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I have been giving empty space much thought. I imagined reaching the edge of the Universe and thought of 2 scenarios(focusing on 1):

  1. There is no more empty space

    1.1 Would space extend with me if say I just crossed over?

    1.2 Could anything exist without empty space? Time?

  2. More empty space - nothing else

I'm working(in thought process) on a conjecture. Maybe I'm on to something, maybe not.

  • I love thought experiments.
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  • $\begingroup$ This is a very opinion based and broad question! $\endgroup$ Commented Jan 22, 2015 at 6:55
  • $\begingroup$ That's not being helpful, any clues? $\endgroup$ Commented Jan 22, 2015 at 6:57
  • $\begingroup$ You might like to think, does the universe actually have an edge? If so, how is this edge defined? If there really was lets say, empty space outside the universe, how would this empty space be different from the universe itself? $\endgroup$ Commented Jan 22, 2015 at 7:00
  • $\begingroup$ If there was NO empty space, could any object be present? I'm wondering if empty space is necessary for anything to exist. Any object fills empty space, like the spot you're occupying right now, without you it's empty space(kind of). whithout empty space, what is there to occupy? Is this even possible? $\endgroup$ Commented Jan 22, 2015 at 7:00
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    $\begingroup$ You first have to properly define what an empty space would be! that would make the whole thought process easier for you. $\endgroup$ Commented Jan 22, 2015 at 7:02

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"Empty Space" is a name that is a little misleading from the standpoint of modern physics.

Suppose we evacuate a vessel, and clad it in impenetrable radiation shielding, so that there are no molecules or atoms within, and there are no gammas or cosmic rays. In everyday speech, we would say that the vessel has "empty space within it".

However, modern physics thinks of space and time to be made of quantum fields: a handful of them. So, our everyday statement would more accurately be rendered: in this region of space, the electron field is in its ground state, the electromagnetic field is in its ground state, and so forth. The quantum fields are in their ground states, but they most assuredly are still there. The process of the vessel's evacuation can now be thought more accurately as the driving of the quantum fields into their ground states, rather than an "emptying process".

Likewise for the question about the "edge of the Universe". We can only exist in spacetime that is already there. We can't reach an "edge" and "make" spacetime as we cross it. It is quite possible that the Universe is topologically compact, meaning roughly that one can in principle follow a "constant direction" path (this notion has some fiddly technicalities, but think of following a great circle on a spherical balloon) and not keep going forever, but rather return to one's beginning point. There are no edges to such a spacetime. Moreover, there is not an "outside" to the Universe: such a thing simply does not exist by definition of the "Universe". It is possible that the universe is finite and compact without edges, or it could indeed be infinite. If the former, there is still no "outside".

So "empty space" really is a kind of "stuff" that can have inhomogeneous properties: in General Relativity, one can quite definitely say that this piece of spacetime over here can have different geometrical properties from another piece over there.

In answer to your title: we, just like empty space, are made of quantum fields, so we couldn't exist without there at least being the possibility of quantum fields in their ground state, i.e. the existence of empty space is a necessary condition for our existence.

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  • $\begingroup$ So objects HAVE TO occupy this empty space to exist? I'm wondering if this empty space is a fundamental necessity, as in if there was nothing in the universe, the only thing left would be empty space and therefor empty space being the universe itself $\endgroup$ Commented Jan 22, 2015 at 7:23
  • $\begingroup$ Just saw your edit, amazing. $\endgroup$ Commented Jan 22, 2015 at 7:24
  • $\begingroup$ @FranklinDeLosSantos: you might be interested in Is Space-Time a special form of energy? $\endgroup$ Commented Jan 22, 2015 at 7:47

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