Scientists are careful to separate fact from opinion when they are doing research. In the scientific world, all research is based on evidence so that future research can be expanded on what is already known.
If you were to say that you think pizza is gross, that is an opinion. Opinions aren't based on evidence that has been gathered.
Facts are information based on evidence.
If poor materials are used to build the foundation of a home, the rest of the home won't be stable. That is why when scientists gather data it is based on evidence and peer reviewed.
The scientific body of knowledge is full of evidence based facts so that it is a consistent, reliable, and growing with each new study.