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.

Summary

This quote explains the concept of how we perceive galaxies. Due to the vast distances involved, the near side of a galaxy is closer to us, allowing us to see it as it was tens of thousands of years ago. However, since galactic events occur over the span of tens of millions of years, considering an image of a galaxy to capture just one moment in time is negligible. Thus, despite the time lag in observing distant galaxies, the idea of them being frozen in time is not significantly distorted.

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