The Horizon Problem in Cosmology

Taken from CMI ministries…Very interesting article!

The cosmic microwave radiation indicates that space is the same temperature everywhere, to within 1 part in 100,000)1. However, the initial conditions of the big bang would have produced wide fluctuations in temperatures between different regions. So to produce the observed temperature uniformity, there must have been a common influence, i.e. all parts of space must have once been in thermal equilibrium.

The fastest way for regions to come into equilibrium would be for electromagnetic radiation to carry heat from one region to another. However, some of these regions are too distant for light to have traversed between them, even in the assumed time since the alleged big bang. The finite speed of light is a ‘horizon’ which can’t be crossed, hence the term ‘horizon problem’. Even when the CMB was emitted, supposedly 300,000 years after the big bang, it already had a uniform temperature over a range at least ten times larger than this horizon.

One of the commonest attacks on the YEC model by old-earthers such as [progressive creationist Hugh] Ross is that light would supposedly not have had enough time to reach earth from distant stars. But the horizon problem is the big bangers’ own ‘light travel problem’. How can old earthers so freely criticize YEC on the very problem that they have not yet solved from their own perspective?

As an ad hoc solution to the horizon problem, Alan Guth (b. 1947) proposed in 1980 that the universe once underwent a period of very rapid growth, called ‘inflation’.4 Guth, then a particle physicist at the Stanford Linear Accelerator Center in California, proposed that 10–35  seconds after the big bang, the universe expanded by a factor of 1025  in 10–30 seconds. 25 orders of magnitude is mind-boggling―it is like going from smaller than a pea to the size of our galaxy. But Guth’s proposal starts with the universe tinier than a subatomic particle. So the different regions of space were so close that they could come to the same temperature before inflation occurred.

It’s important to note that it’s space itself that is expanding, so it doesn’t violate relativity, which prohibits only mass/energy from moving through space faster than light. But, despite that, now it seems that even this may have its own horizon problem. So some physicists have proposed that the speed of light was much faster in the past, which would allow the ‘horizon’ to be much further away and thus accommodate the universe’s thermal equilibrium.

This is ironic, because creationists have been disparaged for suggesting the speed of light may have been faster in the past, with accusations that they don’t understand relativity. Apparently, it is now acceptable to promote a ‘scientific heresy’ if used to support evolutionary scenarios;6,7 and for that matter, to explain fine structure constant changes.

It’s also notable that Guth’s original hypothesis was proven false, and modern inflationary cosmologies have since modified his original proposal. Also, there is no satisfactory physical mechanism for starting inflation, as opposed to playing with mathematical equations. Nor is there a mechanism for halting the inflation, which is known as the ‘graceful exit problem’.


2 thoughts on “The Horizon Problem in Cosmology

  1. It’s funny you brought this up as I just finished reading “Faster than the speed of light” by physicist Joao Magueijo. He was one of the guys responsible for VSL (Variable Speed of Light Theory).

    I recommend reading it as he has a wonderful point of view of the modern scientific community and how restricting it can be if you are going against the accepted norms, he also tears apart the peer review process which is a nice bonus.

  2. Michael, we’ve discussed all this before, and you keep on talking about the temperature of ‘space’. It is the CMB photons that have a very specific temperature with small fluctuations, not ‘space’. Just read my earlier comments again, I do not want to keep on repeating myself.

    But in the second sentence you say: “However, the initial conditions of the big bang would have produced wide fluctuations in temperatures between different regions.”
    Where does this come from ? Why would that be ? This is completely new to me, as a professional cosmologist, so a reference would be nice. The CMI article does not state this either, and just drops this out of thin air. Should I drop the word strawman here ? Quite appropriate.

    Then you (or rather, CMI !) says:
    “It’s also notable that Guth’s original hypothesis was proven false, and modern inflationary cosmologies have since modified his original proposal.”
    CMI reference Coles & Lucchin for this statement, which of course sits on my bookshelf, and which says that the original inflation model was abandoned SOON after is was suggested. A perfectly good scientific approach: you try something, and if it does not work, you try something else. The something else is also not working well, so lots of other inflationary models have been proposed since then. All perfectly fine, as these developments are still relatively recent, i.e. inflation models started to appear about 25 years ago. This is science in action, where a good model has NOT been found yet. As was true for evolution 150 years ago, after all.

    On to the ‘horizon problem’: this is not so much a problem, as a limitation to our observations. We simply cannot observe beyond the horizon. But having a horizon is not a real problem in itself … and introduces interesting scales in the universe, which one can measure.

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