Thanks to observations of galaxy redshifts, we can tell that the universe is EXPANDING! Knowing that the universe is expanding and how quickly it's expanding also allows us to run the clock backward 14 billion years to the way the universe began with a bang.

Check out the Crash Course Astronomy solar system poster here: http://store.dftba.com/products/crash...

If you want to learn more about the creation and death of the universe, watch Crash Course Big History here:    • Big History  


Chapters:
Introduction: The Origins of the Universe 00:00
Distant Galaxies Show a Redshift in Their Spectra 2:07
The Universe is Expanding 4:13
The Big Bang 5:12
Lookback Time 6:06
The Cosmic Microwave Background 7:50
What is the Universe Expanding Into? 9:17
Review 12:12



PBS Digital Studios:    / pbsdigitalstudios  

Follow Phil on Twitter:   / badastronomer  

Want to find Crash Course elsewhere on the internet?
Facebook   / youtubecrashcourse  
Twitter   / thecrashcourse  
Tumblr   / thecrashcourse  
Support CrashCourse on Patreon:   / crashcourse  



PHOTOS/VIDEOS
Hubble Goes to the eXtreme to Assemble FarthestEver View of the Universe http://www.nasa.gov/mission_pages/hub... [credit: NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team]
Out of this whirl: The Whirlpool Galaxy (M51) and companion galaxy http://www.spacetelescope.org/images/... [credit: NASA, ESA, S. Beckwith (STScI), and The Hubble Heritage Team STScI/AURA)]
RedShifts in the Spectra of Extraglactic Nebuale http://articles.adsabs.harvard.edu/cg... [credit: American Astronomical Society, NASA Astrophysics Data System]
Andromeda http://www.nasa.gov/images/content/38... [credit: Bill Schoening, Vanessa Harvey/REU program/NOAO/AURA/NSF]
The Big Bang (video) http://svs.gsfc.nasa.gov/cgibin/deta... [credit: NASA]
The Sun https://www.nasa.gov/sites/default/fi... [credit: NASA/SDO]
Alpha Centauri http://www.eso.org/public/images/eso1... [credit: ESO/Digitized Sky Survey 2, Acknowledgement: Davide De Martin]
Andromeda https://en.wikipedia.org/wiki/Androme... [credit: NASA/JPLCaltech]
Friedmann Universes https://commons.wikimedia.org/wiki/Fi...
Friedmann Equation http://burro.astr.cwru.edu/Academics/...
Penzias and Wilson stand at the 15 meter Holmdel Horn Antenna that brought their most notable discovery. https://en.wikipedia.org/wiki/Arno_Al... [credit: NASA]
Planck CMB http://www.esa.int/spaceinimages/Imag... [credit: ESA and the Planck Collaboration]
Galaxy Superclusters http://irfu.cea.fr/Projets/coast_docu... [credit: Marenostrum Numerical Cosmology Project]