Could Dark Matter Possibly Be . . .

[Martin]

Chris,

Variable Gravity. What are your thoughts on this? Since Newton's laws had to be modified for the extremely small ...isn't it likely that it may need to be modified for the extremely large? Wasn't DM & DE born from the failure of computers to accurately simulate the formation and motion of galaxies which, was based solidly on Newtonian Laws? Can observations be explained just the same by modifying gravity?

[Chris Peterson]

Chris,

Variable Gravity. What are your thoughts on this? Since Newton's laws had to be modified for the extremely small ...isn't it likely that it may need to be modified for the extremely large? Wasn't DM & DE born from the failure of computers to accurately simulate the formation and motion of galaxies which, was based solidly on Newtonian Laws? Can observations be explained just the same by modifying gravity?

I think the idea of "variable gravity" is just that- an idea. It hasn't really risen to the level of a proper theory. And it isn't needed, since current theory seems to do an excellent job of explaining what we observe.

I would not assess dark matter and dark energy in the same sentence. Their observed effects are radically different. We observe dark matter in a variety of ways, not just the motion of galaxies. Attempts to modify the theory of gravity have not been successful in explaining all our observations. They are perfectly explained, however, with no change to fundamental theory at all, by the simple presence of mass- mass which our standard theories of the creation of the Universe also requires. That makes the explanation for dark matter very compelling.

Dark energy however, in the context of general relativity, might indeed be treated as a modification of gravity. The jury is still out on that possibility. But no single variable gravity approach works at both the scale of galaxies and the scale of the Universe.

I would argue that our understanding of gravity, dark matter, and dark energy are pretty well supported by observation and theory, much more so than any theory of variable gravity. So the proper position should be that current theory is probably correct, or nearly so, and variable gravity is probably not. But that also means that nobody should be saying with absolute certainty that either is wrong.

[harry]

G'day from the land of ozzzzz

There is alot work been done on many topics of cosmology. I would say they have about 5 % information if that of the working processes and gravity is one topic that is so close and yet so far.

These are interesting links on gravity shielding

[inappropriate link removed - Nereid]

and

http://arxiv.org/abs/0712.4086

Mass Screening in Modified Gravity
Authors: Gregory Gabadadze, Alberto Iglesias
(Submitted on 26 Dec 2007)

Abstract: Models of modified gravity introduce extra degrees of freedom, which for consistency with the data, should be suppressed at observable scales. In the models that share properties of massive gravity such a suppression is due to nonlinear interactions: An isolated massive astrophysical object creates a halo of a nonzero curvature around it, shielding its vicinity from the influence of the extra degrees of freedom. We emphasize that the very same halo leads to a screening of the gravitational mass of the object, as seen by an observer beyond the halo. We discuss the case when the screening could be very significant and may rule out, or render the models observationally interesting.

and

http://arxiv.org/abs/physics/0701091

Gravity Control by means of Electromagnetic Field through Gas or Plasma at Ultra-Low Pressure
Authors: Fran De Aquino
(Submitted on 8 Jan 2007 (v1), last revised 15 May 2008 (this version, v7))

Abstract: It is shown that the gravity acceleration just above a chamber filled with gas or plasma at ultra-low pressure can be strongly reduced by applying an Extra Low-Frequency (ELF) electromagnetic field across the gas or the plasma. This Gravitational Shielding Effect is related to recent discovery of quantum correlation between gravitational mass and inertial mass. According to the theory samples hung above the gas or the plasma should exhibit a weight decrease when the frequency of the electromagnetic field is decreased or when the intensity of the electromagnetic field is increased. This Gravitational Shielding Effect is unprecedented in the literature and can not be understood in the framework of the General Relativity. From the technical point of view, there are several applications for this discovery; possibly it will change the paradigms of energy generation, transportation and telecommunications.

[Martin]

Chris, I have been looking but I am unable to locate info on the M-Theory as it relates to DM & DE. Does Quantum Mechanics support these theories too?

[Chris Peterson]

Chris, I have been looking but I am unable to locate info on the M-Theory as it relates to DM & DE. Does Quantum Mechanics support these theories too?

String theories might address dark matter, because they address the fundamental nature of particles, and dark matter is most likely composed of ordinary particles. Dark energy isn't really a part of these theories yet, although it conceivably could become so in the context of string theory's attempt to integrate gravity into a grand theory of everything.

QM neither supports nor fails to support dark matter observations. It would be relevant in describing the behavior of dark matter particles, but until the nature of those particles is better known, it is difficult to see how they fit in with QM.

If dark energy is taken as equivalent to vacuum energy, then QM is useful in describing it. If it is taken as an as yet not understood behavior of gravity, than QM is, of course, not useful, as QM and GR (or any other theory of gravity) remain disconnected.

[zooite871]

The blazelabs website doesn't look at all like real science.

[Martin]

Could DM be a reaction/effect of gravitrons entering and passing thru our spacial dimension?

[apodman]

dark matter is most likely composed of ordinary particles

Do I misunderstand "non-baryonic"?

[Chris Peterson]

Could DM be a reaction/effect of gravitrons entering and passing thru our spacial dimension?

Gravitons are completely hypothetical, and not even required by most theories of gravity. The physical existence of dimensions beyond the four we have evidence for is hypothetical and has no supporting observations.

The bottom line is that you could shoot off "could dark matter be..." questions forever, and nothing would be accomplished. There are existing theories about the nature of dark matter- real theories that make predictions and are testable. The most popular theory is also the simplest: dark matter consists of non-baryonic particles. Such particles are known to exist; there's nothing particularly exotic about them. The idea that there may be other, so far unexamined particles in this family isn't difficult to believe.

[Chris Peterson]

dark matter is most likely composed of ordinary particles

Do I misunderstand "non-baryonic"?

I don't know. Non-baryonic refers to particles that aren't made up of baryons. Electrons and neutrinos are examples of particles that are non-baryonic. When I said "ordinary" particles, I didn't mean particles we've already identified, only particles that behave, in general, like other particles or particle families we know of.

[apodman]

Do I misunderstand "non-baryonic"?

I don't know.

Yet you intuitively answered the question I should have asked (what you meant by "ordinary"). Thank you.

Non-baryonic refers to particles that aren't made up of baryons. Electrons and neutrinos are examples of particles that are non-baryonic. When I said "ordinary" particles, I didn't mean particles we've already identified, only particles that behave, in general, like other particles or particle families we know of.

Okay, I should go off and do my own research here, but while I have you on line ...

Since baryons can decay to protons plus whatever, they are all at least as heavy as protons, so it's easy for me to put all the known light-weight particles (electrons, neutrinos) in the class of non-baryons. But (1) are all of the proton-or-heavier particles we have identified baryons? (2) do we think there are proton-or-heavier non-baryonic particles as a constituent of dark matter? and (3) are we thinking about uncharged or charged non-baryonic particles as a constituent of dark matter?

[Chris Peterson]

Since baryons can decay to protons plus whatever, they are all at least as heavy as protons, so it's easy for me to put all the known light-weight particles (electrons, neutrinos) in the class of non-baryons. But (1) are all of the proton-or-heavier particles we have identified baryons?

I'm not a particle physicist, so take what I say with caution. But yes, I think there are heavy non-baryons. Most baryons have a rest mass around 1 GeV. There are a number of mesons heavier than that (the Upsilon particle is nearly ten times more massive). Perhaps more relevant here, there are leptons other than the neutrinos, such at the Tau lepton (1.8 GeV), which are more massive than protons.

(2) do we think there are proton-or-heavier non-baryonic particles as a constituent of dark matter?

I think that's up in the air. We know the total mass of a dark matter cloud when we observe it, but I haven't seen anything to argue for lots of light particles versus fewer heavier ones. There may be something in the Big Bang nucleosynthesis models- those are beyond me. I think that current dark matter theories tend to favor heavy particles, but I don't know the theoretical or observational basis for that.

(3) are we thinking about uncharged or charged non-baryonic particles as a constituent of dark matter?

My understanding is uncharged, or paired particles that produce a net zero charge in bulk material. There's no evidence that dark matter dynamics are caused by anything other than gravity. Given the amount of dark matter that seems to be out there, I don't think there's any way it could have a net charge.

[Martin]

Chris wrote:

Gravitons are completely hypothetical, and not even required by most theories of gravity. The physical existence of dimensions beyond the four we have evidence for is hypothetical and has no supporting observations.

I noticed you did not attempt to answer my direct question but then again how can you or anyone else..so I will not find fault in your reply. but....how closely related is hypothetical to theoretical? I believe the holy grail of Qm is the Graviton -is it not? Why is the subatomic universe not considered a "dimension"?

The bottom line is that you could shoot off "could dark matter be..." questions forever, and nothing would be accomplished.

Oh really? I have been on the same subject for weeks now (sorry). I have only proposed 1 theory and that is... a needed modification to Newton's laws. When a scientists closes his eyes and turns his/her head away from fruitful questions they are no longer scientists but rather they become propagators of faith.

There are existing theories about the nature of dark matter- real theories that make predictions and are testable.

It's not that I blindly disagree because I enjoy to. There is something missing from the theories on DM & DE. Although one cannot deny the importance of falsifiability, one should not undermine the plausibility based solely on our technological barriers. History has proven this point again & again & again.

Also...I think there is something very exotic about atom-less particles that somehow have more gravitational influence on our observable universe than all the observable matter contained in it. Not to mention that this DM theory is also non-testable as well. At least until we overcome some technological barriers, eh?

Chris wrote:

There's no evidence that dark matter dynamics are caused by anything other than gravity.

Elaborate please

[apodman]

Thanks, Chris. I knew the menagerie of known particles once, but the book is buried and the memory is beyond recall. And I just wanted to check my concepts one last time before I go plodding forward.

[Chris Peterson]

Chris wrote:

Gravitons are completely hypothetical, and not even required by most theories of gravity. The physical existence of dimensions beyond the four we have evidence for is hypothetical and has no supporting observations.

I noticed you did not attempt to answer my direct question but then again how can you or anyone else..so I will not find fault in your reply. but....how closely related is hypothetical to theoretical? I believe the holy grail of Qm is the Graviton -is it not? Why is the subatomic universe not considered a "dimension"?

In this context, I mean "hypothetical" as something that is proposed, with little or no theory to support it. The graviton is attractive to QM theorists because it provides a force mediator that is symmetric with the (known) force mediator particles. But simple elegance alone isn't a very strong argument.

Why would the subatomic universe be considered a dimension any more than the Universe at any other scale? Dimensionality has nothing to do with scale.

Chris wrote:

The bottom line is that you could shoot off "could dark matter be..." questions forever, and nothing would be accomplished.

Oh really? I have been on the same subject for weeks now (sorry). I have only proposed 1 theory and that is... a needed modification to Newton's laws. When a scientists closes his eyes and turns his/her head away from fruitful questions they are no longer scientists but rather they become propagators of faith.

Sorry, a minor weakness of English. It would be better to say "one could shoot off..." The point being, there is a big difference between speculation and proposing a concrete theory.

It's not that I blindly disagree because I enjoy to. There is something missing from the theories on DM & DE. Although one cannot deny the importance of falsifiability, one should not undermine the plausibility based solely on our technological barriers. History has proven this point again & again & again.

I don't understand your point about technological barriers. From a theoretical standpoint, DM is on stronger ground than DE (again, I don't know why these get discussed together, when there is absolutely nothing in common between them). Of course, their theory is still being developed, so in a sense you could say something is missing. I have the sense that you mean it in a more philosophical way, however. That is, you don't find the theories personally satisfying.

Also...I think there is something very exotic about atom-less particles that somehow have more gravitational influence on our observable universe than all the observable matter contained in it. Not to mention that this DM theory is also non-testable as well. At least until we overcome some technological barriers, eh?

I don't find the idea of massive, non-baryonic particles particularly exotic. Or at least, no more exotic than the menagerie of particles that already make up the Standard Model! And the idea of non-baryonic DM is eminently testable. We have already made different kinds of observations that are consistent with such matter, and theory predicts other observations we will soon have the capacity to make.

Chris wrote:

There's no evidence that dark matter dynamics are caused by anything other than gravity.

Elaborate please

We can map out the position of dark matter around galaxies and galaxy clusters. If it were charged (that is, if it consisted of particles that individually carried the same charge) the shape of the dark matter clouds would be substantially different. As it is, the shape is just what we'd expect if the cloud were made up of ordinary baryonic particles, with gravity being the dominant force in play. Of course, we know little about the sort of particles involved, so one can't discount something exotic like tiny fractional charges. But I think the simplest viewpoint is that dark matter clouds carry little or no net charge.

Additionally, charged particles interact with EM. We can study clouds of charged particles by examining how the polarization of light passing through them is affected. AFAIK, no observations have shown polarization effects from dark matter. It does seem reasonable that matter which doesn't interact (or only weakly interacts) with EM would itself not carry a charge.

[Martin]

Chris wrote:

I don't understand your point about technological barriers. From a theoretical standpoint, DM is on stronger ground than DE (again, I don't know why these get discussed together, when there is absolutely nothing in common between them). Of course, their theory is still being developed, so in a sense you could say something is missing. I have the sense that you mean it in a more philosophical way, however. That is, you don't find the theories personally satisfying.

Isn't the commonality gravity?
And no -I meant there are still holes in the theories. Thus...why it is still a theory and not a truth. There remains a possibility that we could be chasing our own imagination based on circumstantial evidence. But I do acknowledge that I could be wrong as well. I am just trying to trade thoughts.-forgive me. Just don't pretend that the theory of DM is falsifiable. We are not at that point yet.

My reference to technological barriers was in response to you writing:

There are existing theories about the nature of dark matter- real theories that make predictions and are testable.

I only meant that our technical capabilities should continue to increase with time. Just because we do not have the ability to test something now doesn't necessarily mean it has to be false.

[Chris Peterson]

Isn't the commonality gravity?

No. If there's any commonality, it is that both are part of the Universe's energy budget. But dark matter is just that... matter. Like anything with mass, it is affected by gravity, but otherwise has nothing to do with gravity. Dark energy is... energy. And there's no evidence that it has anything to do with gravity. It's possible to speculate that one explanation for dark energy could involve an adjustment to gravitational theory, but so far that is nothing more than a weak hypothesis that nobody knows how to test.

Just because we do not have the ability to test something now doesn't necessarily mean it has to be false.

I don't think anybody has suggested that. A theory is poor, or even non-scientific, if a reasonable test can't be suggested. In some cases, such a test might be beyond our current technology.

[Sputnick]

Sorry Chris, but Dark Matter (whether it exists or does not exist) was a term 'invented' to possibly explain some observed effects. Like the Big Bang itself, you and apparently most astronomers have taken hold of a possibility and given it a religious conversion to fact. Doing so is not science.

[Doum]

[Nereid]

Sorry Chris, but Dark Matter (whether it exists or does not exist) was a term 'invented' to possibly explain some observed effects. Like the Big Bang itself, you and apparently most astronomers have taken hold of a possibility and given it a religious conversion to fact. Doing so is not science.

Sputnick, I really would encourage you to participate in some of the existing discussions on the nature of astronomy as science.

You see, among other things, it is straight-forward to write the following:

but the electron (whether it exists or does not exist) was a term 'invented' to possibly explain some observed effects. Like the quark, you and apparently most physicists have taken hold of a possibility and given it a religious conversion to fact. Doing so is not science.

(and 'the atom' or 'the nucleus', along with a great many other words, would work too).

I'm pretty sure you don't regard 'the electron' as just as theoretical as 'dark matter', but if all one has to go on is expressions such as that I'm quoting, surely you'd agree that there's no logical reason to conclude otherwise.

And to make the connection with astronomy, how about the association of two prominent green lines in the spectrum of many ('planetary') nebulae (among other astronomical objects) with certain 'forbidden' transitions of doubly ionised oxygen?

[Chris Peterson]

Sorry Chris, but Dark Matter (whether it exists or does not exist) was a term 'invented' to possibly explain some observed effects. Like the Big Bang itself, you and apparently most astronomers have taken hold of a possibility and given it a religious conversion to fact. Doing so is not science.

Indeed. Just like ordinary matter, which also was "invented" to explain observed effects. You've never seen ordinary matter, you've never touched it. We believe in it based on our observations of its electromagnetic interaction with other matter. In the case of dark matter, we believe in it because of our observations of its gravitational interaction with other matter. Our understanding of gravity is as good as our understanding of the electromagnetic force. I see no reason to accept the existence of one kind of matter and not another, when both are well supported by observation.

[Sputnick]

Nereid - comparing an electron to Dark Matter or the Big Bang is a stretch. Electrons are well enough known to have thousands of commercial applications. When Dark Matter reaches the same stage of investigation and application I think your comparison will be appropriate.

Chris - we have never touched matter? Forgive me for not having a dictionary in my pocket but is matter not the solid world around us? Is my computer keyboard, for instance, not composed of matter? You know, I think I'll look up an internet definition of matter .. but even before I do so I am sure my keyboard keys are not composed of Dark Matter just because they're black (with white letters.) Okay .. I found matter in Wikipedia .. if you have a different definition please provide it.

Matter
From Wikipedia, the free encyclopedia
(Redirected from Matter (physics))
Jump to: navigation, search
Matter is commonly defined as being anything that has mass and that takes up space. However this definition is ambiguous, and leads to some problems, leading some physicists to define matter in terms of certain types of elementary particles.

"Normal matter" constitutes about 5% of the mass of the observable universe, the remaining mass being composed of exotic and poorly understood forms of mass, currently known as dark matter and dark energy. There are four phases of macroscopic matter (solid, liquid, gas, and plasma) although some exotic phases (such as Bose-Einstein condensates and quark-gluon plasma) exist as well.

Contents

1 Definitions
1.1 Common definition
1.2 Mass definition
1.3 Quarks and leptons definition
2 Properties of matter
2.1 Bulk properties of matter
2.1.1 Solid
2.1.2 Liquid
2.1.3 Gas
2.1.4 Plasma
2.2 Fundamental properties of matter
2.2.1 Quarks
2.2.2 Leptons
3 Baryonic matter
4 Antimatter
5 Dark matter
6 Exotic matter
7 References
8 External links

Definitions

Common definition

Phosphorus sesquisulfide is a molecule made of four atoms of phosphorus, and three atoms of sulfur arranged in a C3v symmetry.The common definition of matter is anything which both occupies space and has mass. For example, a car would be said to be made of matter, as it occupies space, and has mass. In chemistry, this is often taken to mean what atoms and molecules are made of, meaning anything made of protons, neutrons, and electrons. For example, phosphorus sesquisulfide is a molecule made of four atoms of phosphorus, and three of sulfur (see image on right), and is thus considered to be matter.

However in physics, there is no broad consensus as to an exact definition of matter, partly because the notion of "taking up space" is ambiguous in quantum mechanics, and partly because mass doesn't lead to a "natural classification" of particles. Therefore physicists generally do not use the term matter when precision is needed, preferring instead to speak of the more clearly defined concepts of mass, energy, and particles. In discussions of matter and antimatter, normal matter is also sometimes referred to as koinomatter.[1]

Mass definition
Since space is problematic, a possible definition of matter could be anything that has mass. This leads to some inelegance problems in particle physics, as particles tend to be regrouped into "families" based on properties other than mass. For example, photons

...

[Chris Peterson]

Chris - we have never touched matter? Forgive me for not having a dictionary in my pocket but is matter not the solid world around us? Is my computer keyboard, for instance, not composed of matter? You know, I think I'll look up an internet definition of matter .. but even before I do so I am sure my keyboard keys are not composed of Dark Matter just because they're black (with white letters.)

I don't know what my computer keys are composed of... at least, I don't know by any direct means. They can't be touched, at least not without a high energy particle accelerator, and maybe not then. I get close, and there's this spooky action-at-a-distance force that pushes me away. Maxwell and others came up with some beautiful mathematics that describes this, which seems wonderfully predictive. But it's still just theory, of course, and who knows what the underlying reality is?

As for solid matter... well, I think it is mainly just empty space.

Sorry, I simply don't see a difference between normal matter and dark matter in terms of how we learn about it. All of our observations are indirect, and in both cases we attempt to match those observations to theory. Ordinary matter is easier to work with, so our observations are richer, and we are consequently more confident in our theories. But dark matter is well enough observed that we still have fair confidence in theories about it; dark matter is no more a term "invented" to explain observed effects than ordinary matter is.

[Sputnick]

One more comment for Chris and (Nereid also?)

Chris says, "In the case of dark matter, we believe in it because of our observations of its gravitational interaction with other matter. Our understanding of gravity is as good as our understanding of the electromagnetic force. I see no reason to accept the existence of one kind of matter and not another, when both are well supported by observation."

You believe that something is causing effects on other matter. Okay. You call it Dark Matter. Okay. That would all be acceptable IF you were to say "Something we call Dark Matter may be having these effects on Matter" .. but to say "Dark Matter is having these effects on Matter" is possibly wrong on two counts: 1 - Dark Matter may not exist; 2 - Something else besides anything yet considered may be causing the effects.

Equally as important is the undeniable fact that your statement attempts to include a group of people you are identifying only as 'we'. Is this 'we' you and your brother? You and the professor at university who perhaps presented Dark Matter as a possibility but which you translated into fact? You and a group of scientists who you are willing to name? Or are you using the term "we" to simply multiply the opinion of one person (yourself) into many persons? There is a 'we' on the other side of the table of debate table as well, who I do not know and so who I cannot name and therefore who I will not include in a 'we' when making statements I believe in, saying instead "I believe this may be true". In this forum, the 'we' who disagree that Dark Matter exists and causes the effects on Matter - that side of the debate table I have seen derided with words like "garbage" when expressing explanations they think may be valid. (That word not directed at me, but at a fan of the Plasma electric universe school of thought.) I do not know what the facts are .. not because of lack of education, but because scientists who are highly educated do not know if Dark Matter exists, if the Big Bang happened .. those things are just possibilities no matter how much you, Chris, or others, think they believe them to be facts.

[Sputnick]

[quote="Chris Peterson"]

"As for solid matter... well, I think it is mainly just empty space."

Yes .. from what I have read matter is mainly what is commonly thought of as empty (although I suspect that 'empty' will not apply, that that 'emptiness' is filled with something or somethings) with the particles spaced far, far, far apart. However - in the dimension we live in matter can be seen, tasted, enjoyed. I understand that with proper harmonics and permission from the ultimate power guiding and arranging particles and non-particles I could walk through walls and all that fantastic scientific and beautiful stuff -

but saying you can't touch matter because of someone's idea of electrical repulsion (or some such idea) between the matter your fingers are composed of and the matter your keyboard keys are composed of is simply believing in another idea which may or may not be true. We may be touching matter just as easily as we are not really touching matter. I will use a commonly believed example to say that the matter in Jesus' feet may actually have touched the matter the Sea was made of when he walked upon the water, or he may have been supported by reversed electric or gravitational or magnetic charges or whatever you call them with the matter separated. Enough for now.