| WIKI | FAQ | Tech FAQ | |
 http://csua.com/feed/ | |
| ||||||
| 3/15 |
| 2005/8/10-13 [Computer/HW] UID:39084 Activity:kinda low |
8/10 The thread below has digressed into wikipedia ramblings, so I'll ask
here. I read the essay "Intelligent Design: The Scientific Alternative
to Evolution"
(found here: http://www.intelligentdesignnetwork.org/publications.htm
this weekend trying to figure out what ID proponents are actually
saying. From reading this I found that the authors were making
strawman arguments against evolution and didn't appear to understand
physical science or probability. Have you read this essay? Do any ID
proponents ever address the weak anthropic principle? Is the 10^-150
probability the number they use in general to show something as
unreasonably improbable? -emarkp
\_ Math is hard. Big numbers are scary. Someone must have done it.
\_ I don't understand what the weak anthropic principle is supposed to
explain. I think 'cosmological constant tuning' needs an answer.
On a somewhat related note, I read an article somewhere that some
experimental data shows that possibly some constants aren't really
constant, and change somewhat as time passes. -- ilyas
\_ In that essay I mentioned (in the section "The Fine Tuning of the
Universe") the authors say: "The force of gravity, the mass of
the electron, the charge of the proton, etc. are specific, real
values. Were they even slightly different from what they are, not
only would life not exist, nothing (of any significance) would
exist." They argue that this specifically suggests design. But
the weak anthropic principle is that if the universe weren't
tuned to life, then we wouldn't be here to observe it. This
directly contradicts their assertion--they should at least
address it. The fact that they don't even mention it is
suspicious at best. -emarkp
\_ It is a counterfactual assertion that does not render the
current state of affairs any less puzzling. Sure, if constants
were different nobody would be there to comment. But someone
IS there to comment, and constants ARE the way they are.
-- ilyas
current state of affairs any less puzzling. Sure, if
constants were different nobody would be there to comment.
But someone IS there to comment, and constants ARE the way
they are. -- ilyas
\_ The point is there is a selecting event (i.e. our
existence) which makes those constants unremarkable. If
we were to observe a universe at random and the constants
were amenable to life, that might be something. But our
universe isn't a random one. It had to have those
constants. -emarkp
\_ What you said is exactly right. Our universe doesn't
seem to be a random one.
\_ Let's imagine a lottery winner pondering what events
lead to his winning ticket. He might say: 'well given
that I _did_ win, the particles in the Universe must
have danced just right so I had to have won. So the
fact that I won (at odds of millions to one) is wholly
unremarkable.' Really, the real reason it's not
remarkable is because millions of people played, so
someone had to have won. In other words, lots of
Universes makes our constant unremarkable. Our
existence does not. -- ilyas
\_ But should the lottery winner conclude that
someone chose him to be the winner? -emarkp
\_ He shouldn't he if knows lots of people
played (parallel Universes). Except in
our case, it's unclear whether it's
cheaper to assume lots of players or
a benign lottery agency. I think this
is best taken 'offline.' -- ilyas
\_ Then your analogy falls on its face.
An unlikely event occurs (Bob wins the
lottery). It doesn't follow that Bob
was chosen by a designer. -emarkp
\_ No, it doesn't follow. I wasn't
saying it does. As I said,
Bob knows lots of people play the
lottery. We don't know whether
lots of people play or whether
someone just decided to give us
the ticket. Not only do we not
know, we don't even know whether
it's more _likely_ lots of people
play, or whether someone gave us
a winning ticket. That's the point,
we have less information than Bob
about our situation. But, just as
in Bob's situation, the anthropic
principle doesn't explain anything,
something else does. My point is,
despite the fact our state of
knowledge is different from Bob's
the two situations are exactly the
same, and in Bob's situation, nobody
invokes the anthropic principle.
So we shouldn't invoke it in our
case either, because our state of
belief shouldn't matter as far as
explanations are concerned. -- ilyas
\_ (1) It's "an"thropic.
(2) It's not invoked to explain
anything. It's invoked to show
that the reasoning that
Life=>special is specious.
-emarkp
\_ Anyways, what is your answer
to the following:
P(C=true,L=true) is low, yet
C=true and L=true. Are you
claiming the above probability
isn't low? If so, why? I
claim it is low on
'maximum entropy' grounds.
Notice how the anthropic
principle cannot be used to
answer this question, although
it is essentially the same:
life + constants -> special.
-- ilyas
\_ I know I'm going to regret
getting back into this,
but if P(C) is the
probability that the
laws of physics create
a universe conducive to
the rise of intelligent
life, C=>L. -tom
\_ No, P(C) is the
probability the constants
assume the values they do
in our Universe. -- ilyas
probability the
constants assume the
values they do in our
Universe. -- ilyas
\_ Same conclusion:
C=>L. -tom
\_ I mean what you say
is true, but I
don't see how this
observation helps.
You can conclude
that P(C) <= P(L),
but how does this
address the
question about
P(C,L)? -- ilyas
\_ I mean what you
say is true,
but I don't see
how this
observation
helps. You can
conclude that
P(C) <= P(L),
but how does
this address
the question
about P(C,L)?
-- ilyas
\_ The question
about P(C,L)
is not
meaningful,
since life will
arise if the
conditions
exist for it.
The only
relevant
part is
P(C). -tom
_______________________/
Just because C implies L does not mean
P(C) fully determines P(C,L). For that
to happen you would need C iff L.
I don't understand why event implication
means questions about the joint
distribution are not 'meaningful.'
They seem perfectly meaningful (and
puzzling) to me. -- ilyas
to happen you would need C iff L. I
don't understand why event
implication means questions about
the joint distribution are not
'meaningful.' They seem perfectly
meaningful (and puzzling) to me.
-- ilyas
\_ I was right; I regret getting back
into it. -tom
\_ Go pee somewhere else then.
\_ Non sequitur. We know precisely nothing about any
other universes. If you can point to another
universe that we can observe that has the same (or
similar) constants, that would say something. Since
we can't (yet? ever?) observe other universes, we
can't evaluate how random this one is. -emarkp
\_ Let L be an event 'life exists.' Let C be an
an event 'cosmological constants have the values
they hold in our Universe.' Your claim: P(C|L)
is high. My claim: P(C) is low. That P(C|L) is
high does not explain why C is true, though P(C)
is low. P(C|L) is high just because of the way
conditional probability works. To put it another
way, you have to explain why L is true, even
though P(C,L=true) is low. Or if you like, you
can marginalize out C, and reasonably claim
P(L=true) is also low. Or to put it yet another
way, you are offering features of the distribution
P as an explanation for why we have P and not
some other distribution P*. Naturally, that
kind of argument doesn't make sense. -- ilyas
P(L=true) is also low. That's an entirely
symmetric question, and an entirely symmetric
argument would be 'life exists because our
cosmological constants are the way they are.'
At this point, the argument becomes circular, and
I can ask a question about the joint event:
i.e. why is C=true and L=true, though
P(C=true,L=true) is low. Saying 'it's true
because it happened' isn't answering anything.
-- ilyas
\_ No, I don't "have to explain why L is true".
ID says P(C) is low, thus we were designed.
But that doesn't follow. All we know is that
P(C|L) is nonzero, and that P(~C|L) = 0.
Also, we don't actually know that P(C) is low
in the first place. -emarkp
\_ So you are saying that the joint probability
of the constants being what they are, and
life existing is high? How do you figure
that? -- ilyas
\_ No, I'm saying that P(~C|L) appears to be
low (I think my statement that it =0 may
too strong) and that P(C|L) is nonzero.
Everything else is being pulled out of
someone's rear end. -emarkp
\_ Well, you are right that I am making
an assumption that P(C,L) is
reasonably uniform, but this is a
common assumption in science
(see 'maximum entropy'). The anthropic
principle doesn't answer the 'joint
event question.' If you make the
argument that P(C,L) isn't low then
you have to explain why maximum
entropy isn't an appropriate assumption
to make. -- ilyas
(see 'maximum entropy'). The
anthropic principle doesn't answer
the 'joint event question.' If you
make the argument that P(C,L) isn't
low then you have to explain why
maximum entropy isn't an
appropriate assumption to make.
-- ilyas
\_ Dear lord...I actually find this
conversation interesting. I
think I'd better lie down until
it goes away. -mice
\_ (1) Do we know that P(~C|L) = 0? If either
\_ I already retracted
the claim. -emarkp
\_ sorry, just
saw that.
the fundamental constants change over
time (some evid that they might) or
changes in one could be offset by
changes in another (perhaps yet
unknown constant - there is still
that pesky problem of dark matter and
dark energy) then P(~C|L) may not
be zero weaking the case for design.
(2) What exactly is L? Do we really know?
We have only one data point to look
at. Perhaps other arrangements can
give rise to L.
(3) Why is it less probable that ID is
the answer than say some natural
process that produces an infinite
number of universes? If you have
an infinite number of universes
then you will have an infinite
number of universes EXACTLY like
our own.
\_ I find ilyas arguing FOR intelligent design AGAINST
a Mormon to be highly amusing.
\_ Yeah, because people must always argue from an
agenda, and not just follow where the argument
might lead. Grow up. -- ilyas
\_ ilyas, you always have an agenda.
\_ Grow up anonymous troll. -emarkp
\_ My agenda is to legislate Jesus into
your heart. -- ilyas
\_ You're hurting me. -mice
\_ Width of universe compared to age of universe compared to speed
of light taught me that.
\_ http://www.eso.org/outreach/press-rel/pr-2004/pr-05-04.html
"contrary to previous claims, no evidence exist for assuming a
time variation of this fundamental constant [fine structure
constant]"
http://www.sciencedaily.com/releases/2005/04/050418204410.htm |
| www.intelligentdesignnetwork.org/publications.htm Teaching Origins Science in Public Schools: Memorandum and Opinion , by John H Calvert, Esq. and William S Harris, PhD (as to matters of science), dated March 21, 2001. and Ray Vasvari, JD, Legal Director of the ACLU of Ohio, as moderated by Walter Maripole, Host of the Civic Forum of the Air. This video explores what students are being taught about evolution and why the teaching does not mention the raging scientific controversy over darwinian evolution. htm :: Signs of Intelligence: Understanding Intelligent Design, Edited by Wil liam A Dembski and James M Kushiner, (Brazos Press, 2002). Jonathan Wells, PhD, a cell and molecular biologist, with illustrati ons by Jody Sjogren, MS, CMI (Certified Medical Illustrator). This is a video of Woody's performance at the Na tional Symposium on Intelligent Design held in Kansas City on July 14, 2 000. Remarks of John H Calvert, JD to the Science Standards Committee o f the Ohio State Board of Education on January 13, 2002. Ending the War Between Science and Religion, by John H Calvert, JD and William S Harris, PhD, November 8, 2001. PROPOSALS MADE BY MEMBERS OF IDnet RELATING TO THE FIFTH WORKING DRAF T OF THE KANSAS SCIENCE EDUCATION STANDARDS, August 9, 1999. IDnet Letter to the Kansas State Board, dated September 12, 2000, in response to the remarks of Adrian Melott to the Board on September 12, 2 000. NATURALISM AND ITS SIEGE ON PRATT: A response to Jack Krebs' recent letter to the Pratt Tribune, Published in the Pratt Tribune, December 6, 2000, by John H Calvert. |
| www.eso.org/outreach/press-rel/pr-2004/pr-05-04.html ESO Press Release 05/04 31 March 2004 For immediate release New Quasar Studies Keep Fundamental Physical Constant Constant Very Large Telescope sets stringent limit on possible variation of the fine-structure constant over cosmological time Summary Detecting or constraining the possible time variations of fundamental phy sical constants is an important step toward a complete understanding of basic physics and hence the world in which we live. Previous astronomical measurements of the fine structure constant - the d imensionless number that determines the strength of interactions between charged particles and electromagnetic fields - suggested that this part icular constant is increasing very slightly with time. If confirmed, thi s would have very profound implications for our understanding of fundame ntal physics. New studies, conducted using the UVES spectrograph on Kueyen, one of the 82-m telescopes of ESO's Very Large Telescope array at Paranal (Chile), secured new data with unprecedented quality. These data, combined with a very careful analysis, have provided the strongest astronomical constr aints to date on the possible variation of the fine structure constant. They show that, contrary to previous claims, no evidence exist for assum ing a time variation of this fundamental constant. PR Photo 07/04: Relative Changes with Redshift of the Fine Structure Constant (VLT/UVES) A fine constant To explain the Universe and to represent it mathematically, scientists re ly on so-called fundamental constants or fixed numbers. The fundamental laws of physics, as we presently understand them, depend on about 25 suc h constants. Well-known examples are the gravitational constant, which d efines the strength of the force acting between two bodies, such as the Earth and the Moon, and the speed of light. The fine structure constant de scribes how electromagnetic forces hold atoms together and the way light interacts with atoms. But are these fundamental physical constants really constant? Are those n umbers always the same, everywhere in the Universe and at all times? Contemporary theories of fu ndamental interactions, such as the Grand Unification Theory or super-st ring theories that treat gravity and quantum mechanics in a consistent w ay, not only predict a dependence of fundamental physical constants with energy - particle physics experiments have shown the fine structure con stant to grow to a value of about 1/128 at high collision energies - but allow for their cosmological time and space variations. A time dependen ce of the fundamental constants could also easily arise if, besides the three space dimensions, there exist more hidden dimensions. Already in 1955, the Russian physicist Lev Landau considered the possibil ity of a time dependence of alpha. In the late 1960s, George Gamow in th e United States suggested that the charge of the electron, and therefore also alpha, may vary. It is clear however that such changes, if any, ca nnot be large or they would already have been detected in comparatively simple experiments. Tracking these possible changes thus requires the mo st sophisticated and precise techniques. Looking back in time In fact, quite strong constraints are already known to exist for the poss ible variation of the fine structure constant alpha. It is based on measures taken in the ancient n atural fission reactor located near Oklo (Gabon, West Africa) and which was active roughly 2,000 million years ago. By studying the distribution of a given set of elements - isotopes of the rare earths, for example o f samarium - which were produced by the fission of uranium, one can esti mate whether the physical process happened at a faster or slower pace th an we would expect it nowadays. Thus we can measure a possible change of the value of the fundamental constant at play here, alpha. However, the observed distribution of the elements is consistent with calculations a ssuming that the value of alpha at that time was precisely the same as t he value today. Over the 2 billion years, the change of alpha has theref ore to be smaller than about 2 parts per 100 millions. If present at all , this is a rather small change indeed. But what about changes much earlier in the history of the Universe? To measure this we must find means to probe still further into the past. Because, even though astronomers c an't generally do experiments, the Universe itself is a huge atomic phys ics laboratory. By studying very remote objects, astronomers can look ba ck over a long time span. In this way it becomes possible to test the va lues of the physical constants when the Universe had only 25% of is pres ent age, that is, about 10,000 million years ago. Very far beacons To do so, astronomers rely on spectroscopy - the measurement of the prope rties of light emitted or absorbed by matter. When the light from a flam e is observed through a prism, a rainbow is visible. When sprinkling sal t on the flame, distinct yellow lines are superimposed on the usual colo urs of the rainbow, so-called emission lines. Putting a gas cell between the flame and the prism, one sees however dark lines onto the rainbow: these are absorption lines. The wavelength of these emission and absorpt ion lines is directly related to the energy levels of the atoms in the s alt or in the gas. The fine structure of atoms can be observed spectroscopically as the spli tting of certain energy levels in those atoms. So if alpha were to chang e over time, the emission and absorption spectra of these atoms would ch ange as well. One way to look for any changes in the value of alpha over the history of the Universe is therefore to measure the spectra of dist ant quasars, and compare the wavelengths of certain spectral lines with present-day values. Quasars are here only used as a beacon - the flame - in the very distant Universe. Interstellar clouds of gas in galaxies, located between the qu asars and us on the same line of sight and at distances varying from six to eleven thousand of million light years, absorb parts of the light em itted by the quasars. The resulting spectrum consequently presents dark "valleys" that can be attributed to well-known elements. If the fine-structure constant happens to change over the duration of the light's journey, the energy levels in the atoms would be affected and t he wavelengths of the absorption lines would be shifted by different amo unts. By comparing the relative gaps between the valleys with the labora tory values, it is possible to calculate alpha as a function of distance from us, that is, as a function of the age of the Universe. These measures are however extremely delicate and require a very good mod elling of the absorption lines. They also put exceedingly strong require ments on the quality of the astronomical spectra. They must have enough resolution to allow very precise measurement of minuscule shifts in the spectra. And a sufficient number of photons must be captured in order to provide a statistically unambiguous result. For this, astronomers have to turn to the most advanced spectral instrume nts on the largest telescopes. Captions: ESO PR Photo 07/04 shows measured values of the relative change of alpha from the sample of absorption systems studied by Hum Chand and his colleagues, plotted as a function of the redshift and the correspon ding look-back time. The open circle is the measurement from the Oklo na tural reactor. The horizontal long dashed lines show the area of the pre vious claim of variation of the fine structure constant. Clearly, the ne w UVES data are inconsistent with this range. They recorded the spectra of quasars over a total of 34 nights to achieve the highest possible spectral resolution and the best signal-to-noise ratio. Sophisticated automatic procedures speciall y designed for this programme were applied. In addition, the astronomers used extensive simulations to show that they can correctly model the line profiles to recover a possible variation o f alpha. The result of this extensive study is that over the last 10,000 million y ears, the relative variation of alpha must be less than 06 part per mil lion. This is... |
| www.sciencedaily.com/releases/2005/04/050418204410.htm Email to friend Galaxy Observations Show No Change In Fundamental Physical Constant Tampa, Fla. Their distance from us (7 bill ion light years or more) means that the light we see today left these ga laxies when the universe was less than half as old as it is today. Scientists Discover One Of The Constants Of The Universe Might Not B e Constant (May 12, 2005) -- Physical constants are one of the cornersto nes of physics -- sacred numbers which we know to be fixed -- but what i f some of these constants are changing? Speed Of Light May Not Be Constant, Physicist Suggests (October 6, 1 999) -- A University of Toronto professor believes that one of the most sacrosanct rules of 20th-century science -- that the speed of light has always been the same - is wrong. Astrophysicists Detect Cosmic Shear, Evidence Of Dark Matter (May 11 , 2000) -- Astrophysicists supported by the National Science Foundation (NSF) have announced the first observations of cosmological shear, an ef fect predicted by Einstein's theory of relativity. Discovery Pushes Back Boundaries Of Known Universe (March 13, 1998) -- Astronomers have set a new record for most distant object ever seen, finding a galaxy nearly 90 millions light years farther away than any ev er spotted ... The results are being reported today (Monday, April 18) at the annual mee ting of the American Physical Society (APS) by astronomer Jeffrey Newman , a Hubble Fellow at Lawrence Berkeley National Laboratory representing DEEP2, a collaboration led by the University of California, Berkeley, an d UC Santa Cruz. Newman is presenting the data and an update on the DEEP 2 project at a 1 pm EDT press conference at the Marriott Waterside Hot el in Tampa, Fla. The fine structure constant, one of a handful of pure numbers that occupy a central role in physics, pops up in nearly all equations involving el ectricity and magnetism, including those describing the emission of elec tromagnetic waves - light - by atoms. Despite its fundamental nature, ho wever, some theorists have suggested that it changes subtly as the unive rse ages, reflecting a change in the attraction between the atomic nucle us and the electrons buzzing around it. Over the past few years, a group of Australian astronomers has reported t hat the constant has increased over the lifetime of the universe by abou t one part in 100,000, based on its measurements of the absorption of li ght from distant quasars as the light passes through galaxies closer to us. Other astronomers, however, have found no such change using the same technique. The new observations by the DEEP2 survey team use a more direct method to provide an independent measure of the constant, and show no change with in one part in 30,000. "The fine structure constant sets the strength of the electromagnetic for ce, which affects how atoms hold together and the energy levels within a n atom. At some level, it is helping set the scale of all ordinary matte r made up of atoms," Newman said. "This null result means theorists don' t need to find an explanation for why it would change so much." The fine structure constant, designated by the Greek letter alpha, is a r atio of other "constants" of nature that, in some theories, could change over cosmic time. Equal to the square of the charge of the electron div ided by the speed of light times Planck's constant, alpha would change, according to one recent theory, only if the speed of light changed over time. Some theories of dark energy or grand unification, in particular t hose that involve many extra dimensions beyond the four of space and tim e with which we are familiar, predict a gradual evolution of the fine st ructure constant, Newman said. DEEP2 is a five-year survey of galaxies more than 7-to-8-billion-light ye ars distant whose light has been stretched out or redshifted to nearly d ouble its original wavelength by the expansion of the universe. Though t he collaborative project, supported by the National Science Foundation, was not designed to look for variation in the fine structure constant, i t became clear that a subset of the 40,000 galaxies so far observed woul d serve that purpose. "In this gigantic survey, it turns out that a small fraction of the data seems to be perfect for answering the question Jeff's asking," said DEEP 2 principal investigator Marc Davis, professor of astronomy and of physi cs at UC Berkeley. "This survey is really general purpose and will serve a million uses." Several years ago, astronomer John Bahcall of the Institute for Advanced Study pointed out that, in the search for variations in the fine structu re constant, measuring emission lines from distant galaxies would be mor e direct and less error-prone that measuring absorption lines. Newman qu ickly realized that DEEP2 galaxies containing oxygen emission lines were perfectly suited to provide a precise measure of any change. "When the contradictory results from absorption lines starting showing up , I had the idea that, since we have all these high redshift galaxies, m aybe we can do something not with absorption lines, but with emission li nes within our sample," Newman said. "Emission lines would be very sligh tly different if the fine structure constant changed." The DEEP2 data allowed Newman and his colleagues to measure the wavelengt h of emission lines of ionized oxygen (OIII, that is, oxygen that has lo st two electrons) to a precision of better than 001 Angstroms out of 5, 000 Angstroms. An Angstrom, about the width of a hydrogen atom, is equiv alent to 10 nanometers. "This is a precision surpassed only by people trying to look for planets, " he said, referring to detection of faint wobbles in stars due to plane ts tugging on the star. The DEEP2 team compared the wavelengths of two OIII emission lines for 30 0 individual galaxies at various distances or redshifts, ranging from a redshift of about 04 (approximately 4 billion years ago) to 08 (about 7 billion years ago). The measured fine structure constant was no differ ent from today's value, which is approximately 1/137. There also was no upward or downward trend in the value of alpha over this 4-billion-year time period. "Our null result is not the most precise measurement, but another method (looking at absorption lines) that gives more precise results involves s ystematic errors that cause different people using the method to come up with different results," Newman said. Newman also announced at the APS meeting the public release of the first season of data (2002) from the DEEP2 survey, which represents 10 percent of the 50,000 distant galaxies the team hopes to survey. DEEP2 uses the DEIMOS spectrograph on the Keck II telescope in Hawaii to record redshi ft, brightness and color spectrum of these distant galaxies, primarily t o compare galaxy clustering then versus now. The survey, now more than 8 0 percent complete, should finish observations this summer, with full da ta release by 2007. "This is really a unique data set for constraining both how galaxies have evolved and how the universe has evolved over time," Newman said. "The Sloan Digital Sky Survey is making measurements out to about redshift 0 2, looking back the last 2-3 billion years. We really start at redshift 07 and peak at 08 or 09, equivalent to 7-8 billion years ago, a time when the universe was half as old as it is today." The survey also has completed measurements that could shed light on the n ature of dark energy - a mysterious energy that permeates the universe a nd seems to be causing the universe's expansion to accelerate. The team now is modeling various theories of dark energy to compare theoretical p redictions with the new DEEP2 measurements. As Davis explained it, the amount of dark energy, now estimated to be 70 percent of all the energy in the universe, determines the evolution of g alaxies and clusters of galaxies. By counting the number of small groups and massive clusters of galaxies in a distant volume of space as a func tion of their redshift and mass, it is possible to measure the amount by which the universe has expanded to the present day, which depends on th e nature of dark energy. If there are ... |