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Thread: The premisses of general relativity theory and BB

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    Default The premisses of general relativity theory and BB

    What are the premises of GR and BB? Are the cosmologists aware of them?

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    Default Re: The premisses of general relativity theory and BB

    Kinda dumb asking if they are aware of it? GR is the foundation of cosmology. As for premises, I am not entirely certain of them but the postulates aree

    1. Principle of general relativity

    2. Principle of general covariance

    3. Equivalence principle

    4. Mach principle

    if I am not mistaken.

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    Default Re: The premisses of general relativity theory and BB

    [QUOTE=emperorzelos;60334]Kinda dumb asking if they are aware of it?

    How can you say that it is kind of dumb when you are not certain of them? I think that at least GR suppose one kind of Universe. The Universe where time is 4. dimension. This is not a fact but presupposition, a premise. Time is maybe not a dimension.

    BB suppose an expanding universe because of the movements of the galaxies. The known movements do not mean that the Universe is expanding. It can have other explanations.

    Can you please make more explisit thouse 4 principles?

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    Default Re: The premisses of general relativity theory and BB

    Quote Originally Posted by Olli S View Post
    BB suppose an expanding universe because of the movements of the galaxies. The known movements do not mean that the Universe is expanding. It can have other explanations.
    You are correct that some things are based on the presumption. However, these models are based on a lot of evidence and not only whether or not expansion is observed, but whether expansion is observed in conjunction with the rate of expansion, the cosmic background radiation, ratios of elements along with development of the Standard Model of QM, the formation and evolution of galaxies and the composition and distribution of matter in the universe.
    It is not one free standing assumption, as you suggest, but a series of well studied and documented observations using a large variety of instrumentation both from Earth and In Space.
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    Default Re: The premisses of general relativity theory and BB

    [QUOTE=Neverfly;60343]You are correct that some things are based on the presumption. However, these models are based on a lot of evidence and not only whether or not

    Expansion is not observed, it is deduced from the interpretation of those things you did mention. All those things can be put also in the steady model of the Universe. The movements of the galaxies follow from the limitlessness of the Universe, what it logically is.

    The GR needs some evaluation too, otherwise the expansion follows. Maybe the time in the Universe is not a dimension. The space of the Universe is 3- dimensional, and time is something else. Only the parts have time, the whole Universe does not have time, because it is not a moving particle.

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    Default Re: The premisses of general relativity theory and BB

    Quote Originally Posted by Olli S View Post
    Expansion is not observed, it is deduced from the interpretation of those things you did mention. All those things can be put also in the steady model of the Universe. The movements of the galaxies follow from the limitlessness of the Universe, what it logically is.
    It is observed by the red shift of distant galaxies. The best interpretation we have which explains this is that, the galaxies are moving apart and in fact the very distant ones extremely fast. Whether or not you interpret this to be movement, expansion, or the creation of space itself is irrelevant to your argument. The fact is that in general the overall universe, from our perspective is red-shifted.

    The GR needs some evaluation too, otherwise the expansion follows. Maybe the time in the Universe is not a dimension. The space of the Universe is 3- dimensional, and time is something else. Only the parts have time, the whole Universe does not have time, because it is not a moving particle.
    Ah... now you are hitting on the long old argument of what the actual true definition of time is. In GR space and time are entwined in that they only exist together and changing the parameters of one effects the other.
    Last edited by David M W; 10-29-2016 at 10:04 AM.

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    Default Re: The premisses of general relativity theory and BB

    Quote Originally Posted by David M W View Post
    Ah... now you are hitting on the long old argument of what the actual true definition of time is. In GR space and time are entwined in that they only exist together and changing the parameters of one effects the other.
    What is interesting though is, in my mind, time is the rate of change. Now in theory change is only possible if something exists. If space was completely empty and infinite would time exist?

    Time to start a new thread on this matter OLLI S (pun intended)

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    Default Re: The premisses of general relativity theory and BB

    Quote Originally Posted by Olli S View Post
    Expansion is not observed, it is deduced from the interpretation of those things you did mention.
    This is true for any observation.
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    Default Re: The premisses of general relativity theory and BB

    Quote Originally Posted by Olli S View Post
    Maybe the time in the Universe is not a dimension. The space of the Universe is 3- dimensional, and time is something else.
    We certainly do know that time is not a dimension like the three space dimensions!
    Only the parts have time, the whole Universe does not have time, because it is not a moving particle.
    Can you be more explicit about that?

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    Default Re: The premisses of general relativity theory and BB

    Quote Originally Posted by Olli S View Post
    Quote Originally Posted by emperorzelos View Post
    Kinda dumb asking if they are aware of it?

    How can you say that it is kind of dumb when you are not certain of them? I think that at least GR suppose one kind of Universe. The Universe where time is 4. dimension. This is not a fact but presupposition, a premise. Time is maybe not a dimension.

    BB suppose an expanding universe because of the movements of the galaxies. The known movements do not mean that the Universe is expanding. It can have other explanations.

    Can you please make more explisit thouse 4 principles?
    Because I am not a cosmologist, I am a mathematician.


    Quote Originally Posted by Olli S View Post
    Quote Originally Posted by Neverfly View Post
    You are correct that some things are based on the presumption. However, these models are based on a lot of evidence and not only whether or not

    Expansion is not observed, it is deduced from the interpretation of those things you did mention. All those things can be put also in the steady model of the Universe. The movements of the galaxies follow from the limitlessness of the Universe, what it logically is.

    The GR needs some evaluation too, otherwise the expansion follows. Maybe the time in the Universe is not a dimension. The space of the Universe is 3- dimensional, and time is something else. Only the parts have time, the whole Universe does not have time, because it is not a moving particle.
    General relativity is evaluated over and over and over again, and each time it turns out to be correct.

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