How do you know?

There is one question that is important when thinking about information, and that is: how do you know?

Take Jack and Jill for example. Jack tells Jill that the moon is made of cheese, but Jill claims that it is made of rock. Now, they could argue for hours over the relative merits of their positions and call each other names, or they could just ask each other: how do you know?
So Jack says, 'well, Mackenzie at the pub told me it is' and Jill says, 'I've got a newspaper article NASA wrote'. This is known as referencing. Already we can see a big difference here - one source of information is an individual who may have had a pint too many, and the other is a published piece from an organisation whose job it is to know about objects floating in space. But in this age of cynicism and distrust perhaps that's not enough. So Jack and Jill can go to Mackenzie and NASA and ask: how do you know?

So NASA say, 'we sent someone there and they brought some rocks back, and here's some footage and here's the calculations we did to get there', and it looks pretty solid 'cos there's a lot of fancy sounding information and pretty pictures. But then Mackenzie says, 'I'm a highly qualified astrozoologist. I was carried there by a giant bird and took some pictures of me eating the cheese, and I still have the giant bird skull. You can buy my book for $39.95 - you'll be shocked by NASA's secret conspiracy'. So who's telling the truth? How do you know?
At this point things get harder, and maybe Jack and Jill really need to get the old brains going. They reckon the best thing to do would be to go there themselves, but rockets seem expensive and there don't seem to be any big birds around. But they realise there are at least some things they can check up on, and that might help them decide.

So they read Mackenzie's book and see the bird skull, but it looks a little like it's made of plastic. And they ask for proof that NASA was funded by nazi zombies, but they only get shown a receipt for groceries. And when they check with neighbours to ask if they saw Mackenzie carried away by a giant bird, a couple of them swear there was a party at Macka's place that night and several people were passed out on the lawn. They even ring the university, and discover that there isn't a degree in astrozoology after all. Some things just don't hang together. Then they learn some physics, and check the maths, look through telescopes, and build a model rocket, and chat to some of the NASA employees. They even go to SpaceX to see what NASA's competitors have to say about them. So while not everything is perfect and they don't get to go to the moon, things more or less make sense and they see it could be true.

They go home, content to say that the moon is most likely made of rock and not cheese, satisfied that they have done their best to find out. On the way Jack says, "gee, I hope it's not always that hard". Don't tell him - it's usually harder. But that's how you know.