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Is the total energy of the Universe Zero?

  1. Dec 27, 2008 #1
    Excuse this beginners question, but someone asked me if the Universe can appear out of nothing. I answered yes, because all the energy in the Universe cancels out to make nothing. So, conversely, out of nothing can come equal positive and negative energy. He seemed half convinced.
    Am I correct in what I said? Thanks for any replies.
    Last edited: Dec 27, 2008
  2. jcsd
  3. Dec 29, 2008 #2
    Nice topic..

    We agree that Five minus Five = zero but in noway 0 is the cause of 5.
    Ex: Add / multiply 0 to itself any no of times etc.its still 0.

    There must be a cause for every effect. May be that cause is too subtle to be grasped by human mind. If world is effect, then it is a creation..I mean,there must be something which is eternal and that is what created this world. Existence can not come out of non-existence. This may sound like blind faith but on close observation it's logically correct.Do we not see this phenomenon everywhere in this world.
    i.e, Every effect has a cause. In fact cause is the effect itself but in a finer form.

    Ex:I think of an idea (be it any). When time and space are convenient, that thought will manifest in action. Isn't that how all discoveries made? So THOUGHT (cause) is the ACTION (effect) itself ..may be I can say 'cause' is 'effect' only in a pre-mature stage. So there is a cause for this world as well.
  4. Dec 29, 2008 #3
    There is nothing wrong with equal amounts of positive and negative coming from nothing - mathematically they sum to zero (something analagous to waves cancelling each other out). OK, so what made a Universe appear at all, is at present also up for discussion, but I am not asking that.

    My question is purely technical - is the sum total energy (or matter) in the Universe zero? I assume it would have to be zero?
    Please correct me cosmologists out there.
  5. Dec 29, 2008 #4
    I believe that Alan Guth pointed this out. A rocket traveling into orbit uses thrust to overcome the gravity of the Earth’s mass. So in a way, the effect of the thrust is positive energy and the effect of gravity is negative energy. Energy and matter are the same according to Einstein, and they both have mass. Gravity is a property of mass. So if you could add up all the matter and energy in the universe and then the respective gravity (negative energy) of that matter and energy, the result should be a net energy of zero.
  6. Dec 29, 2008 #5


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    Yes, it is roughly correct, though different "nothings" can be defined and that simply speaking about energy without many added technicalities is not correct. In this case, "nothing" should be interpreted as "no matter, and no spacetime", which is a quite hard "nothing" indeed but still different from "nothing at all". From no matter and no spacetime it is possible to derive matter and spacetime, and from matter and spacetime it is possible to derive more matter, and more spacetime, without violating the laws of physics.
    Last edited: Dec 29, 2008
  7. Dec 30, 2008 #6


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