Comments on: Something powerful lurks nearby

By: Torbjörn Larsson, OM

Torbjörn Larsson, OM — Sun, 23 Nov 2008 00:29:03 +0000

What I meant with Deus Ex Machina that it seem like an easy thing to do to “invent” some invisible stuff which explains all the troublesome observations we come across: rotation speed of galaxies, gravitational lensing and NOW even high energy cosmic rays?

But more importantly it has IIRC been tested, to many sigmas (wasn’t it like 13 or so?); it’s the only mechanism that explain the Bullet Cluster observations and some others recently. A nice property of mechanisms (and theories) is that you don’t need direct observations of their constituents to test them.

By: Brian

Brian — Fri, 21 Nov 2008 11:15:34 +0000

Krystian,
You said, “What I meant with Deus Ex Machina that it seem like an easy thing to do to “invent” some invisible stuff which explains all the troublesome observations we come across: rotation speed of galaxies, gravitational lensing and NOW even high energy cosmic rays?”

But this is exactly what theorists are supposed to do: conjecture explanations for anomalous data. Other theories (MOG, MOND, TeVeS) have also been proposed. The various candidate explanations are constantly being examined and reexamined as more and better data becomes available. Maybe a descendent of TeVeS or some new theory will eventually prevail. But, since no explanation is ever considered incontrovertible, all conclusions are really just tentative, vulnerable to modification or rejection. Interested people are forever trying to think of other theories that seem to match at least some of the data and to look for flaws in the existing theories. I very much enjoy this approach.

By: Brian

Brian — Fri, 21 Nov 2008 10:56:20 +0000

Krystian,
Graphs of the excess electrons vs. energy very closely approximate the pattern predicted for a 620 GEV Kaluza-Klein paerticle. Kaluza-Klein theory was developed in an early attempt to unify gravity and electromagnetism. These attempts preceded the advent of the concept of dark matter, so the postulation of the existence of such particles was in no way related to atempts to support dark-matter theories. Although the discovery of a stable Kaluza-Klein particle would provide a dark matter candidate, the significance of the discovery to the field of particle physics would in many or most ways dwarf the particle’s status as a dark matter candidate.

By: Tim

Tim — Thu, 20 Nov 2008 23:34:47 +0000

Mysterious particles coming from everywhere reminds me of Philip Pullman’s Dust.

By: Krystian Majewski

Krystian Majewski — Thu, 20 Nov 2008 17:33:24 +0000

Gary Ansorge:

What I meant with Deus Ex Machina that it seem like an easy thing to do to “invent” some invisible stuff which explains all the troublesome observations we come across: rotation speed of galaxies, gravitational lensing and NOW even high energy cosmic rays? And although that invisible stuff makes up most of the universe, it just happens not to be where we live? Meh. Remember Luminiferous Aether back when they were trying to construct a model of light? Well, it didn’t turn out so great – the modern explanation is QUITE the can of worms.

Just wanted to vent some skepticism. I’ll shut my mouth as soon as I can buy a plank of dark matter at the DIY superstore.

By: rob

rob — Thu, 20 Nov 2008 16:30:40 +0000

gary:

aaah, yes. i forgot about synchotron radiation and how it goes as v^4. relativistic charges will radiate much better than lower speed charges, which Phil mentioned above.

By: Gary Ansorge

Gary Ansorge — Thu, 20 Nov 2008 16:17:15 +0000

Krystian Majewski:

Dark matter was proposed, not as deus ex machina, but as something we can’t detect thru normal electromagnetic radiation interactions,ie, it doesn’t radiate in the em spectrum. It’s obviously there, which we CAN detect thru its gravitational interaction, we just don’t know (yet) what could do that w/o leaving an E.M. trace.

GAry 7