The hardest challenge for all computers including AI is the physical world.

How can we be sure that the digital representation is accurate? Do you know the weather? 

Do you know if someone really arrived? 

Do you know the house really is in good shape? Is it even there?

Getting physical data into the digital world has become easier with sensors and image recognition, but not verifiable.

And for sure not usable in permissionless, decentralized networks like blockchains. I feel that will be the next big unlock. Solve for verifiable real world inputs into digital systems.