Linked from
The 130 pages that link to Spectroscopy, each with the reason it gives.
Galaxy rotation curveNarrower topic: Spectral measurements turn galaxy light into velocity data.
Rydberg formulaNarrower topic: The formula grew from attempts to organize measured atomic spectra.
Lyman-alpha forestNarrower topic: The forest is identified and measured by analyzing quasar spectra.
Rydberg constantNarrower topic: The constant is inferred and tested through measured atomic spectra.
Solar spectrumNarrower topic: It supplies the measurement methods used to interpret solar light.
NebuliumNarrower topic: Spectroscopy revealed the lines that nebulium was invented to explain.