

Ask HN: Universe expands. What's the area outside the universe called? - htmlpress

Eternity?
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nmc
The Universe is infinite: it has no bounds, or limits.

For instance, you can go on a straight line forever.

It "expands", but it does not "swell", because it does not mean anything for a
boundless space to be "swelling".

The "expansion" phenomenon, known as "metric expansion of space" [1], is not
"swelling" at all. Only the spatial scale of the Universe is expanding.

Furthermore, this process is isotropic, which means wherever you are observing
from, it will always seem like you are at the center of the expansion process.

[1]
[http://en.wikipedia.org/wiki/Metric_expansion_of_space](http://en.wikipedia.org/wiki/Metric_expansion_of_space)

EDIT: fixed typos (damn keyboard)

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andrewcooke
if you mean "what does the universe expand into?" then the answer, as far as
we know, is that "it doesn't work like that".

another way of saying the same thing is that the maths used in the physical
models doesn't "embed" the universe in anything. there's no need for an
external reference. you can do everything internally, consistently. it's quite
neat, actually.

that doesn't mean that there "really is" nothing. just that nothing extra is
needed for the theory, and since nothing extra can be observed, it's simpler
to not have anything.

in other words - you can mathematically describe a universe that expands, but
doesn't need anything to expand into. since that fits observations (within
reason) and is simpler than a model that needs something extra "outside" that
also needs explaining (and how would you explain that?!), it's preferred.

~~~
htmlpress
I suppose there are some things that cannot be explained such as gravity and
that "something extra 'outside' "

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Metatron
From what I understand two terms you use would be inaccurate. First of all
it's not an area, as it has no physical dimensions. Second of all it could not
be called 'eternity' as it is composed of nothing and therefore no change to
it is occurring, and change is the fundamental principle behind time.

Everything that exists, exists within the universe, there is nothing
'outside', there is no 'outside'. At least under the classical understanding,
or theory, of existence. Some multiverse models posit that there may be other
universes that we may one day expand into. Others yet posit that these other
'bubbles' might have differing laws of physics to us, and could destroy us on
contact. Fun.

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anovikov
It's not called anything because it doesn't really exist, it is outside the
horizon of events. Think of it same way as about volume which is inside a
black hole. It doesn't exist... until you get there. Then the world outside
the hole will become nonexistent to you, exactly same way as the area 'outside
the universe' is to us now. Because the black hole will become your universe.
In a way, we are sitting in a giant black hole.

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embro
The simple answer is: the universe.

Just today, Fraser Cain posted a video to answer this question.

Have a look : [http://youtu.be/Kj0TwTonG_8](http://youtu.be/Kj0TwTonG_8)

Hope it helps!

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ddorian43
you can also search/post on reddit.com/r/askscience

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Mankhool
Exoverse.

