Half the universe’s missing matter found

mosaix

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#41
I don’t see a problem in any of this. What’s in a name? Scientists have to start somewhere even if they know there going to end up somewhere completely different.

I remember Jeremy Clarkson (spit) on QI saying ‘Why do people always have to label things?’ He was referring to medical complaints. The reason is so that there’s a simple common language that we can use instead of becoming long winded about it every time we want to have a discussion about something. You know Jeremy, so that we don’t have to say ‘that thing that we depress with our left foot that temporarily disconects the gearbox from the drive shaft so that we can change gear’ - it a clutch BTW for those with an automatic gearbox.
 

Vertigo

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#42
I don’t see a problem in any of this. What’s in a name? Scientists have to start somewhere even if they know there going to end up somewhere completely different.

I remember Jeremy Clarkson (spit) on QI saying ‘Why do people always have to label things?’ He was referring to medical complaints. The reason is so that there’s a simple common language that we can use instead of becoming long winded about it every time we want to have a discussion about something. You know Jeremy, so that we don’t have to say ‘that thing that we depress with our left foot that temporarily disconects the gearbox from the drive shaft so that we can change gear’ - it a clutch BTW for those with an automatic gearbox.
I agree with you re the labeling but the problem I have is whether or not this particular discovery has any impact on the Dark Matter issue which I believe it may not.
 

Joshua Jones

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#43
I don’t see a problem in any of this. What’s in a name? Scientists have to start somewhere even if they know there going to end up somewhere completely different.

I remember Jeremy Clarkson (spit) on QI saying ‘Why do people always have to label things?’ He was referring to medical complaints. The reason is so that there’s a simple common language that we can use instead of becoming long winded about it every time we want to have a discussion about something. You know Jeremy, so that we don’t have to say ‘that thing that we depress with our left foot that temporarily disconects the gearbox from the drive shaft so that we can change gear’ - it a clutch BTW for those with an automatic gearbox.
Yeah, I don't agree with Jeremy Clarkson on not using labels. In my field of study, we use shorthand labels all the time. My concern is when the label doesn't accurately represent the status of the research or gives preference to one possible solution over another. For example, when philosophers of my sort refer to the Problem of Evil, we are using a shorthand term for a complex philosophical argument including multiple forms of argumentation. This could be answered by granting that it is, indeed, a legitimate contradiction or probabilistic likelihood (depending on which aspect is being addressed), or answered by a defense, or a theodicy. But, if we call the Problem of Evil "Theodicy", we are giving a preference from the outset to one solution.

In the case of dark matter, it is also the term used to refer to WIMPs, which is why this discussion has been so confusing. This is because the solution of missing mass is implied directly in the term for the problem, and WIMPs are the proposed solution to that missing mass. But, there are other possible solutions, and we may not even understand the scope of the possible solutions yet. So, my problem isn't with labeling this problem, but the priority given to one solution by the specific label chosen. And, as at least most of us in this discussion are writers, I think we understand the importance of words and how much power they can have.

So yes, by all means, let researchers study WIMPs and whatever other hypothetical solutions exist. Just don't name the problem after a hypothesis, and don't make confident statements like "the universe is 25% dark matter" until the hypothesis is at least a theory.
 

Venusian Broon

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#44
Yes this was my understanding that this discovery is only picking up the missing normal matter but it goes no closer to accounting for the behaviour for which the label dark matter was created. Though I may be wrong; this whole area seem to be becoming something of an understanding minefield for the lay observer! o_O
Finding normal matter can be extremely difficult, astronomically speaking.

Even things that like to shine, like stars, can be obscured, too far away and too puny to be ever picked up by any instrumentation on and around Earth. Hence the large variance in the estimate in the number of stars the Milky way has - ranging from 100-400+ billion at the moment, I believe. We just can't see the (probably) large population of red dwarfs that are likely to be present.

Just to muddy figures these figures come more from other observations of the effective mass of the galaxy. And as RJM points out in one of the articles he brought up, how much of dark matter halo a galaxy might have could be highly variable too, so that adds further mass observation issues.
 

Venusian Broon

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#45
In the case of dark matter, it is also the term used to refer to WIMPs, which is why this discussion has been so confusing. This is because the solution of missing mass is implied directly in the term for the problem, and WIMPs are the proposed solution to that missing mass.
I'm not an astrophysicist, just did condensed matter physics as a PhD, but my understanding of this situation is that 'dark matter' refers to the whole gamut of theories and hypothesis's that exists. WIMPs is one of them, but it also refers to MACHOs, primordial black holes and will also include the modified gravitational theories. And everything else that might explain what's happening.

Yes, perhaps those that have been studying it for years have decided, given the more detailed evidence and understanding they have, might have plumped for one or the other, such as WIMPs. But there are still advocates for the others. Therefore I've never heard of the term dark matter being exclusively tied to just WIMPs.

I do think when their results are being reported by journalist they tend to get lost in transaction, because of the journalist's drive to simplify what the scientists are communicating. Virtually all the time I actually hear a scientist talk/write about their work, they do not state confidentially things like 'the universe is 25% dark matter' (Something, I find, that a tag line on a news article tends to say) but, rather say: 'I/we believe that 25% of the universe could be dark matter', or prefix it with 'On our current understanding/observations the leading hypothesis is...' Usually if you read the article carefully these types of responses are usually buried near the end of the article.

So actually I think it's quite a good term. There are a bunch of observations that seem to imply that there's some mass there that we can't see. That's a good first guess.
 

Joshua Jones

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#46
I'm not an astrophysicist, just did condensed matter physics as a PhD, but my understanding of this situation is that 'dark matter' refers to the whole gamut of theories and hypothesis's that exists. WIMPs is one of them, but it also refers to MACHOs, primordial black holes and will also include the modified gravitational theories. And everything else that might explain what's happening.

Yes, perhaps those that have been studying it for years have decided, given the more detailed evidence and understanding they have, might have plumped for one or the other, such as WIMPs. But there are still advocates for the others. Therefore I've never heard of the term dark matter being exclusively tied to just WIMPs.

I do think when their results are being reported by journalist they tend to get lost in transaction, because of the journalist's drive to simplify what the scientists are communicating. Virtually all the time I actually hear a scientist talk/write about their work, they do not state confidentially things like 'the universe is 25% dark matter' (Something, I find, that a tag line on a news article tends to say) but, rather say: 'I/we believe that 25% of the universe could be dark matter', or prefix it with 'On our current understanding/observations the leading hypothesis is...' Usually if you read the article carefully these types of responses are usually buried near the end of the article.

So actually I think it's quite a good term. There are a bunch of observations that seem to imply that there's some mass there that we can't see. That's a good first guess.
And, I would add, at least from a procedural standpoint, we should start by examining the more simple answers before looking at the complex ones. And, I could completely support statements like "we believe that 25% of the universe could be dark matter" as you cited above. This is a statement of a hypothesis, and it is weighted correctly for that.

My issue comes with exerpts like this from NASA's website, "More is unknown than is known [regarding dark energy]. We know how much dark energy there is because we know how it affects the universe's expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 68% of the universe is dark energy. Dark matter makes up about 27% (Dark Energy, Dark Matter | Science Mission Directorate)." This seems to be the language of a theory, not a hypothesis. Now, this could be a case of Americans overstating their case (as we do on occasion), or it could be a desire to appear to the general public more settled on a matter than we actually are. I don't pretend to know which is the case or if it is something else altogether, but that exerpt makes it seem the matter is settled. And, for the record, I don't think you are wrong when you say that scientists don't typically make such claims when speaking to one another, and many likely are more cautious when speaking to the general public. There are, however, at least some who are not so cautious when communicating with the public, even in media they control.

As this is, and will invariably be the case where individuals are concerned, I think it better to name the problem something which blocks this to an extent, so we can have a more informed populous (a pipe dream in the age of Twitter, I am sure!). If we want to go with something catchy like dark matter, I would think "dark gravity" may be better, as it puts the ambiguity on the gravity, rather than on the hypothesized cause of the gravity.

I know I may be particular on this point, but I do believe words matter, and should be carefully weighed before issued.

Does that make any sense, or am I just being unnecessarily particular?
 

RJM Corbet

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#47
Finding normal matter can be extremely difficult, astronomically speaking.

Even things that like to shine, like stars, can be obscured, too far away and too puny to be ever picked up by any instrumentation on and around Earth. Hence the large variance in the estimate in the number of stars the Milky way has - ranging from 100-400+ billion at the moment, I believe. We just can't see the (probably) large population of red dwarfs that are likely to be present.

Just to muddy figures these figures come more from other observations of the effective mass of the galaxy. And as RJM points out in one of the articles he brought up, how much of dark matter halo a galaxy might have could be highly variable too, so that adds further mass observation issues.
But it appears cosmology has already quite long ago calculated the total baryonic mass of the universe (from big bang data or whatever, I'm clueless) and the point is that the large part of this predicted baryonic mass could not be located until recently.

However the discovery first of these filaments, and then the MUSE discovery of primordial hydrogen clouds, has now completed the package of baryonic matter predicted. They've now got it all. But it's still only capable of generating about 5% of the gravity in the universe.

It seems there is not and can not be any more baryonic matter in existence. 5% of the universe is all its ever going to be.

The exact same 'amount' of dark matter is still out there, unaffected. No change at all. It still makes up about 25% of the universe.

@Joshua Jones: I apologise for restating the commonly used percentage figures here, for convenience. Dark Gravity would indeed probably be a far better label than dark matter, for non-physicists. But the physicists themselves are not confused by it?
 
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Joshua Jones

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#48
But it appears cosmology has already quite long ago calculated the total baryonic mass of the universe (from big bang data or whatever, I'm clueless) and the point is that the large part of this baryonic mass was hidden until recently.

However the discovery first of these filaments, and then the MUSE discovery of primordial hydrogen clouds, has now completed the package of baryonic matter predicted. But it's still only capable of generating about 5% of the gravity in the universe.

It seems there is not and can not be any more baryonic matter in existence. 5% of the universe is all its ever going to be.

The exact same 'amount' of dark matter is still out there, unaffected. No change at all in the fact it still makes up about 25% of the universe, etc?

@Joshua Jones: I apologise for restating the commonly used percentage figures here, for convenience. Dark Gravity would indeed probably be a far better label than dark matter, for non-physicists. But the physicists themselves are not confused by it?
It doesn't seem that there is much confusion for physicists on what is meant by the term, at least from my observations. The problem seems to come when it crosses over to the populous, and there doesn't seem to be much desire to clarify at this point.

And no need to apologize; I understand what you mean, and it is much easier to discuss these things in those terms. I give lay people a pass on the terms they use. Professionals in the field and those who are hired to represent them, however...
 

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