How do we calculate how big the universe is?
In: Physics
You know how when something is moving toward you and it’s making a sound that sound is pitched upward? And when it’s moving away from you and making a sound that sound is pitched downward (The Doppler effect)?
This happens with light too. Things moving away from us appear redder and things moving toward us appear bluer. The redder/bluer they appear, the faster they are moving away/toward us.
Based on this, we can tell that the largest structures of the universe (galaxy clusters) are all moving away from each other (they’re all red shifted). Also, based on those whose distances we already know (from other means such as triangulation and apparent luminosity), the further away they are, the faster they are moving away.
So we have discovered a correlation between how red something appears and how far away it is. So we can look at distance objects, see how much its light has been red shifted, and then determine how far away it is from us based on that.
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