Update from Castiel: please give him a minute, he's just looking it up on Wikipedia.
The Reddit autowikibot has escaped and found a new lair. May God have mercy on our souls.

Update from Castiel: please give him a minute, he's just looking it up on Wikipedia.
When does a theory become a fact?
eg is E=MC2 a fact or could it become E=MC3?
He wasn't the first one either..Observers, Philosophers, Mathematicians, even Theologians had been proposing Heliocentric models for a thousand years before Copernicus. [..]
Longer than that - some ancient Greek philosophers argued in favour of a heliocentric model nearly 2000 years before Copernicus. It wasn't generally accepted, but it was proposed.
e=mc^2 isn't a theory. It's an equation.
A theory never becomes a fact. A theory might become so overwhelmingly supported by evidence that it becomes commonplace to treat it as a fact even in a scientific context, but it's still not actually a fact. Theories explain facts.
For example, the germ theory of disease explains how many diseases are transmitted - by germs.
The diseases are facts. The germs are facts. Experiments were made which showed various other relevant facts, such as the presence of the germs in samples from people with the diseases. The idea that the germs cause the diseases wasn't a fact - it wasn't absolutely proven that there can be no other explanation. It still isn't because it's impossible to do that, but the amount of evidence is now so great that it can reasonably be treated as if it was a fact.