Multiplicity

You could do a community study for fun. Have the two parties that are claiming that there's travel between their systems send their e-mails to a third party community member. The third party member e-mails System A the title, author, and plot summary of a book. System A travels to System B and shares the information about the book. (This, of course, is the weak part of the 'study' as it depends on Systems A & B being moral, honest people and not cheating to pass the information.) System B e-mails the third party member with the details that they learned while traveling. After enough time for all participating travelers to communicate the information and contact their third party, the third parties then post the information sent and the information received so that the whole community can see the results.