Of late there has been obsession that things should be based on scientific facts which, on the surface, sounds like a good idea. Drug policy should be based on the science, global worming is a scientific fact, the medicines our doctors give us have been subject to rigorous scientific evaluation etc and we will all be sure that we are heading to a bright new future.
But there is a problem, there is, no such thing as scientific fact. Surprised? You should be because it can change the way we view the pronouncements made by scientists.
Let me start at the beginning with something called Scientific Method. Basically it looks like this:
Hypothesis - what, after observation, do you think explains something you have noticed.
Experiment - device experiments to test whether you are right
Analysis - does the experiment prove you right or wrong (start again if it shows you were wrong)
Publish Results - a very important stage (called Peer Review) where others can see if they get the same results and conclusions.
If everyone agrees the outcome is sometimes called a scientific fact when all it actually says is 'The experiments carried out seem to confirm the hypothesis.' Notice that word 'seems' - there always remains the possibility that further experiments will come to different, sometimes contradictory, conclusions.
Let me give you 2 examples, one old and one current.
In 1687 Newton published his Philosophiæ Naturalis Principia Mathematica in which, among other things, he formulated methods of calculating the way forces act on bodies to cause motion. At the time these seemed so robust that they became know as Newton's Laws of Motion - laws because they were always right. However in the early 20th century Einstein came along with his Theories of Relativity which, once tested, showed that Newton's 'Laws' didn't always apply.
My second example is still under evaluation but it may turn out to be a very significant find. I, like so many others, was told (at school?) that you tell what the temperature was like in the past by measuring the amount trees grew (tree ring thickness in other words) and we all assumed this was correct. Some researchers in Scotland found they had a good opportunity to check this and their results have come as a very big surprise. It appears that there is virtually no relationship between tree growth and weather but there is one with cosmic ray intensity. If confirmed by peer review the implications for this are enormous; most of what we 'know' about the historical climate is based on tree ring measurements as these were 'known' to be a proxy for temperature but if there is no connection we have been measuring the wrong thing! If our historic data is wrong it throws great doubts on any forecast made using them whether to prove or disprove man made climate change.
So next time someone tells you that something is based on the science remember all it means is that the experiments have shown that that a theory might be totally right, partially right or even wrong (interpretation of data can be very subjective.)