What is the primary observational evidence cited regarding the vast majority of distant galaxies?
Answer
They exhibit a predominant redshift, indicating the universe is expanding.
For very distant galaxies, the overwhelming observation made by astronomers is a redshift. This redshift signifies that these galaxies are generally receding from us, causing their light wavelengths to stretch. This systematic observation provides the primary evidence supporting the cosmological model that the universe is expanding, causing nearly all objects outside our immediate local gravitational cluster to move away from us.
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