Thursday, May 7, 2015

Why science can’t explain everything

The difficulty of explaining everything is not due to our mental weakness, but to the very structure of the universe. In recent centuries we have discovered that the fabric of the cosmos can be considered on several different levels. While the next level has not been discovered, what happens in the previous one cannot be explained, it can just be described. Consequently, for the last known level we can never have explanations, we can only have descriptions.

Let's look at a little history:
  1. Eighteenth-century chemists discovered many new substances. Not knowing what they were, all they could do was describe them in catalogs of properties, but they had no explanation of those properties.
  2. In the early nineteenth century, Dalton formulated the atomic theory, which states that molecules are made of atoms that combine with one another. Along the nineteenth century, when lots of chemical elements (types of atoms) were discovered, many chemical properties could be explained, but the lower level, the atoms, had no explanation, they could only be described. Mendeleev’s periodic system was just a catalog of atoms: an intelligent catalog, but no one knew why the properties of atoms were what they were, or why they were grouped in such a way and not in another.
  3. In the early twentieth century, after the discovery of radioactivity and the first elementary particles, Rutherford and Bohr proposed a model of the structure of the atom. In this way we went down another level, the third: elementary particles (electrons, protons, next neutrons) group together and explain the structure and properties of atoms. Thus three levels were known: molecules, atoms, and particles. But we could just describe the latter. Nobody knew why protons are positively charged and neutrons have no charge, it was just known that this was the case.
  4. Throughout the twentieth century the number of elementary particles increased. In the late sixties Murray Gell-Mann proposed the theory of quarks, which goes down one more level and explains the behavior of some elementary particles, the hadrons. It is now known that a proton has a positive charge because it is formed by two up quarks with a charge of +2/3 and one down quark with a charge of -1/3 (2/3 + 2/3 - 1/3 = 1), while a neutron consists of two down and one up quark (2/3 - 1/3 - 1/3 = 0). but no one knows why quarks and leptons, such as the electron, have the charge they have. We can only describe them.
This is where we are. We know now four levels: molecules, explained by atoms; atoms, explained by elementary particles; these, in turn, explained by fundamental particles (leptons and quarks), which for the time being can only be described, not explained.

What will happen in the future? Perhaps the behavior of the fundamental particles will be explained if a fifth level is discovered, but then this level will not be explained, just described. And we could go on and on. The last level reached will always be unexplained until the next discovery.

The conclusion is obvious: science cannot explain everything. Some physicists think that our universe might be the only possible one. If so, all the values ​​of the fundamental constants would be fixed. They hope that one day we’ll build a grand unified theory (the theory of everything) that would explain the entire universe. I don’t think this will happen. On the other hand, this idea goes against the multiverse theory, which is itself un-provable. Apparently, in their attempt to do without God, some physicists are groping in all directions at once, with conflicting results.


Manuel Alfonseca

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