By analyzing the light from stars and galaxies using a spectroscope, scientists can determine the composition of celestial objects and learn about their motion. Examining the emission spectra of elements reveals their presence. The Doppler effect causes wavelengths to shift based on an object's motion - toward the red end if receding and blue if approaching. All light is redshifted, indicating the universe is expanding from an initial point around 12 billion years ago in the Big Bang.