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Conservation of SPACE

  1. Nov 30, 2008 #1

    Ranger Mike

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    We have Conservation of Energy
    We have Conservation of Matter
    Is there such a thing as Conservation of Space?
     
  2. jcsd
  3. Nov 30, 2008 #2

    D H

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    Re: Conversation of SPACE

    There is no such thing as conservation of matter. Mass can be created and destroyed. Both the atomic bombs used to end lives (and put an end to World War II) and the PET scan used to save lives depend on mass not being conserved.

    The conservation laws include
    • Conservation of energy
    • Conservation of linear momentum
    • Conservation of angular momentum
    • Conservation of electric charge

    Per Noether's theorem, all of the conservation laws result from symmetries in the underlying mathematical description of some system. There is no conservation of space (and what does that even mean?) because the Hamiltonian is not symmetric with respect to linear momentum.
     
  4. Nov 30, 2008 #3

    Ranger Mike

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    Re: Conversation of SPACE

    I assume the folowing is not applicable regarding Conservation of Matter?

    ???


    The law of conservation of mass/matter, also known as law of mass/matter conservation (or the Lomonosov-Lavoisier law), says that the mass of a closed system will remain constant, regardless of the processes acting inside the system. An equivalent statement is that matter cannot be created/destroyed, although it may be rearranged. This implies that for any chemical process in a closed system, the mass of the reactants must equal the mass of the products. This is also the central idea behind the first law of Thermodynamics.

    The law of "matter" conservation (in the sense of conservation of particles) may be considered as an approximate physical law that holds only in the classical sense before the advent of special relativity and quantum mechanics. Mass is also not generally conserved in open systems, when various forms of energy are allowed into, or out of, the system. However, the law of mass conservation for closed systems, as viewed from their center of momentum inertial frames, continues to hold in modern physics.
     
  5. Nov 30, 2008 #4

    ZapperZ

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    Re: Conversation of SPACE

    You need to look at the CONTEXT of anything. In ordinary interactions, mass is certainly conserved. This is true in classical thermodynamics. However, if you want to look at the most general form, then it is the conservation of mass+energy, since in many cases, mass and energy can be converted into one another. However, this doesn't apply to the majority of classical interactions/examples, and thus, there's no conversion from one to the other. Thus, when that is applicable, you have separate conservation laws of energy, and separate conservation law for mass.

    Your idea of the "conservation of space" is meaningless.

    Zz.
     
  6. Nov 30, 2008 #5

    Ranger Mike

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    Re: Conversation of SPACE

    As I attempt to understand TIME Space and how it relates to Gravity,
    I first must understand what Space is...and is NOT.
     
    Last edited: Nov 30, 2008
  7. Nov 30, 2008 #6

    LURCH

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    Re: Conversation of SPACE

    This seems to ma a rather misleading idea. Isn't it more accurate to say that matter and energy can be converted into one another, while mass remains constant? That's the way I've always spoken of it; mass can be converted from matter to energy and back again, but the mass itself remains constant.

    Not trying to be nitpicky, I just think this view promotes a clearer understanding.
     
  8. Nov 30, 2008 #7

    Dale

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    Re: Conversation of SPACE

    Or you can just combine the energy and momentum conservation laws into the conservation of the four-momentum. Then it becomes clear in what sense mass is conserved.
     
  9. Dec 1, 2008 #8

    ZapperZ

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    Re: Conversation of SPACE

    Doesn't this open another can of worms? You're then saying light has "mass" when matter converts to light. Look at all the lengthy threads we have on here regarding this particular topic. I wouldn't call it a "clearer understanding" at all.

    Zz.
     
  10. Dec 1, 2008 #9

    Ranger Mike

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    Space

    Unless I missed something, I have read that there is Matter, Energy and Space in the universe. That is it. ( not going into black holes, dark energy or the like)

    Given that Matter = Mass x Volume
    Matter has Energy
    Matter can be converted to Energy.
    Energy has Mass. Energy can be converted to Matter.
    Space has Mass and Energy.

    My question about conservation of Space was my thinking that the known laws regarding Energy and Matter could be applied or not applied to Space ( The interstellar and intergalactic medium,intergalactic medium what ever ya want to call it).
    I mean it makes up 99.9 % of the universe and has the least amount of writing on it?
    or has this already been done?
     
  11. Dec 1, 2008 #10

    ZapperZ

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    Re: Space

    This is very confusing.

    From what I can tell, you do not know the difference between "dependent variable" versus "independent variable". You make a chain of connection between one to the other, via mathematics, and conclude that they are all the same and thus, the rules apply to every one of them. This is not necessarily valid.

    Example: electron is nothing more than energy, like photon, since E=mc^2.

    This is false. A photon has spin of 1. An electron as spin of 1/2. You can't squeeze a lot of photon to get a spin of 1/2. So there's something missing here.

    A photon also has no charge. An electron has a charge e, by definition. How do you get one from the other?

    You are simply selecting ONE criteria to balance your equation, while ignoring other criteria (spin, charge) that also comes into the conservation law. The mapping from one to the other is NOT one-to-one.

    Thus, your connection from the conservation laws of mass+energy leading to a "conservation of space", simply via induction, is faulty.

    Zz.
     
  12. Dec 1, 2008 #11
    Re: Conversation of SPACE

    I don't think it makes much sense to try to say that "space" is conserved.

    Assuming "space" is distance, and it is measured in meters, the "amount" of space in the universe, one could argue, is a function of how much energy there is in the universe (because of general relativity, more energy = more space). However, the inverse is not necessarily true... more space does not necessarily mean more energy. So, conservation of energy does not imply conservation of space... and we have no reason to believe that there is a limit to the space. Presumably, if you traveled into space at the fastest possible speed (like astronomers say the universe is doing), you are adding to space. The only way that would NOT happen is if the amount of space in the universe gradually decreased as you expanded (the space comes from space already established), which we would probably notice... as we would suddenly find ourselves very close to the sun. So, I may have even just proved that space is NOT conserved! (Not seriously though.)

    It's nice to be creative, but no one is going to care unless there is a point.

    --Bob
     
  13. Dec 2, 2008 #12

    Ranger Mike

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    Re: Conversation of SPACE

    THANK YOU < LURCH!!!
    most replys were about MASS..not MATTER..

    Thank you DH...I appreciate the reply and hope not to offend if I progress a little more along this line..but not much longer.

    Thanks you ZapperZ.. You are correct about my non traditional thinking..but , once I find a few answers i will finalize my idea and post it for all to scrutinize.

    Thanks Bob...I do have a point I am trying to make and need to find a few more answers before posting it and therefore leave NO DOUBT about the fact that it is tuff to stop drinking at 10 in the morning!!

    seriously, Thank you all for your patience and kindness in taking the time to respond.
     
    Last edited: Dec 2, 2008
  14. Dec 2, 2008 #13
    Re: Conversation of SPACE

    I was having a conversation with SPACE once and people thought I was mad!
     
  15. Dec 2, 2008 #14

    atyy

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    Re: Conversation of SPACE

    No, because the conservation laws are related to symmetries of spacetime, eg. that you can do the same experiment at different times and get the same result is related to conservation of energy, that you can rotate your experiment and get the same result is related to conservation of angular momentum.
    http://math.ucr.edu/home/baez/noether.html
    http://www.eftaylor.com/pub/symmetry.html
     
  16. Dec 3, 2008 #15

    Ranger Mike

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    Re: Conversation of SPACE

    thank you atyy..this is going to take some time for me to read the recommended links..wow
     
  17. Dec 3, 2008 #16
    Re: Conversation of SPACE

    Would cosmological co-moving coordinates be considered conserved?
     
  18. Dec 4, 2008 #17
    Re: Conversation of SPACE

    Im confused with mass energy conservation. i get that mass and energy are conserved but i dont understand how mass can become energy and visa versa.. can anyone help explain it to me in another way?

    cheers =]
     
  19. Dec 4, 2008 #18
    Re: Conversation of SPACE

    Im confussed with mass energy conservation. i get that mass and energy are conserved but i dont understand how mass can become energy and visa versa.. can anyone help explain it a different way?
    cheers =]
     
  20. Dec 5, 2008 #19

    Ranger Mike

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    Re: Space

     
  21. Dec 5, 2008 #20

    vanesch

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    Re: Conversation of SPACE

    I think that the OP should try to get a better view on what physics, and physical laws, are about. Also ZapperZ is very right when he talks about the need to place things in a context. That's very important. The "context" is the paradigm, or the theoretical frame in which one places oneself to consider the physics of a certain situation, and that context defines the concepts one is going to use, the definition of the words one is going to use, the fundamental principles one is going to adhere to etc...

    That's why physicists usually talk about "in classical mechanics, blah blah blah...", or "in general relativity, so so ...". With each context, paradigm, theoretical frame, etc... correspond a number of situations, experimental conditions etc... in which people think the use of that context is appropriate. There are boundary cases where discussion can arise about the applicability or not of this or that context.

    Let us take an example: Newtonian mechanics. In Newtonian mechanics, there are things like massive bodies, forces, there is 3-dim space, there is 1-dim time, etc... All this sets up the conceptual and theoretical frame of the paradigm, and there are unwritten rules which make these correspond to observations. In Newtonian mechanics, that correspondence is almost trivial (this is much less so in more advanced theories).

    From those basic concepts, one can derive quantities, and one such quantity is "energy". In Newtonian mechanics, there is something like kinetic energy, and under certain restrictions (conservative forces), there's also something called potential energy, and both together turn out to give a number that doesn't change under the advancement of time. That property is called "conservation of energy" in Newtonian dynamics. There's also something like "conservation of mass", but that is an a priori assumed postulate in Newtonian dynamics.

    In special relativity, there's also an energy concept, but it is different. Energy is the 4th component of the 4-momentum vector. It turns out that numerically, there is a relationship between the "energy" in the Newtonian paradigm, and "energy" in the special relativity framework. In special relativity, it turns out that the total 4-momentum vector is a conserved quantity (again, it means that this mathematical structure turns out to be the same and unchanging when time advances. Now, there is a quantity one can calculate from a 4-momentum vector, called "invariant mass". Of course the total invariant mass of a system remains invariant given that the 4-momentum vector itself remains invariant. This invariant mass finds numerical agreement with the "mass" which was postulated in Newtonian dynamics.
    But this total vector is the sum of contributions, and each of these contributions can have different invariant masses, and these can change during time in special relativity, while they can't in Newtonian dynamics (by postulate). Indeed, it is not true that the "sum of the invariant masses is the invariant mass of the sum". So there is no "conservation of individual invariant masses". Hence you could have 2 massive incoming particles, and have 2 massless outgoing particles. As long as the sum of their 4-vectors remains invariant, that's OK in special relativity. So there is no "law of conservation of invariant mass of components" in SR.

    So in order to even consider something like a "law of conservation of space", one should specify in what context, and what exactly one means by that. Is it a number, a mathematical structure ?
    In a trivial way, you could say that there is the law of conservation of Euclidean 3-dim space: there is a 3-dim space at a certain moment, and that space remains there after some amount of time (it doesn't become a non-euclidean space, or it doesn't become 2-dimensional or so). Yes.
     
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