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Question about the Steady State Theory (Cosmological model)

  1. Jan 7, 2009 #1
    If this should be in the cosmological section, then i don't mind to see it moved, but since it appears to be an abandoned theory, i'm posting this in the classic physics section.

    I was talking to a religious person, and he was claiming that the big bang theory was.... wrong, that it had been "debunked", and that the steady state theory was probably correct.

    Now, i'm a master student of physics, and i can't remember learning more about the steady state model than it being mentioned as a footnote of a theory that turned out to be incorrect during the 60's. Since then i looked it up at Wikipedia:

    http://en.wikipedia.org/wiki/Steady_state_model


    But can anyone give me additional information on it? I've never actually met a physicist who uses this model to-day. Mind you, the guy i'm talking about is of the level of high school education, and only knew about it because it was more compatible with the Bible.
     
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  3. Jan 7, 2009 #2

    Garth

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    Hi Lennox,

    Interesting conversation you were having, back in the 1970's I was in conversation with an atheist who assured me that the Bible was wrong because the Big Bang theory had been disproved by the Steady State theory and therefore there had been no beginning to the universe! He wasn't convinced when I tried to explain that it he who was about twenty years behind the times and it was the Steady State theory that had been disproved.

    The basic flaw with the SS theory was that it was based on the Perfect Cosmological Principle (PCP) that postulated that the Universe is homogeneous and isotropic in space and time, i.e. it looks more or less the same everywhere and at all times.

    Problems had been rising since the 1950's with counts of sources from distant radio objects that had seemed to show an evolution over time, likewise with quasars in the 1960's, although estimates of their distances were problematic, but the observation that finally disproved the PCP was the discovery of the Cosmic Microwave Background in 1964 that proved the universe had gone through a very hot condensed phase in the past that it was not enduring in the present epoch.

    I hope this helps,
    Garth
     
  4. Jan 8, 2009 #3
    Thanks. :approve:
     
  5. Jan 9, 2009 #4
    Just to expand on what Garth said, this is seriously weird. Anyone who knows the history of the big bang theory (creationists seem to know surprisingly little of the history of what they are talking about) will know that it was thought to support religion. Lemaitre, who introduced a version of it in 1927, was a priest. E.A.Milne thought it important to have point of creation because of his religious beliefs. In the 1950's the Pope issued a statement on how it supported the Bible, but was warned by Lemaitre against tieing religion too closely to a science which might be proved wrong. The opposition to the big bang was largely due to its religious associations. Fred Hoyle, one of the originators of the steady state model, and inventor of the term 'Big Bang' as a term of derision, was well known for his atheist views.
     
  6. Jan 9, 2009 #5

    Chalnoth

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    I don't think I'll ever understand why the steady state model of the universe ever held sway. It's basically disproved by simple thermodynamics, as it requires that there be a physical process that continually lowers the entropy of pockets of the universe.

    The same can be said of the more modern cyclic universe hypotheses, which require that the universe go through phases of monotonically increasing and monotonically decreasing entropy.

    This sort of thing also baffles me. The very idea that this sort of question says anything one way or the other about the existence of any deity is simply absurd to me. Though I personally still see a large number of theists standing on both sides of the issue (that is, claiming that the big bang theory supports their creator claims, or claiming that the big bang theory is wrong because it doesn't), I have yet to see an atheist attempt to use the big bang theory (for or against) to attempt to disprove a god.
     
  7. Jan 9, 2009 #6
    I wouldn't be too hasty to use thermodynamic arguments in cosmology, GR doesn't necessarily obey the conservation of energy, and inflation and the accelerating expansion of the universe suffer from the same problems as the steady state model.

    The arguments were mostly the other way round - the big bang was creationism in disguise - but certainly Fred Hoyle linked the steady state model with atheism in the 1950's
     
  8. Jan 9, 2009 #7

    Vanadium 50

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    Yes, but many creationists are members of denominations that don't care much for the Catholic church.
     
  9. Jan 9, 2009 #8

    Chalnoth

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    While it is true that conservation of energy does not hold in an expanding universe (at least not in the typical formalism), the second law of thermodynamics is derived from statistical mechanics, and is thus necessarily true in any system with unitary dynamics (and potentially still true in a system without unitary dynamics, though perhaps with some modification). Neither inflation nor the more recent accelerated expansion are contrary to this, as in each case they increase the entropy, either of a comoving volume of the universe or of the universe inside the future horizon of the model. This is because of the fact that in each case, the universe is driven towards being completely empty of all matter (the highest entropy state a region of the universe can be in).

    The steady state model, however, is very much contrary to this as it would require the spontaneous generation of new matter, which would drive the formation of new stars.

    Yeah, guess I'm not that up on the details of some of the developments of scientists presenting sloppy thinking fifty years ago.
     
  10. Jan 10, 2009 #9
    How can energy conservation be violated in a large scale, cosmological sense?

    If i'm not mistaken, energy is conserved because a non-commutating variable in the Hamiltonian...


    Or am i thinking too deep and is it simple because mass equals energy according to E=MC^2?
     
  11. Jan 10, 2009 #10

    Chalnoth

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    Well, no. Energy is conserved if the Hamiltonian (or Lagrangian) is independent of time.

    However, this isn't the case for an expanding universe, at least not in the way it's usually formulated. Basically, what happens in General Relativity is that because there's an ambiguity of the time variable, conservation of energy just isn't something that makes much sense. I mean, we might be able to consider a metric wherein time is conserved, but if we just change our coordinates, it might not be.

    So instead, in General Relativity, we deal with conservation of the stress-energy tensor. This tensor includes components of energy, pressure, and anisotropic stresses. This works well because what appears to be energy in one observer's frame of reference may look more like pressure in another, and so remains meaningful in the context of curved space-time and arbitrary coordinates: this tensor is always conserved in General Relativity, no matter the shape of your space-time or your coordinates.

    And, it turns out, that the conservation of this object, the stress-energy tensor, forces energy to not be conserved in an expanding universe for any sort of matter that experiences pressure. We can understand this in terms of what I said above, which stems from Noether's theorem: in this case, if the metric is independent of time, energy is conserved. But energy isn't going to be conserved in an expanding universe because the metric (the object which describes the structure of space-time) expands with the universe.

    I should mention that there is an alternative way of formulating General Relativity: the Hamiltonian formalism. In the Hamiltonian formalism, we don't just consider the energy stored in the matter fields, but also the gravitational potential energy. By construction, then, energy is always conserved in the Hamiltonian formalism. We can understand a change in energy in the matter fields as coming from a change in energy of the gravitational potential. For example, if two objects fall towards one another under their own mutual gravity, they will pick up speed. Where did this energy come from? The gravitational potential energy, which became more negative as a result of them getting closer together.
     
  12. Jan 10, 2009 #11
    Very informative post Chalnoth. I'd never heard of that type of Hamiltonian formalism. Would it be fair to state that on an extremely large case, energy AND gravitational potential energy is conserved?
     
  13. Jan 10, 2009 #12

    Chalnoth

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    Well, the sum is.
     
  14. Jan 11, 2009 #13
    You can't say the same for a closed system because of the, in principle, infinite reach of the gravitational force?

    What about the electromagnetic potential energy? Shouldn't it be included for the same reasons? And, if you want to get technical about it, the strong one, even if it's range is 10^-15m ?
     
  15. Jan 11, 2009 #14

    Chalnoth

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    Well, I think you can get around this requirement just by considering the conservation of a current instead of just the energy. By considering the inflow and outflow of energy, there is no problem, as the speed of gravity is finite (believed to be the same as the speed of light).

    Oh, sure! But I think that that is already taken into account through the energy stored in the electromagnetic field (and in the gluon field for the strong force).
     
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