“The Universe Should Not Have Lasted for More than a Second”: The limitations of scientific theories

Stan Hummel called my attention to, and asked for my thoughts on this article: Big Bang Theory Challenged –“The Universe Should Not Have Lasted for More than a Second”.

British cosmologists are puzzled: they predict that the universe should not have lasted for more than a second. This startling conclusion is the result of combining the latest observations of the sky with the recent discovery of the Higgs boson. according to Robert Hogan of King’s College London (KCL), who will present the new research today, 24 June at the Royal Astronomical Society‘s National Astronomy Meeting.

In the new research, scientists from KCL have investigated what the BICEP2 observations mean for the stability of the Universe. To do this, they combined the results with recent advances in particle physics. The detection of the Higgs boson by the Large Hadron Collider was announced in July 2012; since then, much has been learnt about its properties.

Measurements of the Higgs boson have allowed particle physicists to show that our universe sits in a valley of the ‘Higgs field’, which describes the way that other particles have mass. However, there is a different valley which is much deeper, but our universe is preventing from falling into it by a large energy barrier.

The problem is that the BICEP2 results predict that the universe would have received large ‘kicks’ during the cosmic inflation phase, pushing it into the other valley of the Higgs field within a fraction of a second. If that had happened, the universe would have quickly collapsed in a Big Crunch.

It’s tempting to come up with some humorous remark about this prediction, but this is important work.  When a scientific theory makes counter-factual predictions, it demonstrates that the theory is not yet complete.  Of course, I doubt there were many physicists who thought any of the models of cosmic inflation were necessarily complete, but demonstrating it is an important step.

But this also reminds me why I’m usually skeptical when people take these theories and extrapolate grand notions of reality from them (such as bubble universes).  Doing so gives us a possible version of reality, but any certitude about those predictions should be taken with a pound of salt.  There is just too much that is not known, and we often don’t know what we don’t know.

Indeed, every assumption a theory has to make that is not yet empirically testable, weakens the probability of that theory being truth.  And assuming that the structure posited by a successful theory continues unchanged beyond our observations is an assumption.  Often is it a valid one, but the further beyond observations you assume an unchanged structure, the more speculative it becomes.

If you read the history of science, you’ll see the trouble that such theories often run into.  We tend to celebrate the occasional successes of theoretical predictions, but overlook the legions of failure.  From what I’ve read, the theories that tend to be successful are the ones driven by empirical necessities, rather than possibilities.

None of this is to suggest that such theoretical work shouldn’t continue.  This kind of speculation is important.  The fact that most of it will ultimately prove fruitless has to be weighed against the fact that some of it will be fruitful, and there is no way to know ahead of time which category each competently crafted theory will fall into.  But we should be clear about the limitations of these theories, particularly their more speculative extrapolations.

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11 Responses to “The Universe Should Not Have Lasted for More than a Second”: The limitations of scientific theories

  1. Tienzen (Jeh-Tween) Gong says:

    “When a scientific theory makes counter-factual predictions, it demonstrates that the theory is not yet complete.”

    Agree 100%.

    “There is just too much that is not known, and we often don’t know what we don’t know. … but the further beyond observations you assume an unchanged structure, the more speculative it becomes. … and there is no way to know ahead of time which category each competently crafted theory will fall into.”

    I think that there are guidelines for knowing which competent theory is pointing to the right direction. Your first statement above is one of such guideline.

    In general (although not inclusive), there are four steps for the growth of ‘human’ physics.
    Step one, collecting data — knowing the phenomena.

    Step two, finding the pattern (with equations to best fit the data) — these equations have *variables* and *parameters*.

    Step three, finding the underlying causes (dynamics) for the equations (especially for the variables).

    Step four, finding the underlying framework for the *parameters*, deriving parameters from an axiomatic system.

    Now, many parameters (such as, fine structure constant, Weinberg angle, etc.), many frameworks (such as, the 48 Standard Model ‘matter’ particles, …) and many data (such as the Planck data: dark energy = 69.2; dark matter = 25.8; and visible matter = 4.82) are now firmly established as the ‘anchors’ of the accepted known ‘knowledge’. And, these anchors are the guidelines for sorting out the competing theories.

    Of course, tailor-fitting one of the anchors (such as the string-unification) could be done by tweaking some theories. But, tailor-fitting more than two anchors by the same theory will not be easy. Then, the true theory should fit all ‘known’ anchors (at least), if not predict more anchors. Thus, this anchor-fitting test can be a very important guideline for sorting out the winner of competing theories in the arena where theories are no longer testable either in principle or in practice.

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    • I like that framework. I do think it’s crucial that our anchors, to be considered anchors, be firmly grounded in the current results of your step one (while of course utilizing the later steps), and falsifiable by future results from step one. If we ground anchors in anything else, we risk building a house of cards.

      But even then, I fear it only gives us insights into which speculative theory may be more likely to be true. Until that theory itself can be tested in some way, I think we must always keep a question mark on it.

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  2. Great post! Thanks, Stan Hummel for getting SAP to write about this.

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  3. Steve Morris says:

    I think you sum that up very well.

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  4. s7hummel says:

    as if in the presence of all these doubts there is another question… if we use the exact value of the speed of light! which is not actually so obvious. (physicist suggests speed of light might be slower than thought.-phys.org) if that would be true (what also is not so obvious) this not only suffer a lot of very important theorems and data but most suffer seriousness same cosmology! if the terms of a summary of all of those thoughts that might be expected that they will have a lot of sense… and are wonderful. Thanks Michael! just a little sad that there was no Steve in all of this.

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    • Thanks Stan. Glad you enjoyed it, and always happy to hear your thoughts.

      I may well be missing something, but the concern about light possibly traveling slower than what was previously thought seems overblown to me. My understanding is that, if true, it would not change c, the maximum speed of the universe, just the rate of propagation of photons through space. We already know that light travels slower through a dense medium due to interference from that medium. This would just mean that space interferes with the travel to a small degree. 4 hours across 160,000 years seems like a slight difference. It’s hard for me to imagine it changing cosmology on a broad scale, although maybe there are some technical implications I’m not seeing.

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