Answer:
1. The galaxies moving away from Earth
Explanation:
When galaxies move away from us in space, the light they emit appears more red. It's a bit like the sound of a passing ambulance siren changing as it moves away. This shift to the red end of the light spectrum is called redshift. Scientists use redshift to understand that the universe is expanding—galaxies are moving away from each other over time. So, the redshift of galaxies tells us about the motion and expansion of the universe.
