Comments by Geraint

1. Dark Matter And Dark Energy Make Up 95 Percent Of Universe, Detailed Measurements Reveal

Comment #429722 by Geraint on November 5, 2009 at 5:37 pm

There's a page eplaining CMB physics here, which might be useful to people trying to understand the polarization stuff:
http://background.uchicago.edu/~whu/

It does get quite technical though. The scattering of light from free electrons does depend on polarization. The reason you end up with a net polarization at some point rather than everything cancelling out is because radiation reflected from different directions ends up with a different polarization. A region of the Universe will receive different amounts of radiation from different directions (because the Universe isn't completely homogeneous).

The signal is weak though: polarization measurements are much harder to do than total intensity measurements.

Regarding the amount of 'ordinary matter' in the Universe, current estimates are that it makes up about 4.6% of the critical density. Dark matter makes up about 22.8%, so you end up with a total of about 27% of the critical density coming from matter. The rest comes mainly from dark energy, with a very small contribution from radiation. It's thought that the total comes to something very close to 100% of the critical density.

2. I am become Death, destroyer of worlds

Comment #427708 by Geraint on October 28, 2009 at 7:21 pm

Comment #427676 by Sally Luxmoore

I am still reading that paper you referenced - but one quick question - I see that K-T means "Cretaceous–Tertiary" (something I had not known before) but why 'K'? Is it because 'C' is taken by 'Cambrian'?

I think the Carboniferous was the first to bag 'C'.

3. Creation

Comment #383719 by Geraint on June 1, 2009 at 12:35 pm

I can't read this sentence without hearing that deep, gravelly American voice which does the voice-over on adverts for trite, one-dimensional money-spinners.

Unfortunately, the guy you're probably thinking of died last year:
http://news.bbc.co.uk/1/hi/entertainment/7595352.stm

Spawned a thousand imitators though I suppose.

4. Why is Charlotte Allen so mad at atheists?

Comment #380098 by Geraint on May 22, 2009 at 2:33 pm

If I recall correctly, there have been cases in the courts in which it had to be determined whether bridge was a game of chance (and so whether it came under gambling regulations). I know the result was that it was found not to be a game of chance, but I don't remember the details.

5. Believe Me, It's Torture

Comment #372047 by Geraint on May 1, 2009 at 2:34 pm

Well, quite a few people come to cosmology from a particle physics angle; many also come having specialised more in astronomy as undergraduates. That applies especially to cosmologists who don't focus on the very early Universe. Sometimes it seems to me that when someone says "cosmology", a lot of people (even physicists outside astronomy) think straight away of very early Universe cosmology and all the relatively speculative things that go with it.

A great deal of what's considered to be cosmology is instead to do with the subsequent evolution of the contents and structure in the Universe, which depends far less on speculative physics, and more on 'standard' physics but complicated astrophysics (the details of galaxy formation, for example). This is why I have a problem with the generalizations you sometimes see about 'problems' with the subject. To assess a lot of the ideas and results in modern cosmology, a good knowledge of astronomy would be more important than detailed knowledge of particle physics. I'd agree with bethe123 that general relativity is required, of course. I only quibble because I think that the average student who's taken physics to a high level is more likely to have missed out on advanced astronomy courses than advanced particle physics or GR courses. It's certainly the former that I had to catch up on when I started research in cosmology, having come from an applied maths background.

6. Believe Me, It's Torture

Comment #369928 by Geraint on April 25, 2009 at 8:23 am

Quantum Flux
All observations for black holes are based on telescopic images thousands of light years away, in fact the images show a lot of gamma radiation eminating from them which means they're not "black". Astronomers claim that this is due to violent ripping apart of particles entering "the event horizon".....none of that has been directly observerd, it is merely assumed that on the quantum scale things are behaving that way. An assumption of quantum behaviours is by no means a direct observation of behaviours in my book. There are plenty of other ways that X-rays and gamma rays can be generated (just rapidly peel scotch tape or utilize a van-de-graph generator make lightning and you'll find X-rays being emitted), the truth is that astronomers don't know for sure what is going on around these high intensity radiation emitting zones because they don't have the resolutions to make the observations directly. It is tantamount to trying to explain the lines on Mars away as Martian Canals, from a low powered terrestial based telescope when there are much better explanations upon closer examination.

That's not how astronomers explain the emission from black holes; it doesn't depend on the sort of assumptions on 'the quantum scales of things' that you seem to think. Even if all the proposed mechanisms were totally wrong, though, you still have to explain where all the energy's coming from, and it would take a hell of a lot of scotch tape!

Of course it's not all from images either; for most of the real science you're talking about analysis of spectra over a vast range of observational wavelengths, and there's also high-resolution interferometry. We know a lot about the temperature, ionization state, magnetic field etc. of material near the 'compact object'. We don't just have snapshots either, but detailed observations of variability over many time scales (and, in the case of the Milky Way's centre, observations of the dynamics of nearby stars).

Similar mechanisms hold for accretion discs around neutron stars - I don't know if you have a problem with those too - which of course don't have a horizon. In fact you can see the difference between emission from an object where there is a surface for material to hit, and one where there's an event horizon. It's all rather fascinating and I don't think you do it justice.

7. A Conversation With Richard Wrangham From Studying Chimps, a Theory on Cooking

Comment #367375 by Geraint on April 21, 2009 at 4:13 am

Ah, um, ok I've just realised I can right click and select new tab.. doh!

Or Ctrl-click. Or click with the middle mouse button.

8. Texas School Standards: Age of the Universe Erased

Comment #366142 by Geraint on April 17, 2009 at 5:34 pm

77. Comment #366109 by bethe123

You've quoted a speech talking about the inception of cosmology as a precise science in 1989 (when COBE was launched) and then used that to claim that cosmology isn't a precise science. Eh?

And I think cosmologists tend to be quite open about the huge increase in the quality and quantity of data brought about by the launch of COBE (and later WMAP) and the construction of large redshift surveys, etc.

In fact I think there's the opposite problem to the one you claim, whereby people think there's far less data to constrain cosmological models than there actually is. So there are still cranks around pushing their crazy 'electric Universe' models and so on.

9. Seeing and Believing

Comment #325456 by Geraint on January 22, 2009 at 3:05 am

Re. Comment #325350 by Lucas

Smolin's popular book about the topic was called 'The Life of the Cosmos', so that might be worth picking up somewhere if you're interested.

The problem is, as Mad Monkey pointed out, that any mechanism by which 'cosmological natural selection' could happen is highly speculative.

10. EPA Administrator Stephen Johnson On Religion And Science: 'It's Not A Clean-Cut Division'

Comment #300416 by Geraint on December 11, 2008 at 3:45 pm

Roger Stanyard:
I've never figured out quite how Oxford and Cambridge work (I suspect nobody else ever has).

Quite! As far as Royal Charters go, though, each college has its own but it's the University which awards degrees.

11. Palin: average isn't good enough

Comment #284168 by Geraint on November 14, 2008 at 2:37 pm

Seriously, light from any source can be reflected back out of cats' eyes

Hence the name of the things in the road.

12. Astronomers capture first images of newly discovered solar system

Comment #284008 by Geraint on November 14, 2008 at 5:11 am

Well, Fomalhaut is closer, I suppose that helps. And they needed two pictures with Hubble demonstrating that the putative planet had moved before they could confirm a detection, whereas it looks like the HR8799 planets can be detected without that.

Edit: Well, according to the BBC report they did something similar with the HR8799 planets too. I suppose I should get off my arse and read the actual papers.

13. Hubble directly observes planet orbiting Fomalhaut

Comment #284007 by Geraint on November 14, 2008 at 5:08 am

Ah, OK. I guess there was an embargo until that issue came out.

14. Hubble directly observes planet orbiting Fomalhaut

Comment #283985 by Geraint on November 14, 2008 at 4:16 am

Greyman:

19. Comment #283938 by Geraint on November 14, 2008 at 3:08 am

I wonder if it's coincidence that this came out at the same time as the images of the planetary system round HR8799.

Possibly not. Once the instrumentation and techniques has reached the point of being able to detect these things if you look in the rigth place, it then becomes a question of: just how common is the right place to look?

I was more thinking about the way they've come to light on the same day (and from different groups using different telescopes). Maybe they synchronised the press releases.

15. Hubble directly observes planet orbiting Fomalhaut

Comment #283938 by Geraint on November 14, 2008 at 3:08 am

I wonder if it's coincidence that this came out at the same time as the images of the planetary system round HR8799.

16. Astronomers capture first images of newly discovered solar system

Comment #283927 by Geraint on November 14, 2008 at 2:47 am

a non e-moose:
@Steve
I thought it was decades away too, what happened? hubbles been around fr a while, why hasn't it been able to do this before?

edit: I suppose it's the adaptive optics that have improved. Pretty cool how they can improve the hardware like that.

edit: wtf, the whole point of the story is the picture, and cnn put a boring old stock photo (or stock "artists impression") of exoplanets...

Hubble doesn't need adaptive optics: they correct for the effects of the atmosphere, while Hubble is outside the atmosphere.

What the adaptive optics do is allow ground-based telescopes to produce images of similar quality to space telescopes. But ground-based telescopes also have several other advantages over space-based telescopes: they can be much larger (and hence be more senstive to faint objects) and there are fewer limits on what sorts of instruments can be bolted on. You can also try out new types of instrumentation more quickly and cheaply, without having to launch something into space. I don't know if Hubble could have taken this image (though it took the Fomalhaut one, of course).

I agree about the stock movies of exoplanets. I also think they can be confusing; certainly watching the BBC news this morning, they cut straight from the real astronomical image to some computer graphics mockup without ever saying that that's what they did. Better than nothing I guess.

17. Broken symmetry: Answering the solace of quantum

Comment #263060 by Geraint on October 10, 2008 at 7:09 am

Their work was certainly important and subtle. Although the article talks about matter and antimatter, it's perhaps easier to think about time symmetry. All the equations of physics since Newton were time-symmetric, but then experiments suggested that time-symmetry seemed to be violated in some interactions. Kobayashi and Maskawa found a way for this to happen in quantum theory, but realised that for it to work there needed to be a third generation of particles (tauons to go with muons and electrons; top and bottom quarks to go with up, down, charmed, strange, etc.). Third generation particles were then discovered only shortly afterwards.

Symmetries are fundamental to modern particle physics, and time symmetry was an especially important one to see come crashing down.

18. Richard Dawkins replies to Libby Purves

Comment #235821 by Geraint on August 23, 2008 at 4:30 pm

Vaal:
Wow, can you imagine seeing the night sky in 3 billion years with the Andromeda galaxy spanning the entire sky. That would be awesome. Oh, to be an astronomer then.

It would be a bit of a pain in the neck for extragalactic astronomers.

19. Is our universe fine-tuned for life?

Comment #224835 by Geraint on August 5, 2008 at 6:07 pm

healthphysicist:
I'm reading The Black Hole War by physicist Leonard Susskind. He states black holes won't radiate until the surrounding intergalactic space cools further.

Now black holes are absorbing heat. He predicts it will be 10 to the 60th power years before we're likely to detect any black hole radiation (I know our ability to detect is different from its onset, but still...).

They're not currently radiating through Hawking radiation. But they do effectively radiate since the matter that falls into them emits radiation before it's swallowed. In fact, black holes can be highly efficient and spectacular emitters of radiation through this means.

20. Hints of structure beyond the visible universe

Comment #191081 by Geraint on June 10, 2008 at 7:33 am

If you look at the original article, it's 10^100 (ten to the power of one hundred). Sub- and superscript formatting often seems to get killed.

21. Car dealership advert tells atheists to 'shut up'

Comment #185596 by Geraint on May 28, 2008 at 6:53 am

Atheists tell car dealership to 'grow up'.

22. Missing matter found in deep space

Comment #183395 by Geraint on May 22, 2008 at 3:18 am

JeremyH:
...large astrological bodies...

Russell Grant?

23. Missing matter found in deep space

Comment #183376 by Geraint on May 22, 2008 at 2:20 am

Rtambree: This doesn't explain the flat rotation curve of galaxies. Some reporter has misrepresented this.

This is not the matter you are looking for. You can go about your business. Move along.

Actually, I thought it was more carefully written than many science reports. It explicitly says that this is some of the previously undetected baryonic matter, and even contrasts it with the non-baryonic matter that draws the gas into the filaments where it shock-heats.

24. Missing matter found in deep space

Comment #182939 by Geraint on May 21, 2008 at 6:23 am

RickM: I've heard of the filament structure idea before as well. Is this stuff left over from old stars as the universe is "yanked" apart by expansion?

No, these filaments are on larger scales than that. As the denser parts of the Universe collapse, filaments are formed quite naturally, leading to a 'cosmic web' sort of structure.

Here's a picture of it from a simulation of dark matter:
http://www.mpa-garching.mpg.de/galform/millennium/seqB_063.jpg

Edit: I should add, that picture's about three billion light years on a side. We can actually see the filamentary structure in galaxy surveys, because the galaxies are strung out along the filaments. But it's very hard to see the other, diffuse gas in the filaments that hasn't collapsed into galaxies, and that's the point of this news article.

Incidentally, the reference to the 'backbone' is meant to conjure up an image of these filaments being the most important feature of the structure. It's not meant to imply there's one dominant structure somewhere in the Universe. You can see in the simulation that there is complex structure even though the picture is homogeneous on large scales.

25. Missing matter found in deep space

Comment #182830 by Geraint on May 21, 2008 at 2:54 am

rivetheretic: I'm surprised about the oxygen. Why oxygen? Hydrogen and helium I could understand, that's left over from the big bang. Iron or nickel I could understand; other elements tend toward iron and nickel in nuclear reactions because they are the most energetically favorable elements.

As other people have said, plenty of oxygen gets produced. There will be lots of hydrogen and helium in the filaments too, but it's also a matter of what you can detect. For gas at a given temperature, and using a given instrument, only certain species radiate strongly enough in the right wavelength range for the instrument to detect.

26. Discussion between Richard Dawkins and Paula Kirby

Comment #178306 by Geraint on May 11, 2008 at 6:04 am

Over on the forums, someone recently posted this link to a talk by John Maynard Smith related to that question:
http://atheistmedia.blogspot.com/2008/04/john-maynard-smith-royal-institution.html

I assume Dawkins' take would be similar: something to do with the presence of faithful replicators that can generate (near-)infinite variety. That does sound a bit of a strange definition until the rationale's explained, though. Even for someone who can describe the whole course of evolution in three minutes, it would be tough to explain quickly in response to a question after a talk.

27. Is religion a threat to rationality and science?

Comment #173918 by Geraint on May 1, 2008 at 11:04 am

NGC 6397 is over a billion light years away. I should not have used the word 'billions' [as it does imply two or more] in the sense of investigating SNR's within the Milky Way. My apologies.

No it's not. It's a nearby globular cluster.

28. Is religion a threat to rationality and science?

Comment #173880 by Geraint on May 1, 2008 at 10:13 am

We're talking billions of light years here, not accounting for unknown gravitational effects on the speed of light - though this does not affect the actual distance. Don't we think the law of averages would play out and create an even playing field no matter which direction we are looking?

Seeing them in galaxies other than our own would be even harder. We can see supernovae in distant galaxies, but only for a short time after the initial explosion, when they're at their brightest. Seeing old relics is a vastly different proposition. You seem to be trying to make an argument here without knowing even the most elementary things about the relevant astronomy.

29. Is religion a threat to rationality and science?

Comment #173848 by Geraint on May 1, 2008 at 9:41 am

So if we can not see the line [clearly] between phase two and phase three, why can we not see transitional evidence between the two? There should be thousands of SNR's in this transition phase of every flavor if the universe is billions of years old, no?

What I'm saying is that the whole thing is one big transition phase. There is no non-transition phase.

I think to make the argument you're making requires misunderstanding of both the physics and the observational problems. Supernovae happen in the plane of the galaxy, and you'd have to look for faint, diffuse emission against a dense background of literally millions of other point sources and sources of diffuse emission.

The whole argument's just a total non-starter.

30. Is religion a threat to rationality and science?

Comment #173817 by Geraint on May 1, 2008 at 9:10 am

The gist of the creationist's argument is right, observations of ongoing radioactive decay in supernova remnants can only date the very young ones.

My question - we can only 'date' very young ones or only observe very young ones?

We can only date very young ones. They meant what they said.

Similarly, the fact that you can't weigh an aircraft carrier with a set of kitchen scales doesn't mean that aircraft carriers don't exist.

There is no sharp dividing line between different phases in the development of an SNR, as you seem to imply. Different physical processes dominate at different times. As the remnant evolves it gets harder to observe until it blends into the background. This blending process is what introduced heavy elements into the gas that (for example) went on to form the solar system.

Of course, if you're going to use supernova models to date anything you'd need to explain all those neutron stars which are thought to be the relics of stars that went supernova, and the light from supernovae so distant that the light set off well over 100000 years ago.

But really, the whole idea that supernova frequencies are in conflict with cosmological models is just absurd.

31. Lying for Jesus?

Comment #156002 by Geraint on April 6, 2008 at 1:27 pm

Though it depends upon the various sects, most recognize the Humanist Manifesto as authoritative...

Never heard of it.

Is it too hard to imagine people who were just getting on with their lives, came across religious ideas, and thought they were silly?

There were religious bits and pieces at school, but I can't say I ever really thought anyone took them seriously.

Then I came across people who did take it seriously, considered the claims of the religious again, and they still just looked silly.

There's nothing more to it than that. No conspiracy. Just some people who want to get on with their lives without the silliness impinging.

32. Fleabytes

Comment #140418 by Geraint on March 7, 2008 at 9:24 am

mlearnedfriend:

Please learn how to use apostrophes. Cheers.

33. The Salamander's Tale

Comment #139550 by Geraint on March 6, 2008 at 4:26 am

wooter wootered:

If we go to a department store and just take look at the electronics department and see all kinds of equipment, tv, cd players, Mp3 phones, toasters etc,

You do realise none of these things reproduces, right? Maybe you don't; I can't honestly say that would surprise me.

34. Fleabytes

Comment #138520 by Geraint on March 4, 2008 at 1:19 pm

Steve Zara wrote:

Max Tegmark is fun. A bit "way out", but he comes up with exciting ideas.

I only realised this side of him after reading this forum. In fact he publishes a lot of good, solid science papers, and only allows himself one 'wacky' paper for every ten mainstream ones. More typical would be:

http://arxiv.org/abs/astro-ph/0608632

35. Fleabytes

Comment #138195 by Geraint on March 4, 2008 at 3:43 am

Thanks, MPhil. Good old wikipedia...

36. Fleabytes

Comment #138186 by Geraint on March 4, 2008 at 3:29 am

MPhil wrote:

And, he [Quine] has proven that the only abstract entities one needs to assume at minimum are sets.

Maybe I'm being dumb, but what does this even mean? Perhaps it's too technical to go into in a forum post. It's just that the way I understood it, the Russell paradox (which you mentioned above) compelled the development of category theory as a more general framework that avoided some of these contradictions.

37. Bill Maher on Larry King Live

Comment #127237 by Geraint on February 15, 2008 at 4:51 am

Well, fair enough, I haven't done the calculation for different decay paths. But you are extracting energy from the reaction at the end of the day. I just object to the idea of this idea of radioactivity as some sort of mysterious, infectious property spawned by power stations. Radioactivity doesn't come for free, it uses the energy stored in the binding energy of the nuclei.

38. Bill Maher on Larry King Live

Comment #127211 by Geraint on February 15, 2008 at 3:42 am

Nuclear power does create radioactivity, by fissioning relatively stable nucleii into more unstable (and so more radioactive) by-products.

Well, it creates it in the sense I described in the second half of that paragraph: the waste is more radioactive than the fuel, but with a shorter half-life, so is more dangerous in the short term. I still don't think I'd call it 'creating radioactivity', though. After all, Uranium-238 does spontaneously decay into other radioactive isotopes, but with a half life comparable to the age of the Earth. And its decay products have less energy available to produce radiation, else power stations wouldn't be producing power at all!

I suppose it's just a semantic issue, really.

39. Bill Maher on Larry King Live

Comment #127186 by Geraint on February 15, 2008 at 2:51 am

See, I think this is where you and I differ: I don't view radioactivity as harmless, ever. Even if one day the sun expands and envelops the earth, the radioactivity has already caused damage, to us, to other animals, to plants, to the earth. Just because radioactivity will one day (perhaps) be negated to zero, does not mean it is harmless. Difference in ethics perhaps?

Nuclear power doesn't create radioactivity. The fuel for power stations gets dug up out of the ground. What it does do is concentrate radioactive substances - fuel needs to be concentrated to produce useful energy - and produce isotopes that decay more quickly and so are more dangerous than longer-lived ones but for a shorter amount of time. So you can deal with this waste by putting it somewhere safe.

If it was radioactivity I was concerned about, I'd much rather live next to Yucca Mountain than a house in Cornwall built on granite. Naturally occurring radioactive argon is released from the granite, and can accumulate on poorly ventilated houses. I'd also make sure I stayed away from other people, who concentrate naturally occurring radioactive isotopes of potassium in their bodies.

40. Christopher Hitchens Debates Timothy Jackson

Comment #123524 by Geraint on February 7, 2008 at 10:03 am

1. Take the "multiverse" or "parallel universe" idea often quoted by these gentlemen. The idea that additional universes are created by the bazillions over time (past, present and future) requires a "universe generator" mechanism as a minimum. This leads to the question of what created the original universe generator? This is subject to exactly the same logical problems of infinite regression as a god creator.

I think multiverse hypotheses are meant to address the fine tuning problem rather than the question of why there's a universe at all. Explaining a mechanism that can generate any number of universes with various properties might turn out to be simpler than explaining one particular universe with a particular set of properties. Or it might not. I don't see a particular reason to rule a multiverse in or out given the current state of knowledge.

2. The current "big bang" theory, in order to properly explain the present state of the universe, requires an uneven rate of expansion. Most damning in this respect is that in the initial instants it requires expansion at hyper-light speed from what would have to be the largest black hole ever.

Why should the Universe expand at constant speed? It certainly shouldn't according to GR, unless it's empty. Really, I'm a bit puzzled what you're driving at.

Your point 3 is just wrong. Are you trying to claim you know of some observation inconsistent with GR? If so, let's see your calculation.

41. Letters: Theology has no place in a university

Comment #122344 by Geraint on February 5, 2008 at 7:51 am

And the big bang . . . POOF

The rest of that post contains such entertainingly ignorant nonsense that I can only assume anyone who'd bother to post it must be a troll.

42. Letters: Theology has no place in a university

Comment #116516 by Geraint on January 26, 2008 at 5:22 pm

By the way, I have an earned PhD.

I'm glad I didn't have to try to read your thesis.

43. God rest you merry atheist

Comment #99986 by Geraint on December 18, 2007 at 2:49 am

Comment #99915 by Dr Benway on December 17, 2007 at 8:33 pm
...
"Santa" with his jolly red suit and sleigh of eight flying reindeer was an invention of the Coke-Cola Bottling Co. If you don't like it, select another story for the kids.

http://www.snopes.com/cokelore/santa.asp

44. The Four Horsemen: on Christmas

Comment #99972 by Geraint on December 18, 2007 at 2:23 am

Comment #99869 by Ben Jennings on December 17, 2007 at 5:59 pm
Forget audio only, I wanna see more of Hitch's awesome house! ;)

Oddly enough, you can, about half way through his interview on 'In Depth':
http://www.richarddawkins.net/article,1655,In-Depth-Christopher-Hitchens,Book-TV-C-SPAN2

45. Jumbo shrimp, creationist astronomy

Comment #98723 by Geraint on December 14, 2007 at 6:25 am

Nonsense video. I just wanted to add my voice to the 'no Quicktime please' camp.

46. Why Christians should take Richard Dawkins seriously

Comment #76980 by Geraint on October 8, 2007 at 2:39 am

I mean you agree that there are objectively two particles out there (even though they share part of their quantum state), correct?

Well, I'm not quite sure what you mean. Isn't the nature of what's out there what we're trying to ascertain? You seem to be demanding before we start that the fundamental objects must be particles.

In any case, can you describe a model of a physical objective reality that accounts for Bell's test results and which remains coherent for observers in different frames of reference?

How about you tell me what happens in the reduction of a one-particle state first? This Bell's test stuff is all a red herring.

You seem to demand that an objective model of reality forgets about the results of QM (e.g. w.r.t. the nature of particles) and special relativity (simultaneity is observer-dependent). Demanding that physical reality is a tweaked version of Galilean classical mechanics won't work. I'm glad people are trying to understand it rather than writing it off as unknowable as you seem to.

47. Why Christians should take Richard Dawkins seriously

Comment #76816 by Geraint on October 7, 2007 at 11:18 am

Right, but I don't see how the change of wording affects my argument. Let's make away with the wording of "superluminal action" and use "shared quantum state" instead. That state does not exist before the first measurement is made, and the second measurement will always produce the same result as the first one. So epistemological coherence is violated again: The first observer will claim that measuring device A fixed the two particles' shared quantum state and that measuring device B only read that state anew, whereas the second observer will claim the opposite, namely that measuring device B fixed the two particles' shared quantum state and that measuring device A only read it anew. They can't be both right, and both base their claims on the same naturalistic logic (namely on the premise that the two particles objectively exist out there).

It seems to me you're creating a problem where none exists. The particles are always constrained to agree with respect to polarization measurements made in the same direction. You know that before either experimenter makes a measurement at all.

Talking about naturalistic logic implying that 'two particles objectively exist out there' makes it sound like you're still thinking of little bullets trundling along happily, until one gets measured and tells the other how to configure itself. It just doesn't work like that, and only our middle-world experience leads us to think that it should. There is an entangled two-particle quantum state.

48. Why Christians should take Richard Dawkins seriously

Comment #76229 by Geraint on October 5, 2007 at 6:30 am

Bell's test results appear to violate epistemological coherence and therefore to falsify all naturalistic ontologies (or at least all ontologies of scientific realism). The reason is that two observers in different frames of reference will observe different measurements first take place, and therefore will disagree about which measuring device superluminally affected the other. Which is analogous to two observers disagreeing about which tennis player first served the ball.

Only just got around to checking the thread, and I see Danielos will be away. Ah well.

The entanglement in a Bell test type experiment provides a constraint on the joint probabililty of the result of two measurements. The probability is the same in whichever order an observer sees the measurements take place.

This is the whole point about entanglement and non-locality. The two measurements are measurements of one entangled (non-local) quantum state, not two states that superluminally communicate.

49. Letters: Theology has no place in a university

Comment #75667 by Geraint on October 3, 2007 at 8:45 am

Well, the problem isn't the Oxford theology department per se, but the theological colleges which only admit students to read theology. Therefore their members spend all their time with other students also doing theology, and not experiencing the mix of different people and disciplines that an Oxford undergraduate usually experiences. Presumably this social and academic mix is felt to be more important to someone fresh out of school than to a mature student who will tend to be more narrowly concerned with the course offered by the university, rather than with the whole experience offered.

One can be a member of a 'normal' Oxford college and still study theology.

50. Why Christians should take Richard Dawkins seriously

Comment #75219 by Geraint on October 2, 2007 at 4:20 am

The Bell test results falsify all non-local naturalistic models,

Yes.

and, arguably, falsify all models of an objective and direct physical reality.

No, unless objective and direct means tiny billiard balls bouncing off each other. In which case I may as well take theism as requiring a man with a long, white beard sitting on a cloud.

The hard thing about an ontology of QM was and still is the measurement paradox. If anything, the Bell test makes the job easier by restricting the sorts of ontologies we might consider. But I know I should resist getting into this, since I managed to resist on the McGrath thread...

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