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.