⚙️ how
How do scientists tell how fast a galaxy is moving away from us?
Quick Answer
They measure the redshift of its spectral lines. A larger redshift means the galaxy is receding faster on average.
The Full Story
When a galaxy moves away, its light is stretched to longer wavelengths, shifting spectral lines toward the red end of the spectrum. By comparing observed line positions with their known laboratory wavelengths, astronomers calculate redshift. This provides a direct way to estimate recession speed in an expanding universe. For very distant galaxies, the relation becomes more complex because expansion affects space itself over large distances and times.
Key Facts
1.Redshift is measured from spectral lines
2.Greater redshift usually means greater distance
3.This method underpins the study of cosmic expansion
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"How can light tell you a galaxy is racing away?"
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