Does a pure vacuum exist?

Discussion in 'Physics & Math' started by zanket, Jan 2, 2004.

  1. zanket Human Valued Senior Member

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    Is there such a thing as a pure vacuum? Or is it thought that every portion of the universe no matter how small is completely full of energy, such as quantum foam, virtual particles or electromagnetic waves?
     
  2. Crisp Gone 4ever Registered Senior Member

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    Depends on how you define a vacuum.

    Void of particles ? That surely exists.

    Void of electromagnetic radiation ? That's quite a bit harder already. But in theory this can exist.

    Void of virtual particles ? ... well, they say this does not exist. I am not sure what to think of it though, but appearantly this does not exist.

    Bye!

    Crisp
     
  3. Quantum Quack Life's a tease... Valued Senior Member

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    absolute vacuum = absolute nothing.

    Like before the big bang?
     
  4. zanket Human Valued Senior Member

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    Crisp – I define a pure vacuum as a space void of any energy. If every portion of space is taken up by virtual particles at least, how do the virtual particles move? Wouldn’t they be hemmed in on all sides by other virtual particles? The pictures I’ve seen show them moving some distance within an apparently pure vacuum before coalescing. Also, when they disappear, wouldn’t there be a void at that location for some moment of time?

    Quantum Quack – No, just within any portion of the universe now, no matter how small. Like, does a pure vacuum exist anywhere within a donut?
     
    Last edited: Jan 3, 2004
  5. lethe Registered Senior Member

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    because of quantum mechanics, the vacuum should be filled with a zero point energy. there are some thorny issues with this stuff (like, it might be infinite, or at least the theory makes predictions many orders of magnitude too large), but there can be no doubt that it is real. it was measured with the Casimir effect.

    it doesn t really make sense to talk about virtual particles in the vacuum, i think, since virtual particles are, even in principle, not observable. on the other hand, we know that whenever there is interacting matter present, the so called "vacuum bubbles" contribute to the interaction. it is as if the particles which would otherwise be travelling through a vacuum, are seeing pairs of virtual particles. but then again, its not a true vacuum, since i have real particles as well.
     
  6. ScRaMbLe Chaos Inc. Registered Senior Member

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    What the hell is going on here?!!! I go to bed, wake up this morning and all of a sudden the more respected physics posters are acknowledging zero point energy?!! Did I fall into an alternate reality while I was sleeping? Don't get me wrong, I'm so glad you guys are accepting the concept, but WTF? What changed your minds?
     
    Last edited: Jan 4, 2004
  7. Quantum Quack Life's a tease... Valued Senior Member

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    Absolute nothing = absolute vacuum. Absolute vacuum is inverse energy therefore absolute vacuum is infinite energy.

    Absolute nothing has absolute energy by simply being absolute vacuum.

    The absence of pressure means that it has an incredably strong attraction to anything that has pressure and this I believe is gravity, the effect of the attraction ofabsolute vacuum or in other words absolute nothing.

    In the centre of everything is absolute nothing ( vacuum ) which by default is extremely attractive.
     
  8. lethe Registered Senior Member

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    i didn t change my mind. as i said in the other thread: zero point energy is real, but it cannot be tapped to drive your car.

    i am starting to wish i had not called it zero point energy, but instead called it vacuum energy, since the latter is not as often associated with crackpot schemes.
     
  9. ScRaMbLe Chaos Inc. Registered Senior Member

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    See "zero point energy" thread for my explanation. I'll stop hi-jacking this thread.
     
  10. zanket Human Valued Senior Member

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    So far the answer seems to be “no, arguably.” Are physicists really so divided about this or am I just misunderstanding what I’m reading here? When I read about vacuum energy, I see no mention of it being observed within an arbitrarily small volume, like that of a subatomic particle. It's more believable that it exists within larger volumes.
     
    Last edited: Jan 5, 2004
  11. lethe Registered Senior Member

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    if it exists in large volumes, then it must be found in small volumes as well. remember that the vacuum is Poincaré invariant
     
  12. MacM Registered Senior Member

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    Zanket,

    I suspect your definition is flawed in that while it is not a universal idea yet, a Cornell University paper (and others) believe that space is created by energy. No energy, no space.
     
  13. Quantum Quack Life's a tease... Valued Senior Member

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    Vacuum is energy without doubt......just inverse. (My thoughts)
     
  14. rainman Registered Member

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    Pure Vacuum versus Perfect Vacuum

    I think there is a subtle difference between a "Pure Vacuum" and a "Perfect Vacuum". A perfect vacuum is more of a scientific concept that could be attainable given the right technology. A "Pure Vacuum" seems to be more of an artsy concept of simple nothingness. Does or can either one of these ideas/concepts exist in our Universe? That, to me, is the big question.
     
  15. Rick Valued Senior Member

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    Quantum, you said something very interesting ... you said, "BEFORE" big bang; I remember that Space and time are connected (general theory of relativity I believe), so there CANNOT be any thing BEFORE big bang, because time is a conception tightly coupled with space; off course I am a noob to everything, so i could be completely wrong, if so; please excuse me.

    Rick
     
  16. Quantum Quack Life's a tease... Valued Senior Member

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    yes this is a correct view IMO. There can be no moment before time began. Nor can there be any moments after time ceases. So if the universe should end it will do so as if it never had existed in the first place as no historical remnant will remain to demonstrate it.
    One can not separate time from substance nor substance from time as both are more or less the same thing described from differring perspectives. IMO [ time in this context is not the abstraction of clock time we humans utilise to measure with but the actual movement and change that the universe undergoes within itself which we use an abstraction called time to measure that change with. So time has too aspects to it that are often confused.IMO


    Logically the advent of time is what created the universe from nothingness....however since this thread was posted too over 4 years ago much has been learned and thought about and I am still probably just as much a "noob" as you are...
     
  17. AlphaNumeric Fully ionized Moderator

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    And your logic for this is.....?

    Except that isn't how it works, a vacuum isn't attractive. If you opened the door on the Shuttle you aren't sucked out by the 'attractive' properties of the vacuum, you're blown out by the high pressure of the air in the Shuttle. The air is applying an outwards pressure and when you remove the constraint holding the air in (ie open a door) then it'll blast out. The same is true for your body, the fluid and gases are held in because there's an equalising pressure on the other side of your skin due to the atmosphere. If you removed that your blood and lung air wouldn't be sucked out of you, it'd be forcing its way out of you.

    Obviously basic mechanics is another thing you didn't read up on in your twenty years of research. :rolleyes:
     
  18. rainman Registered Member

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    We shouldn't "hedge" when it comes to defining "Pure Vacuum". It should be nothing..period. If you observe energy of any kind within a fixed volume then you do not have a "Pure Vacuum". You have something else. You have a semi-perfect vacuum. Pure vacuum contains nothing. Maybe we could argue whether Pure Vacuum can be contained within a vessel? But the Universe is not a vessel. It is infinite. I like leaving "Pure Vacuum" as a completely empty volume and instead arguing about how pure it can be and still be observed by our rudimentary instruments.
     
  19. thinking Banned Banned

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  20. thinking Banned Banned

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    what............................?
     

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