Q: HOW CAN TWO DISTANT PARTIES CREATE AND SHARE A SECRET KEY FOR COMMUNICATION WITHOUT ACTUALLY SENDING THE KEY?
If there is a single key to unlock a communication, that key must be known by the person doing the locking, and by the person doing the unlocking. At some point, both must know the key. If they are always distant, the key must be sent from one to the other. In other words, you have created a catch-22.
But that is wrong-headed thinking. Public/private key encryption has solved that problem - way back in 1991 with PGP.
Today you can use PGP, GPG, and other tools to accomplish this. You encrypt something with someone's public key - which may be freely distributed or placed on a PGP public server, and only the person with the private key (the person whose public key did the encryption) can decrypt it.