eli5: If the sun revolves around the galaxy, why do we still see the same constellation that was discovered by the Romans (probably 1000s of years ago). surely they should have been scattered by now due to revolution of the sun combined with the revolution of the earth around with sun

Question

Thnx to all, for the answer. I had a good time discussing and clearing my doubt.

In: 179

Answer 1

They do. There even is a term for it in astronomy: “proper motion”

The thing is the sun and all the other stars in the galaxy move around the center of the galaxy together.

You can think of it as riding a carousel and seeing all the other kids on the carousel with you appearing to be staying still in relation to you while you ride in circles together.

Still some stars noticeably move against the background of the stars.

Banard’s star moves at more than 10 arcesecond per year (an arcesecond being a 1/60 of an arcminutes and an arcminure being 1/60 of a degree).

That might not sound like much but it is a far cry from being a fixed star and it adds up to maybe a quarter of a degree over a human lifetime. Meaning it moves about half the apparent size of the moon during a human life is the human has good healthcare.

It is not noticeable for most people but if you have a sci-fi story set a few millennia in the future and you might want to be careful how you show the night sky if you want to avoid angry tweets by Neil deGrasse Tyson.