Will the multiverse cause a change in the scientific paradigm?

Thomas Kuhn

I continue my comments on Man Ho Chan’s article, which reviews and refutes recent attempts to make multiverse theories scientific. In this post I’ll refer to those attempts that try to modify the current scientific paradigm to include the theories of the multiverse, so that they can be considered scientific. To do this, epistemological changes or scientific paradigm changes should be made.

According to Thomas Kuhn, there are five criteria that make it possible to evaluate the paradigmatic character of a theory:

1. Accuracy: Indicates whether the predictions of the theory agree with experimental data discovered after the theory is formulated. This criterion is similar to falsifiability in the Popper-style theory, and corresponds to what I have called in another post validation of the theory. It is clear that multiverse theories do not meet this criterion, since they do not make testable predictions.



Francisco José Soler Gil

2. Consistency: Indicates whether the theory agrees with the experimental data we already have. This corresponds to what I called, in the aforementioned post, model adjustment. It is argued that multiverse theories are consistent with the data we have about fine tuning of the laws of the universe to make our existence possible. Man Ho Chan says that this is true, but that the level of adjustment achieved is very low. He points out two examples that prove it: the first, based on my experiments with Francisco José Soler Gil, which discover that the physical laws of our universe should show a certain time dependence if we follow the most general type of multiverse theories. This time dependence does not happen in our universe. The other is called Q-catastrophe, and was pointed out in 2005 by Garriga and Vilenkin. By analyzing the probability distributions of two anthropic variables (the cosmological constant and parameter Q, which measures primordial density fluctuations) they conclude that the measured value for Q is not the most probable. Therefore, if our universe is representative of those universes compatible with life in the multiverse, the value of Q should be different. Man Ho Chan also points out some examples of internal inconsistency in multiverse theories, but I won’t address this issue here.
3. Broadness of scope: This criterion requires that the theory in question be easy to extend to broader situations. In the case of the multiverse, this is impossible, for the various theories are incompatible with each other, and we do not even know the answer to fundamental questions: what is the origin of the multiverse, the number of universes, and whether or not the fundamental constants are different in various universes.
4. Simplicity: It is argued that multiverse theories provide a simple way to solve the fine-tuning problem. However, although we know that the number of universes required to solve this problem is huge, we do not even know its lower limit. The number usually proposed (10⁵⁰⁰) could still be too small. Furthermore, although the idea of the multiverse is simple, each of the multiverse theories is far from being simple.
5. Fruitfulness: The theory in question should lead to new research results. But the theories of the multiverse, together with string theory and chaotic inflation, on which some of them are based, haven’t been able to propose a single experiment that lets them be confirmed, so they must be considered infertile, not validated, and impossible to validate, at least for the time being.

The conclusion that Man Ho Chan draws from this analysis is that multiverse theories do not meet any of the criteria specified by Kuhn to justify a scientific paradigm shift.

Is this the end of the analysis? Well no. There are those who are so desperate for multiverse theories to be scientific, that they have proposed even more drastic changes. I’ll talk about it in my next post.

The same post in Spanish

Thematic Thread on Multiverse and Fine Tuning: Previous Next

Manuel Alfonseca