Jack raised the point about theories in the lesson this week. In science, a theory has a different meaning to how we use the word in everyday language. Theory can be used to mean a conjecture, idea, speculation or simply a guess about why something happens. This use is fine as long as you realise that words can have multiple meanings, and the context the word is used in is important.
In science, a theory denotes something else. It used to describe statements or principles that not only describe what is happening, they also provide an explanation. It has predictive power, in other words a theory can be used to predict an event or observation that has not yet happened. Theories are well tested and have evidence to support the statements. If you wanted to show that a theory is incorrect, you could show that the predictions it makes do not happen under experimental conditions.
To give an example, let’s take the good old theory of evolution. Broadly speaking, it would predict that organisms closely related would share more genetic similarities than more distantly related organisms. If you found a monkey more closely related to a fish than a gorilla, you could start questioning the theory. Older fossils should be found in older rocks – if you found a human remains mixed in with a T rex’s bones then you may have a problem. So far these things have not occurred, but if they did and were shown to be valid (e.g. not faked) then the theory would be changed. Theories are changed in reponse to new evidence, that’s how science works.
In the example Jack brought up (ATP synthase mechanism) the theory is incomplete because it doesn’t provide an explanation for all observations. Although there is no hierachy of theories, some have been tested more than others so we often consider them to be more robust. Many accepted theories are used simply because they work well enough for the time being, in other words they hold up to testing so far.
Scientific theories are often described as falsifiable. This means that you could potentially cause a theory to be changed or abandoned by evidence that shows its predictions do not hold up in experiment or observation. Knocking down established theories is a good way to get a Nobel prize. But there’s a reason why the big theories are rarely abandoned…