This activity is one of three on the Desk Top Stars site. In this section learners/students will learn about the evidence that suggests that the Universe is expanding and use this evidence to determine the age of the Universe. Astronomers have measured patterns of spectral lines for many of galaxies. They have found that almost all of them are shifted to the red end of the spectrum (longer wavelengths), so they are moving away from us. More distant galaxies have larger shifts, which means they are moving away even faster. This tells us that the Universe is expanding. Topics include: NASA, time, distance, velocity, spectra, interpreting graphs, and the expanding universe.