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Lambda-CDM theory - Woo or not?

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edd said:
http://www.universetoday.com/75164/m31s-odd-rotation-curve/
In before someone else abuses the content.
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Neat! Note the (at first glance) careful and accurate use of ordinary science.

a) The authors identify a specific piece of data that's not currently well modeled. (They do not rail generically against "paradigms" or "ignorance".)

b) The authors cite the recent relevant data, and cite a large suite of attempts to explain that data, which makes it clear that there IS something that needs explaining. (They do not paste together fifteen random Google results as evidence for a vague epistemological problem.)

c) They do a *mathematical* comparison between (a) a clearly-stated magnetic force law and (b) numerical data, with error bars, from clearly-stated sources. The comparison is done in a standard way (chi-squared) and the result suggests that the agreement is good (chi^2 decreases from ~10 to ~1 with one added parameter). They do not insist that math is irrelevant or misleading.

d) They obtain a magnitude and direction for the magnetic field that would make their model work (4.6 uG along the circumference) and compare it to well-understood and specific observations (Faraday rotation) of exactly the systems they're modeling. (They do not avoid this discussion altogether.)

e) They do not discard dark matter. This model's inner disk is, as usual, dark matter dominated, and there's no indication of anything other than HI clouds experiencing the observed force.

The difference? Ruiz-Granados et. al. get their magnetic-field hypothesis published in ApJ Letters, while MM et. al. hang around JREF and complain that astronomers ignore magnetic fields.
 
ben m said:
Neat! Note the (at first glance) careful and accurate use of ordinary science.

a) The authors identify a specific piece of data that's not currently well modeled. (They do not rail generically against "paradigms" or "ignorance".)

b) The authors cite the recent relevant data, and cite a large suite of attempts to explain that data, which makes it clear that there IS something that needs explaining. (They do not paste together fifteen random Google results as evidence for a vague epistemological problem.)

c) They do a *mathematical* comparison between (a) a clearly-stated magnetic force law and (b) numerical data, with error bars, from clearly-stated sources. The comparison is done in a standard way (chi-squared) and the result suggests that the agreement is good (chi^2 decreases from ~10 to ~1 with one added parameter). They do not insist that math is irrelevant or misleading.

d) They obtain a magnitude and direction for the magnetic field that would make their model work (4.6 uG along the circumference) and compare it to well-understood and specific observations (Faraday rotation) of exactly the systems they're modeling. (They do not avoid this discussion altogether.)

e) They do not discard dark matter. This model's inner disk is, as usual, dark matter dominated, and there's no indication of anything other than HI clouds experiencing the observed force.

The difference? Ruiz-Granados et. al. get their magnetic-field hypothesis published in ApJ Letters, while MM et. al. hang around JREF and complain that astronomers ignore magnetic fields.
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They also say that their model is testable, via specific *quantitative* observations (they do not say 'look at this picture! It PROVES my theory!!).

For those reading this thread, who are not as familiar with the relevant astrophysics as most of those who have posted to it are, the rotation curve in the outer part of M31's disk is derived from observations of gas (and/or plasma), not stars.
 
Ziggurat said:
Uh, no. Pay attention:
"The team estimates there are about twice as many free-floating Jupiter-mass planets as stars."
So if they're twice the number of stars, but they're much less massive than stars, then they cannot account for much of the missing mass.
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WRONG!!! That consideration involves *MATHEMATICS* and *LOGIC* which we know is "MISSING" in any analysis by EU groupies. Since some artist drew some pretty +PICTURES+ of these planets for us to see there must be enough ^MASS^ to explain dark matter.
 
Michael Mozina said:
http://science.nasa.gov/science-news/science-at-nasa/2011/18may_orphanplanets/

FYI, even less reason to believe in non-baryonic forms of "dark matter". :(
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Wrong: Since these orphan planets have not been detected in a lab (like dark matter has not yet been detected) and that is your primary criteria for the existence of anything, these orphan planets do not exist :jaw-dropp!

But if we forget about that crank belief then dark matter has even more evidence for its existence than orphan planets.
Ophan planets: evidence from gravitational lensing.
Dark mater: evidence from
  • Galactic rotation curves
  • Velocity dispersions of galaxies
  • Galaxy clusters and gravitational lensing
  • Cosmic microwave background
 
Ziggurat said:
Uh, no. Pay attention:
"The team estimates there are about twice as many free-floating Jupiter-mass planets as stars."
So if they're twice the number of stars, but they're much less massive than stars, then they cannot account for much of the missing mass.
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Indeed, we've been through this 10*Exp[umpteen] times. Here's an example: http://www.internationalskeptics.com/forums/showpost.php?p=5487090&postcount=278

This is data from a microlensing survey. When astrophysicists first proposed that dark planet-y objects (MACHOs) might be the missing mass, the first thing they did was say, "hey, let's do a microlensing survey." They did.

By 1994 it was obvious that MACHOs could not be more than 50% of the dark matter. (Astrophys. J. 424, 550)

By 2003 it was obvious that MACHOs could not be more than 5% of the dark matter. http://arxiv.org/abs/astro-ph/0302325

In other words, microlensing is telling us unambiguously that MACHOs are not the dark matter. It was never telling us they don't exist at all---just that they're rare. How rare are they exactly?

That's the new result---we've now seen enough MACHOs to have some idea of how many there are (rather than just putting upper limits on them). Planet-sized MACHOs, the new data tells us, make up a few times 0.01% of the mass of the Milky Way. Dark matter---the stuff that still, after decades of study, shows every indication of being nonbaryonic---makes up 80%.

How do you look at data that says "planets are common enough to be 0.0001 of the Milky Way mass" and think it's a challenge for the dark matter hypothesis?
 
Ziggurat said:
Uh, no. Pay attention:
"The team estimates there are about twice as many free-floating Jupiter-mass planets as stars."
So if they're twice the number of stars, but they're much less massive than stars, then they cannot account for much of the missing mass.
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Several years ago (3?) we found out that the black holes in the center of galaxies are significantly larger than first estimated. Something like three years ago we found out that you folks grossly underestimated the amount of light and number of stars in a galaxy due to dust. For all you know there could be twice as many large stars in a galaxy as you first estimated. Two years or so ago we found out that you grossly underestimated the number of smaller stars compared to the "larger" ones we could observe. It turns out that there could be four or five times more small stars in a galaxy than you realized, meaning you guys probably underestimated the total number of ordinary stars in a galaxy by whole order of magnitude. Now we find out that there are more detached Jupiter sized objects out there than here are stars in the heavens. Even still, nothing has been done to rectify the "problems" in your "dark matter' theories, or to minimize the need for non-baryonic exotic forms of matter, not even a *SINGLE* percent. Why?
 
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Michael Mozina said:
Several years ago (3?) we found out that the black holes in the center of galaxies are significantly larger than first estimated. Something like three years ago we found out that you folks grossly underestimated the amount of light and number of stars in a galaxy due to dust. For all you know there could be twice as many large stars in a galaxy as you first estimated.
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A factor of 2 won't save you. Especially if the distribution isn't right.

Two years or so ago we found out that you grossly underestimated the number of smaller stars compared to the "larger" ones we could observe.
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The thing about smaller stars is that they're smaller.

Hence, they don't contribute as much to the mass of a galaxy.

Now we find out that there are more detached Jupiter sized objects out there than here are stars in the heavens.
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And if I estimate the number of grains of sand on earth and get that wrong by a factor of 10, it won't make any real difference to the mass of the earth.

Lensing measurements demonstrate quite conclusively that these can't make up the missing mass.

Even still, nothing has been done to rectify the "problems" in your "dark matter' theories, or to minimize the need for non-baryonic exotic forms of matter, not even a *SINGLE* percent. Why?
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For the simple reason that nothing you list can make up the discrepancy, in either magnitude OR distribution. That latter part is especially relevant to the examples you've given.

But it's not even true that physicists aren't looking for alternatives to dark matter. They are (for example). It's just that your preferred alternative is a joke.
 
Ziggurat said:
A factor of 2 won't save you. Especially if the distribution isn't right.
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I'm not looking to be "saved", I'm looking to see if you folks make any real attempt to minimize the need for exotic brands of matter now that you know for a fact that you've been grossly underestimating the amount of ordinary matter in a galaxy.

My favorite line from that last article was this one:

The discovery is based on a joint Japan-New Zealand survey that scanned the center of the Milky Way galaxy during 2006 and 2007, revealing evidence for up to 10 free-floating planets roughly the mass of Jupiter. The isolated orbs, also known as orphan planets, are difficult to spot, and had gone undetected until now. The planets are located at an average approximate distance of 10,000 to 20,000 light years from Earth.
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A few months ago you folks were telling me in this thread or one of the other threads that you'd already accounted for every chuck of material out there down to the size of a small moon. We were talking about "rocks" at that point because our studies were "sooooooooo good". It turns out that until now even Jupiter sized "dark" objects have completely eluded you folks. How do you really expect me take you folks seriously when there is absolutely no attempt by the mainstream to even *MINIMIZE* the need for exotic mass, in spite of all these revelations that your baryonic mass estimated sucked royally?
 
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Michael Mozina said:
I'm not looking to be "saved", I'm looking to see if you folks make any real attempt to minimize the need for exotic brands of matter now that you know for a fact that you've been grossly underestimating the amount of ordinary matter in a galaxy.
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First off, I already pointed out an example of efforts to explain observations without dark matter. And second, you're simply wrong: there is no evidence that the astronomy community has grossly underestimated the amount of ordinary matter in the galaxy.

A few months ago you folks were telling me in this thread or one of the other threads that you'd already accounted for every chuck of material out there down to the size of a small moon.
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I have no reason to believe your characterization of other posters. But it doesn't even matter what someone here said, what matters is the actual state of knowledge within the astronomy community. I'm sure there are error bars on all these mass estimates, and I'm not terribly surprised to learn that there was some systematic error in early estimates. But so what? That error isn't large enough, and it doesn't have the right mass distribution. If you can't fix BOTH those problems, then you cannot eliminate dark matter. And you can't fix either problem with the observations you refer to.

How do you really expect me take you folks seriously when there is absolutely no attempt by the mainstream to even *MINIMIZE* the need for exotic mass, in spite of all these revelations that your baryonic mass estimated sucked royally?
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I already told you that this is simply false. I gave you a link to a paper which is attempting to do precisely this. And what do you do? You simply repeat a false claim. But since you now know it to be false because I just proved to you that it's false, that makes you a liar.
 
The problem with the estimates for all these contributing factors for the mass of galaxies is that they require mathematics. Consequently, EU groupies remain hopelessly confused and will never understand the calculations that demonstrate the existence of dark matter. There is no logic to this; it's merely the way it is.
 
Michael Mozina said:
A few months ago you folks were telling me in this thread or one of the other threads that you'd already accounted for every chuck of material out there down to the size of a small moon. We were talking about "rocks" at that point because our studies were "sooooooooo good". It turns out that until now even Jupiter sized "dark" objects have completely eluded you folks.
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I just linked to, and re-explained, exactly that post.

The mass of the Milky Way is about 6x10^11 solar masses. We can account for less than ~1x10^11 solar masses by counting stars, dust, and gas. There's ~5x10^11 solar masses "missing", mostly in the Galactic halo.

Previous research did not say "we counted every last thing". I never said that it did. If you think I did, you're lying or confused or both. Quote me if you disagree.

What does research say? As I said, by the mid-1990s, research said whatever MACHOs/rocks/black holes are out there, they don't add up to 5x10^11 solar masses. By 2003 or so we said they don't add up to even 0.25x10^11 solar masses. Now we're saying that MACHOs do add up to ~0.0005 x 10^11 solar masses. Sure, there are probably undiscovered rocks/dust/gas/etc. out there. Whatever it is, it doesn't add up to 5x10^11 solar masses.

Please note that this is precisely consistent with what I've said before. You misinterpreted it to make it sound wrong, and to make your own fantasies sound right? I'm not surprised, but that's your problem not mine.

Let me put it another way. You owe $6000 to the mob. Vinnie The Fist shows up at your door and demands payment. You root through your safe; you log into your bank account and empty it out. "There's $1054.88, Vinnie," you say, "I honestly want to make good but as you can see there I don't have another $5000 to my name." Vinnie asks for the kid's piggybank. "OK, there's another $15.30, but you're going to have to accept that the next $5000 isn't there." Vinnie grins and pulls out the couch cushions. He finds some popcorn, a Lego brick, and two quarters. "You say there ain't no money, but lookit them shiny quarters." says Vinnie, "You better not be holdin' out on me."
 
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ben m said:
I just linked to, and re-explained, exactly that post.

The mass of the Milky Way is about 6x10^11 solar masses. We can account for less than ~1x10^11 solar masses by counting stars, dust, and gas. There's ~5x10^11 solar masses "missing", mostly in the Galactic halo.

Previous research did not say "we counted every last thing". I never said that it did. If you think I did, you're lying or confused or both. Quote me if you disagree.

What does research say? As I said, by the mid-1990s, research said whatever MACHOs/rocks/black holes are out there, they don't add up to 5x10^11 solar masses. By 2003 or so we said they don't add up to even 0.25x10^11 solar masses. Now we're saying that MACHOs do add up to ~0.0005 x 10^11 solar masses.

Please note that this is precisely consistent with what I've said before. You misinterpreted it to make it sound wrong, and to make your own fantasies sound right? I'm not surprised, but that's your problem not mine.
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STOP! This is far too much mathematics; draw a picture of a planet.
 
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