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S&T Nov 2010 page 35
"The universe is approximately 13.7 billion years old. Were it not expanding, the farthest
object we could see now would be 13.7 billion light-years distant. But the universe is expanding, and the space
through which light travels grows. Given the observed rate of expansion, astronomers estimate that the radius
of the observable universe is around three times greater than if the universe were stationary, or about 47 billion
light-years." Alan Hirshfeld
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