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As most people who have done any amount of physics know, no object is truly solid; go small enough and you will find vast amounts of space containing atoms, electrons, etc, all relatively enormous distances away from each other.

What would happen, then, if you had a truly solid object? One that, no matter how much you zoomed in, even to atomic scale, was one monolithic piece of substance (I can't even specify a substance, since that would suggest an atomic/molecular structure, which this couldn't have)? How would you even go about trying to answer this? Such an object seems to break everything I know about physics (which isn't a lot). Would any quantity of it just instantly collapse into a black hole?

Edit: The suggested duplicate question, while correcting my erroneous initial statement, doesn't answer the main question, which, as I have rightly been informed, is a 'what if' question about an object entirely comprised of solid matter (as opposed to energy occupying the 'space' within atoms)

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  • $\begingroup$ This is primarily in the philosophical realm, since it has little to do with our actual universe. $\endgroup$ – Jon Custer Dec 3 '19 at 22:43
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    $\begingroup$ The factoid you open with is ... not as true as many pop-sci sources would have you believe and isn't really useful for anything. Solids are solid because the wavefunctions of their consituient parts in fact occupy a large fraction of the space leading to Fermi exclusions effects. You can see that this is true because generating high density states (electron degenerate and neutron degenerate matter) requires pushing particles to high energy, while high (even extreme) pressures that don't generate high energy particles results in relatively modest density changes (small integer factors). $\endgroup$ – dmckee --- ex-moderator kitten Dec 3 '19 at 23:01
  • $\begingroup$ No, “any quantity” of it would not collapse into a black hole. $\endgroup$ – G. Smith Dec 4 '19 at 2:19
  • $\begingroup$ Possible duplicate of Why doesn't matter pass through other matter if atoms are 99.999% empty space? $\endgroup$ – John Rennie Dec 4 '19 at 5:40
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    $\begingroup$ I'm voting to close this question as off-topic because the premise is unphysical. $\endgroup$ – ZeroTheHero Dec 13 '19 at 5:13
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It is the fictional substance of continuum mechanics. Mathematically, a well-studied subject. For starters, you can find the basic equations and properties in Wikipedia: https://en.wikipedia.org/wiki/Continuum_mechanics

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Really high-density states of matter do exist in the form of degenerate matter, but they aren't "solid" in the usual sense as their constituent parts mostly have very high momentum and as a result move freely past one another.1

Such matter is better conceived of as a very high density fluid.

You need to pile up a bit more than two solar masses of neutron-degenerate matter before it collapses into a black hole.


1 OK, in electron degenerate matter, the nuclei may not have particularly high momentum but because the electrons do the nuclei don't form chemical bonds. So they, too, move around.

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It is impossible to answer your question definitively, since it is entirely hypothetical and open-ended. The 'substance' you refer to is necessarily imaginary, and thus one might attribute any imaginary properties one liked to it. If I told you that it was chrome yellow, had a melting point of 298 degrees, a modulus of elasticity of x etc, how would you say whether I was right or wrong?

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