Photons released from hotter, denser areas were more energetic than photons emitted from rarefied regions, so the pattern of hot and cold spots induced by the sound waves was frozen into the CMB.

• 从热而致密的区域释放出的光子，能量会比从舒张区放射出的光子高，所以由声波引起的高低温区的形式便被冻结在CMB里。