I guess scientific facts are different to real facts. The last time I checked, a real fact was something that exists, reality, absolutely true.
Yes, it is. The problem is that human beings aren't born with an encyclopaedic knowledge of the universe, we don't know what those facts are without finding out for ourselves.
When people are investigating a phenomenon scientifically, they're trying to develop a description that is as close to the real fact as possible.
When I say that theory X is considered a fact, I mean that the description we have has been tested sufficiently and shown to be a close match to the real fact.
If something exists and is absolutely true, how does it have the potential to be proven false?
It's not the fact itself that is proven false, but our description of it. In straightforward terms, our description should be testable.
If I suggest that all reality is a figment of my imagination, there's no evidence I can provide which can disprove it, since anything I can come up with could be a part of my imagination. It's unfalsifiable and untestable so there's no way for me to know whether it matches reality or not.
What about if objects are being pulled together, but there is not enough mass around for gravity to do it, would the gravity did it theory be falsified? Or would you spend years digging, and millions of dollars, trying to find an invisible source for gravity?
If, after a couple of centuries of countless tests, it seemed that gravity was pretty consistent in its behaviour over a range of circumstances, it would seem strange to declare it false when you actually
don't know the cause of the above scenario.
In the 30s it was noticed that when certain particles decayed, the energy before wasn't the same as the energy after. What scientists could have done, as you suggest, is just throw out the theory of Conservation of Energy, but it was so well tested that it seemed too good a match to reality to throw it out.
Instead scientists suggested that an as yet invisible, undetectable particle was carrying away the energy. Further tests were done, and the neutrino was discovered.
This is already a long post but I like this quote of Thomas Huxley:
"To hear all these large words, you would think that the mind of a man of science must be constituted differently from that of his fellow men; but if you will not be frightened by terms, you will discover that you are quite wrong, and that all these terrible apparatus are being used by yourselves every day and every hour of your lives."
