Physicists Resurrect an Old, Strange Dark Matter Theory

New submitter rossgneumann writes: Dark matter might not be nearly as exotic as most theories suggest. Instead, it could be macroscopic clumps of material formed from common particles already found within the Standard Model of particle physics. This argument comes courtesy of physicists at Case Western University (PDF). Dark matter is usually thought of in terms of exotic, so-far undiscovered particles. The leading candidates are known as weakly interacting massive particles, or WIMPs. But the Case Western theory suggests that there are no dark matter particles, at least none that exist outside of current knowledge. Instead, there are baseball-sized clumps of "regular" matter formed from unexpected combinations of Standard Model particles.

Comments

Re:Strange?

[Anonymous Coward]

Here's a crackpot idea for you: what if space came pre-"dimpled" at a large scale (in other words: gravity being a property of both space and mass, not just mass), and the galaxies we see are just the result of whatever loose stuff fell into the gravity wells that were already there. Then the massless lenses are simply wells that stars haven't fallen into yet.

Re:In laymen's terms...

[Flavianoep]

In laymen's terms, dark matter is a value that scientists infer from some calculations that albeit all of them correct cannot fit together. Then some scientists calculated the difference and called it dark matter, where 'dark' is a fancy word for 'nobody knows what it is'. To understand the things in the Case Western theory, which is not dark matter, consider that atoms are more than 99% vacuum, while the objects in that theory are mostly matter, not atoms. As such, they account for a large amount of matter, while not being big enough to be detectable by our astronomical instruments. They may react to photons, but most of the objects we are capable of observe in far space are really, relly huge and they are not.

um no

[Charliemopps]

Color me skeptical but from what I'm reading...

a form of matter that could only be formed in the early universe
It makes up 5x as much mass as ordinary mass in the universe
It's transparent to light
It's either transparent to heat or just so happens to give off almost exactly the same amount of heat as it absorbs
It has a density somewhere around the same density of a neutron star
It's not managed to devour/destroy any stars or otherwise clump together
It's a fluid

and there just so happens to be none of it on earth...

Even the studies author writes in the conclusion:

The nature of dark matter is still largely unknown. For this reason, it is prudent to
hedge our bets on what it might be

That's not exactly a ringing endorsement. It's more like "Ok, since we haven't found dark matter yet... this is way out there but hey, why not?"

Re:um no

[amaurea]

To follow up, I'd like to point out plot 2 in the article under discussion (go on, have a look. Opening a PDF isn't that painful). It is a plot of part of the parameter space for dark matter particle candiates, with weakly interacting, relatively light particles in the lower left corner and strongly interacting very heavy particles in the top right corner. MACHOs live to the right in this plot, and WIMPs near and below the bottom. The interesting thing about the plot is that it shows all the regions that have been excluded, color coded by how they were excluded. MACHO territory is basically completely excluded by microlensing. That doesn't mean that MACHOs don't exist - they definitely do (the earth basically qualifies, since it's compact and doesn't shine), but there can't be anywhere enough of them for their gravity to be important.

If you make the MACHOs smaller so that they aren't as good at lensing, you have to compensate by having more of them to get enough gravity, so microlensing can exclude a pretty wide parameter range. But if things get too light the lensing effect gets too small for us to detect, ending the microlensing exlusion range at a particle mass of about 10^24 g, about 1/10000 of the Earth's mass. But if they get a bit smaller, then can then be detected using lensing interferometry (=nanolensing), and for even lighter objects, by their imprints on crystals found in deep mines that act as natural particle detectors.

Anyway, I encourage everybody to read the paper: It details all the different techniques used to exclude models. The paper is really quite the opposite of what the [rant]typical Slashdotter anti-science prejudice[/rant] is. It's not somebody pulling some hypothesis out of thin air and then not bothering to test it. As the plot shows, this is really a case of eliminating slice after slice of the model space, with 75% of the area in the figure already being excluded.

Re:um no

[amaurea]

I was very suspicious when I saw the vixra.org link, but you've actually found a non-crackpot vixra article (if a very short one)! I guess it goes to show that one shouldn't be too quick to judge something by its company.

(Some context for other readers. arxiv.org is where all scientific papers in the fields of astronomy, particle physics and related fields are posted and read by working scientists. In these fields it has in practice supplanted traditional journals - on still submits articles to them, but nobody actually reads them, since articles appear on arxiv much earlier, and arxiv is free to everybody and much more convenient than dozens of scattered journals. But not everybody can post on arxiv. One must either be part of an academic institution or be endorsed by somebody who is. vixra was formed as a completely open alternative where anybody could post. But it quickly drowned in a deluge of crackpots. I've sampled it at several points (mostly the astronomy section), and did not succeed in finding a single remotely worthwhile paper in several pages of listing in any of the attempts. Hence my surprise this time.)

Re:Strange?

[Charliemopps]

So it's strange that this matter may not be exotic?

It's also got the density of a neutron star and is a fluid so... Good luck

Re:Strange?

[PlusFiveTroll]

The issue I have with this theory is, in the 4,000,000,000 years that Earth has been around, wouldn't quite a lot of this 'matter' built up in the crust and core? Where is it at? Sinking deep in to the crust?