[contravariant]

For all intents and purposes there is always an objective truth, the hard question is when you consider it proven.

Even for the flat Earth theory it's hard to dismiss it offhand. I mean sure there are plenty of experiments you can do to show that it is pretty close to a sphere. But who do you trust to do those experiments?

Either the person fact-checking needs to do the experiments/research themselves (which doesn't scale well) or they need to trust other people to have done the experiments. However at that point you're simply placing the word of some people above the word of others, which is not objective at all.

And even assuming you've actually picked honest people acting in good faith you're still relying on people to not be confidently incorrect, which I can fairly confidently say is always going to go wrong at some point.

[goatlover]

> Even for the flat Earth theory it's hard to dismiss it offhand. > I mean sure there are plenty of experiments you can do to show that it is pretty close to a sphere. But who do you trust to do those experiments?

All the various people who have done them, some of which can be repeated by anyone motivated enough, and all the technology that relies on it being the case. This was known to the ancient Greeks. One even calculated the circumference within a reasonable accuracy.