Scientists Expand Knowledge of Dark Matter

nife00 writes "BBC News is reporting that British scientists at Cambridge have expanded the current understanding of the mysterious particles known as dark matter." According to the article: "[The Cambridge Team] has at last been able to place limits on how it is packed in space and measure its "temperature". "It's the first clue of what this stuff might be," said Professor Gerry Gilmore. "For the first time ever, we're actually dealing with its physics," he told the BBC News website."

Comments

Uncertainty

[helioquake]

Give me the sensible error bar estimate on the mass, if they want to be scientific about it.

Just another point of view

[erroneus]

http://science.slashdot.org/article.pl?sid=06/01/2 5/1436243 -- This article points to the idea that there is no such thing as dark matter and explains everything with gravity. Now we're back to dark matter again? I still like science and all that but there are people who don't understand that "we don't really know everything" and that science as we know it today is merely an attempt at forming an understanding of our universe, not a definite mapping.

Re:Just another point of view

[Starker_Kull]

Actually, Godel did no such thing - he demonstrated that in any formal system of logic sufficiently complex to encapsulate basic arithmetic, there will be unprovable statements which are nonetheless true. Note that the reason we can say these unprovable statements are true is because that if they were false, there would exist a provable counterexample to the statement (i.e. an example of the falseness), and thus the statement would not be unprovable - but this knowledge comes from outside the logical system. In other words, he demonstrated that there will be true statements in a logical system that can never be proven within that system to be true; a hypothetical example might be Goldbach's conjecture, that any even number > 4 is the sum of two (not necessarily distinct) primes. If this was, in fact, true, but was somehow "unprovable", we would be left in the uncomfortable position of seeing billions of examples where it is true, not a single example where it was false, but of course there would always be an infinity of cases we didn't check yet. This is, in fact, the present state of our knowledge - and thus why I used it as an example. Of course, some clever egg might stumble upon a proof of Goldbach's conjecture tomorrow - people used to use Fermat's Last Theorem as a potential example of something that might be true but unprovable, until Wiles proved it. This is the problem, that we have no way of knowing what is unprovable in mathematics, because if we did have such a way of "knowing" (i.e. proving that a proposition is unprovable) for a specific proposition, we would have just proven it true, and thus it would not be unprovable! So we will never know what is not provable - we will only suspect that one of Godel's unprovable but true phantasms is staring us in the face.

My point (longwindedly) is that this has little or nothing to do with the physical, mathematically modeled, problems at hand here; if you want a better idea of the type of barrier we are facing in this case, you would be better served by complexity and information theory; look up Shannon and Chaitin for more info - that is the type of problem involved in turbulence simulation, not logical issues of provability and incompleteness.

Re:Just another point of view

[Capt'n Hector]

*Ahem*. Dogs certainly do know calculus.

Re:Just another point of view

[Mr. Slippery]

I was actually wondering, could it be the case that we might not even be able to understand and explain some phonemena simply because our brain power is not adequate.

It sometimes strikes me that every model of the universe is an instance of lossy compression; it's small enough to fit into the human mind and gives you the gist of what's going on, but data is lost.

Re:Just another point of view

[drgonzo59]

Well, that was the point of my post. We are using QM to build things. The math seems to predict the phenomena. Quantum encryption works with entanglement and there has been experimental proof. But it seems that we cannot really understand it. Other phenomena are likewise. So I was wondering whether there is actually a limit as to how much our brains can understand. In other words some phenomena we will comprehend as the science progresses, but some we will never be able to wrap our head around.

This is more of a philosophical debate I guess. Some scientists have claimed that knowing the math and having the equation is all we need, there is no need for conceptual models in our head. Others claim that is not enough and they would want to understand what is really going on.

Still assumes the answer

[AlecC]

I was hoping that this would provide some real evidence for Dark Matter. I have a problem with something so massive which, as far as I can see, is invented to explain a single fact: the anomalously fast rotation of galaxies.

But this article doesn't do that. It says, as I understand it, if the rotation of galaxies is caused by dark matter then dark matter has these properties. If the unexpected rotation is caused by something else, then this is just a curious kind of meta-measurement,

It is a bit like the phlogiston theory. If fire were caused by the release of phlogiston, you could measure the mass of phlogiston - and come out with a negative mass. Which is perfectly logical, but counter-intuitive. Further investigation then makes the phlogiston theory even less attractive - but in the short term, the theory can be patched to work.

Re:Dark Matter Blows

[rknop]

It's always fun to watch people on Slashdot without a clue what they're talking about dismiss so much of our current understanding of cosmology with such an unjustified supercilious attitude.

-Rob

Here's what makes me unhappy

[rknop]

Here's what makes me unhappy:

The Cambridge University team expects to submit the first of its results to a leading astrophysics journal in the next few weeks.

I don't like this "press release before publication" mode of doing science. It's all about making sure that you get the attention and public recognition, and not about propery distributing the results so that others can understand and evaluate what you've done. Alas, it seems that Marketing Is All in the modern world, and not just in the USA any more. You can be sure that the institutions who house these scientists love to get the attention and so forth.

I'd be happier if the paper had already been accepted by some real journal, with a preprint available on www.arxiv.org. As it is... we have a press release and a pop-sci article about an intersting result that's hard to truly evaluate. The article is mostly good and sounds reliable, but in my experience these pop-sci articles usually get something wrong. (For instance, even though 10,000 degrees sounds "hot", given the likely mass of the Dark Matter particle, it still is "cold" in the cosmological sense of "cold dark matter", which really means "nonrelativistic dark matter". I'm not sure how much of a surprise that temperature is, but it's probably not enough to make CDM wrong.)

-Rob