What is the effect called when spectral lines from a distant galaxy shift toward longer wavelengths?

What is the effect called when spectral lines from a distant galaxy shift toward longer wavelengths?

• A. Blueshift
• B. Redshift
• C. No shift
• D. Random shift

Answer: (B)

Light from a galaxy that is moving away from us stretches as it travels, so the wavelengths of its spectral lines shift toward the red end of the spectrum. This shift toward longer wavelengths is called redshift. It happens because of the Doppler effect: recession makes light appear redder. If an object were moving toward us, the lines would shift toward shorter wavelengths, which is blueshift. No shift would mean there’s no relative motion affecting the light. The idea that light shifts randomly isn’t a standard concept in astronomy. In cosmology, redshift also increases with distance, reflecting the expansion of the universe, and helps scientists measure how far galaxies are.

Light from a galaxy that is moving away from us stretches as it travels, so the wavelengths of its spectral lines shift toward the red end of the spectrum. This shift toward longer wavelengths is called redshift. It happens because of the Doppler effect: recession makes light appear redder. If an object were moving toward us, the lines would shift toward shorter wavelengths, which is blueshift. No shift would mean there’s no relative motion affecting the light. The idea that light shifts randomly isn’t a standard concept in astronomy. In cosmology, redshift also increases with distance, reflecting the expansion of the universe, and helps scientists measure how far galaxies are.