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To my understanding, matter is just crystallized energy. So is dark matter the crystallized form of dark energy? Sorry if this is a bit of a stupid question, just couldn't get it off my mind.

Any answers would be much appreciated - thanks.  

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I think clever people invented dark matter / energy to make less clever people feel even less clever than they actually are! e.g. Yours truly!  

Possibly.  What I'm getting at, somewhat clumsily, is that perhaps scientists should not name unexplained phenomena after hypothetical solutions.  It might have  been better to refer to these as

I agree with what you say but would say that while "We don't know" is true in the sense we can't point to a dark matter or energy particle we do know quite a lot about their properties. In a way it is

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Matter (mass) and energy are related by Einstein's famous equation.  As for dark matter and dark energy, they have been hypothesised and their effects  seem to be known, but they have not been identified or pinned down so to speak.  Therefore it would be difficult I suppose to suggest how they might be related in the way that known matter and energy are.

Not really helpful, but these are after all mysterious entities.  

Just my thoughts.  I'm sure others will have useful contributions to make.

Doug.

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Are their distributions not different though ? Dark Matter seems to be 'lumpy', concentrated round (in) galaxies and galaxy clusters. (Its distribution being mapped out by gravitational lensing in many cases)  Much less is known about Dark Energy but quintessence and other models suggest that it is smoothly distributed throughout the universe.

I could be wrong, its all well above my pay grade :) !

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The word "dark" is a replacement for "we've got no idea what this is, we just know that it is something and can see its effects", both forms are pretty much unknown, so it's not possible to say if they are related - they didn't name them both "dark" because they are related, just because we don't know what either is.

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Unfortunately the naming of dark matter and dark energy implies they physically exist.  Whereas really what they refer to are two observed and unexplained phenomena - an anomalous gravitational effect (dark matter) and the accelerating expansion of the universe. 

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1 hour ago, Ouroboros said:

Unfortunately the naming of dark matter and dark energy implies they physically exist.  Whereas really what they refer to are two observed and unexplained phenomena - an anomalous gravitational effect (dark matter) and the accelerating expansion of the universe. 

Clever people invented dark matter / energy as most likely cause of observed differences to the expected universe.

Could be the base equations are not as all encompassing as first thought???

Paul

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57 minutes ago, Paul73 said:

Clever people invented dark matter / energy as most likely cause of observed differences to the expected universe.

I think clever people invented dark matter / energy to make less clever people feel even less clever than they actually are! e.g. Yours truly! ;) 

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3 hours ago, Ouroboros said:

Unfortunately the naming of dark matter and dark energy implies they physically exist.  Whereas really what they refer to are two observed and unexplained phenomena - an anomalous gravitational effect (dark matter) and the accelerating expansion of the universe. 

However, that is quite normal in Physics. In the same way Newton invented Gravity, Maxwell, Faraday et. al. invented the EM fields and Einstein curved space-time to explain observed but as yet unexplained phenomena. The same could be said for energy, entropy and much more but the point is we are more comfortable with them due to familiarity and the longevity of the ideas. I accept they are still lacking in direct laboratory evidence but this is normal in astronomical scale physics and I agree much still needs to be explained. Again, this is still not unusual. The underpinning of thermodynamics by the "atomic" theory still has many fundamental issues.

Regards Andrew.

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1 hour ago, Paul73 said:

Clever people invented dark matter / energy as most likely cause of observed differences to the expected universe.

Could be the base equations are not as all encompassing as first thought???

Paul

Possibly. 

What I'm getting at, somewhat clumsily, is that perhaps scientists should not name unexplained phenomena after hypothetical solutions.  It might have  been better to refer to these as the anomalous gravitational effect and anomalous universal expansion, rather than dark matter and dark energy. Less catchy obviously, but descriptions not leading people to assume such entities as dark matter and dark energy actually exist.  

A similar example is the phrase used to refer to the observation at the beginning of the 20th century  that the amount of radiation emitted from hot bodies departed from that predicted by theory. So rather than refer to this by some hypothetical particle or other entity  the phenomenon was called the ultraviolet catastrophe.  It turned out of course that it was the result of the quantisation of electromagnetic energy into what we now call photons. 

 

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34 minutes ago, Ouroboros said:

A similar example is the phrase used to refer to the observation at the beginning of the 20th century  that the amount of radiation emitted from hot bodies departed from that predicted by theory. So rather than refer to this by some hypothetical particle or other entity  the phenomenon was called the ultraviolet catastrophe.  It turned out of course that it was the result of the quantisation of electromagnetic energy into what we now call photons. 

But, this is what they did. The anomalous rotation of galaxies helped lead to the proposal that dark matter existed (along with other evidence). The dark in "Dark matter" actually refers to the proposal that it does not interact with the EM field in the way normal matter does but only via it's bending of space-time.

Dark energy (was a very bad term and here the dark was used in your sense as unknown) was proposed to explain the observed, and unexpected, acceleration of the universe. However, in GR the possibility of such a force was well established idea initially introduced by Einstein in the mistaken idea that with it he could have a steady state universe. In this view of "Dark energy" it is an underlying very small curvature of space-time.

Regards Andrew

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14 minutes ago, andrew s said:

But, this is what they did. The anomalous rotation of galaxies helped lead to the proposal that dark matter existed (along with other evidence). The dark in "Dark matter" actually refers to the proposal that it does not interact with the EM field in the way normal matter does but only via it's bending of space-time.

Dark energy (was a very bad term and here the dark was used in your sense as unknown) was proposed to explain the observed, and unexpected, acceleration of the universe. However, in GR the possibility of such a force was well established idea initially introduced by Einstein in the mistaken idea that with it he could have a steady state universe. In this view of "Dark energy" it is an underlying very small curvature of space-time.

Regards Andrew

I think I'm probably not explaining myself very clearly, I'm also probably being a bit pedantic about how we name things. I'll just say this: suppose it turns out that one, other or both dark energy and dark matter do not exist. The phenomena we observe turn out to have some other explanation. They will then be looked upon by future historians of science as the "aethers" of our time. 

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18 minutes ago, Ouroboros said:

They will then be looked upon by future historians of science as the "aethers" of our time. 

Absolutely, along with philostogen (and I suspect all the proposed super symmetric particles) but without naming things it is difficult to make progress.

In fact what physicists understand as a photon or an electron now are very different from the ideas held initially.

Regards Andrew

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10 hours ago, andrew s said:

Absolutely, along with philostogen (and I suspect all the proposed super symmetric particles) but without naming things it is difficult to make progress.

In fact what physicists understand as a photon or an electron now are very different from the ideas held initially.

Regards Andrew

My understanding of both photon and electron has changed fundamentally over the past year alone. I've gone from a position of talking confidently about their nature to now, where at least I know with certainty, that my understating is limited and in error! Small progress, but one nonetheless of which I'm quite proud :)    I think the frustration over naming and models used by Physicists comes from the mistaken belief by the public that science delivers absolutes. The reality of course is more in the realm of temporal truths.  I'll admit to a naming convention that does frustrate me though; it frustrates me when common language is used such as colour or flavour in connection with particles or even worse when we anthropomorphise by taking about the life of a muon or "what would we experience in a black hole".  This type of playful language I think can lead to deep seated to misconceptions. That said, I am as guilty as any, it's is hard to convey ideas about theses concepts without using language that is familiar.

 

Jim

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23 hours ago, Patrick2568422 said:

To my understanding, matter is just crystallized energy. So is dark matter the crystallized form of dark energy? Sorry if this is a bit of a stupid question, just couldn't get it off my mind.

Any answers would be much appreciated - thanks.  

I don't  know either way. But it's quite an interesting idea. 

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On 10/04/2017 at 19:34, saac said:

This type of playful language I think can lead to deep seated to misconceptions. That said, I am as guilty as any, it's is hard to convey ideas about theses concepts without using language that is familiar.

 

Jim

Indeed. If language becomes entirely unfamiliar it ceases to be language and simply becomes a noise! Didin't I read somebody quote, then extend, an Eddington remark that you might as well call these entities Slithy Toves because that's exactly what they are!

:icon_mrgreen:lly

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34 minutes ago, ollypenrice said:

it's is hard to convey ideas about theses concepts without using language that is familiar.

and

34 minutes ago, ollypenrice said:

If language becomes entirely unfamiliar it ceases to be language and simply becomes a noise!

I agree absolutely. However, you gain familiarity through study and trying ideas out. With the internet a whole world of quality sources are available (as well as a lot of dross) to study and see how different authors put things. I guess it is just simpler to cast your ideas to the wind than study what is currently being discussed in real science.

Regards Andrew

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1 hour ago, andrew s said:

and

I agree absolutely. However, you gain familiarity through study and trying ideas out. With the internet a whole world of quality sources are available (as well as a lot of dross) to study and see how different authors put things. I guess it is just simpler to cast your ideas to the wind than study what is currently being discussed in real science.

Regards Andrew

The relationship between language and modern physics really is an interesting area though. Bohr famously said, 'I feel somehow suspended in language.' When we don't have a name for something, but we feel we should have, we are in an exasperating conceptual never-never land, I think.

Olly

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I read about this on phys.org this morning.... dark matter has been photographed for the first time using gravitational lensing to reveal how it ties a 'web' between galaxies... since dark matter has no measurable mass and does not reflect light, this is the only way "they" have found to prove it even exists....

Here's the composite photo taken by the University of Waterloo... the 2 whiter ares are galaxies and the red areas are the dark matter bridging the gap between them:

waterloorese.jpeg

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29 minutes ago, Art Gecko said:

since dark matter has no measurable mass

A truly magnificent image. Just one point it does have significant mass-energy otherwise it would not bend the light to enable us to compute where it was from gravitational lensing. What we don't have a clue about is what form it takes. The image supports the idea that it is cold (i.e. not moving at relativistic speeds) otherwise the webs of dark matter would dissipate.

Regards Andrew

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1 hour ago, ollypenrice said:

The relationship between language and modern physics really is an interesting area though.

Indeed it is. The language of modern physics is mathematics. We name the entities the mathematics relate to one another and the observables we control and measure. When these are at "human" scale we can grasp them reasonably well but when the are too big or two small we fail more often than not. If you are comfortable with abstraction then you don't need to worry you just trust the computations and compare them with what we measure.

However, it is not the only area where we have difficulty in understanding e.g. emotions. As a prince once infamously said "what is love anyway"!

Regards Andrew

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19 minutes ago, andrew s said:

A truly magnificent image. Just one point it does have significant mass-energy otherwise it would not bend the light to enable us to compute where it was from gravitational lensing. What we don't have a clue about is what form it takes. The image supports the idea that it is cold (i.e. not moving at relativistic speeds) otherwise the webs of dark matter would dissipate.

Regards Andrew

You are correct of course... All matter has mass, and it's estimated that dark matter makes up 25% of all the mass in the universe.... I guess I meant to say it doesn't emmit, absorb or reflect light, which is why it's so hard to pinpoint what it is exactly, but I do agree, it's a lovely image for something we know so little about!

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Dark matter may be the answer to the 'missing mass' issue. But have a read up on Modified Newtonian Dynamics - or gravity behaving differently at slow acclerations - interesting stuff. Doesn't discount Dark Matter , but it's predictions are very exacting.

Just goes to show we really don't know.

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45 minutes ago, AlistairW said:

Dark matter may be the answer to the 'missing mass' issue. But have a read up on Modified Newtonian Dynamics - or gravity behaving differently at slow acclerations - interesting stuff. Doesn't discount Dark Matter , but it's predictions are very exacting.

Just goes to show we really don't know.

I have read up on modified gravity theories. This is a currently active area of research along with Dark Matter and Dark Energy. We never "really know" in science we just have theories we test against reality and select the ones that do best . Even when proved wrong in some situations theories can still have practical utility.

Regards Andrew

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