⚙️ how
How do astronomers know the universe is expanding?
SpaceCosmology
Quick Answer
They observe that distant galaxies’ light is redshifted and that farther galaxies recede faster, on average. This relationship is known as Hubble’s law.
The Full Story
In the 1920s, Edwin Hubble and others found that galaxies outside the Milky Way are moving away, with speed increasing with distance. The farther away a galaxy is, the more its light is redshifted because space itself is stretching. Modern surveys refine the exact expansion rate, called the Hubble constant, using multiple methods. Expansion is a cornerstone of the Big Bang model and is also why very distant galaxies are seen as they were in the past.
Key Facts
1.Hubble’s key work dates to the 1920s
2.The expansion rate is called the Hubble constant
3.Redshift is evidence of stretching space
YouTube Angle
Suggested video title for this topic:
"How astronomers discovered the universe is growing"