Description: 宇宙微波背景（CMB）是宇宙大约 38 万年前，光与重子解耦自由传播遗留至今的电磁辐射。它提供了有关宇宙的组成、几何（形状）、演变和结构演化的信息。早期的致密宇宙是由自由粒子（质子、中子、电子）和光（光子）组成的 "热汤"。在CMB产生之前，光子与自由电子的相互作用阻碍了光的远距离传播。宇宙的膨胀和冷却使自由电子与质子结合形成氢原子，并使光得以在宇宙中传播。宇宙膨胀随后拉长了这些光子的波长，使它们如今可以在电磁波谱的微波区域被探测到。

Related Terms:

• 宇宙大爆炸理论
• 宇宙学
• 暗能量
• 微波辐射
• 电子

Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher
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