# Sci-Faith Extract I: Scientific Theories

Preparations for the publication of my book "Sci-Faith - The Compatibility of Faith and Science" are in full swing and I am confident that it will be published by the beginning of October.

UPDATE: The book is now available here!

To give you a sneak peek of what to expect from this book, I'll be posting a first reading sample in this blog post.

The main reason why many think that faith and science are incompatible is that they do not have a full understanding of the nature of scientific theories. For some, they are just ideas without sound evidence; for others, they are beyond doubt. Therefore, the first chapter of my book explains how scientific theories actually work:

## Evolution of Theories

"I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me." - Sir Isaac Newton1

To answer the question of the nature of theories, let's first be clear about what we are trying to accomplish in science in the first place. To do this, let's take a bit of a swing and look at the beginnings of modern science:

### The Beginning of Modern Science

According to legend, before Newton established his three axioms, he was lying under a tree when he saw an apple fall to the ground2. This raised the question in his mind why this apple flew downward and not in another direction. In other words: What force moved the apple and all other objects to fall to the ground, or to stay there? Obviously, Newton did not let go of this question and he established three axioms to describe these forces, which are known today as Newton's three axioms.

Now, what is an axiom?

An axiom is something like the starting point of a theory. It is a set of statements postulated without proof and assumed to be valid. Every theory needs such a starting point, which will always remain without a proof. Therefore, a theory can never be considered as completely proven. From these axioms then conclusions are drawn, which, if they refer to nature, can be confirmed in physical experiments. In Newton's case, the axioms served to establish classical mechanics and thus to form a foundation for theories based on it. From these axioms a law of gravity could be postulated, which predicted the planetary motion in our solar system and was confirmed by astronomical observations.

Is the theory proven then?

Not at all. It has only been shown that the conclusions we get from the theory are consistent with our observations. However, it is quite possible that the theory may or may not make predictions that we can or cannot measure in experiments. In the case of Newton's law of gravity, this is exactly the case: If we observe the planet Mercury, which is closest to the Sun, precisely, we notice that its perihelion is rotating. According to Newton's laws, planets move on elliptical orbits and the point closest to the Sun is called the *perihelion*. A rotation of the perihelion, which results in the planets moving in rosette orbits (see Fig. 13), can be explained in part by Newton's theory of gravity, given the influence of the other planets. However, Mercury's perihelion rotates farther than predicted by calculations taking into account all known celestial bodies of influence. Therefore, it was initially assumed that there is a hitherto unknown planet, called Vulcan, which is responsible for this deviation. However, this planet could not be detected even after intensive research.

To explain this deviation from Newton's theory, a theory had to be found that incorporated Newton's laws but extended them so that perihelion rotation could be explained by it. In addition it should make further predictions, which can be confirmed then experimentally. Albert Einstein succeeded in 1915 with his theory of general relativity to find this extension.4 According to this, space (or space-time) is curved and planets move on geodesics which describe the shortest distance between two points in a curved space. From this one can derive the elliptical planetary orbits, as well as the perihelion rotation and other previously unknown effects.

### Fundamental and Effective Theories

It should be noted, however, that this does not make Newton's theory of gravity wrong. It is, as the physicist says, merely not valid on all energy scales.

What does this mean?

This means that the Newtonian theory of gravitation is valid only in a certain range to describe nature. For example, this theory is able to describe the gravitation that we experience every day here on Earth and, with a few exceptions, all gravitational effects that take place in our solar system. But if one comes to higher energies, i.e. to higher gravitational forces (e.g. in the environment of a black hole), the Newtonian theory of gravity loses its validity and must be replaced by the theory of general relativity. Moreover, at the atomic level, the gravitational force becomes so small that it becomes negligible compared to the other forces (e.g., the electromagnetic force). Also, general relativity cannot be made into a quantum field theory, which are the theories we use to describe physics at the subatomic level. Therefore, we have not yet succeeded in describing gravity at this energy scale, and many physicists are still searching for a theory of quantum gravity today.

Theories that are not valid at all energy scales are called *effective theories*, while a theory that is valid at all energy scales is a *fundamental theory*. So far, we have been able to only find effective theories in physics. One candidate for a fundamental theory is string theory, but it seems to be far from experimental confirmation.

General relativity and Newton's theory of gravity are both effective theories and differ fundamentally in their interpretation. Therefore, it can be assumed that a fundamental theory will provide an interpretation that will be completely different from the previous theories, while containing them within the respective energy range. Thus, it also becomes clear that while effective theories are often able to accurately describe measurements at a particular energy scale, their interpretation is thereby not beyond question. In the case of fundamental theories, one assumes that their interpretation is correct because it makes the correct predictions at all energy scales. However, it is not at all out of question that there could be several fundamental theories with different interpretations, which all make the correct predictions on all energy scales, and differ fundamentally in their interpretations.

From this one can see the limitations that scientific theories have: Even if they are able to predict and describe everything we can measure, they can never be proven, and especially the interpretation of a theory is by no means beyond doubt.

In summary, theories describe and explain facts based on certain assumptions that are accepted without proof. In particular, a theory is characterized by making predictions that not only explain what we already know, but also make predictions about things we don't yet know that we can use to test that theory.

This is all very theoretical and I will try to illustrate this in the second extract of my book in next blog post.

Sir David Brewster, Memoirs of the Life, Writings, and Discoveries of Sir Isaac Newton, 1855.

William Stukeley, Memoirs of Sir Isaac Newton’s life, 1752.

Bild: Kes47 (?)Original autor:Markus Schmaus in der Wikpedia auf Englisch, CC-BY-3.0.de

Albert Einstein, Erklärung der Perihelbewegung des Merkur aus der allgemeinen Relativitätstheorie., In: Sitzungsberichte der Preußischen Akademie der Wissenschaften.,1915, S. 831-839.