Asked by udontknow
Which of the following indicates that the universe is expanding?
The spectra of Cepheid variables, which are found in all galaxies, are blue shifted.
The spectra of Cepheid variables, which are found only in our galaxy, are red shifted.
The spectra of Cepheid variables, which are found only in our galaxy, are blue shifted.
The spectra of Cepheid variables, which are found in all galaxies, are red shifted.
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The spectra of Cepheid variables, which are found in all galaxies, are red shifted.
Reason: Redshift (spectral lines shifted to longer wavelengths) indicates objects are receding from us (Doppler effect), and the systematic redshift of galaxies as a function of distance is the observational evidence for the expanding universe (Hubble's law).
Reason: Redshift (spectral lines shifted to longer wavelengths) indicates objects are receding from us (Doppler effect), and the systematic redshift of galaxies as a function of distance is the observational evidence for the expanding universe (Hubble's law).
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