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NASA and DoE Team On Dark Energy Research
Posted by
timothy
on Fri Nov 28, 2008 05:08 AM
from the what's-the-opposite-of-illuminati? dept.
from the what's-the-opposite-of-illuminati? dept.
Roland Piquepaille writes "NASA and the U.S. Department of Energy have teamed up to operate the future Joint Dark Energy Mission. As you probably know, recent astronomical measurements have showed that about 72% of the total energy in the universe is dark energy, even if scientists don't know much about it, but speculate that it is present almost since the beginning of our Universe more than 13 billion years ago. The JDEM 'mission will make precise measurements of the expansion rate of the universe to understand how this rate has changed with time. These measurements will yield vital clues about the nature of dark energy.' The launch of a spacecraft for the JDEM mission is not planned before 2015."
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Need a better marketing department (Score:3, Insightful)
Come on.... "Dark Energy" this should have everyone wearing some form of mask and a black uniform with just a simple white spark on it or something. We complain about not getting kids into science and then when we get something with one of the coolest sounding names around we make it into something dull and boring.
"Dark Energy has been around for 13 billion years but no-one has been able to harness it. Do you have what it takes to join the Legion of Dark Scientists?"
Re:Need a better marketing department (Score:4, Funny)
Mechanical voice:
- Come join us understand the real nature of the Universe. Together we will understand the deepest secrets of matter and energy...
Darth Vader approaches a group of scientists wearing white clothes, looking at a telescope and talking to each other.
- And you can be sure the smartest minds of the planet will be with you in this journey. May the energy, dark and bright, be with you, my friend.
Parent
Re: (Score:2)
They [wikia.com] have already taken over. Grab a crowbar and follow Freeman. He is our only hope.
Oblig. Simpsons (Score:4, Funny)
Lindsay: Yes. For example, no one was showing up for jury
duty, so we made the experience more exciting by
synergizing it with his comic book collection.
[cut to Moe's tavern. Moe opens an envelope]
Moe: [reading] You have been chosen to join the Justice
Squadron, 8 a.m. Monday at the Municipal Fortress of
Vengeance. Oh, I am *so* there!
Parent
Department of Dark Energy (Score:3, Funny)
what i don't get is... (Score:4, Interesting)
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When it's close, you can see it even thou your standing in the middle of it, it looks completely different, yet the same thing.
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if there's so much dark energy in the universe
AIUI, dark energy is theorized to be everywhere. Including within our own solar system. However, the amount of it in any given space is tiny. Current best estimate is 10^{29} grams per cubic centimeter, which is basically nothing. We can't detect that on any reasonable space. It's only because huge quantities of it are (theorized to be) scattered in the vast distances between galaxies that we are able to detect any effect of it at all.
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I wrote:
Current best estimate is 10^{29} grams per cubic centimeter
Somehow a minus sign got deleted from that post. I blame slashdot's unicode filtering.
That should, clearly, be 10^{-29} g/cm^2.
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Yes. We're able to measure the CMBR, but it's electromagnetic radiation. If dark energy primarily or solely interacts gravitationally, that's a world of difference. The electromagnetic and gravitational interactions have very different strengths. We can't detect the gravitational effects of the CMBR at all, since it's about 100,000 times less energetic than dark energy. Dark energy has only recently been detectable at all through its gravity. That's (one reason) why it's so hard to directly detect dar
Re:what i don't get is... (Score:4, Informative)
According to the current theory, dark energy does exist in our solar system, its just that you need many, many more than only 9 decimal places to measure it.
Its repulsive effect however increases with scale, so the larger distances you probe, the easier it is detect.
Parent
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Even though it's 72%, we have those great laws of probability to thank for that.
Let's say I shoot a basketball from the free throw line for 100 shots and I get in 43 of them. From that small set of data, one could say I have a 43% shot accuracy at the free throw line.
Now if I were to make another 100 shots, I wouldn't get exactly 43. I may get more or less, but 43 would be a good representation of an average.
In the case of the dark matter, just because the estimate is that it comprises 72% of the universe d
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Dark matter doesn't have anti-gravity effects. The whole reason why it was postulated in the first place was because of its positive gravity effects: to explain the "missing mass" contributing to galactic rotation curves.
It doesn't exactly have "anti-" light effects. The main working theory is just that it doesn't interact with light (electromagnetic radiation), because it's not electrically charged.
Dark Matter/Emergy Does Not Exist (Score:5, Interesting)
I was always a skeptic when it came to Dark Matter(I am not an astronomer, so this all technically an uniformed opinion). But now I know that it really is all a load of idle speculation coupled with incomplete investigation, and an excessive dose of hype. It only took a few minutes of googling to come up with this paper [arxiv.org].
One of the biggest pieces of evidence for Dark Matter is the Galaxy Rotation Problem [wikipedia.org]. Basically the rotations of Galaxies do not behave as astronomers expect them to do, leading to the hypothesis that there is more matter in them that we cannot see, "Dark Matter". The velocity profiles that Astronomers expect to see are Keplerian. That is, they expect star systems in galaxies to behave like planets in solar systems when it comes to orbit speed and distance from the focus of rotation.
The bottom line is, as shown in the paper, this assumption is totally unjustified. The integrals in the 2D galactic disc case do not work out using Shell Theorem [wikipedia.org], which cannot be applied. They are instead quite nasty singular integrals, but twenty minutes with MATLAB and the "QUAD" function will be all it takes to see that basic gravitational theory most certainly does not predict that Galaxies should have Keplerian(Solar System-like) rotation curves, and there is no reason whatsoever for astronomers to assume this. It's all basic mathematical physics well withing the reach of many reading this post.
The galactic rotation problem is not evidence for Dark Matter. It is only evidence of the need for more applied mathematics courses in astronomy undergraduate degrees. Of course the Galactic rotation problem is not the only evidence for Dark Matter, but it is a big part. The other big piece of evidence was the Galactic Cluster mass problem. It's been a while since I read the relevant papers, but as I recall, Zwicky played hard and fast with the virial theorem, in particular making assumptions about the stability of Galactic clusters.
Again of course, I am not an astronomer. I am essentially a lay person in these matters, so my posts and opinions (not only in this thread) should be taken with a pinch of salt. Still, I stand by my overall skepticism of Dark Matter theories, and I stand quite firmly on my objections to the interpretation of the Galactic rotation problem. I expect that in the near future, as our ability to analyse and simulate galatic dynamics improves, Dark Matter will finally be debunked.
Re:Dark Matter/Emergy Does Not Exist (Score:4, Insightful)
And even if Dark Matter/Dark Energy really does not exist, I think it's justifiable that people search for it. If the experiments don't match what the scientists say about it, we'll know we need another explanation. The money will not be spent in vain.
Parent
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Echoing what Andr. T said in his previous post, but in hopefully a little more detail: the evidence for Dark Energy is completely orthogonal to that for Dark Matter. Like you, I'm not an expert on this subject but have done a little reading, and find the D.E. evidence a lot more convincing. Unless there's something fundamentally wrong with general relativity and our understanding of its implications, there is some kind of repulsive force acting on galaxies to push them away from each other.
Now, I'm not to
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Unfortunately, it does generally take a genius to take the big leaps in our understanding; to forge all our data and half-truths into a coherent whole - that's why it took 200 years (as it turns out, the amount of time between one genius (Newton) and the next) to solve the last one. With the greater number of people studying science and higher accessibility in the world today, hopefully it'll take less time before the next one in the field emerges. Let's hope.
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My problem with both theories is that they seem to be band-aids applied to current physics to tweak the result to something that matches our observations.
That's how science works. If you see something anomalous, you start by applying the most minimal possible tweak to explain the anomaly. If that doesn't work, you expand your hypotheses to be more radical until you hit upon something that works.
As it happens, the most vanilla, boring possible modification — a cosmological constant — seeems to explain our observations, agreeing with both supernova luminosity-redshift relations and the cosmic background radiation angular power spectrum. That dis
Re:Dark Matter/Emergy Does Not Exist (Score:5, Insightful)
Does this temper your skepticism any? [stanford.edu]
I find it hard to accept the idea that some lone guy on slashdot has found a problem in the maths used by all the astronomers in the world who describe galaxy rotation, or indeed that even if you had, it seems galaxy rotation is not the sole piece of evidence for dark matter [wikipedia.org].
Parent
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It only took a few minutes of googling to come up with this paper [arxiv.org].
Note that "this paper" has not yet been refereed and accepted by a journal. It is conventional, when submitting papers to arxiv, to indicate to what journal the paper has been submitted, whether it has been refereed and accepted or not. There is none of that information here. Normally a paper submitted in March 2008 would have been accepted and published by end of Nov 2008 if it had been. I suspect that it has been rejected.
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I think you're quite right, and hence the use of the "epicycle" tag on this story.
Epicycles, if you don't know, were the artificial additions to the "circular" orbital theory, which became more and more clumsy and unwieldly, until some bright spark called Copernicus simplified the whole thing. And then when we finally worked out orbits were elliptical, not circular, we looked back on epicycles and said "Of course! How could we have been so stupid!"
Epicycles. Dark Matter.
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There's nothing wrong with epicycles as a theory. It's just Fourier analysis. The real problem with epicycles is not that they're wrong, but they're not predictive. (There's no theory to say what the Fourier coefficients ought to be.)
Dark matter is not like epicycles. You can put in assumptions about dark matter inferred from one set of observations (e.g., galaxy scale physics), and make predictions about different observations (e.g., the cosmic background radiation), and you find that the predictions w
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I was always a skeptic when it came to Dark Matter(I am not an astronomer, so this all technically an uniformed opinion). But now I know that it really is all a load of idle speculation coupled with incomplete investigation, and an excessive dose of hype. It only took a few minutes of googling to come up with this paper.
Oh yeah. A few minutes of Googling turns up an unpublished manuscript which overturns 80 years of research and thousands of papers. A manscript written by a guy who runs a mail-order crystal business and a former Xerox employee who studies fluid droplets. (I bet I'm going to hear "but Einstein was a patent clerk" real soon now ...) Which cites Electric Universe theory papers. That's totally credible.
It is only evidence of the need for more applied mathematics courses in astronomy undergraduate degrees.
Yeah, everyone who has worked on dark matter flunked basic undergraduate astronomy. That's probably it.
Damnit! (Score:2)
Bush even got it into an arms research race with the Protoss!
We'd best just leave it alone . . . (Score:3, Funny)
If NASA and the DoE start yanking on the Dark Energy in the Universe, they might find that attached to the other end are . . . Dark Energy Creatures.
They might not be amused with the antics of NASA and the DoE.
"Hey, you, Earthling! Is this your Joint Dark Mission Probe, that just broke my window?"
You have been warned.
So that is what a ZPM gets it's power from now we (Score:2)
So that is what a ZPM gets it's power from now we need a way to make them and we better do that off world.
Wrong physics? (Score:2)
This will kill my karma, but I just have to ask: isn't all this "something we can't see that's messing up our physics" putting us off the possibility that our physics models may just be flat out wrong?
I mean, would we have a relativity theory if Einstein had stuck to Newtonian physics and stated that the errors measured were caused bay some misterious force/matter/energy that we couldn't see?
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This will kill my karma, but I just have to ask: isn't all this "something we can't see that's messing up our physics" putting us off the possibility that our physics models may just be flat out wrong?
Yes, and that's why various dark energy theories introduce new physics (such as new types of particles or modifications to gravity).
I mean, would we have a relativity theory if Einstein had stuck to Newtonian physics and stated that the errors measured were caused bay some misterious force/matter/energy that we couldn't see?
Would we have discovered Neptune if we had tried to invent new physics instead of postulating that some unseen body was perturbing the orbit of Uranus?
Anyway, Einstein's solution was to modify Newton's theory of gravity. The leading solution is to modify Einstein's theory of gravity by adding a cosmological constant. (Actually, it's really just restoring Einstein's theory to
What the mission is and why DoE is involved (Score:2)
For those wondering why the Department of Energy is building a space telescope rather than focussing on nuclear things, the Department of Energy funds the SLAC Linear Accelerator centre at Stanford and it's people at that centre who have designed SNAP, a spacecraft that happens to fulfill exactly the requirements NASA put forth for JDEM.
The Dark Energy Mission is a wide-field high-resolution space telescope; a hundred million or so pixels of 0.2 arcsecond extent, and a five-foot main mirror. The idea's to
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For those wondering why the Department of Energy is building a space telescope rather than focussing on nuclear things, the Department of Energy funds the SLAC Linear Accelerator centre at Stanford and it's people at that centre who have designed SNAP
Uh... not to fan the flames of any Bay-Area turf wars, but that team [lbl.gov] is led by people from Lawrence Berkeley National Laboratory and University of Califoria at Berkeley. Yes, there are a couple Stanford people who work on things like electronics and pointing, but they're a small fraction of the whole project.
You were close, though: the Department of Energy funds Lawrence Berkeley National Laboratory. :)
Let me go on record (Score:2)
Re:The realm of the DoE (Score:4, Informative)
Actually DOE has always been deeply involved [doe.gov] in high energy (particle physics) research. They fund a number of accelerators, including Fermilab. Its not clear that any of that research would lead to usable energy sources either.
You can see the Dark Energy research as the intersection of high energy physics (DOE) and cosmology (NASA).
Parent
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You can see the Dark Energy research as the intersection of high energy physics (DOE) and cosmology (NASA).
Except, I don't really see how high energy physics is involved. I mean, it's not as if anybody has proposed a high-energy experiment that could detect it.
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Except, I don't really see how high energy physics is involved. I mean, it's not as if anybody has proposed a high-energy experiment that could detect it.
Ultimately, there must be a particle-physics-based explanation for Dark Energy, whether from string theory or something other theory.
And just because Dark Energy not accessible via "classical" accelerator experiments, this does not mean that it should not be considered experimental particle physics research. In other words, instead of using a ground-based accelerator, the Universe is the "poor man's" accelerator [discovermagazine.com].
Re:The realm of the DoE (Score:4, Informative)
Actually DOE has always been deeply involved in high energy (particle physics) research. They fund a number of accelerators, including Fermilab. Its not clear that any of that research would lead to usable energy sources either.
Good so far.
You can see the Dark Energy research as the intersection of high energy physics (DOE) and cosmology (NASA).
Yes, but don't forget that DOE has its own cosmologists, too. The DOE end of JDEM is being handled by Lawrence Berkeley National Laboratory, which has quite a bit of stuff [lbl.gov] going on in cosmology, mostly under its physics [lbl.gov] division.
(I [lbl.gov] do some work with one of the collaborations [lbl.gov] based there.)
Parent
Re:It's a silly thing to measure. (Score:5, Informative)
Of course being a couch-scientist (worse than amateur scientist), I might be hugely wrong, but somehow, I don't think I am (surprisingly).
Unfortunately, you are wrong, and I guess it's not that surprising, considering your ... interesting take on cosmology. Einstein's work was intimately concerned with the nature of spacetime, so saying that "he looked soley[sic] at matter" is flat-out wrong.
Space and matter are the same? Then either space has a gravitational effect, or they're the "same" in a way that doesn't include a fundamental property of matter, which is to say that they're not the same at all (you'll recognise the quote "in exactly the same way that bricks don't" -- it speaks to nature of classification rather elegantly I think).
So why hasn't the gravitational effect of space been detected? Oh, wait, because the scientists missed something. Silly scientists!
Parent
Re: (Score:3, Interesting)
Space can have a gravitational effect: in general relativity, gravity gravitates. A black hole is a vacuum solution of the Einstein field equations. And if you object to it being vacuum because you can't say what's at the singularity, there are non-singular vacuum solutions too, like gravitational geons [wikipedia.org]. However, they're not stable, so attempts to describe matter as pure space have failed. (Another attempt which also largely failed is to describe particles as wormhole mouths.)
Some people think that dark
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Once scientists understand that space and matter is the same thing (something you should be able to test and prove here on earth) they should understand that dark matter is just space.
Although attempts have been made to unify matter and space (see Wheeler's geon idea), they've all failed. Matter and space appear to be different. But even if they were unified, so what? What's the practical difference between "matter which is secretly some aspect of space" and "matter"? I mean, I can say that an electron is really just "space", but that doesn't prevent it from acting like matter.
it's really interesting that they aren't doing it with a clear understanding about what they're measuring or why.
They have quite concrete ideas of what they're measuring. They just don't happen to agree with your pet ide
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The lack of specificity in your invitation to a dick-swinging contest is ... illuminating.
What do you have against aether? (Score:5, Insightful)
The idea of a luminiferous aether followed naturally from the observation that light acted like a wave, and one of the fundamental things about waves is that they travelled in a medium.
This lead to experiments designed to detect the medium of light (like the famous Michelson-Morley one), to the Lorentz transformations and the Theory of Relativity. The aether conjecture is science at its best: hypothesis, experiment, falsification, paradigm shift. Why it's used as a metaphor for stupidity has always been a mystery to me.
Parent
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In fact, paradigm shift was a useful expression long before it was hijacked by business consultants. I suppose this is the destiny of any phrase that describes, shall we say, a great leap forward -- to be misused and misapplied until people end up forgetting what it once actually meant.
How would you prefer the search for a unification theory to proceed? And why are you so angry? It's not for you to decide how people who are smarter than either of us should spend their time.
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Remember "epicycles?"
This is another of those "dumb science" metaphors that are flung around with no regard for history. The heliocentric model of the solar system did nothing to solve the problem of epicycles, and given what was known at the time, would you have come up with ellipses?
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given what was known at the time, would you have come up with ellipses?
Probably not. But the elliptical solution had been known for around 1000 years before it became generally accepted, having been discovered by Aryabhata, c. 500CE.
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My understanding is that Aryabhata also used epicycles to model planetary movement (and by the way, even if they're not literally there, they can be incredibly accurate, which only adds to my annoyance at the way they get ridiculed). I've heard about the ellipse thing, but never seen any evidence (which, naturally, doesn't mean it's not true!)
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scientists don't know much about it, but speculate that it is present almost since the beginning of our Universe
BAD BAD BAD... REALLY?! I could've sworn that [it] WAS present.
And here I was thinking that it has been present.
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If you want to reconstruct the expansion history of the universe, you need to know where various objects were located in the past.
By looking at the redshifted light from a distant star, you can tell by what factor the universe has expanded. (It's equal to the factor by which the wavelength of light is stretched.) By the Hubble distance-redshift relation, you can tell how far away the star is: in an expanding universe, faster moving and more redshifted stars are farther away. That relation only works if