Question

3. Galaxies look stationary, so why do scientists say that they rotate?

Answer 1

Answer:

It's because galaxies are unimaginably huge. An object traveling at high speed across a very long distance appears to be moving slowly when viewed from far away

Explanation:

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Answer 2

Answer:

because the galaxies are not stationary if we use a telescope and use it to look at any star and taking the light from it through a prism we see that the red color is more which means that the wavelength is more for those star light which appears to us which is red shifted or it's going away like the Doppler effect as this is not only in case of any one star if we take many into account we see blue and red shifted stars(ref shifted is more) too which means that the galaxies are towards us by moving away likewise it can happen if we rottate and move away