There are proofs that are not physical in nature. The same story from entirely different people who do not know one another, for example. Or...or recognizing something specific in the way they act that can only be explained by their story.

So, yes, it can be proven without showing me the world. Please don't be discouraged. Surely, if you are so certain they are lying it means your world is not among those with this...affliction. Honestly, I've been waiting so long to meet someone from another world with a kind, benevolent God...