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Q & A: Is the universe flat?

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Most recent answer: 09/26/2009
is the universe flat?
- william spence (age 33)
sacramento, california, usa
By and large the universe is flat except near massive gravitational bodies where it can be curved. One of the consequences of  'flatness'  is that light travels in straight lines. The earliest experiment that showed the effect of gravity on light was the verification of a prediction by Einstein that starlight passing near to the sun would be bent by a very small amount.  During an eclipse of the sun in 1919 such an effect was observed, launching both Einstein and General Relativity into international fame.

Near a black hole space can get real, real curvy.
One of the most sensitive experiments to show the overall  flatness of the universe is the measurement of the spatial distribution of thermal fluctuations in the cosmic microwave background (CMB).  Specific calculations can be made for these fluctuations and experimental results agree quite well with overall flatness. 
Here is another web site that is a bit complicated but shows how measurements of the CMB can be used to determine flatness.


(published on 09/26/2009)

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