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How to challenge a scientific theory, method 2: propose an alternative

Posted at 10:00 on 26 October 2020

This is the third post in a series of three.

  1. How to challenge a scientific theory
  2. How to challenge a scientific theory, method 1: Evidence that contradicts it
  3. How to challenge a scientific theory, method 2: propose an alternative

How do you respond to a scientific theory, such as evolution, with which you disagree?

So far, we have looked at the basic rules of honesty and accuracy that your challenge needs to obey, and one way in which you can challenge the theory by presenting some evidence that contradicts it. We discussed what does and does not count as evidence, and what kinds of standards evidence needs to meet in order to actually contradict a theory.

This week, we will take a look at another way to argue against a scientific theory: by proposing an alternative.

What kind of alternative?

Now just as you can't cite any old rubbish as evidence against a theory that you don't like, in the same way you can't just postulate any old nonsense as a legitimate alternative. If you could, then you would be able to claim that bananas are marsupials, that cars run on gravy, and that salmon live in trees and eat pencils. That is hardly a recipe for being taken seriously by anyone.

No, your theory needs to meet a few basic requirements.

1. It must explain all the evidence that the existing theory explains, in at least as much detail.

It is not sufficient to come up with an overarching explanation that only paints broad brush strokes. Your theory needs to be able to drill right down into the details, at least as far as the existing theory reaches. Where measurements are involved, your alternative needs to be able to account for the precise values, including any patterns and trends that are evident in the data.

This means that you need to understand, at least generally, just how much evidence the existing theory explains, in how much detail, and with how much precision, because that is the bar that is set for your alternative. The more evidence that the existing theory explains, the higher the bar becomes and the harder it gets to devise a credible alternative.

2. It must make testable predictions.

Your theory is not of much use if it is not testable. It is even more useless if the theory you are challenging has a successful track record of making testable predictions of its own. Furthermore, the predictions that your alternative makes must be at least as precise as the predictions made by the original theory.

In many cases, the predictions that the original theory makes even have commercial value. Oil exploration is one such example. If this is the case, then you need to be able to demonstrate that the predictions made by your alternative can do the same. When science meets business, your theory will only get taken seriously if it can do one of two things: decrease costs, or increase revenue.

3. It must be consistent with the rest of science.

Consilience is one of the most important rules of science. Whatever model you come up with must be consistent, both with itself and with every other area of science that you are not challenging.

Science is not a collection of independent systems, each acting in isolation from each other. It is a unified whole, in which every constant, every equation, every mechanism, every effect, is interrelated with the others. Changing one factor will have a knock-on effect on just about everything else imaginable.

Take, for example, the fundamental constants of nature, such as the speed of light. Could this have been any different in the recent past from what they are today, as people such as Barry Setterfield claim? The problem here is that these constants all depend on each other. For example, the speed of light itself is related to the electrical permittivity and the magnetic permeability of a vacuum:

$latex c = \frac 1 { \sqrt { \mu_0 \epsilon_0 } } &s=2$

It determines the relationship between mass and energy, as Einstein's famous equation spells out:

$latex e = m c^2 &s=2$

It determines the fine structure constant, a value that itself determines the chemical properties of the elements:

$latex \alpha = \frac {e^2} {4 \pi \epsilon_0 \hbar c } &s=2$

Now you may not know exactly what all these equations and symbols mean, but it only takes some basic understanding of school-level algebra to see that when you change one of them, it has a knock-on effect on all the others. This means that even minor changes to the speed of light in the recent past would have had very, very far reaching and dramatic consequences. Any theory that postulates that the speed of light, or nuclear decay rates, could have changed needs to be able to fully account for these consequences.

A theory that only explains one thing in grand isolation from everything else is not going to cut it. Introducing one new law of physics to try and accommodate your alternative explanation usually means that you have to add other new laws of physics to accommodate the knock-on effects from your first new law, and then to add on other new laws of physics to accommodate their knock-on effects, and it all very, very quickly spirals into absurdity.

A tall order?

If all this sounds like a tall order, then perhaps it is. But it is a fair one. These are simply the standards that the theory you are challenging had to meet in the first place. Science is far, far more rigorous than most lay people believe it to be. The scrutiny is far more stringent, and the standards of quality control are far higher. That is why so many people give up on science at the first possible opportunity at age sixteen: they find its exact standards too easy to get wrong and too difficult to get right, so instead they choose to specialise on easier subjects that concern the vagaries of humans and other living beings instead.

But if you are to challenge a scientific theory, you do need to allow your challenge to be subjected to the same level of rigour and scrutiny as the theory itself. If your challenge stands up to scrutiny, then you're onto a winner (and possibly even a Nobel Prize). On the other hand, if your challenge can't pass the test, then perhaps you need to acknowledge that the theory you are challenging is more robust than you thought it was.

Featured image: The Large Hadron Collider. Photo courtesy of CERN.