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Difference between Nothing & Vacuum

  1. Feb 6, 2010 #1
    Difference between "Nothing" & Vacuum

    Could you please tell me what is the difference between "Nothing" an a "theoretical perfect vacuum" ?

    The question is serious.
    Regards
     
  2. jcsd
  3. Feb 6, 2010 #2

    Doug Huffman

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    Gold Member

    Re: Difference between "Nothing" & Vacuum

    Virtual particles may occur in vacuum while nowhere in this universe is nothing.
     
  4. Feb 10, 2010 #3
    Re: Difference between "Nothing" & Vacuum

    Difference between “nothing” and vacuum?

    Jgabase, if “nothing” had properties, it would not be nothing. But “a theoretically perfect vacuum” does has properties, it has volume, dimension, inertia, elasticity, even a energy density. Even if the our Universe (our gravitational world) were empty or completely devoid of all rest masses, it would still have an intrinsic energy, and therefore a effective mass.
     
    Last edited: Feb 10, 2010
  5. Feb 10, 2010 #4
    Re: Difference between "Nothing" & Vacuum

    Vacuum is just an empty space. It can theoretically hold something. Nothing is just nothing.
     
  6. Feb 11, 2010 #5
    Re: Difference between "Nothing" & Vacuum

    Thanks LouieHussey, after 25 replies in two forums your answer is the closer to my concept of vacuum and the closer to my intuition. I undestand matter as a kind of confined energy, Vacuum as other kind of confined energy with a very low density in this case. And electromagnetic radiation as free or released energy. Vacum is therefore a structure of energy, rigid enough to allow a straight and stable flow of electromagnetic radiation between celestial bodies, but at the same time, sufficiently elastic to manifestate distortion because of gravitational fields. In my opinion it have also gravitational properties by itself and probably could explain something like "dark matter". So your answer is the begining of a new and very interesting question.

    How could you prove or demonstrate the gravitational properties of a "infinite and uniform distribution of mass" ?
    Please watch the video --->
    To understand what I mean.
     
    Last edited by a moderator: Sep 25, 2014
  7. Feb 13, 2010 #6
    Re: Difference between "Nothing" & Vacuum

    *Jgabase, I generally concur with your view of empty space in our gravitational world (our Universe) (I could add some detail and refinements to your concept of the elasticity and structure of empty space, but I will not get into that here), and I agree with you that the intrinsic energy density of empty space is a component of “dark matter” (although not the only one)—although some do not consider it as dark matter). Incidentally Jgabase, I know nothing about your background, but I sense your wonder about the Universe and about physics, and I sense that you have a inherent “feel” for physics--I know not whether such a “feel” for physics is genetic or acquired or what, but not everyone has it.

    *Now for your new question: How could you prove or demonstrate the gravitational properties of a “infinite and uniform distribution of mass”?

    *I took a look at the YouTube video you referenced. I concur with the reasoning presented there, but differ with its assumption that the Universe is infinite--but I am sure the reason he extended the mass distribution to infinity was to get around the boundary effects of the mass distribution, for at the boundary the distribution does have effects. In any case, we have reason to believe that the Universe is finite but unbounded (It is closed upon itself in its spatial dimensions but effectively open in the temporal dimension, if you will). If the video’s reasoning is applied to a finite but unbounded universe, it would show that any element of static mass in a universe in which the mass of the Universe is distributed uniformly throughout the Universe would suffer no gravitational forces from the rest of the Universe, until it is displaced. But this is what would be expected from the symmetry of the model.

    *In any case, after watching the YouTube video you referenced, I think I have a little better understanding of what you are asking. Since the video is produced with the mass distribution of the Universe in mind, and with the idea that many of the gravitation forces of the Universe tend to cancel out because of symmetry, I propose that you take the word “infinite” out of your new question and add a reference to the Universe to make it read:

    *If the mass of the Universe were uniformly distributed throughout the Universe, how would you detect or measure the gravitational properties of the Universe?

    *With your indulgence, I will reply to your question as modified above. Incidentally, although there are lumps of mass scattered throughout the Universe, the average mass in the Universe is more or less uniformly distributed. Furthermore, as is generally conceded in the literature today, the amount of visible mass in the Universe is very small compared to the amount of unseen mass in the Universe, dark matter as it is usually referred to. The amount of rest mass in the Universe, seen or unseen, is also quite small compared to the amount of effective mass in it. And, as noted earlier, there is reason to believe that even if the Universe had no rest mass in it at all, that it would still have an effective mass due to the intrinsic energy density of empty space.

    *The possibility of the intrinsic energy density of empty space comprising a major component of dark matter has been addressed in the literature. In fact, the YouTube video you referenced has another YouTube video entitled “The Mystery of Empty Space” on the same page in which Kim Griest, a physicist of the division of natural sciences at UCSD, is telling us that the energy density of empty space is a component of “dark matter”. (See the video entitled, “The Mystery of Empty Space” at: http://www.youtube.com/watch?v=Y-vKh_jKX7Q&feature=channel). He is also telling us that if it exists, the expansion of the Universe will be increasing with time rather than slowing, and that experiments have recently been made in which it was unexpectedly observed that the expansion of the Universe actually is increasing with time, experiments that also measured the rate of acceleration of expansion. (The rest mass in the Universe would slow it. The reason that the energy density of empty space increases it is that the volume of space is increasing with the expansion.) These measurements enabled the researchers to go a step further and calculate the equivalent mass density of empty space, which turned out to be, according to Griest, about 10 to the -26 kilograms per cubic meter (which is about 1 proton mass per cubic foot). (There are questions in my mind about whether other sources of “dark matter” (and I know that there are other sources), which are technically not part of the energy density of empty space, are large enough to skew this result, but evidentially they are not). In any case, this is one experiment that has arguably “demonstrated the gravitational properties of the Universe”.

    Note: I think the name of this research project, a coordinated effort made by astronomers from various telescopes about the world, was named “The Supernova Cosmology Project”, and that it was based at Lawrence Berkeley National Laboratory in California. It used data from the redshift of type IA supernovae in wide ranging galaxies to determine the expansion rate and acceleration of the expansion of the Universe.

    *Einstein, by the way, included the mass density of empty space in the equations of his general relativity theory (which is actually a theory of gravity), a constant that he referred to as the now famous “Cosmological Constant”. Although he later regretted it, calling it his greatest blunder, because of the problems and complications it presented to his theory (it opened a can of worms so to speak)--but he was kind of stuck with it, it was something of a necessary evil, so to speak, for the theory is less complete without it--it has to be there. Physicists, however, have disagreed in the literature over what the value of the Cosmological Constant might be.

    *Now let me show you something interesting (and I am telling you this in order to put some meat on the concepts we have been discussing). Empty space, as already noted, has certain physical properties, including springiness and inertia, and it momentarily compresses or stretches when an oscillating gravitational wave passes through it. The speed of transverse waves moving through media that possess springiness and inertia (such as the speed of gravitational waves moving through empty space) is equal to the square root of the ratio of the springiness of the media (of space in its spatial dimensions) to its inertia (See, for example, chapter 3, pg 32 of the teacher’s edition of the fascinating little book entitled: Similarities in Wave Behavior, by Dr. John N Shive, director of education and training Bell Telephone Laboratories, Waverly Press, Inc., third printing 1964. (Springiness is designated by a spring constant, which gives the ratio of the force to the stretch). These physical properties of space (springiness and inertia) are directly related to Newton’s universal gravitational constant, and to a gravitational constant that is the gravitational analogue of the magnetic force constant in electromagnetism, and they can be written in terms of these constants). The speed of gravitational waves through empty space in terms of these gravitational constants is equal to the square root of the ratio of Newton’s gravitational constant to the gravitational analogue of the magnetic constant. Now although we have not physically detected or measured the speed of gravitational waves, there is reason to believe, on purely theoretical grounds, that the speed of gravitational waves is the speed of light.

    *We can summarize all this as: S/I = G/M = c, where c is the speed of light, G is Newton’s gravitational constant, M is what I will call the “massnetic field” constant (the massnetic field is the gravitational analog of the magnetic field, and the “massnetic” field constant is the analog of the magnetic field constant), S is the spring constant that characterizes the springiness of empty space, and I is the inertia (or equivalent mass) of empty space. Now since both the ratios in this equality pertain to the gravitational properties of empty space, there is reason to believe that S corresponds to G, and I corresponds to M, in which case the constant M would be the inertia of empty space. So if the constant M were integrated over the volume of our entire Universe (remembering that this volume is finite), it would yield the total mass of our Universe (not including the rest mass in it, but which is believed to be negligible by comparison). In any case, M, which is the mass in a unit volume (a cubic meter of space) is the inertia of a cubic meter of space. Plugging in the known quantities, M is (7.421 X 10 to the -28) kilograms/cubic meter. If this reasoning is correct, then this is the effective mass per unity volume of empty space in our gravitational universe.

    *Comparing this result to the equivalent mass density of empty space obtained by the researchers in their “expansion of the Universe” measurements cited above, we see that this is within approximately an order of magnitude of their value. Surprisingly close, when you consider that the value that Kim Griest gave in his video was an order of magnitude approximation of what the researchers calculated, and when you consider that he said that the equivalent mass of the empty space of the Universe was about twice that of the dark matter in it, which could cause it to be off by as much as half—I do not have copies of the original paper to see if more accurate numbers are available).

    *Now let me show you something else that is very interesting. Realizations of Mach’s theory that enable us to derive interactions between local mass and the mass of the Universe yields a fascinating relationship between the total mass of the Universe and the radius of the Universe (remembering that the Universe is finite in both its volume and in its mass). See, for example, the paper “On Possible Realizations of Mach’s Program”, by F.A. Kaempffer, “Canadian Journal of Physics”, Vol 36 (February 1958). This is one of best papers I have seen on Mach’s theory, it is straight forward and easy to understand, and it covers the progress in the field to the date of publication. And I highly recommend it. In it, Kaempffer derives Newton’s second law for linear acceleration and also for rotational motion from Mach’s program. The derivation exactly yields Newton’s law if and only if the ratio of the total mass of the Universe to the radius of the Universe is equal to a constant, namely to c squared divided by G, where c is the speed of light and G is Newton’s universal gravitation constant.

    This only gives the ratio of mass to radius, and not the actual mass or radius, but the equation from which this came is [4(pi)G(ro)(R squared)/3(c squared)] = 1, where ro is the mass density of the Universe, G is the universal gravitational constant, and R is its radius, which relates the mass density of the Universe to its radius. And we already determined the mass density of the Universe to be (7.4210 X 10 to the -28 kilograms per cubic meter), and plugging it into this equation we get R = 6.584051073526e+026 meters (or 6.959495e+10 light years).

    Note: the radius of the Universe has also been calculated from Einstein’s general theory of relativity, also using a spherical model of the Universe. And the expression used to derive this Einstein radius (the radius of curvature of space in Einstein’s universe), an expression that came out of Einstein’s general theory, is identical to the Machian expression given above except that the 3 is missing from the denominator. As a result, the “Einstein radius” would differ from that derived above by a factor of three, all else being equal. Both derivations give a radius for the Universe on the order of 10 to the 10 light years.

    Note: there is one caveat to the Mach theory paper: since the authors of this paper had to assign a geometry and mass distribution to the Universe for the purpose of making their calculations, they arbitrarily assumed that the mass of the Universe was essentially uniformly distributed over a sphere (just as was done for the Einstein radius calculations from the theory of general relativity). We know that the mass of the Universe is indeed essentially uniformly distributed, but that it is not a sphere, so their expression for the ratio of the mass of the Universe to its radius may be off by a numerical factor. But this is no big problem, for the geometry does not negate the argument, and we can always come back later, plug in the correct geometry, and recalculate to get the exact results.

    In conclusion, the numbers discussed here are subject to change as the model of the Universe used in the calculations changes and so on, but the relationships discussed here are what is important. What I am trying to point out here is that our gravitational Universe is finite but unbounded, that the empty space in it (and therefore the Universe itself) has properties like springiness and inertia that can be measured and used to determine the total mass and radius of our universe, that our Universe would possess an intrinsic energy and effective mass even if there were no rest mass in it, and that the ratio of the mass of our Universe to its radius is a constant. And in the process, I hope to have demonstrated how you can detect or measure the gravitational properties of the Universe.
     
    Last edited: Feb 13, 2010
  8. Feb 14, 2010 #7
    Re: Difference between "Nothing" & Vacuum

    Thanks for your answer LouieHussey, Iḿ not physicist but an engineer who could not work without the tools of the physics and the mathematics. At least Iḿ happy to know that there are many people studing all the things I like regarding Physics and Astronomy, and my only worry is that many Scientists including very powerful minds, cannot avoid our natural temptation of converging or accepting ideas only because many people seem to have accepted it. That way, sometimes Iḿ under the impression that science is not free of dogmas, or popular beliefs that are supported only by feelings, conservative spirits, and the idea of many people that the Truth is under Democracy.

    So believe me when I say that your answer is pleasingly more than I expected from a popular forum, and because of your knowledge of the subject, I suppose that in the past you have studied these concepts with an special interest.

    Just the same as you, I do not believe in an infinite Universe, but probably because of my understanding of relativity I use to deal with the idea that every location in the Universe can be considered, the center of the Universe with independence of its state of movement (always relative movement). So in my opinión, any initiative triyng to prove or calculate the energy density of the outer space vacuum, or its gravitational properties could be carried out without taking care about the question if the Universe is infinite or not, and without a worry about symmetry affairs.

    Besides this clarification, my question refers only to vacuum and not to the density of the whole Universe including celestial bodies. That way it could be reduced to the question: How could you demonstrate or calculate the gravitational properties of the outer space vacuum? ... with this link to the youtube video I was only calling your attention to the fact that practical attempts to get any measurement will have to confront a noticeable problem: If we think in the outer space vacuum as an uniform distribution of mass (or energy with gravitational properties), we and our measurement tools will be always in the center of this distribution where all forces cancel. Together with this problem, I suspect that any enterprise to obtain measurements has to confront also the fact that celestial bodies and even measurement tools, because their weight, or enormous density relative to vacuum, will affect in a dramatic way to any measurement, and then We will suffer a special sort of Uncertainty Principle.

    I am very grateful for your explanations about how other Scientists have tried to obtain data about the density or radius of the Universe with theoretical methods, I will have a look to these references. But you have to know that whenever I try to approach the understanding of the Universe I can not avoid feeling myself as a little mite in the middle of a beach. A mite could easily obtain conclusions about an expanding universe just studing the movement of the grains of sand under the force of the wind, but its universe could not be greater than a little area of the beach. The same way, I don know how big is our Universe, but intuitively I assume that it could be substantially bigger than we can see from our little planet, and to be honest I do not feel confident to talk about an Age or a Radius of the Universe, as many other people do. So I dont know if far away, our universe is under contraction or how many universes are out there. far in the distance or in the time. But on the contrary my mind can deal and get satisfaction with a concept of the Universe, as you said, closed upon itself, where perhaps the closest as well as the furthest location away from any location is the same location. And then the effective radius of de Universe would be half of the distance between a location and the same location. It could be possible beacuse, in my opinion, it is impossible to keep a matematical straight line in our Universe. This question suggest therefore that, for example, a perfectly calibrated laser focused to the outer space could not avoid open itself in all directions like magnetic fields, and there will be a bending curve and a maximum distance where the light can reach from its source. If anyone is interested in the radius of the Universe I would suggest him to study this matter.

    ...now I am going to watch to the video you referenced “The Mystery of Empty Space”..... see u latter.
     
    Last edited by a moderator: Sep 25, 2014
  9. Feb 14, 2010 #8
    Re: Difference between "Nothing" & Vacuum

    Jgabase, just a few comments. You say: “…and my only worry is that many Scientists including very powerful minds, cannot avoid our natural temptation of converging or accepting ideas only because many people seem to have accepted it. That way, sometimes I’m under the impression that science is not free of dogmas, or popular beliefs that are supported only by feelings, conservative spirits, and the idea of many people that the Truth is under Democracy.” I agree. Many examples could be given. But this attitude was absent in many of the greatest physicists, including Newton, Einstein, and de Broglie.

    It is true, as you say, that any location in our Universe can be considered the center of our Universe. Position is relative to the observer, and this is part of the relativity of position-- any observer has the right to consider himself to be located at the “center” of our Universe. Technically speaking, the center of mass of our Universe is not actually located in our Universe; it is outside the surface that we live in—but in another sense, any point in the surface of our Universe can be considered the center of the Universe. (That would not be true if the Universe occupied the volume of a sphere by the way, but it would be true of its surface).

    I understand your reason for wanting to consider an infinite universe in your reasoning. Physicists do use such things as point charges, infinitely long lines of electrical charge, and integration to infinity to mathematically simplify their calculations, and they do it all the time, even though such things do not physically exist. And this is a legitimate technique, nothing wrong with it. But the problem with infinite Universes is that a effective mass density or energy density for them would imply an infinite total mass (or infinite energy). But anything that obeys a conservation law, such as energy, cannot be infinite. Generally speaking, if you were to plug infinite quantities into the equations of physics, they would blow up on you. Occasionally, physicists and engineers have had equations blow up on them (produce infinite results), and when that happens, they have to back up and do it another way. You have to be careful when using infinity, for it can lead to logical paradoxes. If our Universe had an infinite radius, it would have an infinite mass (even if the rest mass in it had a limited volume).

    Finally, your statement: “I don’t know…how many universes are out there”, is rather insightful. I have written a mathematically based paper that I will not get into here except to say that it implies that there are multiple dimensions and multiple space-times. The curious thing about it is that all of the space-times are four dimensional, each having three spatial dimensions and one time dimension, and the spatial dimensions, which can be different dimensions than the three dimensions in our own Universe, curl up on themselves giving rise to finite but unbounded universes. This is why I sometimes refer to the Universe that we see as “our” Universe. We cannot see these other Universes. Some of these Universes are so tiny that we cannot see them even with our most powerful microscopes; others are so big and vast that we do not know they are there--our entire gravitational Universe is, unbeknownst to us, linearly traveling through one of these much larger universes (but in a direction different from our three spatial dimensions). The paper also implies other interesting things about these worlds that I will not get into here, things that fall under the category of unified field theory. These results are not entirely new, for ideas similar to these have been discussed in the literature from time to time over the years.
     
  10. Feb 16, 2010 #9
    Re: Difference between "Nothing" & Vacuum

    ...but then.., do you think that there is a border between vacuum and the “Nothingness”? If you talk about a center of mass of the Universe, it is because you are thinking about a certain geometry… and my problem is that, at the moment, I cannot imagine a geometric figure based on maths without a border…..

    Or perhaps our Universe has not a border with Nothingness but with other Universe, property or dimension..…
     
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