Ask Lemmy

If we're talking about things that are easily quantifiable, not very much at all.

Reading it once on social media

It varies widely depending on a combination of whether it impacts me directly, whether it contradicts or is inconsistent with information I have already accepted as fact, and the source. The source includes being reliable and if the fact could be something that serves the source's self interest as that would require corroboration.

Until recently, if NASA tells me their current data shows that black holes exist at the center of a galaxy I take their word for it. They have been consistently reliable for decades and their entire mission is about increasing knowledge and sharing it with the entire world. With recent administrative changes I am more skeptical and wouldn't trust something that contradicts prior scientific discoveries without corroboration from an external agency like the European Space Agency. I would take the ESA at their word currently.

If a for profit company says anything I want corroboration from a neutral 3rd party. They have too much incentive to lie or mislead to be trusted on their own.

Something from a stranger that fits into prior knowledge might be accepted at face value or I might double check some other source. Depends on how important it is to me and whether believing that would lead to any obvious negative outcome. I will probably also double check if it is interesting enough to want to check, and I'll use skepticism as an excuse.

That covers actual factual stuff that could possibly be corroborated by a third party. Facts like the Earth orbits the sun or Puerto Rico is a US territory type stuff.

Then there are other things that can be factual but difficult to determine and that is a combination of experience and current knowledge, plus whether believing it would be a benefit or negative. If someone tells me the ice isn't thick enough based on their judgement I will treat it as a fact and not go out on it unless I had some reason not to believe them. If they told me apples were found to be unhealthy I would check other sources.

It isn't quantity. It is the quality and logical reasoning.

If I can find three reputable sources that say the same thing, I feel pretty confident in accepting it as fact. The real trick is finding reputable sources. Media Bias Fact Check is really helpful for this.