Doppler Effect in Light Ever wondered how scientists know if a star is moving toward or away from us? It’s all thanks to the Doppler Effect in light! When a star moves toward Earth, its light waves get compressed, shifting the spectral lines toward the blue—this is called a blue shift. When it moves away, the waves stretch out, causing a red shift. These tiny shifts in light tell us about the motion of stars, galaxies, and even the expansion of the universe! | Fadhel Mahdi