If the universe is expanding like a balloon, is it hollow?
Category:
Science > Astronomy & Space
Keywords:
expansion, expand, balloon, hollow, universe
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other
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Answer:
The balloon analogy is very confusing. In fact, there is no direction in the universe which corresponds to inward or outward on the balloon. Thus the universe is not like a hollow balloon because there is no "inside" to be hollow.
Other books use the analogy of rising raisin bread dough (where the raisins represent galaxies). This has different problems (e.g., the Universe doesn't have anything analogous to the crust), but it doesn't raise questions of inside and outside.
All analogies break down eventually. The balloon analogy breaks down sooner than most.
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