Another question: How can you predict the expansion of cosmos by looking at stars.?
Answers
If the universe is expanding, then why the constellations of stars are not distorting in shape?
Originally Answered: If everything in the universe is moving swiftly and expanding, why do the shapes of the constellations stay the same? (as viewed from Earth, of course)
I have read the three answers you have received so far and, in my humble opinion, it is slightly different.
Yes, the constellations aren’t as they were before. For example, the , the starting point of reference in astro-navigation, has moved many degrees since it was set by the constellation of Aries, in the antic Greece.
But what we see as “stars” are both stars from our Milky Way galaxy and distant galaxies. From here, there is no way to know unless you have a very powerful telescope.
The expansion of the universe works for distant galaxies only. Not stars in a galaxy or galaxies in a cluster like, our Milky Way and Andromeda.
As for the expansion, we can only observe it as being at its center. Therefore, their relative position don’t change. Imagine you are at the center of a sphere on the surface of which there are many dots. As the sphere inflates, the relative angle between the different dots don’t change, right?
In fact, the surface of the observable universe is … the Big Bang. And this is why the Cosmic Microwave Background (CMB), the energy left of the Big Bang, can be observe as coming from all directions in the sky: It is a sphere around us