People need to stop throwing science around so casually without actually understanding it, so here are a few tidbits to make you more informed.
A scientific hypothesis is an educated observation of a causal relationship; meaning you see something happen, and you guess what made it happen.
A scientific theory is a more worked out version of a hypothesis; it's a model of how things should work, but as of yet has not been completely proven through repeatable controlled experimentation.
A scientific fact is an observation which can be proven using a physical repeatable controlled experiment; repeatable, meaning you or anyone attempting it have to be able to the experiment over and over with the same results; physical, meaning it can be carried out in the real world where causality is most assured; controlled, meaning you must control every factor involved to show direct cause and effect of what your theory states.
Here are some examples:
Scientific Fact: Evolution-Over time by mixing certain animals in a species the species will evolve this, can be seen through physical repeatable controlled experimentation; this can been seen in breeding, by taking the cows that give the most milk and mating them with the bulls which produce the most meat you will get a line of cows which give a lot of milk and meat.
Scientific Theory: The Theory of Evolution- That all animals have evolved from a common ancestor; this will always be a theory for the simple fact that it has already happened and there is no repeatable controlled experiment which can be done. The same goes for the Theory of Human Evolution; although both are sound theory, there is no conceivable way for them to become fact.
Scientific Theory: CO2 Caused Global Warming-That a rise in CO2 alone can cause the greenhouse effect to increase. Since the world is so big with so many variables, it is impossible to do a controlled experiment to see the exact cause and effect relationships occurring. Computer models are not a physical test, they do not happen in the real world, so they can not prove anything, they can only help support theories.
Scientific Theory: Cigarette Smoking Causes Cancer-Since the human body so complex there is no way to do a controlled experiment to see the exact causality. The best which can be achieved is a correlation; but correlations do not prove anything, if every time I ride my bike I fall down and skin my knee the correlation between riding my bike and skinning my knee is very strong, but the causality is not.
