In one of the most empty regions of space between the galactic superclusters there is a giant space bubble, with a radius of about 1,000,000 light years. Most of this bubble is one molecule thick although parts of it are two molecules thick as molecules stick to the base layer of molecules of this space bubble. This bubble is made of a flexible material or materials that can stretch, and compress.

What might this bubble be made of?

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    $\begingroup$ How empty is this region of space? Even micrometeorites wouldn't have much trouble puncturing almost any molecular film, and with a radius of a million light years, that's a lot of surface area to puncture. (Also, is the bubble rigid? Otherwise, it's going to collapse in on itself.) $\endgroup$
    – jdunlop
    Commented Jul 20, 2017 at 22:31
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    $\begingroup$ Does the bubble need to be able to withstand any sort of forces? Micrometeor erosion would be rare but present, and could puch holes through the bubble. Also, over an extreme time period the bubble would be gravitationally unstable, so it'll need to have some internal force keeping it "inflated" so to speak. $\endgroup$ Commented Jul 20, 2017 at 22:31
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    $\begingroup$ It is perhaps worth noting that if you set aside the problem of what this material is made of (!!!!!!), it would take ............... 10 million years ............. to build such a thing, and that's assuming you can move material at the speed of light. Which you can't. $\endgroup$
    – Fattie
    Commented Jul 20, 2017 at 23:24
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    $\begingroup$ This material must be a lot more stretchable than a reader's willingness to believe weird things... $\endgroup$
    – Burki
    Commented Jul 21, 2017 at 8:09
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    $\begingroup$ hi @running.t - note that for the self-assemblers to make something (Say) 1 mile across, they have to (obviously) move at least one mile. if it is one million light years across, they have to move one million light years !! $\endgroup$
    – Fattie
    Commented Jul 21, 2017 at 15:53

2 Answers 2


This is so spectacularly, epically, unrealistic,

that you would have to go immediately to

sub- sub- sub- atomic particles.

Not atom engineering (!), not proton engineering (!!!!), not quark engineering (!!!!!!!!!!), you would have to hypothetize a culture which...

...engages in engineering, actually in the domain of string theory.

wiki article

So, in some handwaving sense, their engineers would be able to manipulate the fundamentals of the "things" that make up quarks

Repeat: they would be able to manipulate the things which make up quarks

(... which make up protons, which make up atoms, which make up everyday matter).


In some handwaving sense, they could create pure "string concepts" which would form in to "matter-like" sheets.

The sheets would be - wow - not merely "an atom thick" but a trillionth of an atom thick. The sheets would (of course!) be the odd few hundred million square light years in size, as you say, perhaps shaped in to a big ball.

It would all be as strong as the forces that hold together protons...

(aside ..... holy shit!)

...and could easily bend, stretch, or do anything you want.

(Since, notably, the superstrings, uh, define the nature of dimensional reality. So, you will have no trouble say "stretching them".)

String theory has a handwavey thing about "resonances" (it's a funny observation that your story, would not be much more more handwavey than .. string "theory" itself :-) ) which you could surely play with in the plot.

TBC it is "utterly inconceivable" that any normal nanomaterial as you ask about could be millions of lightyears across and a few atoms thick.

Forget nanoengineering (which is "merely" messing about with whole atoms and molecules).

You can read up on quark matter which goes one better than nanoengineering.

But as I say, even some sort of "quark engineering" ("!!") is just totally out of scale for what you need.

Your only hope is a culture that can literally engineer at the string theory level. Hell!

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    $\begingroup$ Effectively your answer is no. The galactic bubble cannot be made of ordinary atomic matter, so molecules are out. Plus it cannot even be made of quark matter. Possibly, only subquark matter could be suitable. An awesome exercise in extrapolation. Plus one. $\endgroup$
    – a4android
    Commented Jul 21, 2017 at 7:02
  • $\begingroup$ Nice answer indeed. Maybe a word or two why molecules and quarks are out would improve it further. $\endgroup$
    – Burki
    Commented Jul 21, 2017 at 8:07
  • $\begingroup$ I'd be interested in the maths that led to this (admittedly inescapable) conclusion, just because I want to see the exponents involved! $\endgroup$
    – Joe Bloggs
    Commented Jul 21, 2017 at 13:46
  • $\begingroup$ @a4android: I think Effectively answer is yes. Especially if we're talking about hard sf :) $\endgroup$
    – running.t
    Commented Jul 21, 2017 at 14:55
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    $\begingroup$ @running.t The OP wanted a bubble made of molecules. This demonstrates that isn't possible, and quite conclusively too. Made of subquark matter, possibly yes, but molecules no. A subquark bubble would be plausible in had sf, but not molecules. $\endgroup$
    – a4android
    Commented Jul 22, 2017 at 2:00

So, what you're talking about seems to be an almost incomprehensibly large rubber ball.


Molecules can be big.

  • $\begingroup$ A molecule that big would also be heavy enough to collapse past the point of electron degeneracy and form a neutron star... $\endgroup$
    – Joe Bloggs
    Commented Dec 4, 2018 at 15:20
  • $\begingroup$ no, the hollow sphere needs be a molecule or two thick, there is no need (in the question as asked) for the whole construct to be one or two molecules in total, just as there is no requirement for a sheet of metal to be one molecule of metal. There's also no assumption that the construct is entirely uniform nor that there are no external forces or utter lack thereof, contributing to the maintenance of stability. $\endgroup$
    – Giu Piete
    Commented Dec 4, 2018 at 17:16
  • $\begingroup$ And the fact remains that any number of atoms arranges in a sphere of that size, be they one glorious molecule (as your answer seems to suggest) or many, are heavy enough to collapse down into a neutron star. If there are additional forces actively stabilising the sphere then you have considerably more than a ‘rubber ball’ going on. $\endgroup$
    – Joe Bloggs
    Commented Dec 4, 2018 at 17:25
  • $\begingroup$ The question asks for a hollow sphere of matter in a relatively empty region of space. What constitutes 'empty' is open to interpretation, but even a cluster of 10 solar systems in 'intergalactic space' can be considered to be ina relatively empty region of space. The fact a space bubble is there in the first place means that it is certainly of higher density than none at all, so there is no assumption required to determine that there is some matter. You seem to be making a whole series of assumptions re: the answer and the question that are unnecessary. $\endgroup$
    – Giu Piete
    Commented Dec 4, 2018 at 18:16
  • $\begingroup$ There are well understood forces that can counteract the most base expression of natural gravitational impulse, you occasionally leave you desk. Without knowing what is inside the bubble or outside of it, anything more is just more speculation, which we can do, but is not strictly necessary to answer the question. $\endgroup$
    – Giu Piete
    Commented Dec 4, 2018 at 18:19

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