9
Universal Expansion: Balloon Analogy
•Simulation of a “closed” spherical universe expanding:
•http://www.astro.ucla.edu/~wright/Balloon2.html 
•
•The points here are that
–Expansion looks the same from each galaxy
–There is no “center” of the universe
–Galaxies do not expand
–Photons are redshifted because space itself is expanding
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