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Arun Cg asked this question about Astrophysics for People in a Hurry:
In the first chapter, he mentions that the universe is two light years across. And then later he says that two minutes have passed. The universe cannot be two light years across unless a year of time has passed, right? Is there something that I am missing?
Ana A light-year is a measure of distance, not time; it refers to the distance light can travel through a year (9.4607 × 10^12 km or nearly 6 x 10^12 mile…moreA light-year is a measure of distance, not time; it refers to the distance light can travel through a year (9.4607 × 10^12 km or nearly 6 x 10^12 miles).
When Neil says the universe is two light-year across, it's a reference to its "size" at a certain point in time (and then he continues to write about another point in time, two minutes later). (less)
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Astrophysics for People in a Hurry
by Neil deGrasse Tyson (Goodreads Author)
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