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View Full Version : Hearing the Early Universe’s Scream: Sloan Survey Announces New Findings



Fraser
2015-Jan-06, 11:30 PM
Imagine a single mission that would allow you to*explore the Milky Way and beyond, investigating*cosmic chemistry, hunting planets, mapping galactic structure, probing dark energy and analyzing the expansion of the wider*Universe. Enter the Sloan Digital Sky Survey, a*massive*scientific collaboration that*enables*one thousand astronomers from 51 institutions around the world to do just that. At*Tuesday’s AAS briefing […]

More... (http://www.universetoday.com/117896/a-new-universe-unleashed-sloan/)

mkline55
2015-Jan-07, 01:08 PM
One component of SDSS is exploring dark energy by “listening” for acoustic oscillation signals from the the acceleration of the early Universe...

Surely I have a different interpretation of 'acoustic' than the author. Does the study also propose a medium for transfer of acoustic signals?

Cougar
2015-Jan-07, 02:26 PM
Surely I have a different interpretation of 'acoustic' than the author. Does the study also propose a medium for transfer of acoustic signals?


Imagine an overdense region of the primordial plasma (https://en.wikipedia.org/wiki/Structure_formation#Primordial_plasma). While this overdensity gravitationally (https://en.wikipedia.org/wiki/Gravitationally) attracts matter towards it, the heat of photon-matter interactions creates a large amount of outward pressure (https://en.wikipedia.org/wiki/Pressure). These counteracting forces of gravity and pressure create oscillations (https://en.wikipedia.org/wiki/Oscillations), analogous to sound waves (https://en.wikipedia.org/wiki/Sound_waves) created in air by pressure differences. - wiki



But the expansion of the early universe was decelerating.... until its increasing volume and corresponding increase in the amount of dark energy turned things around.

mkline55
2015-Jan-07, 02:57 PM
Ah. So 'acoustic' is now loosely equivalent to oscillation of any form and is no longer associated just with sound waves. I hope the dictionaries get updated. I think I'll go out and listen to Mars's very low frequency acoustic orbit tonight.