Dark Matter Life/Civilizations

[Zachary Smith]

As I understand the current theory, most of the universe is composed of "dark matter" of unknown and unobservable material. We are aware of it only because of its gravitational effects on the visible universe and this is detectable only on the cosmic scale. None the less, as the theory goes, the vast majority of the universe is composed of this "exotic" material. We, the matter we are familiar with and the energy we know are minor constituents.

Here then is a question. Given the above to be true, is it then not only possibly but LIKELY that life exists, perhaps intelligent life and maybe even entire civlizations are present in the univserse, but composed of "dark matter"? If, after all, you assume life as we know it to be a consequence of natural conditions and functions and assuming the type of matter we are composed of is relatively rare, is it not reasonable to expect that life would have also developed and evolved from even MORE common "elements" in the universe? Could this life, these civilizations, actually be co-existing with us, before our very eyes, as it were, and we simply are unaware of them because we have not yet developed the means to "view" this "dark matter"? We may be surrounded by a gang of "dark matter" worlds and civilizations and simply cannot perceive them, right?

 

[Ronald Held]

We would have to know what the dark matter was composed of.
I cannot it see it being likely with the proposed potential particles.

 

[Zachary Smith]

Ronald Held said:
We would have to know what the dark matter was composed of.
I cannot it see it being likely with the proposed potential particles.

It all pretty much presupposes that they general laws of physics remain in play for "dark matter" also. There's no guess if that's the case or not. I forgot to mention that.

 

[Christopher]

It doesn't necessarily follow that dark matter can be the basis for life just because there's more of it than other stuff. I mean, over 98 percent of the non-dark matter in the universe consists of hydrogen and helium, but life can't be made of hydrogen and helium. Sure, we have hydrogen in us in various compounds (water, carbohydrates, amino acids, etc.), but most of the stuff of life is made of that remaining 2 percent: the carbon, the oxygen, the nitrogen, the phosphorus, assorted minerals in trace quantities. Life is made of the rare stuff, not the common stuff. (Well, it's made of the relatively common parts of the rare stuff. C, O, and N are pretty abundant compared to most other elements. But they're still quite scarce compared to hydrogen and helium.)

Also, the reason dark matter is virtually undetectable (so it's theorized) is because it doesn't interact much with anything, even other dark matter, except by gravity. And life is all about interactions.

Of course, we don't know very much about dark matter. But given what we do know, it's unlikely that it could be the basis for life of any sort.

 

[scotthm]

Christopher said:
the reason dark matter is virtually undetectable (so it's theorized) is because it doesn't interact much with anything, even other dark matter, except by gravity.

In other words, from a chemist's viewpoint, Dark Matter is pretty boring stuff.

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[Zachary Smith]

scotthm said:

Christopher said:
the reason dark matter is virtually undetectable (so it's theorized) is because it doesn't interact much with anything, even other dark matter, except by gravity.

In other words, from a chemist's viewpoint, Dark Matter is pretty boring stuff.

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If that's all true it would make it hard for there to be any dark matter elements comperable to the "regular" matter species. Then again, how much does anyone really know and how much is total theory?

 

[Christopher]

^^Well, first of all, in science, a theory isn't an unproven idea; that's a hypothesis. A theory is a systematic model that explains existing observations and makes predictions that can be tested by further observation and experiment. If those predictions are borne out, the theory is judged reliable. Everything in science, even the conclusively proven parts, is total theory, because the goal of science is to formulate theories (systematic models) that encompass and explain all knowledge. You can't really know what anything means until you have a theory to explain it, so "what we know" and "theory" are not opposites at all.

We believe dark matter exists because of our theory of gravitation -- or rather, because the observed motion of visible matter in the universe doesn't conform to what the theory predicts. So either the theory is incomplete or there is an unseen kind of matter producing the observed effects. While there are some physicists who have proposed a revised theory of gravitation that would explain those observations without the need for dark matter, new observations in recent years have not been consistent with that theory's predictions. Instead, those observations have been consistent with the current theory's (i.e. General Relativity's) predictions of the gravitational effects of dark matter.

So we do have observational evidence for the existence of an unseen form of matter. You don't have to see something directly to know it exists, because its effect on things you can see is real evidence that it's there. For instance, you can't see the wind, but if you see a flag waving and flapping on a pole, you know it's windy. By the same token, if you see that the stars in a galaxy are moving in ways that can only be explained by the presence of an invisible form of matter exerting a gravitational effect on them, then you know that matter is there.

The rest is largely deduction. We know that most of the dark matter can't be simply dark forms of ordinary matter (like rogue planetoids or brown dwarfs), because those would cause detectable gravitational microlensing of the light coming from behind them and would give off or reflect at least some light. Searches for such massive compact halo objects (MACHOs) have found little to no evidence of their existence. There may be some there, but nowhere near enough to account for all the missing mass.

So that means dark matter can't be ordinary (baryonic) matter, the kind that interacts electromagnetically and by strong nuclear force and forms elements and molecules and solid objects. If it were, it would clump into detectable MACHOs. That leaves weakly interacting massive particles (WIMPs), which would interact only by gravity and weak nuclear force, and thus wouldn't form into nuclei or molecules or bigger things.

So we haven't detected WIMPs directly, but we've ruled out most of the other possibilities. We may not have proof of what they are, but we have confirmed that there are a lot of things they can't be.

http://en.wikipedia.org/wiki/Dark_matter

 

[Zachary Smith]

^^

So, in essence, we're looking at the possibility of a dark-matter/energy "ether" spread more or less uniformly across the entire universe composed of "non-baryonic" elementary particles, right? This would be the equilvalent to the envelope of water that sea-going creatures live in, or our own atmosphere--a presence so ubiquitous we generally don't notice it, visible to us only due to its effect on objects we CAN notice and revealing of itself only if we can leave the vicinity of its environment behind, if I understand correctly. Truely, space would not be "empty" until and unless you could void it of EVERY particle, normal, dark and energy. Say, for the sake of discussion, you had a mechanism for emptying a square yard of literally EVERY particle, every last IOTA of material and energy of ANY sort. What would you have then? A block of "nothing"? What would conditions be like in that area?

I ask this in relation to the thought that I have long held that "space", even a "void of nothing" must be SOMETHING. If "space" were nothing, one should be able to pass the distance between "here" and "there" instantaneously. Clearly, it IS a "something" (a dimension? but if so, what is a "dimension" composed from--clearly neither matter nor energy but some even more fundamental components).

Obviously even "empty" space is a construct of some kind. It exists. We cannot interact with it, detect the material of its composition yet it "exists". This is demonstated by the fact that it takes time to traverse it. While energy is not required if the object traveling through a given space is already in motion, the fact that it costs TIME to cross proves that "something" is there. Otherwise, as I said before, the movement from "here" to "there" would be instantaneous. "Distance" would be a measure of the "size" of space we are examining, therefore whatever it is, it CAN be measured. If it were "nothing", it could not.

So, even more fundamentally, even beyond the miasma of "dark matter/energy" that occupies it, what IS space? I suppose in a gross terminology it could be called "reality" but what might its constituent components be made from? Something more elementary than "elementary particles" at the very least.

 

[Christopher]

Zachary Smith said:
So, in essence, we're looking at the possibility of a dark-matter/energy "ether" spread more or less uniformly across the entire universe composed of "non-baryonic" elementary particles, right?

No, dark matter does "clump" gravitationally. Indeed, that might be why galaxies exist in the first place -- the dark matter became concentrated in clumps and its gravity concentrated baryonic matter along with it. Our galaxy, like any galaxy, is immersed within a much larger halo of dark matter. (This is how we found dark matter -- the motion of stars in other galaxies was consistent with the presence of a lot of unseen mass pervading and surrounding them.) Astronomers even recently detected a "dark matter galaxy" -- a dark-matter concentration of the sort that surround galaxies, but without actual stars within it. Perhaps that's the kind of proto-galaxy that a "real" galaxy would eventually form in.

But because the particles are weakly interacting, these concentrations are pretty much just loose clouds of the stuff, existing on a very large scale, rather than forming into molecules or solid bodies.

Truely, space would not be "empty" until and unless you could void it of EVERY particle, normal, dark and energy. Say, for the sake of discussion, you had a mechanism for emptying a square yard of literally EVERY particle, every last IOTA of material and energy of ANY sort. What would you have then? A block of "nothing"? What would conditions be like in that area?

Well, this isn't a hypothetical question, since an immense void empty of both normal and dark matter was actually discovered just months ago:

http://space.newscientist.com/article/dn...ars-across.html

How it formed and what it means to our cosmological models are questions still being explored. It's believed that it's evidence of dark energy at work, though. See the article for an explanation.

 

[Meredith]

I think they make up Dark Matter and Dark energy because they don't yet know exactly how gravity and matter work. Think of the typical though experiment with the rubber sheet and Ball bearing.

You stretch the rubber sheet over a large cylinder then place a ball bearing on top of it. The ball bearing creates a dimple.


Now what about this analagy I have just created.


You take a large cylinder and fill it with water to the top, then you stretch a rubber sheet over the top of the open cylinder and seal it. Place the ball bearing on top and what happens?

Well near the ball bearing it slopes down, however much further away from it rises due to water below the sheet not wanting to compress.


Could space-time operate in a simular manner? Matter causes a dimple when it is clumped together, but further out it acts in a slighly repulsive manner?


It could explain the "repulsive" force of Dark Energy.

 

[Christopher]

^^Fine. Now express it in the form of mathematics that are consistent with what we do know about the universe and that make testable predictions about the new stuff.

The idea that the effects attributed to dark matter are an illusion resulting from an inadequate understanding of gravitational theory was the gist of MOND (Modified Newtonian Dynamics), a theory that proposed an alternate set of equations for gravity that, according to its proponents, was consistent with the observed gravitational effects attributed to dark matter as well as with more familiar gravitational effects (because a new theory has to explain everything, including the old stuff). The idea was that gravity doesn't follow a simple inverse-square law but drops off more gradually over large distances.

However, as I mentioned above, more recent observations of the interactions and stellar motions of distant galaxies gave results that are not consistent with MOND's equations but are consistent with the predictions of the dark matter model. And there have been other observations consistent with dark matter as well. We do have an increasing amount of evidence that it is real, and that alternative explanations requiring new laws of gravitation aren't consistent with the facts.

 

[Ronald Held]

The dark matter model fits the observations better at this time and does not have to have any modifications made to GR.

 

[JuanBolio]

I'm kinda dubious about that one. Cosmologists just pulled "dark matter" and "dark energy" out of their collective asses to account for the giant X factor in galactic cohesion and the expanding universe.

 

[Ronald Held]

It is a little more physically based than that. Which would you prefer, changing the form of the Physical laws or to therorize dark matter particles and dark energy which, I think, is the comsological constant?

 

[Christopher]

JuanBolio said:
I'm kinda dubious about that one. Cosmologists just pulled "dark matter" and "dark energy" out of their collective asses to account for the giant X factor in galactic cohesion and the expanding universe.

Hey, that's what Maxwell did when it occurred to him that electricity and magnetism could be parts of the same thing, or when Newton realized that celestial motion and earthly motion could be explained by the same force of gravitation, or when Einstein had the insight that our perceptions of time, distance, and motion were relative to our frames of reference. They looked at unexplained ideas and imagined what might fill in the gap. That's how science works. That's how it comes up with new ideas in the first place: by imagining things to account for the gaps in our knowledge.

What you're overlooking is that those ideas pulled out of the imagination can be tested by observation and experiment. Yes, when dark matter was first proposed, it was just an educated guess, a possibility with no proof to back it up. But as I already explained, the theory makes specific predictions which have been tested and confirmed. That has increased the likelihood that it really exists. It's gone beyond the stage of being an educated guess; it's proven to be successful at predicting actual results.

True, it's not absolutely conclusive, and there's still a lot we don't know. But that doesn't mean the idea is worthless or is just a wild guess. The evidence is mounting in its favor, and the evidence for rival theories isn't there.

 

[FordSVT]

Zachary Smith said:

scotthm said:

Christopher said:
the reason dark matter is virtually undetectable (so it's theorized) is because it doesn't interact much with anything, even other dark matter, except by gravity.

In other words, from a chemist's viewpoint, Dark Matter is pretty boring stuff.

---------------

If that's all true it would make it hard for there to be any dark matter elements comperable to the "regular" matter species. Then again, how much does anyone really know and how much is total theory?

I'd think there's a greater chance for extra-dimensional lifeforms we can't interact with than dark matter life forms, but since we know very little about the science of either, who's to say?

 

[Zachary Smith]

FordSVT said:

Zachary Smith said:

scotthm said:

Christopher said:
the reason dark matter is virtually undetectable (so it's theorized) is because it doesn't interact much with anything, even other dark matter, except by gravity.

In other words, from a chemist's viewpoint, Dark Matter is pretty boring stuff.

---------------

If that's all true it would make it hard for there to be any dark matter elements comperable to the "regular" matter species. Then again, how much does anyone really know and how much is total theory?

I'd think there's a greater chance for extra-dimensional lifeforms we can't interact with than dark matter life forms, but since we know very little about the science of either, who's to say?

Here's a question then: would "extra-dimenstional matter" exert any gravitational influence detectable in the visible universe and, if so, could dark-matter itself then be of "extra-dimensional" nature?

 

[FordSVT]

That would depend on the nature of gravity. Some propose that the reason the major forces are so unbalanced (nuclear forces are tremendously strong but only over very small areas, gravity is very weak but acts over very large areas) is because they're spread out among dimensions. Hell, we can't even prove there ARE extra dimensions, it just looks that was because it's the only way physicists can get things like superstring theory to work.

I have a great interest in the subject matter and I read all the layman books I can (Greene, Hawking, et al), but it's hard to keep some of this stuff straight when you're not immersed in it a great deal of the time. I'm certainly not as well versed in it as Mr. Bennett appears to be, and I'm sure he's not as well versed as people who actually work in the field.

 

[Christopher]

^^Oh, definitely. I'm just an interested layperson who follows the science news. But the idea that some of the "missing mass" could be extradimensional matter exerting a gravitational force across dimensions has definitely been proposed. And it would be consistent with the observations we have, if we assume that the matter in those parallel universes is clumped in much the same general areas where galaxies clump in our universe. But without any observational or experimental support for the idea, there's no reason to favor it over the notion of weakly interacting massive particles within our universe.

But both hypotheses are saying the same thing: that there is extra mass we can't see, that it isn't just an illusion caused by an incomplete theory of gravity. We don't know what it is yet, but we have good evidence that it does exist.

 

[Zachary Smith]

Christopher said:
^^Oh, definitely. I'm just an interested layperson who follows the science news. But the idea that some of the "missing mass" could be extradimensional matter exerting a gravitational force across dimensions has definitely been proposed. And it would be consistent with the observations we have, if we assume that the matter in those parallel universes is clumped in much the same general areas where galaxies clump in our universe. But without any observational or experimental support for the idea, there's no reason to favor it over the notion of weakly interacting massive particles within our universe.

But both hypotheses are saying the same thing: that there is extra mass we can't see, that it isn't just an illusion caused by an incomplete theory of gravity. We don't know what it is yet, but we have good evidence that it does exist.

In that case, would not the sheer volume of mass suggest that some of these other dimensions might be larger than current models indicate? Aren't most of the extra-dimensional planes thought to be VERY SMALL, on the order of microns or something? Unless they are packed to the gills with matter, how could they be so tiny and yet still contain most of the matter in the universe? Alternatively, there would have to either be MORE than the theorized 10 or 11 dimensions or some of them would have to be LARGER than current theories suggest. If so, they may be larger enough to enter. Or, perhaps, be ALREADY occupied.