Please choose the correct answer to the question: Scientists measured the patterns of spectral lines given off by distant galaxies and concluded that almost all of these galaxies are moving away from Earth. What did the scientists observe directly?

Answer1: a shift toward longer wavelengths of light Answer2: a shift toward shorter wavelengths of light Answer3: the absence of wavelengths in the visible light range Answer4: the compression of wavelengths in the visible light range

Answer format: answer1/answer2/answer3/answer4
Answer: answer1