CMB: Sound Waves in the Early Universe
CMB: Sound Waves in the Early Universe
CMB: Sound Waves in the Early Universe
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<strong>Sound</strong> <strong>Waves</strong><br />
Each <strong>in</strong>itial overdensity (<strong>in</strong> dark<br />
matter & gas) is an overpressure<br />
that launches a spherical sound<br />
wave.<br />
This wave travels outwards at <br />
57% of <strong>the</strong> speed of light.<br />
Pressure-provid<strong>in</strong>g photons<br />
decouple at recomb<strong>in</strong>ation.<br />
<strong>CMB</strong> travels to us from <strong>the</strong>se<br />
spheres.<br />
Eisenste<strong>in</strong>