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y_feldblum
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I have seen people here state that "the universe is a plenum" from time to time. I have never fully understood what was meant by this statement, and I have never seen a full philosophical justification for it.

What does "the universe is a plenum" mean?

What is the evidence of the senses which supports this statement?

What is the philosophical justification, stemming from the evidence of the senses, for this statement?

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Which, um, which definition of plenum is being used here?

1.the state or a space in which a gas, usually air, is contained at a pressure greater than atmospheric pressure. 2.a full assembly, as a joint legislative assembly. 3.a space, usually above a ceiling or below a floor, that can serve as a receiving chamber for air that has been heated or cooled to be distributed to inhabited areas. 4.the whole of space regarded as being filled with matter (opposed to vacuum).

I guess you could sort of regard the Universe as a plenum because it's full of matter. What purpose does this question serve, really?

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It is a question of metaphysics. I have seen it asserted a few times that materially "the universe is a full plenum." The meaning often given is: "there is no such thing as a vacuum; there is something everywhere." It is generally asserted that philosophy justifies and mandates this conclusion. This conclusion is typically leveled at the conclusion from the Michaelson-Morley experiment that there does not exist an aether. I am curious, what is the proof of the conclusion that "the universe is a full plenum?"

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That sounds more like a physics question than a metaphysics question. The particular nature of matter and thus, of outer space, can only be dealt with in the special sciences. So, I'm moving this thread.

Actually, it is a metaphysical question rather than a physics question. It's not an issue of what is there, which might be more along the lines of physics, but the issue is: Why is there no nothing? And that basically comes down to the fact that existence exists, whereas non-existence does not exist. If one were to find this little or big patch of absolutely nothing, then one would be able to point to it and say,"Here is non-existence!" But, one cannot do that because existence exists, and it exists everywhere within existence -- and there is no outside of existence. It also involves oneself in a direct contradiction to point to that area of absolutely nothing and say, "Here it is! The NOTHING, right here, that has no existence or attributes or being of any type." The void cannot be an it, nor can it have a place.

Now, this doesn't necessarily imply an aether in the sense of something specific that we have discovered with specific properties, because we haven't discovered its properties, yet. Personally, I use "the aether" as a place holder for that which exists in between other things like rocks, planets, particles, etc. Because there is no nothing, there has to be something there, so the question is what is there? And the only way to answer that is to investigate and find out what is there. The 19th and early 20th century physicists tried to prescribe all sorts of matter-like properties to the aether, when they had no evidence, so it was an a priori train of thought -- like it had to be made of particles or flow like a river or move like the wind and effect things in it accordingly. But we won't know what is there nor what its properties are until we discover it; though there is something there because there is no nothing.

Edited by Thomas M. Miovas Jr.
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Why is there no nothing? And that basically comes down to the fact that existence exists, whereas non-existence does not exist.

This is utterly specious and a remarkable piece of rationalistic thinking. There can indeed be nothing, as in the lack of something specific. Thus, if you can say that hard vacuum is *nothing* because it contains no molecules, or that air is *nothing* (such as, there's nothing in this room) because it contains no solid objects.

The idea that the universe is a plenum draws heavily on the idea that it is filled wall to wall with *matter*, a fact that is patently not true. The matter is unevenly spread out, leaving large gaps that contain no matter (or very, very little.)

Since this is entirely a semantic distinction, it has little or no value.

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The idea that the universe is a plenum draws heavily on the idea that it is filled wall to wall with *matter*, a fact that is patently not true. The matter is unevenly spread out, leaving large gaps that contain no matter (or very, very little.)

You are taking matter, as in electrons, protons, and neutrons as a primary conception of what is there. However, there is something there between, say, the earth and the moon, leading to the gravitational attraction between the two bodies, and so far as we know, that stuff, whatever it is, is not composed of electrons, protons, and neutrons.

I'll grant you that the term "nothing" can mean something like having an empty box, but we know that there is air in the box, so it is not a non-existence inside the box.

The point is not just one of semantics, but the entire conception of existence existing. If one where to have an actual perfectly empty patch, like an empty box full of void, one could point to it and say that existence does not exist inside the box; and if one jumped inside the box, one would be leaping into non-existence.

So, the concept of "nothing" is contextual. In ordinary usage, one can say there is nothing inside an empty box, meaning there are no large objects in there; however, by this one does not mean that one has a box of void, since the void has no existence.

Edited by Thomas M. Miovas Jr.
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What of the case of a "patch" where no matter whatever has been detected. For example, no light originates from that patch, and casting various particles into that patch elicits no phenomena indicating any kind of interaction between those particles and anything that might be in that patch?

Physicists have been looking for just this kind of matter for centuries, but have so far been unable to discover it by means of observation, whether direct or indirect.

I do not understand the philosophical argument against saying "there isn't anything over here." It sounds like one is simply reifying space and reifying the void. When you say "one could [...] say that existence does not exist inside the box", you are neither using the definition "the sum total including everything that exists" nor using the definition "the property of an entity whereby that entity is instead of is not." Neither is applicable, and neither makes sense in the context. What do you mean by that statement?

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You are taking matter, as in electrons, protons, and neutrons as a primary conception of what is there. However, there is something there between, say, the earth and the moon, leading to the gravitational attraction between the two bodies, and so far as we know, that stuff, whatever it is, is not composed of electrons, protons, and neutrons.

The Standard Model lists numerous elementary or subatomic particles (some of which are composed of others) which have been discovered, and predicts others which have yet to be discovered (and which occur only in very unusual circumstances, such as in proximity to extraordinarily large quantities of energy). These, which include electrons, protons, neutrons, and photons, and gravitons, are the basic primary substances making up everything that there is which we have to date observed (leaving "dark matter" aside). All matter and all interactions among pieces of matter are explained through the elementary particles of the Standard Model.

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I do not understand the philosophical argument against saying "there isn't anything over here." It sounds like one is simply reifying space and reifying the void.
If you reify the void, and also have a really stripped-down universe with just three particles, and they're in a line in the order A,B,C, then you can ask "What is between A and C", the answer being at least "B". Now what's between B and C. Nothing? And what does "nothing" mean? Or does some void exist between B and C? If you say that a void exists between B and C, you contradict the fact that the universe only has three things. Now if you don't reify the void, then the question of what is "between" B and C is meaningless, or, rather, is based on a false presupposition. The relation between B and C is correctly described by the proposition "It is not the case that there exists an x between B and C", i.e. "There is nothing between B and C". This is a case where casual-language statements of the problem may get us into problems. If you thing that "There is nothing between B and C" means "It is not the case that there exists an x between B and C" (and not "There exists x s.t. x is between B and C & x is nothing"), there exists no problem :lol:. However, you have to explain why "There is a cat between B and C" doesn't submit to a similar semantic analysis.

If you reify space, then "where" is completely independent of stuff; space is not relational, it is absolute. That is one view, and another is that space is a relation between entities. Rather than saying that there exist N space-units between A and B containing no particles or other stuff, A has an N-unit separation relation to B. This is, as I see it, the main philosophical issue, namely (and only partially) what is the nature of the concepts "entity", "space" and "void". Whether the physical implications of certain of these ontologies are scientifically correct is, well, utterly beyond me.

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My question is: what observations of reality lead ultimately to the conclusion of the universe as full plenum.

So far the argument for that conclusion has been: it is necessary because denying it amounts to claiming that there exists a thing, "nothing", which is not anything but which nevertheless is.

But that is not sufficient. Objectivism does not begin with "Existence exists. Now let me go out and observe it." Quite the opposite. Objectivism begins with "all this that I see ... is." Every philosophical conclusion must be reducible to observation of reality. What observations of reality give rise to this particular conclusion?

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The Standard Model lists numerous elementary or subatomic particles (some of which are composed of others) which have been discovered, and predicts others which have yet to be discovered (and which occur only in very unusual circumstances, such as in proximity to extraordinarily large quantities of energy).

I don't remember if it was you or not, but someone mentioned that magnetism can be accounted for via photon exchange, and gravity can be accounted for by graviton exchange. I suppose under this sort of thinking, a charge can be explained via some sort of photon or particle exchange as well. I'd like to know how that works, if you can point to an article on the web -- a brief one without a lot of mathematical jargon would be preferred.

So, from my understanding, things like magnetic fields and gravitational fields must be explained by something -- something that is acting on the far away particle or matter; that is the evidence I am going by. The earth is here, the moon is way over there, and there must be something in between that makes gravitational attraction possible, because there is no action at a distance. One can make a similar argument for electric fields and magnetic fields

When I bring one magnet into close proximity to another magnet, the magnet not held in my fingers begins to move -- that is evidence that something is acting on the unheld magnet. It cannot be a nothing or a void acting on it, as the void is not a thing that could act on anything. There is something there.

I mean, unless scientists have shown that a magnet radiates out photons, and that these radiated photons get absorbed by the unheld magnet, and then get propelled in the direction that would lead to a significant force on the unheld magnet, then I don't see how magnetism can be explained via photons. I've seen those vanes in a light bulb, where the vanes are painted white on one side and black on the other, and the rotating motion of the vanes can be explained by photon absorption and then photon re-radiating, but I have never heard of this being applied to magnets.

Also, are gravitons absorbed and then emitted in a similar fashion leading to gravitation under this model? Like the earth radiates out a gazillion gravitons, which are absorbed by the moon, and then so happen to re-radiate out from the moon on the opposite side from the earth, thereby creating a force towards the earth? I mean, I just don't see how that would work. As in why would the gravitons only be emitted on the opposite side of the moon?

So, by observation, we know that something must be going on in between, say, the earth and the moon leading to gravitation -- I'm just not sure we know that that something or the mechanism is.

And I'm not sure if physicists are being rationalistic about the "dark matter" and the "dark energy" or not. They seem to have some sort of mathematical equation that predicts an answer of 1, and they are only finding 1/3 taking everything they know regarding matter into account; hence they come up with "dark matter' and "dark energy" to fill that 2/3 gap. I'm not even sure if that stuff in between matter would have mass in the sense of containing matter (as in particles), but it might have resistance to changes, which gets closer to Newton's original conception of mass as resistance to change of motion (rather than a quantity of matter).

But basically, an absolute void, almost by definition, does not exist -- it is not a thing that can be somewhere because it is not anything.

Or let me put it the way someone I knew many years ago put it: If there wasn't anything in between two objects, then they would be touching one another.

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Caveat: I have a good understanding of the motivation for, the math of, and the philosophy behind (an objective interpretation of) special relativity; and an OK understanding of general relativity. I know very little about quantum mechanics or the Standard Model of elementary particles, but enough to speak a little on the topic.

There is no such existent as a "gravitational field," "electric field," or "magnetic field." Fields are mathematical abstractions from forces due to physical interaction. The gravitational force of one body on another is carried by gravitons emitted by one body traveling to and interacting with the other. Likewise with the electric and magnetic forces and photons. The interaction of the magnetic force is far more complicated than the interaction of the electric force, which is why the simple weathervane experiment applies to the electric force but not the magnetic force.

"why would the gravitons only be emitted on the opposite side of the moon?" They are not. The mathematics is complicated wrt forces and fields and surfaces enclosing volumes of various shapes, of course.

"So, by observation, we know that something must be going on in between, say, the earth and the moon leading to gravitation" That does not follow. We know, by observation, that the earth acts on the moon via some mechanism or other. We have investigated and determined that a particle called the graviton, which travels between the two, is responsible for this interaction. But it does not follow that there is something "going on in between."

Dark matter and dark energy are matter and energy for whose existence there is indirect evidence, but which cannot be directly observed by ordinary means. The indirect evidence includes, for example, the fact that the gravitational effect which a certain quantity of matter at a certain location would exhibit is in fact exhibited, but we currently have no means of seeing this matter more directly. Physicists suspect the existence of vast quantities of matter because there is indirect evidence for it and it would easily explain many things, and so now physicists are looking for this matter, and are looking for new techniques of finding it. It cannot be seen, with current methods; it is therefore called "dark".

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I have seen people here state that "the universe is a plenum" from time to time. I have never fully understood what was meant by this statement, and I have never seen a full philosophical justification for it.

What does "the universe is a plenum" mean?

What is the evidence of the senses which supports this statement?

What is the philosophical justification, stemming from the evidence of the senses, for this statement?

Ah, back to Parmenides, whom I believe is the earliest known proponent of the universe existing as a continuous, indivisible plenum. The universe, to Parmenides, was an undifferentiated oneness or unity, completely filled and without voids or interstices in its constituent material any kind. In Parmenides universe there was no emptiness. In other words, Parmenides's universe was a plenum. Apparently Aristotle agreed with this point to at least some degree, famously stating that: "Nature abhors a vacuum."

Zeno's paradoxes concerning motion were developed to bolster his pedagogue's (Parmenides was Zeno's teacher) view regarding reality as a universal plenum. We can see why Zeno would have been concerned with motion when we consider the following argument made by Parmenides. Parmenides argued that motion was illusory because in a plenum motion is impossible. Why? Because in a plenum there is no emptiness into which material can move. I find Zeno's arguments against motion more inspired and suggestive of a different conclusion.

I don't know what Ayn Rand's view on Parmenides and the universal plenum are but I'd appreciate edification if someone would elaborate.

Also, I think Zeno's Runner Paradox has been borne out to be in agreement with what QM has shown about the discrete nature of matter. Pretty cool to strike upon truth when you're actually arguing something as ostensibly silly as the implausibility of motion! :)

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Also, I think Zeno's Runner Paradox has been borne out to be in agreement with what QM has shown about the discrete nature of matter. Pretty cool to strike upon truth when you're actually arguing something as ostensibly silly as the implausibility of motion! :)

I don't know much about QM but I wouldn't be so quick as to say that a silly scenario like that adds to it. Hell, it may turn people off!

On a technical note, I'd always thought Zeno's paradox was flawed because it uses a certain assumption while wrecking the context that makes that assumption valid. It assumes that one cannot complete an infinite series because it would take infinite time, but if one looks at the sums right one finds that it also shows that the time required is actually finite in this instance. There is not just the one infinite series to complete, there are TWO, and one cancels out the other. The one is the sum of the successively smaller distances - but the other is the successively smaller amounts of time required to traverse those distances. The latter is not summed up in time, it is time, and comes to a finite number that represents the amount of time required to complete the first infinite series.

Pure rationalism done for fun, but Zeno's paradox was itself rationalist drivel to begin with. If QM people take that paradox seriously as adding any weight to their thinking then I raise an eyebrow at them in suspicion of lacking objectivity.

JJM

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Also, I'd mention that the idea of the universe existing as a plenum does seem to be true, though not in a strict Parmenidean sense exactly. Consider for instance deep interstellar space which is filled with cosmic microwave background radiation. And though a specific portion of interstellar space may be w/o matter, QM posits that particles pop in and out of existence in otherwise "empty" regions of space.

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I don't know much about QM but I wouldn't be so quick as to say that a silly scenario like that adds to it. Hell, it may turn people off!

On a technical note, I'd always thought Zeno's paradox was flawed because it uses a certain assumption while wrecking the context that makes that assumption valid. It assumes that one cannot complete an infinite series because it would take infinite time, but if one looks at the sums right one finds that it also shows that the time required is actually finite in this instance. There is not just the one infinite series to complete, there are TWO, and one cancels out the other. The one is the sum of the successively smaller distances - but the other is the successively smaller amounts of time required to traverse those distances. The latter is not summed up in time, it is time, and comes to a finite number that represents the amount of time required to complete the first infinite series.

Pure rationalism done for fun, but Zeno's paradox was itself rationalist drivel to begin with. If QM people take that paradox seriously as adding any weight to their thinking then I raise an eyebrow at them in suspicion of lacking objectivity.

JJM

To dismiss the Runner's Paradox as rationalist drivel is to abandon a brilliantly conceived thought experiment. Here's my take on the Runner's Paradox. I think the argument can be distilled down to this form, and still be true to its original essence:

Zeno sees the distance the runner must traverse as though its the Real Number Line. The Real Number Line represents an infinite series of points, no matter the length of the line. In the paradox these points represent the positions the runner must traverse in order to finish the race. Now the question becomes, well is the runner really occupying an infinite number of positions in traveling from the start to the finish? And to think that he (or she) is seems to defy common sense, for how can an object exist in an infinite number of locations at all! much less over a finite duration, i.e. the time it takes for the runner to complete the race. And I think that solving it mathematically, i.e. showing that the infinite number of points between two adjacent integers on a number line add up to the smaller integer+1 misses the point of the argument. In I think a big way, it boils down to whether our mathematical depiction of the world is correct. I would argue that this is a solid argument against the applicability of the Real Number Line to distances in the physical world (though it was not originally conceived to be so). The paradox is resolved if you consider that the number of positions an object occupies in traversing any distance is finite. Representing the distance as an Integer Number Line where at the quantum scale the runner is moving discontinuously from position to position, hopping from integer to integer, would be more accurate.

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Our mathematical understanding of the world is correct. The fact that, when you depressed buttons with letters on them, corresponding letters showed up on a screen is living proof.

The runner does in fact occupy an infinite number of positions, and occupies each position for a quantity of exactly zero time, in moving from the start to the finish. The runner is not moving discontinuously; he is moving continuously.

Zeno's paradox states that, given a certain understanding of motion, motion is impossible. Well, we do not use that understanding of motion. We use a better, accurate one, immune to Zeno's paradox, and we have Newton and Leibniz to thank for it.

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The runner does in fact occupy an infinite number of positions, and occupies each position for a quantity of exactly zero time, in moving from the start to the finish. The runner is not moving discontinuously; he is moving continuously.

Please explain how an object can occupy a position for no quantity of time.

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First, on Newtonian and Einsteinian physics, location is not absolute. It is a meaningless statement that "this object is here, in an absolute sense." Location is not a property of the universe or of entities as such. Instead, it is a relationship among entities, and it must not be reified.

Second, it is clear from all observations that entities move continuously. Anything else would require instantaneous teleportation.

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First, on Newtonian and Einsteinian physics, location is not absolute. It is a meaningless statement that "this object is here, in an absolute sense." Location is not a property of the universe or of entities as such. Instead, it is a relationship among entities, and it must not be reified.

The paradox doesn't refer to an absolute or privileged frame of reference. I agree that location is a relationship among entities. We need to consider the location of the runner relative to the start and finish lines.

Second, it is clear from all observations that entities move continuously. Anything else would require instantaneous teleportation.

It is true that macroscopic objects always seem to move continuously -- this is our daily experience. But it's not always the case at atomic or subatomic scales. Take alpha decay for example. An alpha particle does not have the kinetic energy to overcome the strong nuclear force and escape from the nucleus of a Plutonium atom. However, the wave function of the alpha particle can extend beyond the potential barrier of the nucleus allowing it to spontaneously hop out and escape. This is because of the hybrid, wave-particle nature of the alpha particle. Quantum mechanics has been very successful in explaining phenomena like this. Classical mechanics would have a hard time somehow asserting a continuous path out of the nucleus in the case of alpha decay.

Quantum tunneling works with other particles too. Its used in Flash memory to cause electrons to hop through thin layers of electric insulator.

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Zeno's Paradox itself never referred to the universe as discrete. Your resolution does. I am completely baffled how a view of the universe as discrete can avoid requiring a privileged coordinate system.

Tunneling and instantaneous teleportation are vastly different phenomena with vastly different properties. One of them is real and one of them isn't. Attempting to resolve Zeno's Paradox by reference to quantum tunneling does not help in the slightest, because quantum tunneling assumes a continuous universe.

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Zeno's Paradox itself never referred to the universe as discrete. Your resolution does. I am completely baffled how a view of the universe as discrete can avoid requiring a privileged coordinate system.

I don't see why a discrete universe requires a privileged coordinate system any more than a continuous universe does.

Tunneling and instantaneous teleportation are vastly different phenomena with vastly different properties. One of them is real and one of them isn't. Attempting to resolve Zeno's Paradox by reference to quantum tunneling does not help in the slightest, because quantum tunneling assumes a continuous universe.

I was careful not to make any claims about what kind of movement quantum tunneling represents except to suggest that it wasn't classical continuous motion. Now I'm intrigued -- how does quantum tunneling assume a continuous universe?

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If one can travel 1m to the right and 1m forward, one comes to a position 1.717...m away from where one starts. The ancient Greeks took one look at this and gave up with mathematics. It took two millennia for mathematics to pick back up with the inclusion of polynomial roots, transcendentals, and complex numbers into the mathematician's toolchest.

Quantum tunneling is based on the notion of a "probability cloud" where a particle's position is a continuous probability distribution over an unbounded region of space.

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