Red-shift is an increase in observed wavelength compared with the same spectral feature measured in the laboratory. Light from most distant galaxies is red-shifted, indicating that they are moving away from us. Greater red-shift generally indicates a greater recession speed; it means spectral lines move towards longer wavelengths, not that every galaxy simply looks red. Example: Define red-shift. Observed wavelengths are longer than the reference wavelengths. Use clear labels. State assumptions.