The shift of the hydrogen absorption spectrum of a galaxy primarily provides evidence for the following:
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Expansion of the universe - The redshift observed in the hydrogen absorption spectrum indicates that galaxies are moving away from us, which supports the concept of an expanding universe.
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Motion of the galaxy - The shift can also indicate the motion of the galaxy in relation to Earth, including both radial (toward or away from us) and transverse motion.
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The Big Bang theory - The evidence of redshift in the light from distant galaxies supports the Big Bang theory, suggesting that the universe has been expanding since its inception.
Thus, the three correct answers are:
- Expansion of the universe
- Motion of the galaxy
- The Big Bang theory
(Note: While the composition of the universe and temperature of the galaxy can be inferred through other methods, the redshift itself is not directly indicative of these elements.)