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NASA and DoE Team On Dark Energy Research
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."
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?"
An Eye for an Eye will make the whole world blind - Gandhi
maybe it's like fog, when it's far away it looks like a solid cloud.
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.
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.
Any life is made up of a single moment, the moment in which a man finds out, once and for all, who he is.
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 totally convinced that this is tied in to the whole cosmological constant business (particularly of the value-varying-over-time variety, which is what this mission appears to be designed to test); that's a hypothesis that has obvious attractions but AFAICS it has received undue attention and there ought to more investigation of alternative hypotheses. But that's an unrelated matter. Something is clearly happening that we don't understand, ergo we need to know more about it.
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. For example, we assume that general relativity works the same for superclusters of galaxies as it does here in our solar system. Problem is the results it gives don't match our observations. So is this evidence that the theory breaks down over very large scales? Nope, it just means the universe is mostly made of invisible energy with negative pressure that only interacts through gravitation.
The whole situation reminds me of the aether theories of early physics. The problem then was that Newton's explanation of light provided a very good explanation for reflection, but not refraction or diffraction. The assumption was that since the theory worked well on one set of problems, it must work equally well on another similar set. It didn't, but no matter. By assuming light travels through a medium, the aether, you could tweak the equations to give results close to the observations.
Over the next 200 years this aether gained more and more 'magical' properties to tweak the results of other theories. It had to be a fluid, but also millions of times more rigid than steel. It had to be massless, completely transparent, incompressible and a whole host of other things all at the same time. Everyone was aware of the obvious problems here, but because so many physical theories (theories that gave pretty accurate predictions) were based on it it was just assumed to exist.
In the end aether theory was made obsolete when Einstein re-wrote the incomplete physics that relied on it to deliver accurate predictions. Physics was stuck in a rut for 200 years because it assumed aether must exist, and everyone's efforts were aimed at incorporating aether into physical theories. I just hope this isn't happening again with Dark Matter/Energy.
Disclaimer: I am not a physicist or cosmologist, I just have a passing interest in this stuff, so take what I've said as nothing more than an opinion.
Murphey's fighting Occam, and we're in the stands.
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.
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.
Does this temper your skepticism any?
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.
(1.21 gigawatts) / (88 miles per hour) = 30 757 874 newtons
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 ideas of what they're "really" measuring.
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. I bet they can't implement Newton's law of gravity in an N-body simulation either.
I don't really feel like working through their manuscript, but it seems rather reminiscent of the Cooperstock and Tieu paper which tried to do away with dark matter by introducing a thin disk of regular matter (e.g., here). It was also reported on Slashdot, and debunked within a month. (I suspect the only reason anyone bothered to write up a rebuttal is that Cooperstock has a reputation in gravity and people were worried someone might buy it. Most of these flawed papers just get ignored.)
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 disappoints a lot of theorists who want to come up with new dark energy theories. In fact, it's not even really a modification of existing theory. A cosmological constant has been present in Einstein's theory from the very beginning, in 1915. Einstein later took it out of his theory because he didn't see a need for it. Now we do, because we can make more sensitive measurements.