The Chicagoland Observatory for Underground Particle Physics (COUPP)

The Chicagoland Observatory for Underground Particle Physics (COUPP) collaboration looks for bubbles in chambers filled with a compound containing carbon, fluorine and iodine. The fluid is superheated beyond the boiling point but has no rough surface to form bubbles. When a specific type of particle interacts in the chamber, it can deposit enough energy to boil the fluid and make a bubble. Electrons do not produce bubbles, while a dark matter particle interacting with a nucleus can – making this the key for dark matter detection. See:Bubble chamber gets more precise in dark matter search

Bold added for emphasis.

See Also: Bubble chamber gets more precise in dark matter search

***

The accelerating universe is the observation that the universe appears to be expanding at an increasing rate, which in formal terms means that the cosmic scale factor a(t) has a positive second derivative,^[1] implying that the velocity at which a given galaxy is receding from us should be continually increasing over time^[2] (here the recession velocity is the same one that appears in Hubble's law; defining 'velocity' in cosmology is somewhat subtle, see Comoving distance#Uses of the proper distance for a discussion). In 1998, observations of type Ia supernovae suggested that the expansion of the universe has been accelerating^[3][4] since around redshift of z~0.5.^[5] The 2006 Shaw Prize in Astronomy and the 2011 Nobel Prize in Physics were both awarded to Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess for the 1998 discovery of the accelerating expansion of the Universe through observations of distant supernovae.^[6][7]

***

In cosmology, baryon acoustic oscillations (BAO) refers to an overdensity or clustering of baryonic matter at certain length scales due to acoustic waves which propagated in the early universe.^[1] In the same way that supernova experiments provide a "standard candle" for astronomical observations,^[2] BAO matter clustering provides a "standard ruler" for length scale in cosmology.^[1] The length of this standard ruler (~150 Mpc in today's universe^[3]) can be measured by looking at the large scale structure of matter using astronomical surveys.^[3] BAO measurements help cosmologists understand more about the nature of dark energy (the acceleration of the universe) by constraining cosmological parameters.^[1]

***

SDSS III: 2008-2014

In mid-2008, SDSS-III was started. It comprises four separate surveys, each conducted on the same 2.5m telescope: ^[9][10]

• Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• Baryon Oscillation Spectroscopic Survey (BOSS)
• Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS)^[11]
• Sloan Extension for Galactic Understanding and Exploration 2 (SEGUE-2)

Baryon Oscillation Spectroscopic Survey (BOSS)

The SDSS-III's Baryon Oscillation Spectroscopic Survey (BOSS) will map the spatial distribution of luminous red galaxies (LRGs) and quasars to detect the characteristic scale imprinted by baryon acoustic oscillations in the early universe. Sound waves that propagate in the early universe, like spreading ripples in a pond, imprint a characteristic scale on the positions of galaxies relative to each other ^[12] .

***

See Also:

• SuperCDMS An Improvement on Detection 
• There Be Dragons on the Dark Matter Issue? 
• Sounding Off on the Dark Matter Issue