How do we know the Universe is expanding?

Cosmological redshift was our first clue the universe was expanding. A century ago, Edwin Hubble discovered galaxies outside our own supercluster are all moving away from us. But how do we get from redshift to an expanding universe? That's the tricky part and most people get it wrong.
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VIDEO ANNOTATIONS/CARDS

Is The Universe Infinite:
   • Is The Universe Infinite?  

What is the Universe expanding into?
   • What is the Universe expanding into?  

How Do We Know Things About Stars?
   • Basics of Hertzsprung-Russell (HR) Diagrams  

What the HECK is Light?!
   • What the HECK is Light?!  
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RELATED YOUTUBE VIDEOS

PBS Space Time on Cosmological Redshift:
   • How Do You Measure the Size of the Universe?  

PBS Space Time on the CMB:
   • Cosmic Microwave Background Explained  
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HUGE THANK YOU TO THESE PATRONS

** Andy Kirkham, Nikko Lai, Clint Cloys, Evgeny, Rick Finn, Preston From, Christian McCracken **
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SUPPORT THE SCIENCE ASYLUM

Patreon:
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Advanced Theoretical Physics (eBook):
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OTHER SOURCES

https://arxiv.org/abs/1204.5493
https://arxiv.org/abs/astro-ph/0211011
http://www.astro.ucla.edu/~wright/cos...

Wavelength to RGB:
http://www.wolframalpha.com/widgets/v...
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LINKS TO COMMENTS

Expanding? - seastormsinger:
   • Why is Light the Fastest Thing?  

Redshift - Yair Eshel Cahansky:
   • Is The Universe Infinite?  

FLOWER Metric - Guest Informant:
   • Is The Universe Infinite?  

List of Topics - aThrasheR:
   • Is Math the Language of the Universe?  
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IMAGE CREDITS

Cosmic Microwave Background:
http://www.esa.int/Our_Activities/Spa...

Spectroscope at Lick Observatory:
https://commons.wikimedia.org/wiki/Fi...

Thumbnail Background:
https://www.nasa.gov/image-feature/go...