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Dark Matter.
Topic Started: Jan 14 2007, 01:42 PM (202 Views)
Alfryd
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1. [Cooker's] thread was started "... to produce a schematic dragon that can operate without magic." Presumably we are to produce a dragon that behaves according to established principles of physics.

2. Within established physics there exists an energy of which we have virtually no understanding called "Dark Energy"... ...or anything about the behavior of it. About the only thing we do know about dark energy is that it cause visible matter to move.

Actually, the properties of dark energy are very well defined in a scrupulous mathematical sense, so I don't see why you say we have no 'understanding' of the stuff, any more than we have no understanding of, say, the weak nuclear force. The question is whether it exists.
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3. Science doesn't explain how this dark energy came to be, why we can't directly detect it...

It's envisioned, I believe, as a consequence of virtual particles and quantum indeterminacy implying that a certain 'zero point energy' exists even in an apparent total vacuum, so if space expands at the same time it logically follows that 'negative energy' of some kind is involved. I think. I'm very hazy on the subject.
As to why we can't directly detect it, that's a matter of definition- non interaction except through gravitational effects, which are too weak to be useful with conventional instruments.
Now, if you want to say that the universe *isn't* expanding at observed rates and thus dark energy is not needed as 'fudge factor', go ahead, but then you will also have a great deal of expalining to do to maintain consistency with available observation. All else equal, it seems a little fudging by way of 'alpha' is more 'theoretically parsimonious.'
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4. We also estimate that there is so much dark energy that the vast majority of the universe is purely dark energy. So much in fact that everything we can see or otherwise detect through observations, instrumentation, etc. is just 4% of the totality of the universe.

Masswise, yes.
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5. Furthermore, this dark energy is distributed throughout the entire universe (it's not just present in Black holes or some other unusual phenomena -- it's basically everywhere).

6. The power of this energy immense. By some calculations its estimated the dark energy will eventually rip the universe in to bits. In comparison, moving a dragon around a bit is nothing.

Yes, but moving the dragon a bit relative to the region of space it presently inhabits is another question, givien, as you pointed out, dark energy supposedly acts with equal force, everywhere, all the time.
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7. Normally this energy is homogeneously distributed through the universe, but if a slight fluctuation occurred at some point in space it would cause a gravitational irregularity.

8. If this irregularity happened near an observable mass (say a large scaly avian creature) it would appear that the object was moving in a manner inconsistent with "normal" observable physical phenomena, but in fact it was just the force of dark energy.

Yes, but there's nothing in the current definition of dark energy which suggests this 'irregularity' could occur, or that a dragon could manufacture such an irregularity, or make safe use of it.

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So what might appear to be 'magic' is just a little known force called 'dark energy'.  And what is magic after all, but simply a mysterious natural force that most people have little understanding of.

There's a very significant difference between 'magic' and dark energy- magic has no fixed definition or reliable behaviour, according to what you say above. You may argue that dark energy is not an 'elegant' concept, but it does not lack definition, understanding or reliable behaviour.
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Dumble Dwarf
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Dark energy only seems well defined in the sense that we know how much our current model of the universe fails to meet current observations.
If I was controller (the person in charge of the money) of a large company or governmental body and I had a budget of 4 billion dollars for the year, but at the end of the year I discovered that I over spent my budget by 96 billion dollars, you wouldn't say I was a competent controller because I was later able to tell you exactly how much I overspent the budget right down to the dollar.
Now I'm not trying to "blame" dark energy or dark matter on someone, but it seems to me that somewhere along the line someone made an assumption in the universal model that wasn't true. Perhaps the speed of light isn't a constant, or perhaps something else is wrong, but I think serious consideration should be taken to examine alternative models before embracing this idea the the universe is mostly stuff we can't detect and only exists in a mathematical sense.
If I was to claim that the universe was mostly made of pixie dust and proceeded to launch in to a 100 pages of impressive algebra and calculus to substantiate my claim culminating with the exclamation, "See the equation balances out, the universe is pixie dust.", I would hope that my theory would be viewed with extreme scepticism even if my math appeared to be correct.
Dark energy is just one of ever increasing "inelegant" explanations of the universe.
I mean we can have discussion of dark energy without bringing up the subject of cosmic inflation? The idea that at some point in the universe a made up thing ('made up' in the sense that it has never actually been observed or in some way confirmed to exist -- but in order to talk about something you have to call it something and 'pixie dust' doesn't sound scientific enough for a new research grant) called an 'Inflaton' took over and accelerated the universe to it's current state seems a wee bit fanciful, even if it does balance out the equation.
At what point shall we say, "Enough is enough, we aren't going to give you any more money unless you stop making stuff up to explain why observations of the the universe aren't jiving with your theoretical predictions".
Couldn't anyone come up with a model of the universe and toss in all kinds of omegas, epsilons and lambdas to solve all the problems with the model, when it was really a bad model to start with?
Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works.
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Alfryd
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...but I think serious consideration should be taken to examine alternative models before embracing this idea the the universe is mostly stuff we can't detect and only exists in a mathematical sense.

If you're talking about trying to initiate some kind of Kuhnian paradigm shift, well, you're welcome to try, but revolutionary breakthroughs of this kind are not easily done, and, as a non-physicist, I don't see how I can really assist you in this endeavour. In the case of Dark Matter, alternate theories such as MOND (modification of newtonian dynamics, for those of us who don't read sci-am,) have, I gather, recently shown severe discrepancies with observations. Which is disappointing, I concede, but that's not the universe' problem. The universe gave us the standard model for quantum mechanics, which one can hardly describe as elegant.

The other issue is how much of this 'model' you speak of is really a 'model' as opposed to a direct deduction from observations. From what I am given to understand, the brightness and spectra of certain supernovae types are fixed, so by measuring the brightness and red shift you can plot both position in spacetime and 'rate of deperature' quit accurately. If you want to refute that interpretation, you will, again, have a lot of existing theories, which seem, on individual bases, to accord pretty solidly with available data, to overturn.

Now maybe some wild new paradigm will cause the whole dark matter/energy debacle to boil away like phlogiston. Be my guest. Until then, I will happily take the word of the scientific establishment on a subject of such slight relevance that I may focus more easily on, say, the british government's encroaching surveillance state.
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