- In the pop sci world, facts are frequently treated as solid, immovable things. When commonly known theories change, lay people can get up in arms over the changing of 'facts.'
- We teach students facts as if they were eternal, but few ideas are unchanging.
- Every scientific theory was once a hypothesis. Someone had to gather the evidence, take the measurements, and pull together a working idea.
- Scientific facts are not self-evident.
I think facts are more like stones in a wall. You can build a serviceable, sturdy wall out of rough hewn stones. There may be weak points and gaps. When someone does the hard (and often tedious) work of refining those stones, gaps are closed, and the structure becomes sturdier. Sometimes, despite years of acceptance, we find a stone doesn't fit with its neighbors any more. Sometimes that stone is changed and adapted. Sometimes it is removed altogether and replaced with one that fits better – a theory that explains better.
A key ingredient to scientific thought is falsifiability. You accept – perhaps expect! – that someone else with more evidence could come along and prove you wrong.