Hermitcraft season 10 – Episode 3: Progress & Neighborhood Shenanigans! 
Einstein’s General Relativity tells us that space and time together form a 4-dimensional spacetime that is curved by the presence of matter and energy. If we could produce the proper state of matter and energy, the spacetime could curve enough to permit travel into the past. But ordinary forms of matter are not sufficient. Instead we would need exotic material with negative energy density. The possibility of time travel depends on whether quantum mechanics can provide us with the proper negative-energy-density state. The lecture will present the state of the art in designing a time machine or proving that it is impossible to do so, and the related issues of wormholes and faster-than-light travel. Time-travel ideas related to quantum mechanical correlations and tunneling of a signal through a barrier will be briefly discussed.
