Speaker 1: Welcome to brain Stuff from how Stuff works dot com
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Speaker 1: com slash brain Stuff today for details. I am Marshall
Speaker 1: brain with today's question. If we were to move all
Speaker 1: of the matter in the universe into one corner, how
Speaker 1: much space would it take up. It's hard to answer
Speaker 1: this question exactly because there are some unknowns, but if
Speaker 1: you're willing to accept three assumptions, we can come up
Speaker 1: with an answer that at least sounds reasonable. The first
Speaker 1: question is how big is the universe. No one knows,
Speaker 1: but based on observations, we might guess that it's a
Speaker 1: sphere that's thirty billion light years across. That means that
Speaker 1: the whole universe contains about ten to the thirty second
Speaker 1: power cubic light years. It's incredibly big. The next question
Speaker 1: is how much matter does the universe contain. The mass
Speaker 1: of the universe is a source of debate right now,
Speaker 1: because there's no easy way to put the universe on
Speaker 1: a scale NASA estimates that it's about ten to the
Speaker 1: sixtims for the whole thing. Other estimates give other numbers,
Speaker 1: but they're all in that same ballpark. The next question
Speaker 1: is what density do you want to assume that the
Speaker 1: mass will have once you push it all into one corner.
Speaker 1: If you were to really do this, if you actually
Speaker 1: didn't move all of the mass of the universe into
Speaker 1: one corner, it would condense into a black hole. But
Speaker 1: let's say that you could keep it from doing that,
Speaker 1: and you were somehow able to keep all the mass
Speaker 1: evenly distributed at a density of the sun. If you
Speaker 1: are willing to accept these three assumptions, then all of
Speaker 1: the matter in the universe would fit into about one
Speaker 1: billion cubic light years, or a cube that's approximately a
Speaker 1: thousand light years on each side. Compared to the size
Speaker 1: of the universe, that's tiny. Imagine a despec Compared to
Speaker 1: Planet Earth. The universe is an incredibly empty place. Do
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Speaker 1: please send me an email at podcast at how stuff
Speaker 1: works dot com. For more on this and thousands of
Speaker 1: other topics, go to how stuff works dot com.