A scientific theory (1) is not just an unsupported idea of how scientists think something occurs, but is a structured idea supported by extensive evidence, which is tested, pulled apart and challenged in order to refine the idea in to a clear concept. The reason the term ‘Theory’ is used instead of ‘Fact’ is simply because it cannot be ‘Proven’ because the types of tests required to prove that the theory is unequivocally true are either currently unfeasible because the technology currently does not exist or there is not current way of testing it. Theories are not set in stone but are changeable, because they are open to influence from new findings and new data, and so can be refined and changed over time. This is not the same as a hypothesis, which is a suggestion of how something could work, but which needs to be tested, as it does have some initial evidence to support it but it is not as well defined and as rigorously tested as a theory.
The wonderful thing about science is that if you don’t agree or believe in a theory, it does not mean that it is not true or does not exist, just because you do not believe in gravity does not mean you will suddenly start floating away. Of course, there are big differences between types of theories. Theories in physics, like gravity, have a lot of complicated maths and for the most part, factors which are unobservable and untestable. However, more contentious theories, like those of biology, can be seen but take place over huge time scales, which are subsequently very hard for people to conceive of; the most famous would be Darwin’s theory of Evolution, because many people believe that acknowledging this would be to discredit religion.
Any concept that challenges religious beliefs has always been a difficult, often resulting in much religious outcry and persecution. One of the best known instances of this is where Galileo was persecuted for his theory of heliocentrism, because it suggested that all of the planets in the solar system orbited the sun, and so was seen as heresy and going against the bible and the church, after a long inquisition and trial he was sentenced to house arrest for the rest of his life (2). Fortunately the theory of heliocentrism is now almost universally accepted, and anyone suggesting that the earth is the centre of the universe would be ridiculed. Sometimes it just required a passage of time before the general population can embrace a new scientific theory.
E Markham (2012). Thoughtful Theories Blogspot