How big is the universe?

If all the matter in the universe was pushed into one corner, how much space would it take up? Listen in as Marshall Brain explores the size of the universe in this podcast from HowStuffWorks.

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Episode Transcript

Speaker 1 (00:00):
Welcome to brain Stuff from how Stuff works dot com
where smart happens. This podcast is brought to you by
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com slash brain Stuff today for details. I am Marshall

(00:24):
brain with today's question. If we were to move all
of the matter in the universe into one corner, how
much space would it take up. It's hard to answer
this question exactly because there are some unknowns, but if
you're willing to accept three assumptions, we can come up
with an answer that at least sounds reasonable. The first
question is how big is the universe. No one knows,

(00:47):
but based on observations, we might guess that it's a
sphere that's thirty billion light years across. That means that
the whole universe contains about ten to the thirty second
power cubic light years. It's incredibly big. The next question
is how much matter does the universe contain. The mass
of the universe is a source of debate right now,

(01:09):
because there's no easy way to put the universe on
a scale NASA estimates that it's about ten to the
sixtims for the whole thing. Other estimates give other numbers,
but they're all in that same ballpark. The next question
is what density do you want to assume that the
mass will have once you push it all into one corner.

(01:29):
If you were to really do this, if you actually
didn't move all of the mass of the universe into
one corner, it would condense into a black hole. But
let's say that you could keep it from doing that,
and you were somehow able to keep all the mass
evenly distributed at a density of the sun. If you
are willing to accept these three assumptions, then all of

(01:51):
the matter in the universe would fit into about one
billion cubic light years, or a cube that's approximately a
thousand light years on each side. Compared to the size
of the universe, that's tiny. Imagine a despec Compared to
Planet Earth. The universe is an incredibly empty place. Do
you have any ideas or suggestions for this podcast? If so,

(02:14):
please send me an email at podcast at how stuff
works dot com. For more on this and thousands of
other topics, go to how stuff works dot com.