How a scientific theory differs from a guess or an opinion?

Answer 1

A hypothesis is a guess based on the knowledge of the scientist who makes it about what will happen in certain conditions. An experiment is designed to test the hypothesis, or observations are made in the conditions that the hypothesis describes. If the experiment or observation proves that the hypothesis is wrong, then the hypothesis is modified or discarded. If many, many different experiments and observations, performed many, many times, by many, many different scientists all seem to support the hypothesis, then the hypothesis comes to be accepted by the scientific community as a good working model for the conditions it describes. It then becomes a theory. At any time, an observation could disprove a theory or at least force it to be modified, but all theories currently accepted at any given time have lots of strong scientific evidence supporting them. (It is impossible to PROVE a theory, only to provide evidence in support of it). A theory will alwaysbe reconsidered in the face of new evidence. An opinion may not be. A theory also has much more evidence behind it than a guess.

Answer 2

A theory initially begins with a question that needs answering - like is the moon made of cheese

An experiment can be designed based on the researchers guess, opinion, previous experiments, existing theory.

The experiment is conducted and results are analysed. Here is where it gets tricky because the researcher needs to discuss the results. If the results are inconclusive the researcher may make a guess and an opinion based on experience etc. Even if he /she beleives the results are conclusive they are still open to scrutiny, has the experiment been designed properley, does the researcher have enough experience in the field, has the test been contaminated etc

There are certain things that reinforce a theory such as 'gold standard' methodology, other experiments in the field which obtain similar results, acknowledgement by experts in the field and of course the repeatabilty of the results of another researcher following the same or similar experiment.

If all the right boxes are ticked then the scientific community accept it as scientific theory, there may be conflicting theories and not everyone will agree but it stays as such until it is dis-proven by another experiment or a piece of incontrovertible evidence against the theory.

In answer to the question a scientific theory can have an element of guess or an opinion in all areas of its construction. without scientific methodology it remains just that a guess or an opinion.