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Old 13-10-2010, 05:02 PM
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CraigS
Unpredictable

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Join Date: Jul 2010
Location: Australia
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The Dark Matter Part

Dark Matter is defined as being undetectable by emitted or scattered electromagnetic radiation (such as the CMBR). It is inferred to exist through its interaction with gravity and is thus observable via several means such as gravitational lensing or hi-energy neutrino emissions (via mutual annihilation).

The most likely candidate for dark matter in the current standard cosmological model is in the form of WIMPs (Weakly Interacting Massive Particles). They are theorized to be of relatively large mass, relatively slow moving (non-relativistic) and hence energetically, ‘cold’. They may be entirely transparent to the EM spectrum and thus, they wouldn’t be visible (or appear as ‘holes’), in the measured CMB spectra. Dark matter density information however, can be derived from part of the CMBR power density spectrum.

The Planck spacecraft has multiple objectives. One is to observe gravitational lensing of the CMB. We may learn more about the ‘clumpiness’ and locations of Dark Matter from the onboard technology. Lensing observed with the Hubble telescope has been used to create a 3D model of the large scale distribution of Dark Matter.

Hope this helps as an adjunct to Steven’s description of the CMBR.

Cheers.
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