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How is it possible to take up space from a space less dimension? The universe expanding, begs the question what is it expanding into?

If it is something then why is it therefore not still part of the universe and therefore it is not expanding. And if it is ‘no thing’ how can something occupy space into something that doesn’t exist?

Damian H
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Gordian Knot
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    The universe expanding means that its parts are moving away from each other, this is perfectly intelligible without adding any external container. Just because we are used to seeing expanding things expand into something ambient in everyday experience does not mean that the concept "begs" it. – Conifold Mar 17 '21 at 20:17
  • @Conifold They are expanding away from each other. Great, and then they hit an edge and start to pile up? Is that your explanation? Or there is no end to the universe? – Gordian Knot Mar 17 '21 at 20:23
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    Even rubber balloons manage to expand without having an edge. But an explanation of concept does not need to involve an analogy to something one sees around when going for a walk. Nor is it advisable to draw conclusions from such analogies, be they edges or containers. – Conifold Mar 17 '21 at 20:28
  • A balloon is expanding into a space that exists @Conifold. The universe must have an edge if at first it was all contained in a singularity. – Gordian Knot Mar 17 '21 at 20:31
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    Didn't I just tell you to draw conclusions from concepts, and not analogies? Mathematicians define manifolds without placing them into any containers, and their sizes (maximal distances between points) can increase nonetheless. – Conifold Mar 17 '21 at 20:33
  • @Conifold delegating to ignorance doesn’t make something go away. Either the universe was a singularity and then exploded or it didn’t. Either it has an edge or it doesn’t. – Gordian Knot Mar 17 '21 at 20:34
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    Whether there was a singularity or not is currently debated, in any case it has no relation to having an ambient space. And the universe has no edges on current theories, it is a 3D closed manifold (sphere) in spatial slices. – Conifold Mar 17 '21 at 20:37
  • @Conifold which you cannot prove, neither can you prove it doesn’t have an edge. Regardless, the question asks whether darkness can exist outside the universe. – Gordian Knot Mar 17 '21 at 20:41
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    There is no darkness in this post, nor does it ask for proving anything. Only how the universe "can" expand. And that is what mathematics describes without any edges or "something it expands into". – Conifold Mar 17 '21 at 20:46
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    Possible duplicate on physics: https://physics.stackexchange.com/q/7359/195139 – Sandejo Mar 17 '21 at 22:46
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    "what is it expanding into?" The universe is all that there is: there is no "container" into which the universe lives. – Mauro ALLEGRANZA Mar 18 '21 at 06:42
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    This is not a philosophical question and there is no mystery here. You can either a) satisfy yourself with analogies about balloons etc., which are necessarily imprecise albeit useful or b) learn the elementary basics of general relativity. Distances between events in the 4d spacetime manifold are defined with respect to the metric, the metric is changing to increase the distances; the manifold itself does not need to be embedded in a larger space, all of these concepts and the universe's expansion can be described intrinsically. – Rollo Burgess Mar 18 '21 at 08:32
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    also, in the spirit of this being a philosophy site rather than me being a pedant (though that is also true ;) ) - I think that you mean it raises the question, not begs the question. – Rollo Burgess Mar 18 '21 at 08:34
  • @MauroALLEGRANZA you know that how? And where does that leave the multiverse hypothesis? Also it’s impossible that the universe is not contained for there are natural laws like equilibrium and pressure that dictate the limits of a limited and therefore not infinite universe... I would go on but since this question is deemed irrelevant to the moderators I’ll seek to find intellectuals elsewhere who can address my question, which at its core is philosophical, even if it’s being denied by some – Gordian Knot Mar 20 '21 at 04:47
  • @RolloBurgess general relativity has its shortcoming, hence special relativity and this only to deny Michelson-Morley’s experiment that showed a stationary, geocentric world with a moving ether. If one is to make mathematical calculations and ignore whether the universe is infinite or contained, then it doesn’t raise the question, it begs it because any mathematical model that ignores one portion cannot arrive at a correct answer, even if by accident. The universe has a pressure and pressure demands a container, if it were infinite there could not be pressure. – Gordian Knot Mar 20 '21 at 04:54
  • @Sandejo I was of the impression that duplicates had to be on the same stack. Asking philosophers is different from asking physicists. – Gordian Knot Mar 20 '21 at 04:56
  • In general relativity there is the concept of a "foliation" of a 4D spacetime into a sequence of 3D spacelike surfaces, since there is no absolute simultaneity there are different ways you can do this for a given spacetime, but if you use the simultaneity convention of the coordinate system most commonly used for the FLRW metric (where the fluid filling the universe is homogenous and isotropic in each simultaneity surface), then you get the conclusion that particles at rest relative to the fluid are moving apart. – Hypnosifl Apr 19 '22 at 03:28

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We can observe far away nebulae, outside our galaxy, using telescopes. We can also observe redshifts in light reaching us from them.

These redshifts are interpreted as being caused by the continuously increasing distance between those nebulae and earth.

Wherever we look in the sky, we find the distance between us and other faraway things is continuously increasing.

This is colloquially referred to as "things moving away from us" and "space is expanding", but the English language is not the appropriate medium to accurately describe such things and the meaning of words like "space" is not the same as we are used to in daily life.

So our primary observation is that distances seem to be expanding, which is then explained to laypersons by saying the universe is expanding, as well as more accurately among scientists by building conceptual and mathematical models to explain this observation.

Pranab
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  • Given binary stars (which are considered to be touching, hence very close to each other) have been shown to have one star red shifting and the other blue shifting, it puts into question the whole redshifting hypothesis and what it’s supposed to mean and represent. What we observe and how this is interpreted does mean the conclusion is correct even if everyone agrees unanimously. What is true and what is perceived to be true doesn’t always align. What is proven mathematically and what is proven by a real experiment is also different. It’s circular reasoning to assume variables in mathematics – Gordian Knot Mar 20 '21 at 12:53
  • And when I mean that one is red shifting and the other blue shifting I mean by so much that they couldn’t possibly be touching much less in the same galaxy if the redshift interpretation is correct. – Gordian Knot Mar 20 '21 at 20:47