Dark matter and Dark energy

[iantresman]

Where are all the scientists, that BeAChooser keeps inferring about, who are earning an easy and affluent living by ignoring evidence and criticism?!

In his own mind, no conspiracy theory works without conspirators.

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While the statements are somewhat overgeneralized, the idea that some scientists are "ignoring evidence" is not without foundation, see for example:

• British scientists exclude 'maverick' colleagues, says report (2004)
• Trial by peers comes up short (2003)
• Rejecting Nobel class papers (2003)
• Suppression Stories (1997)
• Challenging dominant physics paradigms (2004)
• Publications on whistleblowing and suppression of dissent

 

[iantresman]

Plasmas also conduct electricity, dust and gas don't.

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Actually it's a little more interesting than that. While dust does not conduct electricity per se, it can become charged, especially in interplanetary space, resulting in "dusty plasmas". Sometimes the dust itself can become the domiinant charge carrier (rather than the electrons or ions).

 

[The Man]

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While the statements are somewhat overgeneralized, the idea that some scientists are "ignoring evidence" is not without foundation, see for example:

Without a doubt, but evidence of ignorance does not demonstrate ignorance of evidence.

 

[robinson]

Without a doubt, but evidence of ignorance does not demonstrate ignorance of evidence.

Do you have any evidence to show that is true?

 

[The Man]

Do you have any evidence to show that is true?

Usually referred to as a jury trial, both ignorance and evidence are required but ignorance of the evidence is something they hope to avoid.

 

[robinson]

So, what is your point?

 

[The Man]

Exactly! A fine exemplification of my point, thanks.

 

[Belz...]

Just because plasma is described as an ionized gas, does not necessarily mean it is a kind of gas. It means that plasma is derived by ionizing a gas. For example, we could describe liquid water is melted solid ice, but that does not mean that liquid water is some kind of solid.

There are many many sources which describe plasma as the forth state of matter, and although it may sometimes have gas-like properties, it is not a gas.

Historically, the description of plasma as an ionized gas goes back to the days of gas discharge tubes. Sir William Crookes call it "radiant matter". It was not until 1928 that Irving Langmuir coined the word "plasma".

I would argue that it is the other way around, gases are a subset of plasmas, because plasmas have more diverse properties, including all those exhibited by gases.

It is also common to simplify the behavior and properties of plasmas, modelling them as gaseous fluid, whereas gases never exhibited some of the properties of plasmas (eg. electrical conductivity, self-generating magnetic and electric fields, filamentation, negative pressure, charge separation, etc etc)

Sounds kinda in-between, doesn't it ?

 

[Belz...]

Oh those pesky scientist, always making stuff up.

Are you going to contribute to the discussion, at one point, or are you just going be cynical and unhealthily skeptical ?

 

[robinson]

My additions are called "dark postings", you can't see them, but they are 10 times more massive than the observable postings, and influence the course of the conversations. We know this from observing the visible post elements. Something is causing them to move forward, when there isn't enough content in them to explain the motion.

 

[iantresman]

My additions are called "dark postings", you can't see them, but they are 10 times more massive than the observable postings, and influence the course of the conversations. We know this from observing the visible post elements. Something is causing them to move forward, when there isn't enough content in them to explain the motion.

Proof of "dark logic", if ever I saw it.

 

[~enigma~]

dark matter

when you can't make a theory work, make something up!

Like god?

 

[~enigma~]

In fact, dark matter can be described as merely matter that doesn't shine under its own light. Our planet could be dark matter, since it is practically invisible from a distance.

However, I believe that it is now considered unlikely for planets like ours to make up anything but a small percentage of dark matter.

Hmm...I thought that dark matter was just non-baryonic matter. What does light have to do with that?

 

[robinson]

See? More evidence of dark posting. There is no observable content by me, yet a response!

I should seek funding....

 

[~enigma~]

He also thinks that the sun is powered by electricity

That must be one HUGE electric bill. I'm never gonna complain about my measly $90 bill again

 

[Ziggurat]

Hmm...I thought that dark matter was just non-baryonic matter. What does light have to do with that?

Strictly speaking, dark matter just means matter we cannot see. From various indirect observations we've concluded that most of this is probably non-baryonic matter, but the term itself doesn't specify that aspect.

 

[sol invictus]

Hmm...I thought that dark matter was just non-baryonic matter. What does light have to do with that?

Dark matter's primary characteristic is that it's dark - hence the name. It doesn't emit (or absorb) much if any light or other EM radiation, which makes it hard - but not impossible - to detect.

It is probably non-baryonic because we can infer some of its properties roughly from its gravitational effects, and those don't match what is expected of any known baryonic stuff. However the case is not completly closed on that.

 

[~enigma~]

Dark matter's primary characteristic is that it's dark - hence the name. It doesn't emit (or absorb) much if any light or other EM radiation, which makes it hard - but not impossible - to detect.

It is probably non-baryonic because we can infer some of its properties roughly from its gravitational effects, and those don't match what is expected of any known baryonic stuff. However the case is not completly closed on that.

Okay...but Chandra was able to take this picture...



Isn't that dark matter?

 

[robinson]

The part that just seems woo woo, is that "dark matter" doesn't act like matter. Forget the "fact" it doesn't emit, adsorb, or re-radiate any form of EM, it also doesn't attract either matter, or itself, nor does it form structures, or do anything that real matter does.

 

[sol invictus]

Okay...but Chandra was able to take this picture...

[qimg]http://www.internationalskeptics.com/forums/imagehosting/thum_1325747b9dde63eccf.jpg[/qimg]

Isn't that dark matter?

Yes it is, but the coloring in that image corresponds to the density of dark matter as reconstructed via its gravitational lensing effects. It's roughly analogous to using sonar to determine the location of an object underwater - it might be much too far away or too dark to see, but you can use sound instead to detect it and reconstruct an image of it.

The part that just seems woo woo, is that "dark matter" doesn't act like matter. Forget the "fact" it doesn't emit, adsorb, or re-radiate any form of EM, it also doesn't attract either matter, or itself, nor does it form structures, or do anything that real matter does.

That's completely incorrect. It of course attracts both itself and ordinary matter gravitationally - that's what that image shows, along with rotation curves, structure formation simulations, acoustic peaks in the CMB spectrum, and a host of other measurements.

Again, all that is necessary to explain DM is a form of matter that doesn't interact strongly with EM radiation. That's it, and there are many candidates we already know about. Neutrinos could have been DM if they had turned out to be a little heavier. Burned out stars or primordial black holes formed in the early universe from baryonic matter are still (just barely) viable candidates, depending on whose numbers you believe. It's just not necessarily very exotic, and I find it completely unsurprising that, in 2008, we don't have a good picture of all the mass in the universe. We didn't in 1998, or 1988, and certainly not before that. The difference is that now we have enough precision to see we're missing something.

It's very interesting, but it's just not surprising or weird. Wouldn't you find the opposite assertion - that today, as never before, we have a complete accounting of all the matter in the universe - a little surprising?