ideas). Here, the role of the observer is critical in determining how the
universe evolves. In the (almost) standard ``Copenhagen'' interpretation,
the critical events in time are the moments of wave-function collapse when
the act of observation singles out a concrete state from undetermined
possibilities (e.g. spin up or down?). In this sense, the act of the
observer is necessary in order to bring the universe into being at all."

SH: If the act of the observer is necessary in order to bring the universe
into being
then one would normally think that the observer exists prior to the
existence of the
universe in order to act upon it. However, a fair amount of people believe
the universe
existed first and that observers evolved from or within that universe.
Barrow and Tipler make an effort to dispel what appears to be a chicken and
the egg, which came
first, time paradox.

Another resource for papers is citeseer:
http://citeseer.nj.nec.com/calude94algorithmically.html
"We may observe, following Davies [17], that "random" events in the Universe
"may not be random at all". As we previously noticed, randomness is not
algorithmically testable: A sequence of quantum mechanical measurements
appears random, but we cannot prove this!"

Paul Davies: "The building blocks of life are easy to make because their
synthesis is thermodynamically favoured. But stringing them together in an
aqueous environment into complex molecular chains like proteins and RNA is
thermodynamically 'uphill'. Just as a pile of bricks alone don't make a
house, so organic building blocks alone don't make life. Put a stick of
dynamite under a pile of bricks, and you don't make a house, you just make a
mess. In the same way, merely throwing energy willy-nilly at a collection of
amino acids, for example, to drive it against the thermodynamic gradient,
won't produce a protein. Just as a house requires the delicate assembly of
bricks into an elaborate and specific arrangement, so amino acids need to be
carefully linked in a precise way to make a functional protein, rather than
gunk. The same goes for nucleic acids.

http://xxx.lanl.gov/abs/astro-ph/9903225 Entropic Principles, by John D.
Barrow

http://xxx.lanl.gov/abs/hep-th/0309170
We examine recent claims of a large set of flux compactification solutions
of string theory. We conclude that the arguments for AdS solutions are
plausible. The analysis of meta-stable dS solutions inevitably leads to
situations where long distance effective field theory breaks down. We then
examine whether these solutions are likely to lead to a description of the
real world. We conclude that one must invoke a strong version of the
anthropic principle. We explain why it is likely that this leads to a
prediction of low energy supersymmetry breaking, but that many features of
anthropically selected flux compactifications are likely to disagree with
experiment.

www.altavista.com search engine returned:
http://www.geocities.com/robleh.geo/...trial_life.htm
Barrow-Tipler Argument against Extra-Terrestrial Life

In Chapter 9 of their book The Anthropic Cosmological Principle, physicists
John Barrow and Frank Tipler propose an argument they claim shows that
Extra-Terrestrial Intelligent life does not exist anywhere in our Galaxy.

http://xxx.lanl.gov/abs/hep-th/0211048 by Andre Linde (SH: Really good!)
Inflation, Quantum Cosmology, and the Anthropic Principle
http://www.anthropic-principle.com/primer.html
Anthropic principle can help us to understand many properties of our
world. However, for a long time this principle seemed too metaphysical and
many scientists were ashamed to use it in their research. I describe here a
justification of the weak anthropic principle in the context of inflationary
cosmology and suggest a possible way to justify the strong anthropic
principle using the concept of the multiverse. A total of over thirty
anthropic principles have been formulated and many of them have been defined
several times over-in nonequivalent ways-by different authors, and sometimes
even by the same authors on different occasions. Not surprisingly, the
result has been some pretty wild confusion concerning what the whole thing
is about. Some reject anthropic reasoning out of hand as representing an
obsolete and irrational form of anthropocentrism. Some hold that anthropic
inferences rest on elementary mistakes in probability calculus. Some
maintain that at least some of the anthropic principles are tautological and
therefore indisputable. Tautological principles have been dismissed by some
as empty and thus of no interest or ability to do explanatory work.

Necessary but sufficient?
Stephen

Radi Khrapko wrote:
An answer to the Fermi's question, `Where are they?', is
presented. The answer is: we are alone because our Universe
is bad for a civilization. The combination of physical constants
does not need to be more fine tuned than is necessary to permit
one civilization and, since extreme fine tuning of the constants
is a very unlikely event, it is most likely that our Universe is
just good enough to permit development of only one
civilization. The alternative anthropic principle can be
formulated as follows: `It is most likely to observe a universe
in which civilized life is an extremely rare phenomenon.'

Astronomical and Astrophysical Transactions 22 (2003) 847-850

Radi Khrapko


Another way to say the same thing is: If civilizations are common then
the earth would have been colonized a long time ago and we (a
pre-starflight culture) wouldn't be here.

--

Jeffery wrote:

What on Earth makes you suspect that Earth is the only world with life
in the universe?

There is not an iota of evidence indicating life elsewhere.

Bob Kolker