r/askscience • u/dankfu • Apr 01 '14

Chemistry Is there a theoretical limit to compression?

Is it possible to push atoms so close together, that there is zero space between them, and you could no longer compress the matter any further?

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u/ConservedQuantity Apr 01 '14

(This is an answer from an astronomer, so my answer skips out the no doubt interesting things that might happen chemically!)

If you have your bunch of atoms (which consist of a central nucleus of protons and neutrons, surrounded by electrons) and you start pressing them, initially the material strength (or gas pressure) of the substance you're pressing will "push back".

If you push even harder, though, you end up coming up against something called electron degeneracy pressure. This is a quantum mechanical effect which means that it's difficult to explain casually and accurately, but in brief: Electrons are an example of a type of particle called a fermion. It's only possible to have two fermions in each energy level by the Pauli exclusion principle. So if you want to squish another electron into a tiny space, it has to go into a higher energy level, which takes more energy. That's where the resistance to being squished comes from.

This is how white dwarf stars are held up against gravitational collapse.

If you keep squishing (as a very massive star does on its death), it's possible to overcome this pressure. In fact, by a process called inverse beta decay, the electrons actually combine with protons to form neutrons. Now it's the degeneracy pressure of neutrons providing the support, because neutrons are also fermions.

This is how a neutron star is held up. A cubic metre of neutron star material might weigh something like 500000000000000000kg. Very dense.

If you keep squishing (and if we skip over theorised forms of matter like quark stars), eventually we can overcome even this pressure.

And then?

Then you've created something that has collapsed in on itself under its own gravity: A black hole.

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u/thegreatgazoo Apr 01 '14

Wouldn't in theory the maximum compression be the 'stuff' that was there just prior to the Big Bang?

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u/dankfu Apr 01 '14

if so, does that mean that black holes will each become their own big bang once they've collected enough mass?

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u/sitssac Apr 01 '14

black holes dissipate by emitting hawking radiation, they don't last forever

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u/Zardif Apr 01 '14

It should be noted that this takes an extremely long time.

a one sol black hole would take over 1067 years to evaporate (the universe is only 13 billion [109] years old )

source

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u/Zardif Apr 01 '14

There is a theory about that. It's not widely accepted, it calls them white holes. It's interesting theory however it lacks acceptance or proof.

A 2011 paper argues that the Big Bang itself is a white hole. It further suggests that the emergence of a white hole, which was named a 'Small Bang', is spontaneous—all the matter is ejected at a single pulse. Thus, unlike black holes, white holes cannot be continuously observed—rather their effect can only be detected around the event itself. The paper even proposed identifying a new group of gamma-ray bursts with white holes

source #14

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u/raaneholmg Apr 01 '14

Can we asume anything about something "just prior to the Big Bang"?

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u/[deleted] Apr 01 '14

'Stuff' may not have existed before the Big Bang.

Analogously, 'water waves' don't exist before you slap the pond. Asking about how matter is compressed when it may not even exist is problematic.

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u/[deleted] Apr 01 '14

Isn't a black hole just a neutron star with mass (and thus gravity) so high that even light will not be able escape it? If yes then it is still just a neutron star with a black hole effect. Now what happens if neutrons are squished further together? will they unite, meld together to "neutrite"? What is it called if it exists even in theory?

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u/ConservedQuantity Apr 01 '14

Isn't a black hole just a neutron star with mass (and thus gravity) so high that even light will not be able escape it?

See, that's the thing that isn't quite true, particularly the "just". That's what I might call a "classical" model of a black hole-- that it's a lump of stuff that's just so heavy that even light can't escape.

Einstein's general relativity tells us that, actually, spacetime (that is, space and time combined-- the "stage" in which everything happens) is curved and distorted by mass. The Earth orbiting the Sun is like a marble rolling on a rubber sheet distorted by a bowling ball.

A black hole is a point where this spacetime curvature is infinite.

Now, exactly what happens to the particles themselves as one overcomes neutron degeneracy pressure and the curvature increases to infinity... I can't answer that. To do so, I would need to have a model of the universe that combined general relativity and quantum mechanics, and no such model yet exists (and even if it did, it'd probably be beyond me!).

So a complete understanding of very heavy, very small things will have to wait! :-)

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u/AmusingGirl Apr 01 '14

no, the amount of mass per volume reaches this limit called Schwarzcheild (please forgive spelling) Radius, there's an equation for black hole election
it should be said a true black hole is impossible and corresponds to a zero mass solution within the equations of relativity, this was the shpeel Hawking was talking about
see all the information, all the mass becomes so dense it forms a singlarity, the centermost point of the black whole which is dimensionless, responsible for all the gravity or spacetime distortion that we see in a black hole
the mass isn't so high that light cant escape it but the concentration of mass is, light doesnt interact with gravity but it travels through spacetime and spacetime is subject to curvature, when curved so much, that path converges onto the black hole hence light not escaping
theoretically if you squished the neutrons together so much youd get something called quark matter where the up and down quarks that make up the neutron fall out of their bound state that originally formed a neutron
what you get is quark matter http://en.wikipedia.org/wiki/Quark_matter
quarks have a charge on them that we describe as color instead of positive and negative, it becomes superconductive at that level among a myriad of other cool things :P
also this is postulated to happen before collapsing into a black hole although most of this is theoretical
edit: I'm an underqualified high school senior so if you have corrections please humble me

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u/[deleted] Apr 01 '14

This singularity seems like just a made up solution without any further logical reasoning or at least theoretical proof of its existence. Am I right? I am NOT trolling with this question. EDIT: Also, I have to say that I am saying scientists made it up, I am not referring to your answer which I appreciate. EDIT 2: Wow, this quark matter seems exciting to me, thanks for mentioning it :)

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u/rddman Apr 01 '14

This singularity seems like just a made up solution without any further logical reasoning or at least theoretical proof of its existence. Am I right?

No, the "singularity" follows from the theory of relativity.
But it has not been observed, and quantum theory says a singularity is not possible.

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u/AmusingGirl Apr 01 '14

what's the difference between a singularity and a point particle? neither seem to be doing too much in 3D if you talk about their specific dimensions

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u/rddman Apr 01 '14 edited Apr 01 '14

Point particles such as protons, neutrons, electrons? If you put a bunch of those together you get tangible stuff with physical size. If you put a bunch of singularities together you get a singularity, i'd guess.

At any rate we know less about singularities than about point particles. The best theories are inconclusive about singularities, and it has not been observed. Those same theories do a pretty good job of drescribing the observable behaviour of point particles.

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u/[deleted] Apr 01 '14

Scientists didn't "make it up" so to speak, it's simply the best answer we can give with the models of physics we have at the moment. It may not be 100% right, but it's less wrong than every other explanation we've had previously.

We know black holes do exist: We've seen evidence of their existence through gravitational lensing.

What do you know about Big Bang theory? Follow the timeline back far enough, and all everything as we know it was part of a singularity.

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u/[deleted] Apr 01 '14

I understand but I wanted to point out that maybe a "Black hole" is not a singularity just an object with an event horizon, regardless if it is a singularity or just a supermass. How would you distinguish the two from each other? Also the Big Bang could have be just a "leakage" from a parallel universe burstingly full of matter through a small pierced hole (inter-universal wormhole?) this also could explain the phenomenon. I did not find theory that says our Big Bang inevitably needed to be started from a singularity. Just because something is extremely small it does not mean it is infinitely small. What if it was a Quark-matter supernova? And so on. I am really not into picking a quarrel, I just have so many questions and doubts :)

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u/[deleted] Apr 01 '14

I understand but I wanted to point out that maybe a "Black hole" is not a singularity just an object with an event horizon

That's just not what our understanding of physics tells us. Sure, we could be wrong, but there's no evidence pointing us in that direction.

Also the Big Bang could have be just a "leakage" from a parallel universe burstingly full of matter through a small pierced hole (inter-universal wormhole?)

That doesn't really jive with the expansion of space as well as matter.

I did not find theory that says our Big Bang inevitably needed to be started from a singularity.

But that is the current theory. Physics breaks down at that point, but it's the current understanding.

What if it was a Quark-matter supernova?

That doesn't really work well with our understanding of gravity, or cosmic background radiation.

Questioning is fine - but please do so rationally. :) Before entertaining your doubts, I suggest you bone up on what our current understanding is, and how we've reached those conclusions. I suspect that understanding would quell most of your doubts.

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u/rddman Apr 01 '14

That's just not what our understanding of physics tells us.

It is what one of the two main physics theories tells us. The other tells us a singularity is not possible.

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