What is space made of?

[Drunk Vegan]

Ok, bear in mind that I'm a lay person who just happens to be very interested in astronomy and I read science articles and books for fun and also quite a bit of science fiction.

But I'm curious, on an atomic/subatomic level, what is vacuum? If I'm understanding what I've read correctly, "empty" space is composed of particles that are constantly appearing and disappearing from the observable universe every Planck length of a second.

Which is... weird. Is the only word. Where does it go to and where does it come from? Some other dimension which we can't detect? Another universe? Nowhere? I can't wrap my head around it.

[Abelian Grape]

Ok, bear in mind that I'm a lay person who just happens to be very interested in astronomy and I read science articles and books for fun and also quite a bit of science fiction.

But I'm curious, on an atomic/subatomic level, what is vacuum? If I'm understanding what I've read correctly, "empty" space is composed of particles that are constantly appearing and disappearing from the observable universe every Planck length of a second.

Which is... weird. Is the only word. Where does it go to and where does it come from? Some other dimension which we can't detect? Another universe? Nowhere? I can't wrap my head around it.

Hey, you don't stick to easy questions, do you? You allude here to concepts like virtual particles and quantum foam, both of which are on the fringe of anyone's understanding.

At least one of your questions may be answerable: virtual particles can come into existence essentially from nowhere, per Werner Heisenberg's Uncertainty Principle, as long as the product of their mass energy and the time they exist does not exceed a factor related to Planck's constant. They are created as matter and antimatter pairs, and annihilate each other in a really short time period. This is similar to the perhaps more well known relation between uncertainty of momentum and position.

There is also the idea here that if you look really closely at space, you reach a point (actually a line) of the order of the Planck length where space sort of crumbles, and it makes no more sense to try to divide it.

In short, you're talking cutting edge of physics; no one yet has firm answers. Hint: quantum physics is weird. We have to deal with it. Hope that helps.

[speedfreek]

How about the idea that space is simply the gaps between things? If virtual particles can appear in "empty space", then space is the gaps between the particles, not the particles which have appeared in that space.

[cosmocrazy]

How about the idea that space is simply the gaps between things? If virtual particles can appear in "empty space", then space is the gaps between the particles, not the particles which have appeared in that space.

I agree, why would we need space to be made of anything? why can't it just be empty space? Zero anything?

[Ken G]

The main problem here is that your question could either mean, "what is space actually made of", or it could mean "in theory of space such-and-such, what are the attributes afforded to space by that theory?". If the question is the former, the answer is "the question is composed of the three key words that are having a little fight: "space", "actually", and "made". So there is no answer to the first version of that question. If the second version, the theory that is being referenced must be specified. I'm sorry, but this is just how it is.

[Drunk Vegan]

But is the idea of a quantum foam of virtual particles appearing and then annhilating each other constantly a theory that has developed because of actual observations (in which case, it's a fact) or is it a pure mathematical conjuring?

Not to suggest mathematical conjurings are bad. Einstein's have held up superbly. But it is still only math until the observations confirm it.

[Neverfly]

But is the idea of a quantum foam of virtual particles appearing and then annhilating each other constantly a theory that has developed because of actual observations (in which case, it's a fact) or is it a pure mathematical conjuring?

Not to suggest mathematical conjurings are bad. Einstein's have held up superbly. But it is still only math until the observations confirm it.

A little bit of each and a lot of neither.

[speedfreek]

But even assuming the quantum foam exists, I would also assume that if a particle appears and disappears then there was space there before it appeared and it leaves space behind when it disappears.

Even if, in whatever space you examine you find a virtual particle, does the particle exist in space or is it part of space?

If you fill a bath with water, is the space in the bath now made of water, or does the space contain water?

[Drunk Vegan]

Now we're getting philosophical.

This is trying to define "what is nothing" - the absence of something?

But... how can something exist by not existing? It can't.

I would say that the virtual particles * are * space. I can't even begin to try to define nothingness without venturing into the minefields of philosophy and religion.

[Ken G]

It sounds like the question here is really "what is the best way to think of space to do the most accurate calculations possible". The answer to that is probably something like the treatment of space used in quantum field theory, but I doubt even that is unique-- the deeper you go into the mathematics of these theories, the more possibilities you open up that are not ruled out by observation. So I'd like to stress three things about this kind of question:
1) it is not a question about reality, it is a question about our best theories for any given type of calculation, but if we insist on treating it as a question about reality the discussion will quickly fall into meaningless philosophical semantics,
2) in some situations, the simplest theory is the best one to use, not necessarily the most accurate or the most general-- in such cases, thinking of space as nothing more than some kind of undefined milieu that imposes a concept of distance is usually best,
3) in other situations, you want the most accurate and profound theory we have, and that's when you get into virtual particles and whatnot, but one should still never mistake theories like that for what "space really is", because it would be ludicrous to imagine that humanity 1000 years from now (if we maintain our scientific progress) will think of it in an even remotely similar way than whatever is going to be said on this thread.

I don't mean to be a killjoy, I just think it's important for us to actually raise the level of what we think we can really do here on Q&A. What theory are you trying to learn more about? What level of mathematical sophistication do you need? But don't say "I just want the truth", and not because you can't "handle the truth", it's simply that there is none to handle.

[Drunk Vegan]

The theory discussed is the one I was interested in primarily, but I'd love to hear about any opposing theories.

I'm not really interested in the math behind it, just the theories and any observations that have confirmed or refuted them.

Thanks to all responders by the way, I've already got a clearer picture of the quantum foam / virtual particle theory.

[Neverfly]

Now we're getting philosophical.

This is trying to define "what is nothing" - the absence of something?

But... how can something exist by not existing? It can't.

I would say that the virtual particles * are * space. I can't even begin to try to define nothingness without venturing into the minefields of philosophy and religion.

I would define "nothing" as a noplace where even Light cannot travel through. Without any dimensions at all.
Even Space has dimension, light and radiation can traverse it.
Nothing- would have none of that.

[Drunk Vegan]

But what is darkness? An absence of light.

Darkness, really, doesn't exist. It has no source, it's caused by a location being out of the line of sight of a light source, not generated by some force.

As for the opposite of matter that's antimatter, but its something that can be detected and studied, so it's not actually "nothing."

[thecolorofash]

But is the idea of a quantum foam of virtual particles appearing and then annhilating each other constantly a theory that has developed because of actual observations (in which case, it's a fact) or is it a pure mathematical conjuring?

Not to suggest mathematical conjurings are bad. Einstein's have held up superbly. But it is still only math until the observations confirm it.

Check out the casimir effect.

[Ken G]

But is the idea of a quantum foam of virtual particles appearing and then annhilating each other constantly a theory that has developed because of actual observations (in which case, it's a fact) or is it a pure mathematical conjuring?

The "conjuring vs. fact" dichotomy has uses, but we should also recognize that it is at its core a false dichotomy. Every theory used in science that refers to a vacuum is based in some observations, so none are "pure conjuring", yet it is equally true that the goal of a physics theory is to organize and unify facts, not to be a fact. The "fact" here is, "theory X is useful for understanding the vacuum", where X can be quite a few different things and still make the sentence correct.

[blueshift]

To start with, using quantum physics for describing what space is made out of can be a touch difficult. So maybe we should start with the macro-level and work toward quantum physics?

Space sets limiting conditions for motions and shapes that energy matter must obey. It dictates that events, forces and surfaces ( points, lines and planes in Euclidean language) are subcomponents that make up all 3 dimensional objects. It dictates that the shape containing the smallest volume enclosed with 4 sides is a tetrahedron made out of any material. It dictates how shapes stellate and truncate. And it is likely quantized.

To describe what it is "made out of" can be a trapping akin to what string theory gets caught into. In that latter case if strings are the most fundamental particle in the universe then they cannot be made out of anything or those subdivisions would be the most fundamental and not strings. The same goes with space. Your question forces us to leap into other dimensions so that we can call all of this a subcomponent of some kind. Just as points, lines and planes cannot exist by themselves in this 3D world with volume cannot exist alone in higher dimensional space configurations. We would only be features.

As for virtual particle/antiparticle pairs annihilating and influencing spatial limits, it could be possible that "where they go when annihilated" could be into curled up dimensions. Those curled up dimensions (if they exist) might have the property of becoming excited when annihilations do occur and, like bounded electrons do with photons with particular frequencies, they absorb them temporarily to where they no longer can exist independently and cannot find the independent shapes and directions of travel they find here. Extra curled up dimensions might be reacting to virtual particle/antiparticle pairs by creating a pressure with stresses that force us with tetrahedra as basic, minimal volume enclosures.


I would take this whole last paragraph with a suspicious grain of salt. More testing is needed.

[Argos]

But even assuming the quantum foam exists, I would also assume that if a particle appears and disappears then there was space there before it appeared and it leaves space behind when it disappears.

But 'space' in this sense would be a superposition of existing and non-existing particles. It´s never really devoided of particles. Quantum foam would be an irreducible state; the background against which reality is constructed.

[John Mendenhall]

Try this link (usual caveats about Wiki):

http://en.wikipedia.org/wiki/Virtual_particle

And if it doesn't give you a headache, nothing will.

[Cougar]

"Since Einstein's general theory of relativity requires that gravitational fields and space-time be one and the same mathematical objects, this means that space-time itself is also subject to the kinds of uncertainty required by quantum systems. This indeterminacy means that you cannot know with infinite precision BOTH the geometry of space-time, and the rate of change of the space-time geometry, in direct analogy with Heisenberg's Uncertainty Principle for quantum systems.

Wheeler imagined that this indeterminacy for space-time required that at the so-called Planck Scale of 10^-33 centimeters and 10^-43 seconds, space-time has a foaminess to it with sudden changes in its geometry into a wealth of complex shapes and textures....

The problem is that we have no evidence that 1) gravity is a quantum field and 2) that space-time has this type of structure at these scales. -- source

[phunk]

As for the opposite of matter that's antimatter, but its something that can be detected and studied, so it's not actually "nothing."

Antimatter is poorly named in my opinion. It is not the opposite of matter, it is just a different arrangement of matter.

[mugaliens]

From a macroscopic perspective, it's incredibly empty.

Once it's smaller than the atomic level, however, it's made of quantum foam, constantly bubbling in an out of existence...

[cosmocrazy]

From a macroscopic perspective, it's incredibly empty.

Once it's smaller than the atomic level, however, it's made of quantum foam, constantly bubbling in an out of existence...

In and out of existence? from where to where?

[Drunk Vegan]

In and out of existence? from where to where?

Now there's an impossible question. If we can't observe the place they are coming from it's impossible to speculate where they come from/go to.

All I know is they supposedly appear in the observable universe and disappear from it. What it is we can't observe and/or is outside our known universe is a puzzle that will probably never be solved except through abstract thinking such as string theory.

[loglo]

The reason why virtual particles are invoked in Quantum Theory is because they make all sorts of really useful calculations of subatomic particle interactions possible. But is QT, which describes particle interactions via fields, an appropriate theory to describe an arena lacking any such interactions? To me the OP seems to be asking too much of QT and perhaps only a theory of quantum gravity, if ever found, will supply a more reasonable answer to the question.

[mugaliens]

In and out of existence? from where to where?

If something bubbles out of existence, it no longer exists, right? So "where" is it?

Nowhere - the same "place" from where it came.

Don't think of the particle going somewhere, or coming from somewhere. Think of it as a quantum kink in the space-time continuum which lasts about a Planck unit of time, is about a Planck length in dimension, and then unkinks itself.

[cosmocrazy]

If something bubbles out of existence, it no longer exists, right? So "where" is it?

Nowhere - the same "place" from where it came.

Don't think of the particle going somewhere, or coming from somewhere. Think of it as a quantum kink in the space-time continuum which lasts about a Planck unit of time, is about a Planck length in dimension, and then un-kinks itself.

Ok i can understand that concept. Does this not violate the conservation law?

[Drunk Vegan]

Ok i can understand that concept. Does this not violate the conservation law?

I've been wondering the same thing myself actually. If it's a particle (other than a photon, which some say IS a wave not a particle) then it has mass. And if mass is appearing randomly that would appear to violate conservation of matter/energy.

[Neverfly]

In physics, it hasn't been all that unusual to observe something that appears to violate a physical law.
But upon further study, you learn that it was just the appearance, and there were other factors going on that you didn't know about before.

I get a kick out of how Science Fiction often portrays us or aliens as recognizing an alien species as advanced when they discover the atom.

Is that really such a big deal?

I don't mean to offend any particle physicists in the house but--- Q.M. really is in its infancy.
We know so very little.
The stuff is freakin' TINY!

It doesn't surprise me in the least when Q.M. hands us a surprise... We have so very very much yet to learn.

[mugaliens]

Ok i can understand that concept. Does this not violate the conservation law?

I've been wondering the same thing myself actually. If it's a particle (other than a photon, which some say IS a wave not a particle) then it has mass. And if mass is appearing randomly that would appear to violate conservation of matter/energy.

What if, for any given volume of space where volume >> (planck length)³, the net change in mass were zero? By ">>", I don't mean vastly greater, but just enough greater so that we're no longer dealing with individual quanta, but with sums of quanta.

Would that violate conservation of matter/energy? What if when one quantum pops out of existance in one moment of Planck time, that instability causes an adjacent area of space, within a Planck length, to kink into existence, thus balancing the equation? Suppose the two events aren't actually separated by Planck time, but are occurring simultaneously during each transition from one Planck moment to the other?

Consider the following: 1000101110 (it's 558, in dec, but it was randomly generated, so, no matter)

The rules are thus:

1. Each digit may change, or it may not (50% change) during each iteration.

There may be other rules, but I'd be guessing at them...

Throwing this into Excel and reiterating it about a hundred times shows that, on average, the sum of the binary digits equals 5, which is what we'd expect if there's an even chance for ten digits to be either 1 or 0.

The rules of quantum physics, with quarks and leptons being the two elementary particles which comprise matter, are varied.

Leptons (electrons, muon neutrinos, and tau neutrinos) are 1/2 spin particles, with charges of +1 or -1. They do not strongly interact (electroweak force).

Quarks (protons, neutrons) do strongly interact (strong force) and are also 1/2 spin particles, but they have a charge that's either +2/3 or -1/3.

The non-matter "particles" are call Bosons, and include the photon, the gluon, the z-boson, and the w-boson. Both the photon and gluon are chargelesss and massless, while the z-boson has a zero charge and spin of 1, and the w-boson has a charge of +/-1, and a spin of 1.

The question is: What, exactly, keeps popping into and out of existence in this quantum foam?

I swear, every time I hear about things popping into and out of existence in quantum foam, I recall the first time I poured a bowl of Rice Krispies and listened to the sharp, high-pitch pops.

[Drunk Vegan]

Is it possible maybe that the virtual particles aren't actually leaving our spacetime at all, but are just moving to the other positions and becoming visible there again?

Maybe they don't "go" anywhere outside spacetime, they simply move around to new locations in the foam so quickly that we don't observe them travelling, we just see them "reappear" at their new location.