Exotic Matter??

[dreadmoc]

Well, some of you who have been here for a long while my remember my rants against the still undiscovered 'Dark Matter', or 'Dark Energy' that the Theorists have, as Al Gore would put it, finally built a consensus about, to the point that many laymen now actually believe that it does exist.

My contention is, of course, that nothing actually exists until you prove by accepted scientific methods, that it does exist. Until then, it is only theory, and the attempts by theoretical astrophysicists to rally around the possibly erroneous calculations of their peers, and beat down all opposition has not created a reality. Until the dragon is led into the village with a rope around it's neck, it is only a myth. The fact that villagers go missing does not create a dragon.

But more importantly, does the creation of the dragon not mask the real reason that the villagers are missing? The acceptance of the myth thus forestalls the solution of the mystery. So the purveyors of the myth collect their rewards, and the villagers continue to go missing.

I'm sure we all now understand that the rewards, whatever they were, were the whole reason for the myth?

Now we have ‘exotic matter’, proposed, I believe, as the catalyst (?) for the stability (?) of wormholes.

For God’s Sake Gentlemen! When will it end?! I understand the importance of publishing in your field, but please tell me when the existence of ‘wormholes’ was even established. Your profession is turning into a huge game of dungeons and dragons. (No offense meant to D&D players)

I realize that all of the easy discoveries have been made. And I know what great pressure you are under to break new ground, and publish your findings. But please! Let’s stick to reality. Your field is a field of great thinkers. (Obviously not all theoretical physicists are great thinkers). But whatever you do, don’t let your chosen field go the way of the environmentalists, and become the laughing stock of the scientific community.

 

[Shpaget]

So, are you saying that there was no light until it somebody scientifically proved it, and others accepted those claims?
Oh... that's why they call it the Dark Ages.

 

[ramparts]

I'm not sure what you mean that dark matter and dark energy haven't been "discovered." They're not just, as you seem to suggest, edifices that theorists created because they were bored. We have abundant evidence of the effects of both of them. Not knowing what they are doesn't mean we don't know that they exist.

So what, to you, would constitute a "discovery" of dark matter or dark energy, that we haven't already done? For example, we've imaged gravitational effects coming from regions where there's no light (see the Bullet Cluster); what would you consider sufficiently robust to call a discovery?

 

[scottb50]

So what, to you, would constitute a "discovery" of dark matter or dark energy, that we haven't already done? For example, we've imaged gravitational effects coming from regions where there's no light (see the Bullet Cluster); what would you consider sufficiently robust to call a discovery?

I wonder if instead of a mysterious form of matter it is the accumulated mass of free matter, particles to small to image but particles that are made of the same thing everything else is made of. Stars are made up of this dust that is gravitationally collected into bigger and bigger masses that attract more and more matter. While widely dispersed ordinary matter would be impossible to detect, but the mass could easily add up.

If the matter hasn't built up to a visible object it could still show gravitational effects on other objects. That it has to be an unknown exotic form of matter seems to go against observed natural materials. In other words it may be our lack of observational fidelity then some unknown matter.

 

[ramparts]

If you had that much "normal" matter in that small a space, you'd see light. This stuff has to be something different. We know it's there, we know its characteristics, we're just less clear on what exactly it is.

 

[dreadmoc]

So, are you saying that there was no light until it somebody scientifically proved it, and others accepted those claims?
Oh... that's why they call it the Dark Ages.

Not even a similar analogy. I don't want to get drawin into a discussion concerning the existence of light, but the only way I can see that idea would have relevance is if we were blind! If so, how would one prove the existence of light?

There are certainly ways, I'm sure, and were we all blind, the existence of that phenomena not visible to us would soon be proven.

In that case, yes! To have claimed the necessity of it's existence with no idea as to source or substance, based solely on a certain effect (the sound of birds at regular intervals?), would probably be considered speculative, at best, since it is possible that there could be other reasons for that particular effect, or any other, for that matter.

 

[dreadmoc]

If you had that much "normal" matter in that small a space, you'd see light. This stuff has to be something different. We know it's there, we know its characteristics, we're just less clear on what exactly it is.

No, we do not 'know it is there'. Interpretation of instrumentation indicates something. If you accept 'theories' of galactic dynamics, you are likely to interpret readings to reflect what you already believe. And all ideas relating to galactic dynamics are only theories.

Gentlemen! Before you use a hypothesis to support additional speculation, please, prove your original hypothesis. Just as with global warming, you have not followed the necessary steps to arrive at your correct destination. You are attempting to chart the river without using a compass, and are now lost in a completely uncharted tributary.

 

[Shpaget]

Why my light analogy wouldn't be appropriate?
Just seeing light's effect on our world is not scientific proof of its existence, nor does it describe it's nature.

We see the effects of "something" out there that might explain the way things move around, but we cannot see that "something" directly, just like we see the objects that are illuminated, but can't see the stuff that illuminates them.

We are not blind, but we can't see the photons themselves. We can, however, see how it effects illuminated objects.
We can't see the dark matter, but we can see it's effects on universe.

 

[ramparts]

If you had that much "normal" matter in that small a space, you'd see light. This stuff has to be something different. We know it's there, we know its characteristics, we're just less clear on what exactly it is.

No, we do not 'know it is there'. Interpretation of instrumentation indicates something. If you accept 'theories' of galactic dynamics, you are likely to interpret readings to reflect what you already believe. And all ideas relating to galactic dynamics are only theories.

Gentlemen! Before you use a hypothesis to support additional speculation, please, prove your original hypothesis. Just as with global warming, you have not followed the necessary steps to arrive at your correct destination. You are attempting to chart the river without using a compass, and are now lost in a completely uncharted tributary.

And you also don't know you're not a brain in a vat. Your acceptance of your existence in this Universe is entirely dependent on your interpretation of your sense instrumentation. That's what this whole thread is about: standards of knowledge. When does something leave the realm of hypothesis and become knowledge? I can totally Sorites you here, by the way. Do we consider ourselves to know that gravity locally follows an inverse square law? That light waves are fluctuations of electromagnetic fields? That electrons exist? That neutrinos have mass? That dark matter exists and is non-baryonic? All of these are things which we have very reasonable experimental evidence for, and which we can't prove directly without appealing to some set of assumptions, which almost always include a dependence on certain experimental apparatuses. So where do we draw lines? I think this is a pretty interesting question.

The answer for most physicists is to pay lip service to the fact that we can't actually prove anything, and then have some sort of mental threshold - 99% probability or what have you - to accept something as "true enough." So let's take this and get back to the issue at hand: dark matter. This thread isn't just about scientific epistemology, it's also about physics, so let's get into the interesting stuff. Take the Bullet Cluster; gravitational lensing is showing us that most of the mass is in a place where almost none of the light is. Let's ignore, for now, the fact that this cluster conforms very closely to what the cold dark matter model had predicted for this sort of situation for nearly two decades, which inevitably drives up our confidence in the theory. Let's look for alternatives. You could claim that all of that matter is in something which doesn't emit much light but still has fundamentally different dynamics from gas and stars, but somehow is baryonic. I have no idea what that would be and have never heard a good suggestion; you're welcome to come up with one, but make it compelling, of course. You could also reject the whole premise and say that the gravitational lensing is caused by something entirely different than mass, but that would not only put you in the awkward position of trying to find something which is there causing the lensing but isn't massive, but would put you in the super-awkward position of refuting a key prediction of general relativity, an extremely well-tested theory, with no alternative, no theoretical motive, and no way to remove the lensing from general relativity while keeping all of the stuff that does satisfy those very tight experimental and observational constraints (including all of the solid examples of lensing we do have).

So maybe you see why I, and most physicists, have so much confidence in the cold dark matter model. There just isn't all that much wiggle room about it now. There's a very good reason that even the people who were pushing MOND and other modified gravity alternatives to dark matter are now saying that their theories require some dark matter to fit the observations. But as I said, if you have alternatives which are laid out mathematically, accord well with known physics and observations, and are more compelling on some level than dark matter, I implore you to let me know.

 

[Kessy]

Dreadmoc, I want to start by reminding you that the universe simply is - it does not require human validation, nor does it feel the need to necessarily make sense to us. Whether or not dark matter or any of the rest actually exists has nothing at all to do with what humans think or say about the subject.

You're also making a fundamental mistake by thinking that because astronomers have but a label on something that means they are categorically asserting that there is such a thing and that they know exactly what all its properties are. Sometimes a label is just a place holder. For example, I doubt you'll find many people who'll say that the phrase "dark energy" is anything more then a shorthand for "The mysterious and unexplained reason the expansion of the universe is accelerating."

In your analogy of a village beset by a dragon, you shouldn't look at it as necessarily being a literal large fire breathing reptile. From the villagers' point of view, all they know is that there is something in a particular place making anyone who goes near disappear (and presumably die). A dragon is a perfectly reasonable way to express this, whatever the cause, because it quite concisely expresses what the villagers know - that there's something dangerous in this particular place and you should avoid the area.

I would also point out that you're abusing the word "theory" - mixing up its colloquial and scientific meanings. Pick one and stick to it. My personal immediate reaction is that anyone who uses the phrase "it's just a theory" is almost certainly using deliberately misleading wording to make a political argument, not a scientific one.

I think your characterization of the scientific community "rally(ing) around the possibly erroneous calculations of their peers, and beat down all opposition," is extremely unfair and just plain wrong. Generally speaking, the scientific consensus follows the evidence. While it is true that the scientific community, like all communities, has a certain inertia to its thinking that can make it difficult for unconventional ideas to get thoroughly heard out, in the end it's the evidence that carries the day. For example, when quantum mechanics was first proposed, it's hard to imagine a more iconoclastic, bizarre, or counter intuitive idea. But because the evidence said unequivocally that as strange as it is, it is correct, the consensus eventually embraced it. No one is trying to silence anyone. Actually, in this day and age, with the internet, proponents of unconventional ideas are better able to get their ideas out there then ever before. The fact that certain people are ignored because they have no convincing arguments to back up their ideas is *not* the same as being silenced. It is *your* responsibility to back up what you say. I have some unconventional opinions myself, but I don't expect anyone to accept them as likely being true unless I can support them.

On the particular subject of dark matter, right now the mainstream model of it is the simplest idea that matches observations, so by Occam's razor that's what is mostly being looked at. But the topic is an open one that is being actively researched from a variety of points of view, and as more information becomes available, the mainstream model will certainly evolve, as it has been doing since the idea of dark matter was first introduced. And on one level, the existence of *some* dark matter is quite certain - you're sitting on a big lump of it called "The Earth" right now.

One last thing - it's extremely well established that climate change *is* in fact happening; there are mountains of evidence in support of it. In some case, literal mountains, such as the disappearance of alpine glaciers around the world. As far as I can tell the only people still trying to deny it are doing so for political, ideological, or economic reasons.

 

[MeteorWayne]

Nice post, Kessy!!

 

[captdude]

As the force of gravity is considred to be weak compared to the other fundamental forces of nature (the strong force, weak force & electromagnitism) and dark energy and dark matter express themselves gravitationally; this would seem to indicate to me that gravity must be exerting itself in ways we do not as yet understand.
I have read several articles stating that gravity may be the only force "leaking" into higher dimensions. If gravity can leak into higher dimensions - why couldn't other forces or particles from higher dimensions "leak" into our 3-D space/time to create the observed effects of dark matter? (or dark energy)
Are there any theories or trains of thought along these lines?

 

[Shpaget]

There are higher dimensions?