Back-in-Time and Faster-than-Light Travel in General Relativity

For the past 20 years causality violations and superluminal motion have been the object of intensive study as physical and geometrical phenomena. How much "exotic matter" would it take to create a time machine or a warp drive? What is the difference between a "discovered" time machine and a created one?

In ultimii 20 de ani, incalcarile cauzalitatii si miscarea superluminala au facut obiectul unui studiu intens ca fenomene fizice si geometrice. Cat de multa „materie exotica” ar fi nevoie pentru a crea o masina a timpului sau o unitate de urzeala?