• John
  • Felde
  • University of Maryland
  • USA

Latest Posts

  • James
  • Doherty
  • Open University
  • United Kingdom

Latest Posts

  • Andrea
  • Signori
  • Nikhef
  • Netherlands

Latest Posts

  • CERN
  • Geneva
  • Switzerland

Latest Posts

  • Aidan
  • Randle-Conde
  • Université Libre de Bruxelles
  • Belgium

Latest Posts

  • TRIUMF
  • Vancouver, BC
  • Canada

Latest Posts

  • Laura
  • Gladstone
  • MIT
  • USA

Latest Posts

  • Steven
  • Goldfarb
  • University of Michigan

Latest Posts

  • Fermilab
  • Batavia, IL
  • USA

Latest Posts

  • Seth
  • Zenz
  • Imperial College London
  • UK

Latest Posts

  • Nhan
  • Tran
  • Fermilab
  • USA

Latest Posts

  • Alex
  • Millar
  • University of Melbourne
  • Australia

Latest Posts

  • Ken
  • Bloom
  • USLHC
  • USA

Latest Posts

Byron Jennings | TRIUMF | Canada

View Blog | Read Bio

String Theory and the Scientific Method

It seems some disagreements are interminable: the Anabaptists versus the Calvinists, capitalism versus communism, the Hatfields versus the McCoys, or string theorists versus their detractors. It is the latter I will discuss here although the former may be more interesting. This essay is motivated[1] by a comment in the December 16, 2014 issue of Nature by George Ellis and Joe Silk. The comment takes issue with attempts by some string theorists and cosmologists to redefine the scientific method by eliminating the need for experimental testing and relying on elegance or similar criteria instead. I have a lot of sympathy with Ellis and Silk’s point of view but believe that it is up to scientists to define what science is and that hoping for deliverance by outside people, like philosophers, is doomed to failure

To understand what science is and what science is not, we need a well-defined model for how science behaves. Providing that well-defined model is the motivation behind each of my essays. The scientific method is quite simple: build models of how the universe works based on observation and simplicity. Then test them by comparing their predictions against new observation. Simplicity is needed since observations underdetermine the models (see for example: Willard Quine’s (1908 –2000) essay: The Two Dogmas of Empiricism).  Note also that what we do is build models: the standard model of particle physics, the nuclear shell model, string theory, etc. Quine refers to the internals of the models as myths and fictions. Henri Poincaré (1854 – 1912) talks of conventions and Hans Vaihinger (1852 –1933) of the philosophy of as if otherwise known as fictionalism. Thus it is important to remember that our models, even the so-called theory of everything, are only models and not reality.

It is the feedback loop of observation, model building and testing against new observation that define science and give it its successes. Let me repeat: The feedback loop is essential. To see why, consider example of astrology and why scientists reject it. Its practitioners consider it to be the very essence of elegance. Astrology uses careful measurements of current planetary locations and mathematics to predict their future locations, but it is based on an epistemology that places more reliance on the eloquence of ancient wisdom than on observation. Hence there is no attempt to test astrological predictions against observations. That would go against their fundamental principles of eloquence and the superiority of received knowledge to observation. Just as well, since astrological predictions routinely fail. Astrology’s failures provide a warning to those who wish to replace prediction and simplicity with other criteria. The testing of predictions against observation and simplicity are hard taskmasters and it would be nice to escape their tyranny but that path is fraught with danger, as astrology illustrates. The feedback loop from science has even been picked up by the business management community and has been built into the very structure of the management standards (see ISO Annex SL for example). It would be shame if management became more scientific than physics.

But back to string theory. Gravity has always been a tough nut to crack. Isaac Newton (1643 – 1727) proposed the decidedly inelegant idea of instantaneous action at a distance and it served well until 1905 and the development of special theory of relativity. Newton’s theory of gravity and special relativity are inconsistent since the latter rules out instantaneous action at a distance. In 1916, Albert Einstein (1879 – 1955) with an honorable mention to David Hilbert (1862 – 1943) proposed the general theory of relativity to solve the problem. In 1919, the prediction of the general theory of relativity for the bending of light by the sun was confirmed by an observation by Arthur Eddington (1882 – 1944). Notice the progression: conflict between two models, proposed solution, confirmed prediction, and then acceptance.

Like special relativity and Newtonian gravity, general relativity and quantum mechanics are incompatible with one another. This has led to attempts to generate a combined theory. Currently string theory is the most popular candidate, but it seems to be stuck at the stage general relativity was in 1917 or maybe even 1915: a complicated (some would say elegant, others messy) mathematical theory but unconfirmed by experiment. Although progress is definitely being made, string theory may stay where it is for a long time. The problem is that the natural scale of quantum gravity is the Planck mass and this scale is beyond what we can explore directly by experiment. However, there is one place that quantum gravity may have left observable traces and that is in its role in the early Universe. There are experimental hints that may indicate a signature in the cosmic microwave background radiation but we must await further experimental results. In the meantime, we must accept that current theories of quantum gravity are doubly uncertain. Uncertain, in the first instance, because, like all scientific models, they may be rendered obsolete by new a understanding and uncertain, in the second instance, because they have not been experimentally verified through testable predictions.

Let’s now turn to the question of multiverses. This is an even worse dog’s breakfast than quantum gravity. The underlying problem is the fine tuning of the fundamental constants needed in order for life as we know it to exist. What is needed for life, as we do not know it, to exist is unknown. There are two popular ideas for why the Universe is fined tuned. One is that the constants were fine-tuned by an intelligent designer to allow for life as we know it. This explanation has the problem that by itself it can explain anything but predict nothing. An alternate is that there are many possible universes, all existing, and we are simply in the one where we can exist. This explanation has the problem that by itself it can explain anything but predict nothing.  It is ironic that to avoid an intelligent designer, a solution based on an equally dubious just so story is proposed. Since we are into just so stories, perhaps we can compromise by having the intelligent designer choosing one of the multiverses as the one true Universe. This leaves the question of who the one true intelligent designer is. As an old farm boy, I find the idea that Audhumbla, the cow of the Norse creation myth, is the intelligent designer to be the most elegant. Besides the idea of elegance, as a deciding criterion in science, has a certain bovine aspect to it. Who decides what constitutes elegance? Everyone thinks their own creation is the most elegant. This is only possible in Lake Wobegon, where all the women are strong, all the men are good-looking, and all the children are above average (A PRAIRIE HOME COMPANION – Garrison Keillor (b. 1942)). Not being in Lake Wobegon, we need objective criteria for what constitutes elegance. Good luck with that one.

Some may think the discussion in the last paragraph is frivolous, and quite by design it is.  This is to illustrate the point that once we allow the quest for knowledge to escape from the rigors of the scientific method’s feedback loop all bets are off and we have no objective reason to rule out astrology or even the very elegant Audhumbla. However, the idea of an intelligent designer or multiverses can still be saved if they are an essential part of a model with a track record of successful predictions. For example, if that animal I see in my lane is Fenrir, the great gray wolf, and not just a passing coyote, then the odds swing in favor of Audhumbla as the intelligent designer and Ragnarok is not far off. More likely, evidence will eventually be found in the cosmic microwave background or elsewhere for some variant of quantum gravity. Until then, patience (on both sides) is a virtue.

Though the mills of science grind slowly;
Yet they grind exceeding small;
Though with patience they stand waiting,
With exactness grind they all.[2]

[1] I have already broken my new year’s resolution to post no more philosophy of science blogs but this is the last, I promise.

[2] With apologies to Henry Wadsworth Longfellow (1807 – 1882)

Share

Tags: ,

  • Jeh Tween

    Byron Jennings: “… that it is up to
    scientists to define what science is and that hoping for deliverance by outside
    people, like philosophers, is doomed to failure…. Thus it is important to
    remember that our models, even the so-called theory of everything, are only
    models and not reality.”

    First, George Ellis and Joe Silk are
    physicists, not philosophers. Why should their view be not part of the
    physicists’ definition about physics?

    Second, two philosophers (Otávio Bueno and Jody Azzouni) discussed the issue of
    ‘epistemological accesses’ in a general term (encompassing all disciplines, of
    course, including physics), and their discussions were discussed at Scientia
    Salon. Some comments there (http://scientiasalon.wordpress.com/2015/01/07/apa-2014-5-on-the-reality-of-atoms-and-subatomic-particles/comment-page-1/#comment-10811
    ) might be
    useful as a comment for your article here too.

    Third, yes, physics is invented by human via the loops of theories and
    testing, but the laws of Nature are ontological ‘realities’. Anti-realism on
    the epistemological sense is okay. Any anti-realism on the ontological level is simply wrong.

  • SJ

    So… you are saying that intelligent design = multiverse theory = string theory?

    What is it that you study again?

  • Jake Purches

    Byron Jennings is a theoretical nuclear physicist. I guess that makes him reasonably qualified.

  • Byron Jennings

    You are not reading very carefully. At no point did I equate multiverse theory with string theory. I believe some versions of mutliverse come out of some versions of string theory.

    Intelligent design and at least some versions of multiverse theory currently are based on a similar epistemology in that each explains everything but predicts nothing. I did not imply that they were the same in content.

  • Jeh Tween

    Byron Jennings: “Let’s now turn to the question of multiverses. … The underlying problem is the fine tuning of the fundamental constants needed in order for life as we know it to exist. … There are two popular ideas for why the Universe is fined tuned.

    One is that the constants were fine-tuned by an intelligent designer to allow for life as we know it. … An alternate is that there are many possible universes, all existing, and we are simply in the one where we can exist. … perhaps we can compromise by having the intelligent designer choosing one of the multiverses as the one true Universe.”

    There is another alternative; all nature constants {the Cabibbo and Weinberg angles, Alpha, electric charge, mass-charges, ħ (Planck constant), etc.} and many measured parameters {such as, Planck data (dark energy = 69.2; dark matter = 25.8; and visible matter = 4.82)} can be ‘derived’ (calculated). I am showing the simplest one below.

    Beta = 1/alpha = 64 (1 + first order mixing + sum of the higher order mixing)

    = 64 (1 + 1/Cos A (2) + .00065737 + …)

    = 137.0359 …

    A (2) is the Weinberg angle, A (2) = 28.743 degree

    The sum of the higher order mixing = 2(1/48) [(1/64) + (1/2) (1/64) ^2 + …+(1/n)(1/64)^n +…]
    = .00065737 + …

    Many other calculations are available at http://scientiasalon.wordpress.com/2014/06/05/the-multiverse-as-a-scientific-concept-part-ii/comment-page-1/#comment-3158
    .

  • Byron Jennings

    I would suggest your last statement is incorrect. O. V. Quine in his essays “On what there is” and “Two dogmas of Empiricism” gives the counter argument. Poincare’s “Hypothesis and Science” also has a contrary view.

  • SJ: “The many-worlds interpretation is an interpretation of quantum mechanics….” — from the opening of the Wikipedia article on that topic, which I commend to you. (It has nothing to do with “Intelligent Design”.)

  • Raul Romea

    If I remember correctly, multiverse came not as an alternative to intelligent design, but as a consequence of no-boundary. Per Hawking/Mlodinov, in The Grand Design.

    Personally, I find it even harder to believe that we are the only universe.