Astronomers have thoroughly mapped the stars in this part of the Milky Way galaxy. That’s how we know our sun’s location with respect to the galaxy’s center. Likewise, astronomers have plotted the Milky Way’s position with respect to the nearest galaxies – but the universe as a whole is a far bigger place than just our Local Group of galaxies.
Also, the universe is constantly expanding. The galaxies are moving away from each other. So we see the galaxies where they “were,” not where they “are.” Trying to determine the Milky Way’s location would be like trying to find your way across a terrain where the landmarks aren’t really where they appear to be!
So it’s difficult – or maybe not even possible – to talk about where the Milky Way is, with respect to the rest of the universe. Astronomers generally avoid the problem of describing where the Milky Way is by saying when it is. And when is thought to be 12 to 15 billion years after the Big Bang – believed to be the only moment in the history of the universe when all matter existed at the same place.
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