The near side of a galaxy is tens of thousands of light-years closer to us than the far side; thus we see the front as it was tens of thousands of years before the back. But typical events in galactic dynamics occupy tens of millions of years, so the error in thinking of an image of a galaxy as frozen in one moment of time is small.
Carl SaganAbout author
- Author's profession: Scientist, Physicist
- Nationality: american
- Born: November 9, 1934
- Died: December 20, 1996