宇宙线(cosmic ray)
贯穿银河系的高速粒子（原子核或电子）。其中一些粒子来自太阳，但大部分来自太阳系外，称为银河宇宙线。到达地球大气层顶部的宇宙线粒子称为初级宇宙线，它们与大气中的原子核碰撞後，产生次级宇宙线。大部分初级宇宙线受星际磁场和地球磁场的强大影响，具有很高的能量，速度相当於光速的87%或更高。由人造地球轨道卫星进行的γ射线测量显示，宇宙线主要集中在银河系的银盘上，只有很小比例的部分来自周围的银晕。涉及宇宙线产生和加速过程的细节至今还不清楚，但来自超新星的膨胀冲击波似乎能够完成宇宙线的加速。从1930年代初期到1950年代，对於宇宙线的研究在科学研究原子核和它的组分上起过重要作用，因为它们是唯一的高能粒子源。通过宇宙线的撞击发现了短寿命的亚原子粒子，因而建立了粒子物理学领域。甚至在功率强大的粒子加速器出现後，粒子物理学家仍在有限的规模上继续研究宇宙线，因为宇宙线中一些粒子的能量是在实验室条件下远不能达到的。
English version：
cosmic ray
High-speed particle (nucleus or electron) that travels through the galaxy. Some cosmic rays originate from the sun, but most come from outside the solar system. Primary cosmic rays that reach earth's atmosphere collide with nuclei in it, creating secondaries. Because lower-energy primaries are strongly influenced by the interplanetary magnetic field and earth's magnetic field, most of those detected near earth have very high energy, corresponding to speeds about 87% that of light or more. Observations from satellites indicate that most cosmic rays come from the galaxy's disk, but the highest-energy ones are probably extragalactic. Details of their production and acceleration remain unclear, but apparently expanding shock waves from supernovas can accelerate particles. From the early 1930s to the 1950s, cosmic rays were the only source of high-energy particles used in studying the atomic nucleus and its components. Short-lived subatomic particles were discovered through cosmic-ray collisions, leading to the rise of particle physics. Even powerful particle accelerators cannot impart energy anywhere near that of the highest-energy cosmic rays. See also Victor Francis Hess.