What is redshift in astronomy?
Quick Answer
Redshift is the stretching of light to longer wavelengths, making objects look redder than they really are. In astronomy it is a key clue that distant galaxies are moving away.
The Full Story
Redshift happens when light’s wavelength is increased, usually because an object is moving away from the observer or because space itself is expanding. Edwin Hubble’s observations in the 1920s showed that more distant galaxies generally have larger redshifts, a finding now known as Hubble’s law. Astronomers use redshift to estimate distances, study the early Universe, and measure cosmic expansion. A related concept is blueshift, which occurs when an object is moving toward us.
Key Facts
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Suggested video title for this topic:
"Why distant galaxies look redder—and what that tells us about the Universe"