isotropic radiation

In physics, anisotropy refers to the property of exhibiting different values when measured along different directions. This is commonly observed in single crystals where atoms are arranged in regular lattices, leading to directional variations in properties like the speed of light or electrical resistivity.1

In contrast, isotropic radiation is radiation that is the same in all directions. A prime example is the cosmic microwave background (CMB), which is electromagnetic radiation filling the universe as a remnant of the big bang. While the CMB is largely isotropic, precise measurements have detected very small fluctuations, or anisotropies, which are crucial for understanding the formation of structures like galaxies.2