Physics · Space physics. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Light from most distant galaxies reaches us with a longer wavelength than the same light produced on Earth. The light is shifted towards the red end of the spectrum, so this is called red-shift. It shows that the galaxies are moving away from us.
The further away a galaxy is, the bigger its red-shift, so the faster it is moving away. This is what we would see if space itself were expanding.
The Big Bang theory says the universe began from a very small region that was extremely hot and dense, and has been expanding ever since. Red-shift is evidence that supports it.
Students write that red-shifted galaxies are red or hot. Red-shift is a change in wavelength caused by motion away from us, not a colour or a temperature.
Answer: Galaxy Q is further away.
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